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Sample records for der waals energy

  1. van der Waals

    Indian Academy of Sciences (India)

    University education was beyond reach for van der Waals as he had to work for earning his daily bread ... languages, which was a prerequisite for entering a University those days. van der Waals worked as a school ... take academic examinations at the University yet, van der Waals continued studying at Leiden. University ...

  2. Thermionic Energy Conversion Based on Graphene van der Waals Heterostructures

    Science.gov (United States)

    Liang, Shi-Jun; Liu, Bo; Hu, Wei; Zhou, Kun; Ang, L. K.

    2017-04-01

    Seeking for thermoelectric (TE) materials with high figure of merit (or ZT), which can directly converts low-grade wasted heat (400 to 500 K) into electricity, has been a big challenge. Inspired by the concept of multilayer thermionic devices, we propose and design a solid-state thermionic devices (as a power generator or a refrigerator) in using van der Waals (vdW) heterostructure sandwiched between two graphene electrodes, to achieve high energy conversion efficiency in the temperature range of 400 to 500 K. The vdW heterostructure is composed of suitable multiple layers of transition metal dichalcogenides (TMDs), such as MoS2, MoSe2, WS2 and WSe2. From our calculations, WSe2 and MoSe2 are identified as two ideal TMDs (using the reported experimental material’s properties), which can harvest waste heat at 400 K with efficiencies about 7% to 8%. To our best knowledge, this design is the first in combining the advantages of graphene electrodes and TMDs to function as a thermionic-based device.

  3. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

    KAUST Repository

    Govyadinov, Alexander A.

    2017-07-14

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  4. Van der Waals black hole

    Directory of Open Access Journals (Sweden)

    Aruna Rajagopal

    2014-10-01

    Full Text Available In the context of extended phase space, where the negative cosmological constant is treated as a thermodynamic pressure in the first law of black hole thermodynamics, we find an asymptotically AdS metric whose thermodynamics matches exactly that of the Van der Waals fluid. We show that as a solution of Einstein's equations, the corresponding stress energy tensor obeys (at least for certain range of metric parameters all three weak, strong, and dominant energy conditions.

  5. Dispersion (van der Waals) Forces and TDDFT

    Science.gov (United States)

    Dobson, John F.

    A semi-pedagogic discussion is given of the use of response theory and Time Dependent Density Functional Theory to describe van der Waals (dispersion) energies, within the context of Adiabatic Connection and the Fluctuation-Dissipation theorem.

  6. Strong pressure-energy correlations in van der Waals liquids

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Bailey, Nicholas; Schrøder, Thomas

    2008-01-01

    in the crystal and glass phases reflect an effective inverse power-law repulsive potential dominating fluctuations, even at zero and slightly negative pressure. In experimental data for supercritical argon, the correlations are found to be approximately 96%. Consequences for viscous liquid dynamics are discussed.......Strong correlations between equilibrium fluctuations of the configurational parts of pressure and energy are found in computer simulations of the Lennard-Jones liquid and other simple liquids, but not for hydrogen-bonding liquids such as methanol and water. The correlations that are present also...

  7. Van der Waals potential and vibrational energy levels of the ground state radon dimer

    Science.gov (United States)

    Sheng, Xiaowei; Qian, Shifeng; Hu, Fengfei

    2017-08-01

    In the present paper, the ground state van der Waals potential of the Radon dimer is described by the Tang-Toennies potential model, which requires five essential parameters. Among them, the two dispersion coefficients C6 and C8 are estimated from the well determined dispersion coefficients C6 and C8 of Xe2. C10 is estimated by using the approximation equation that C6C10/C82 has an average value of 1.221 for all the rare gas dimers. With these estimated dispersion coefficients and the well determined well depth De and Re the Born-Mayer parameters A and b are derived. Then the vibrational energy levels of the ground state radon dimer are calculated. 40 vibrational energy levels are observed in the ground state of Rn2 dimer. The last vibrational energy level is bound by only 0.0012 cm-1.

  8. Salient signature of van der Waals interactions

    Science.gov (United States)

    Via-Nadal, Mireia; Rodríguez-Mayorga, Mauricio; Matito, Eduard

    2017-11-01

    van der Waals interactions govern the physics of a plethora of molecular structures. It is well known that the leading term in the distance-based London expansion of the van der Waals energy for atomic and molecular dimers decays as 1 /R6 , where R is the dimer distance. Using perturbation theory, we find the leading term in the distance-based expansion of the intracule pair density at the interatomic distance. Our results unveil a universal 1 /R3 decay, which is less prone to numerical errors than the 1 /R6 dependency, and it is confirmed numerically in H2 and He2 molecules. This signature of van der Waals interactions can be directly used in the construction of approximate pair density and energy functionals including vdW corrections.

  9. Electron attachment to Van der Waals molecules

    International Nuclear Information System (INIS)

    Hatano, Y.

    1986-01-01

    A survey is given of recent experimental studies of low-energy electron attachment to O 2 , N 2 O and other molecules in dense gases and in sonic nozzle beams with emphasis on the important role of pre-existing van der Waals molecules in the attachment mechanism. The experimental results particularly for O 2 are compared with recent theories. A survey is also given briefly of recent studies on electron solvation and localization in the condensed phase from the viewpoint of the studies on electron interaction with van der Waals molecules. (Auth.)

  10. Electron attachment to Van der Waals clusters

    International Nuclear Information System (INIS)

    Stamatovic, A.

    1988-01-01

    This paper deals with attachment of thermal electrons to Van der Waals clusters at zero energy. The underlying theory is treated briefly. Three different major types of experiments for studying thermal electron attachment to molecules and clusters: swarm experiments, beam experiments and collisions with Rydberg atoms, are described and some results are reviewed. 42 refs.; 5 figs

  11. Effects of Interlayer Distance and van der Waals Energy on Electrochemical Activation of Partially Reduced Graphite Oxide

    International Nuclear Information System (INIS)

    Yoo, Hyun Deog; Jang, Jong Hyun; Cho, Kyeongjae; Zheng, Yongping; Park, Yuwon; Ryu, Ji Heon; Oh, Seung M.

    2015-01-01

    Partially reduced graphite oxide (GOpr) inherits expanded interlayer distance from the parent, graphite oxide (GO), and electronic conductivity from the grandparent, graphite. Indebted to the dual properties, GOpr shows unique behavior so-called electrochemical activation in organic electrolytes; when GOpr is polarized over a certain electrode potential, graphitic layers in GOpr are injected by solvated ions and become ion adsorbing sites permanently. Resultant gravimetric or volumetric capacitance (up to 200 F g −1 or 150 F ml −1 ) exceeds that of commercially available activated carbon electrodes for electric double-layer capacitor (EDLC). Previous literatures have reported that larger interlayer distance (d) lowers the on-set potential of electrochemical activation of graphitic carbons. However, the reason of this phenomenon has not yet been studied. In this paper, we combined experimental and theoretical approaches to reveal the effect of interlayer distance and van der Waals energy (U vdW ) on the electrochemical activation of graphitic carbon. More specifically, we compared the energy for the electrochemical activation (U EA ) and the van der Waals energy with respect to the interlayer distance. For this purpose, we devised an experimental method to measure U EA from cyclic voltammogram, and this method was verified by in-situ electrochemical dilatometry. The theoretical value of U vdW was calculated by semi-empirical density functional theory (DFT) and those experimental and theoretical values were linearly in accordance with each other. This finding signifies that (1) the electrochemical activation of graphitic carbon occurs by overcoming van der Waals energy to expand the interlayer distance, (2) and the on-set potential for electrochemical activation is varied by the interlayer distance because of the different van der Waals energy

  12. Esaki Diodes in van der Waals Heterojunctions with Broken-Gap Energy Band Alignment.

    Science.gov (United States)

    Yan, Rusen; Fathipour, Sara; Han, Yimo; Song, Bo; Xiao, Shudong; Li, Mingda; Ma, Nan; Protasenko, Vladimir; Muller, David A; Jena, Debdeep; Xing, Huili Grace

    2015-09-09

    van der Waals (vdW) heterojunctions composed of two-dimensional (2D) layered materials are emerging as a solid-state materials family that exhibits novel physics phenomena that can power a range of electronic and photonic applications. Here, we present the first demonstration of an important building block in vdW solids: room temperature Esaki tunnel diodes. The Esaki diodes were realized in vdW heterostructures made of black phosphorus (BP) and tin diselenide (SnSe2), two layered semiconductors that possess a broken-gap energy band offset. The presence of a thin insulating barrier between BP and SnSe2 enabled the observation of a prominent negative differential resistance (NDR) region in the forward-bias current-voltage characteristics, with a peak to valley ratio of 1.8 at 300 K and 2.8 at 80 K. A weak temperature dependence of the NDR indicates electron tunneling being the dominant transport mechanism, and a theoretical model shows excellent agreement with the experimental results. Furthermore, the broken-gap band alignment is confirmed by the junction photoresponse, and the phosphorus double planes in a single layer of BP are resolved in transmission electron microscopy (TEM) for the first time. Our results represent a significant advance in the fundamental understanding of vdW heterojunctions and broaden the potential applications of 2D layered materials.

  13. Strain engineering of van der Waals heterostructures

    NARCIS (Netherlands)

    Vermeulen, Paul A.; Mulder, Jefta; Momand, Jamo; Kooi, Bart J.

    2018-01-01

    Modifying the strain state of solids allows control over a plethora of functional properties. The weak interlayer bonding in van der Waals (vdWaals) materials such as graphene, hBN, MoS2, and Bi2Te3 might seem to exclude strain engineering, since strain would immediately relax at the vdWaals

  14. Charge Versus Energy Transfer in Atomically Thin Graphene-Transition Metal Dichalcogenide van der Waals Heterostructures

    Science.gov (United States)

    Froehlicher, Guillaume; Lorchat, Etienne; Berciaud, Stéphane

    2018-01-01

    Made from stacks of two-dimensional materials, van der Waals heterostructures exhibit unique light-matter interactions and are promising for novel optoelectronic devices. The performance of such devices is governed by near-field coupling through, e.g., interlayer charge and/or energy transfer. New concepts and experimental methodologies are needed to properly describe two-dimensional heterointerfaces. Here, we report an original study of interlayer charge and energy transfer in atomically thin metal-semiconductor [i.e., graphene-transition metal dichalcogenide (TMD, here molybdenum diselenide, MoSe2 )] heterostructures using a combination of microphotoluminescence and Raman scattering spectroscopies. The photoluminescence intensity in graphene /MoSe2 is quenched by more than 2 orders of magnitude and rises linearly with the incident photon flux, demonstrating a drastically shortened (about 1 ps) room-temperature MoSe2 exciton lifetime. Key complementary insights are provided from a comprehensive analysis of the graphene and MoSe2 Raman modes, which reveals net photoinduced electron transfer from MoSe2 to graphene and hole accumulation in MoSe2 . Remarkably, the steady-state Fermi energy of graphene saturates at 290 ±15 meV above the Dirac point. This reproducible behavior is observed both in ambient air and in vacuum and is discussed in terms of intrinsic factors (i.e., band offsets) and environmental effects. In this saturation regime, balanced photoinduced flows of electrons and holes may transfer to graphene, a mechanism that effectively leads to energy transfer. Using a broad range of incident photon fluxes and diverse environmental conditions, we find that the presence of net photoinduced charge transfer has no measurable impact on the near-unity photoluminescence quenching efficiency in graphene /MoSe2 . This absence of correlation strongly suggests that energy transfer to graphene (either in the form of electron exchange or dipole-dipole interaction) is the

  15. Charge Versus Energy Transfer in Atomically Thin Graphene-Transition Metal Dichalcogenide van der Waals Heterostructures

    Directory of Open Access Journals (Sweden)

    Guillaume Froehlicher

    2018-01-01

    Full Text Available Made from stacks of two-dimensional materials, van der Waals heterostructures exhibit unique light-matter interactions and are promising for novel optoelectronic devices. The performance of such devices is governed by near-field coupling through, e.g., interlayer charge and/or energy transfer. New concepts and experimental methodologies are needed to properly describe two-dimensional heterointerfaces. Here, we report an original study of interlayer charge and energy transfer in atomically thin metal-semiconductor [i.e., graphene-transition metal dichalcogenide (TMD, here molybdenum diselenide, MoSe_{2}] heterostructures using a combination of microphotoluminescence and Raman scattering spectroscopies. The photoluminescence intensity in graphene/MoSe_{2} is quenched by more than 2 orders of magnitude and rises linearly with the incident photon flux, demonstrating a drastically shortened (about 1 ps room-temperature MoSe_{2} exciton lifetime. Key complementary insights are provided from a comprehensive analysis of the graphene and MoSe_{2} Raman modes, which reveals net photoinduced electron transfer from MoSe_{2} to graphene and hole accumulation in MoSe_{2}. Remarkably, the steady-state Fermi energy of graphene saturates at 290±15  meV above the Dirac point. This reproducible behavior is observed both in ambient air and in vacuum and is discussed in terms of intrinsic factors (i.e., band offsets and environmental effects. In this saturation regime, balanced photoinduced flows of electrons and holes may transfer to graphene, a mechanism that effectively leads to energy transfer. Using a broad range of incident photon fluxes and diverse environmental conditions, we find that the presence of net photoinduced charge transfer has no measurable impact on the near-unity photoluminescence quenching efficiency in graphene/MoSe_{2}. This absence of correlation strongly suggests that energy transfer to graphene (either in the form of electron

  16. Electromagnetic-energy-density distribution around a ground-state hydrogen atom and connection with van der Waals forces

    International Nuclear Information System (INIS)

    Passante, R.; Power, E.A.

    1987-01-01

    A spinless hydrogen atom coupled to the electromagnetic field is considered within the context of nonrelativistic quantum electrodynamics. The atom-field interaction is taken in the minimal-coupling form and the Coulomb gauge is used. When the coupled system is in its ground state the electromagnetic field fluctuates away from the vacuum state and the atom has virtual admixtures from its uncoupled lowest eigenstate. The electric- and magnetic-field-energy densities that arise from the fluctuations are determined as functions of the distance from the atom. The relationship between these field-energy densities and the retarded long-range van der Waals forces is also discussed

  17. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 14; Issue 12. Molecule Matters van der Waals Molecules - Noble Gas Clusters are London Molecules! E Arunan. Feature Article Volume 14 Issue 12 December 2009 pp 1210-1222 ...

  18. van't Hoff-van der Waals osmotic pressure and energy transformers

    Science.gov (United States)

    Zener, Clarence; Levenson, William

    1983-01-01

    We find the van't Hoff relations between osmotic pressure, freezing point depression, and boiling point elevation provide a clue on how, by using salt solutions, one may lower the cost of extracting power from low-grade heat sources. In particular, the ratio of 7 between the heat of evaporation and the heat of freezing of pure water suggests a chemical system that raises 7-fold the temperature difference between heat source and heat sink, while decreasing by the same factor the heat flux. Heat exchangers dominate the cost of heat engines operating upon low-grade heat. Their area for a fixed power output is inversely proportional to the available temperature differential. Herein lies the potential for a great cost reduction. We show that the simple van der Waals concept of a gas of hard elastic spheres suffices to understand the colligative properties of salt solutions, at least up to the concentration of the eutectic composition. This concept enables us to physically interpret the thermodynamic processes during the concentration of salt solutions by evaporation and during the mixing of ice and solid salt hydrates at their eutectic temperature. These are identical to the thermodynamic processes taking place during the isothermal compression and expansion of gases in pumps and in turbines. PMID:16593343

  19. van't Hoff-van der Waals osmotic pressure and energy transformers.

    Science.gov (United States)

    Zener, C; Levenson, W

    1983-07-01

    We find the van't Hoff relations between osmotic pressure, freezing point depression, and boiling point elevation provide a clue on how, by using salt solutions, one may lower the cost of extracting power from low-grade heat sources. In particular, the ratio of 7 between the heat of evaporation and the heat of freezing of pure water suggests a chemical system that raises 7-fold the temperature difference between heat source and heat sink, while decreasing by the same factor the heat flux. Heat exchangers dominate the cost of heat engines operating upon low-grade heat. Their area for a fixed power output is inversely proportional to the available temperature differential. Herein lies the potential for a great cost reduction. We show that the simple van der Waals concept of a gas of hard elastic spheres suffices to understand the colligative properties of salt solutions, at least up to the concentration of the eutectic composition. This concept enables us to physically interpret the thermodynamic processes during the concentration of salt solutions by evaporation and during the mixing of ice and solid salt hydrates at their eutectic temperature. These are identical to the thermodynamic processes taking place during the isothermal compression and expansion of gases in pumps and in turbines.

  20. Potential energy surface and rovibrational energy levels of the H2-CS van der Waals complex.

    Science.gov (United States)

    Denis-Alpizar, Otoniel; Stoecklin, Thierry; Halvick, Philippe; Dubernet, Marie-Lise; Marinakis, Sarantos

    2012-12-21

    Owing to its large dipole, astrophysicists use carbon monosulfide (CS) as a tracer of molecular gas in the interstellar medium, often in regions where H(2) is the most abundant collider. Predictions of the rovibrational energy levels of the weakly bound complex CS-H(2) (not yet observed) and also of rate coefficients for rotational transitions of CS in collision with H(2) should help to interpret the observed spectra. This paper deals with the first goal, i.e., the calculation of the rovibrational energy levels. A new four-dimensional intermolecular potential energy surface for the H(2)-CS complex is presented. Ab initio potential energy calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and midbond functions. The potential energy surface was obtained by an analytic fit of the ab initio data. The equilibrium structure of the H(2)-CS complex is found to be linear with the carbon pointing toward H(2) at the intermolecular separation of 8.6 a(o). The corresponding well depth is -173 cm(-1). The potential was used to calculate the rovibrational energy levels of the para-H(2)-CS and ortho-H(2)-CS complexes. The present work provides the first theoretical predictions of these levels. The calculated dissociation energies are found to be 35.9 cm(-1) and 49.9 cm(-1), respectively, for the para and ortho complexes. The second virial coefficient for the H(2)-CS pair has also been calculated for a large range of temperature. These results could be used to assign future experimental spectra and to check the accuracy of the potential energy surface.

  1. Oscillator representation and generalized van der Waals Hamiltonians

    International Nuclear Information System (INIS)

    Dinejkhan, M.

    1996-01-01

    The method called the oscillator representation is extended to calculate the energy spectrum of bound state described by axially symmetrical potentials in the parabolic system coordinates. In particular, the method is applied to calculate the energy of the ground and excited states of the hydrogen atom in the uniform electric field and van der Waals field. The method gives the perturbation formulas for the analytic spectrum of the hydrogen atom in the generalized van der Waals field and defined oscillator strengths for transitions from the ground state to the perturbed manifold n=10, m=0. 14 refs., 1 fig

  2. Using the minimum principle for the Helmholtz free energy in the analysis of the equilibria of a van der Waals fluid

    International Nuclear Information System (INIS)

    Ascoli, Sergio; Malvestuto, Vincenzo

    2004-01-01

    For a fluid system, obeying a state equation of the van der Waals type, the gas and the liquid phases can coexist in equilibrium, at a given temperature, only if the volume of the system is kept fixed. Thus, in order to study the two-phase equilibria of a fluid system, it seemed quite natural to choose the molar volume as the independent variable, and, consequently, the Helmholtz free energy as the proper thermodynamic potential for the application of the minimum principle. Specific computations are here carried out for a single van der Waals fluid, namely, pure water at 300 0 C. As a result, the present treatment indicates a simple and effective way to identify the whole range of molar volumes where the equilibrium preferred by the system is a two-phase equilibrium. This range results to be wider than the interval of strict instability of the van der Waals isotherm. Finally, it is pointed out that all the results, obtained here for the van der Waals state equation, can be extended to all the state equations of the same type

  3. Effect of the van der Waals interaction on the electron energy-loss near edge structure theoretical calculation.

    Science.gov (United States)

    Katsukura, Hirotaka; Miyata, Tomohiro; Tomita, Kota; Mizoguchi, Teruyasu

    2017-07-01

    The effect of the van der Waals (vdW) interaction on the simulation of the electron energy-loss near edge structure (ELNES) by a first-principles band-structure calculation is reported. The effect of the vdW interaction is considered by the Tkatchenko-Scheffler scheme, and the change of the spectrum profile and the energy shift are discussed. We perform calculations on systems in the solid, liquid and gaseous states. The transition energy shifts to lower energy by approximately 0.1eV in the condensed (solid and liquid) systems by introducing the vdW effect into the calculation, whereas the energy shift in the gaseous models is negligible owing to the long intermolecular distance. We reveal that the vdW interaction exhibits a larger effect on the excited state than the ground state owing to the presence of an excited electron in the unoccupied band. Moreover, the vdW effect is found to depend on the local electron density and the molecular coordination. In addition, this study suggests that the detection of the vdW interactions exhibited within materials is possible by a very stable and high resolution observation. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 7. Molecule Matters van der Waals Molecules - Rg•••HF Complexes are Debye Molecules! E Arunan. Feature Article Volume 15 Issue 7 July 2010 pp 667-674. Fulltext. Click here to view fulltext PDF. Permanent link:

  5. Cluster ions and van der Waals molecules

    CERN Document Server

    Smirnov, Boris M

    1992-01-01

    This review discusses current ideas in the physics and chemistry of cluster ions and Van der Waals molecules as well as presenting numerical data on their parameters and the processes involving them. It is also a detailed reference on basic data relating to many species.

  6. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    1884-03-24

    Petrus Josephus Wilhelmus Debije (Peter Joseph Williams Debye) was born on March 24, 1884 in Maastricht, Netherlands, which is. 167.5 km from Leiden, where van der Waals was born 37 years earlier [1,2]. Debye had his early education in maths and physics and got a degree in electrical engineering in 1905. Debye ...

  7. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 14; Issue 12. Molecule Matters van der Waals Molecules - Noble Gas Clusters are London Molecules! E Arunan ... Author Affiliations. E Arunan1. Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India.

  8. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 7. Molecule Matters van der Waals Molecules - Rg•••HF Complexes are Debye Molecules! E Arunan ... Author Affiliations. E Arunan1. Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India.

  9. Van der Waals and Molecular Science

    International Nuclear Information System (INIS)

    Kox, A J

    1997-01-01

    For many years it has been a source of amazement to scientists and historians of science that no serious scientific biography of J D van der Waals existed. When, more than ten years ago, I became engaged in a correspondence with the Russian historian of science B E Yavelow on the topic of van der Waals, whose biography he was writing, I was both pleased and a bit puzzled. It was clear that Yavelow had not done any archival research in the Netherlands himself, yet he was intimately familiar with many obscure facts from the life of van der Waals. Naturally, I was very curious to see the end result, which appeared in 1985, but although the Amsterdam University Library obtained a copy, my limited knowledge of Russian kept me from forming a judgement on the book. Finally, after more than ten years, an English edition has appeared. The two original Russian authors have joined forces with the well known scientist J S Rowlinson (who earlier edited an English translation of van der Waals's dissertation) to produce a revised and enlarged English version of the Russian original. Now that I have finally been able to study this work, I must admit to being much impressed. Both the life and the work of van der Waals are dealt with in an exemplary way: the authors' command of primary and secondary sources is impressive, as is their understanding of the Dutch social and educational circumstances in the last century. Teaching and research at the newly-founded University of Amsterdam, as well as activities in the Academy of Sciences, are discussed in great and interesting detail. Van der Waals's education and rise from a simple teacher to one of the foremost theoretical physicists in Europe teaches us much about his personality as well as about the opportunities offered by the Dutch educational system. In their discussion of the development of van der Waals's ideas and their impact (including an interesting chapter on the reception in Russia) the authors are not afraid to go into

  10. A notable difference between ideal gas and infinite molar volume limit of van der Waals gas

    Science.gov (United States)

    Liu, Q. H.; Shen, Y.; Bai, R. L.; Wang, X.

    2010-05-01

    The van der Waals equation of state does not sufficiently represent a gas unless a thermodynamic potential with two proper and independent variables is simultaneously determined. The limiting procedures under which the behaviour of the van der Waals gas approaches that of an ideal gas are letting two van der Waals coefficients be zero rather than letting the molar volume become infinitely large; otherwise, the partial derivative of internal energy with respect to pressure at a fixed temperature does not vanish.

  11. Effective field theories for van der Waals interactions

    Science.gov (United States)

    Brambilla, Nora; Shtabovenko, Vladyslav; Tarrús Castellà, Jaume; Vairo, Antonio

    2017-06-01

    Van der Waals interactions between two neutral but polarizable systems at a separation R much larger than the typical size of the systems are at the core of a broad sweep of contemporary problems in settings ranging from atomic, molecular and condensed matter physics to strong interactions and gravity. In this paper, we reexamine the dispersive van der Waals interactions between two hydrogen atoms. The novelty of the analysis resides in the usage of nonrelativistic effective field theories of quantum electrodynamics. In this framework, the van der Waals potential acquires the meaning of a matching coefficient in an effective field theory, dubbed van der Waals effective field theory, suited to describe the low-energy dynamics of an atom pair. It may be computed systematically as a series in R times some typical atomic scale and in the fine-structure constant α . The van der Waals potential gets short-range contributions and radiative corrections, which we compute in dimensional regularization and renormalize here for the first time. Results are given in d space-time dimensions. One can distinguish among different regimes depending on the relative size between 1 /R and the typical atomic bound-state energy, which is of order m α2. Each regime is characterized by a specific hierarchy of scales and a corresponding tower of effective field theories. The short-distance regime is characterized by 1 /R ≫m α2 and the leading-order van der Waals potential is the London potential. We also compute next-to-next-to-next-to-leading-order corrections. In the long-distance regime we have 1 /R ≪m α2. In this regime, the van der Waals potential contains contact terms, which are parametrically larger than the Casimir-Polder potential that describes the potential at large distances. In the effective field theory, the Casimir-Polder potential counts as a next-to-next-to-next-to-leading-order effect. In the intermediate-distance regime, 1 /R ˜m α2, a significantly more complex

  12. Potential energy surface of the CO{sub 2}–N{sub 2} van der Waals complex

    Energy Technology Data Exchange (ETDEWEB)

    Nasri, Sameh; Ajili, Yosra [Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA, Université de Tunis El Manar, Tunis (Tunisia); Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France); Jaidane, Nejm-Eddine [Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA, Université de Tunis El Manar, Tunis (Tunisia); Kalugina, Yulia N. [Department of Optics and Spectroscopy, Tomsk State University, 36 Lenin Ave., Tomsk 634050 (Russian Federation); Halvick, Philippe; Stoecklin, Thierry [Institut des Sciences Moléculaires, Université de Bordeaux, CNRS UMR 5255, 33405 Talence Cedex (France); Hochlaf, Majdi, E-mail: hochlaf@univ-mlv.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France)

    2015-05-07

    Four-dimensional potential energy surface (4D-PES) of the atmospherically relevant CO{sub 2}–N{sub 2} van der Waals complex is generated using the explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in conjunction with the augmented correlation consistent triple zeta (aug-cc-pVTZ) basis set. This 4D-PES is mapped along the intermonomer coordinates. An analytic fit of this 4D-PES is performed. Our extensive computations confirm that the most stable form corresponds to a T-shape structure where the nitrogen molecule points towards the carbon atom of CO{sub 2}. In addition, we located a second isomer and two transition states in the ground state PES of CO{sub 2}–N{sub 2}. All of them lay below the CO{sub 2} + N{sub 2} dissociation limit. This 4D-PES is flat and strongly anisotropic along the intermonomer coordinates. This results in the possibility of the occurrence of large amplitude motions within the complex, such as the inversion of N{sub 2}, as suggested in the recent spectroscopic experiments. Finally, we show that the experimentally established deviations from the C{sub 2v} structure at equilibrium for the most stable isomer are due to the zero-point out-of-plane vibration correction.

  13. Van der Waals Interactions in Aspirin

    Science.gov (United States)

    Reilly, Anthony; Tkatchenko, Alexandre

    2015-03-01

    The ability of molecules to yield multiple solid forms, or polymorphs, has significance for diverse applications ranging from drug design and food chemistry to nonlinear optics and hydrogen storage. In particular, aspirin has been used and studied for over a century, but has only recently been shown to have an additional polymorphic form, known as form II. Since the two observed solid forms of aspirin are degenerate in terms of lattice energy, kinetic effects have been suggested to determine the metastability of the less abundant form II. Here, first-principles calculations provide an alternative explanation based on free-energy differences at room temperature. The explicit consideration of many-body van der Waals interactions in the free energy demonstrates that the stability of the most abundant form of aspirin is due to a subtle coupling between collective electronic fluctuations and quantized lattice vibrations. In addition, a systematic analysis of the elastic properties of the two forms of aspirin rules out mechanical instability of form II as making it metastable.

  14. Thermal response in van der Waals heterostructures

    KAUST Repository

    Gandi, Appala

    2016-11-21

    We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation. © 2016 IOP Publishing Ltd.

  15. Refined ab initio intermolecular ground-state potential energy surface for the He-C2H2 van der Waals complex

    DEFF Research Database (Denmark)

    Fernández, Berta; Henriksen, Christian; Farrelly, David

    2013-01-01

    A refined CCSD(T) intermolecular potential energy surface is developed for the He-C2H2 van der Waals complex. For this, 206 points on the intermolecular potential energy surface, evaluated using the CCSD(T) method and the aug-cc-pVQZ basis set extended with a set of 3s3p2d1f1g midbond functions...... previously by Munteanu and Fernández (J. Chem. Phys., 123, 014309, 2005) but differs notably at short range. The improved potential energy surface should, therefore, be particularly useful for computations of collision line broadening. Dynamical calculations of a number of rovibrational bound state energies...

  16. Low-energy scattering parameters for van der Waals perturbation theory

    Energy Technology Data Exchange (ETDEWEB)

    Benofy, L.P.; Buendia, E.; Guardiola, R.; de Llano, M.

    1986-06-01

    The low-energy two-body scattering S- and P-wave parameters, together with a shape-dependent S-wave quantity, which appear in the well-known low-density expansions for the ground-state energy of many-boson and many-fermion systems, are accurately calculated for several central pair potentials for spin-polarized atoms, helium atoms, and nucleons. An integral-equation method allowing accurate determination of the coefficients of the above-mentioned parameters expanded in powers of the attraction strength of the pair potential is presented and applied. The results are needed for perturbation studies of ground-state energies of various quantum many-body systems.

  17. Quantum Analysis of Dispersion and Induction Energies in Organic van der Waals Nanoclusters

    Science.gov (United States)

    Popova, Anna M.; Komarov, Viacheslav V.; Schmidt, Lothar; Jungclas, Hartmut

    2017-11-01

    A new analytical method is presented, which describes the interactions of three neutral organic molecules forming an isolated nanocluster. We assume that one of the three molecules has a permanent dipole moment. The induction processes and Coulomb interactions inside the nanocluster are considered taking into account molecular charges and structure properties. The functions of the dispersion and induction energies are obtained in analytical form without any phenomenological representations. The method was applied to a specific cluster consisting of two pyrene molecules and one pentene molecule with a dipole moment equal to 0.6 D. The values of the intermolecular interaction energies for these molecules are calculated and presented versus intermolecular distances.

  18. The dependence of scattering length on van der Waals interaction ...

    Indian Academy of Sciences (India)

    2016-06-16

    Jun 16, 2016 ... DOI 10.1007/s12043-016-1221-y. The dependence of scattering length on van der Waals interaction and reduced mass of the system in two-atomic collision at cold energies. HASI RAY1,2,3,4. 1Study Centre, S-1/407/6, B.P. Township, Kolkata 700 094, India. 2Department of Physics, New Alipore College, ...

  19. Strong van der Waals attractive forces in nanotechnology

    Science.gov (United States)

    Reimers, Jeffrey

    The Dobson classification scheme for failure of London-like expressions for describing dispersion is reviewed. New ways to measure using STM data and calculate by first principles free energies of organic self-assembly processes from solution will be discussed, considering tetraalkylporphyrins on graphite. How strong van der Waals forces can compete against covalent bonding to produce new molecular isomers and reaction pathways will also be demonstrated, focusing on golds-sulfur bonds for sensors and stabilizing nanoparticles.

  20. Photoresponse of Natural van der Waals Heterostructures.

    Science.gov (United States)

    Ray, Kyle; Yore, Alexander E; Mou, Tong; Jha, Sauraj; Smithe, Kirby K H; Wang, Bin; Pop, Eric; Newaz, A K M

    2017-06-27

    Van der Waals heterostructures consisting of two-dimensional materials offer a platform to obtain materials by design and are very attractive owing to unique electronic states. Research on 2D van der Waals heterostructures (vdWH) has so far been focused on fabricating individually stacked atomically thin unary or binary crystals. Such systems include graphene, hexagonal boron nitride, and members of the transition metal dichalcogenide family. Here we present our experimental study of the optoelectronic properties of a naturally occurring vdWH, known as franckeite, which is a complex layered crystal composed of lead, tin, antimony, iron, and sulfur. We present here that thin film franckeite (60 nm power-resolved and temperature-resolved photocurrent measurements reveal that the photocarrier generation and recombination are dominated by continuously distributed trap states within the band gap. To understand wavelength-resolved photocurrent, we also calculated the optical absorption properties via density functional theory. Finally, we have shown that the device has a fast photoresponse with a rise time as fast as ∼1 ms. Our study provides a fundamental understanding of the optoelectronic behavior in a complex naturally occurring vdWH, and may pave an avenue toward developing nanoscale optoelectronic devices with tailored properties.

  1. Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures

    Science.gov (United States)

    2018-02-19

    AFRL-AFOSR-JP-TR-2018-0012 Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures PHILIP Kim HARVARD COLLEGE PRESIDENT... Atomically Controlled van der Waals Quantum Heterostructures 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-15-1-4003 5c.  PROGRAM ELEMENT NUMBER 61102F...Final Report for AOARD Grant FA2386-15-1-4003 “Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures” 2/18/2018 Name of

  2. Average and extreme multi-atom Van der Waals interactions: Strong coupling of multi-atom Van der Waals interactions with covalent bonding

    Directory of Open Access Journals (Sweden)

    Finkelstein Alexei V

    2007-07-01

    Full Text Available Abstract Background The prediction of ligand binding or protein structure requires very accurate force field potentials – even small errors in force field potentials can make a 'wrong' structure (from the billions possible more stable than the single, 'correct' one. However, despite huge efforts to optimize them, currently-used all-atom force fields are still not able, in a vast majority of cases, even to keep a protein molecule in its native conformation in the course of molecular dynamics simulations or to bring an approximate, homology-based model of protein structure closer to its native conformation. Results A strict analysis shows that a specific coupling of multi-atom Van der Waals interactions with covalent bonding can, in extreme cases, increase (or decrease the interaction energy by about 20–40% at certain angles between the direction of interaction and the covalent bond. It is also shown that on average multi-body effects decrease the total Van der Waals energy in proportion to the square root of the electronic component of dielectric permittivity corresponding to dipole-dipole interactions at small distances, where Van der Waals interactions take place. Conclusion The study shows that currently-ignored multi-atom Van der Waals interactions can, in certain instances, lead to significant energy effects, comparable to those caused by the replacement of atoms (for instance, C by N in conventional pairwise Van der Waals interactions.

  3. NATO Advanced Research Workshop on Dynamics of Polyatomic Van der Waals Complexes

    CERN Document Server

    Janda, Kenneth

    1991-01-01

    This publication is the Proceedings of the NATO Advanced Research Workshop (ARW) on the Dynamics of Polyatomic Van der Waals Molecules held at the Chateau de Bonas, Castera-Verduzan, France, from August 21 through August 26, 1989. Van der Waals complexes provide important model problems for understanding energy transfer and dissipation. These processes can be described in great detail for Van der Waals complexes, and the insight gained from such studies can be applied to more complicated chemical problems that are not amenable to detailed study. The workshop concentrated on the current questions and future prospects for extend­ ing our highly detailed knowledge of triatomic Van der Waals molecule dynamics to polyatomic molecules and clusters (one molecule surrounded by several, or up to sev­ eral tens of, atoms). Both experimental and theoretical studies were discussed, with particular emphasis on the dynamical behavior of dissociation as observed in the dis­ tributions of quantum states of the dissociatio...

  4. Van der Waals interactions: Corrections from radiation in fluids

    Directory of Open Access Journals (Sweden)

    Magnus H. Waage

    2013-02-01

    Full Text Available We consider induced van der Waals interactions with corrections due to radiation in fluids consisting of polarizable hard spheres. The fluctuating polarizations are quantized while the positions of particles are treated classically. First the well known result for the induced Casimir free energy for a pair of particles is used to establish the resulting free energy at low density. The Casimir interaction includes the full effect of the quantized radiating electromagnetic field. Then the situation with electrostatic dipole-dipole interactions is considered for general density. For this situation the induced interactions are the van der Waals interactions, and we evaluate numerically the free energy based upon analytic results obtained earlier. These analytic results were obtained by extending methods of classical statistical mechanics to the path integral of quantum mechanics. We have realized that these methods can be extended to time-dependent interactions too. Thus we here also make the extension to the radiating dipole-dipole interaction between pairs of particles to obtain explicit results for more arbitrary fluid densities, and radiation corrections to the induced free energy are found both analytically and numerically.

  5. Modified Van der Waals equation and law of corresponding states

    Science.gov (United States)

    Zhong, Wei; Xiao, Changming; Zhu, Yongkai

    2017-04-01

    It is well known that the Van der Waals equation is a modification of the ideal gas law, yet it can be used to describe both gas and liquid, and some important messages can be obtained from this state equation. However, the Van der Waals equation is not a precise state equation, and it does not give a good description of the law of corresponding states. In this paper, we expand the Van der Waals equation into its Taylor's series form, and then modify the fourth order expansion by changing the constant Virial coefficients into their analogous ones. Via this way, a more precise result about the law of corresponding states has been obtained, and the law of corresponding states can then be expressed as: in terms of the reduced variables, all fluids should obey the same equation with the analogous Virial coefficients. In addition, the system of 3 He with quantum effects has also been taken into consideration with our modified Van der Waals equation, and it is found that, for a normal system without quantum effect, the modification on ideal gas law from the Van der Waals equation is more significant than the real case, however, for a system with quantum effect, this modification is less significant than the real case, thus a factor is introduced in this paper to weaken or strengthen the modification of the Van der Waals equation, respectively.

  6. Theory of electron attachment to van der Waals clusters

    International Nuclear Information System (INIS)

    Fabrikant, Ilya I

    2005-01-01

    A theory of electron collisions with van der Waals clusters is developed which is capable of describing the vibrational Feshbach resonances (VFRs) recently observed in electron attachment to CO 2 clusters. VFRs appear below vibrational excitation thresholds of one molecular unit and their energy decreases with the increase of the cluster size. The selectivity observed in vibrational excitation of individual components of a Fermi dyad is substantially reduced in the attachment spectra. We also calculate elastic electron scattering and vibrational excitation (VE) of one molecular unit in a cluster environment and demonstrate a strong influence of the VFRs on the VE cross sections. Theoretically predicted VFRs are much narrower than observed. We explain the VFR broadening by contribution of several neutral precursors, contribution of different cluster conformations and the dependence of the resonance energy on the position of the molecular unit in the cluster. A model is developed to describe the latter effect quantitatively

  7. A cartography of the van der Waals territories.

    Science.gov (United States)

    Alvarez, Santiago

    2013-06-28

    The distribution of distances from atoms of a particular element E to a probe atom X (oxygen in most cases), both bonded and intermolecular non-bonded contacts, has been analyzed. In general, the distribution is characterized by a maximum at short E···X distances corresponding to chemical bonds, followed by a range of unpopulated distances--the van der Waals gap--and a second maximum at longer distances--the van der Waals peak--superimposed on a random distribution function that roughly follows a d(3) dependence. The analysis of more than five million interatomic "non-bonded" distances has led to the proposal of a consistent set of van der Waals radii for most naturally occurring elements, and its applicability to other element pairs has been tested for a set of more than three million data, all of them compared to over one million bond distances.

  8. van der Waals interactions in a magnetodielectric medium

    International Nuclear Information System (INIS)

    Spagnolo, S.; Dalvit, D. A. R.; Milonni, P. W.

    2007-01-01

    The van der Waals interaction between two ground-state atoms is calculated for two electrically or magnetically polarizable particles embedded in a dispersive magnetodielectric medium. Unlike previous calculations which infer the atom-atom interaction from the dilute-medium limit of the macroscopic, many-body van der Waals interaction, the interaction is calculated directly for the system of two atoms in a magnetodielectric medium. Two approaches are presented, the first based on the quantized electromagnetic field in a dispersive medium without absorption and the second on Green functions that allow for absorption. We show that the correct van der Waals interactions are obtained regardless of whether absorption in the host medium is explicitly taken into account

  9. Entanglement growth during Van der Waals like phase transition

    Directory of Open Access Journals (Sweden)

    Hao Xu

    2017-09-01

    Full Text Available We address the problem of describing the coexistence state of two different black holes and Van der Waals like phase transition in Reissner–Nordström–AdS space–time. We start by a small charged black hole, then introduce a collapsing neutral thin-shell described by Vaidya metric to form a large one. The formation of the large black hole does not change the temperature and free energy of the initial state. We discuss the entanglement growing during the phase transition. The transition is always continuous and the saturation time is determined by the final state. It opens a possibility for studying the holography from excited states to excited states.

  10. Equations of State: From the Ideas of van der Waals to Association Theories

    DEFF Research Database (Denmark)

    Kontogeorgis, Georgios; Economou, Ioannis G.

    2010-01-01

    The ideas of van der Waals have resulted to cubic equations of state like Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) which are widely used in the petroleum and chemical industries. It is often thought that the range of applicability of van der Waals-type models is limited to mixtures...... of compounds relatively similar in size. We employ in this work an approach for investigating the various terms of cubic equations of state by looking at the excess Gibbs energy and activity coefficient expressions which are derived from these equations of state. We illustrate that the results of cubic...... equations of state are sensitive to the mixing and combining rules used. Moreover, it is shown that previously reported deficiencies for size-asymmetric systems are more related to the van der Waals one fluid mixing rules used rather than the functionality of the cubic equation of state itself. Improved...

  11. Graphene on metals: A van der Waals density functional study

    DEFF Research Database (Denmark)

    Vanin, Marco; Mortensen, Jens Jørgen; Kelkkanen, Kari André

    2010-01-01

    We use density functional theory (DFT) with a recently developed van der Waals density functional (vdW-DF) to study the adsorption of graphene on Co, Ni, Pd, Ag, Au, Cu, Pt, and Al(111) surfaces. In contrast to the local-density approximation (LDA) which predicts relatively strong binding for Ni...

  12. (AJST) ANALYSIS OF VAN DER WAAL EQUATION NEAR THE ...

    African Journals Online (AJOL)

    ABSTRACT:- The van der Waal equation of state is redefined in a functional manner that reveals some additional critical ... The law of corresponding states is also shown to apply to the lower limits of reduced temperatures. .... This is a cubic function Vmc(b) in and would in general have three solutions. Graphically, the ...

  13. Franckeite as a naturally occurring van der Waals heterostructure

    NARCIS (Netherlands)

    Molina-Mendoza, Aday J.; Giovanelli, Emerson; Paz, Wendel S.; Ninõ, Miguel Angel; Island, J.O.; Evangeli, Charalambos; Aballe, Luciá; Foerster, Michael; Van Der Zant, Herre S.J.; Rubio-Bollinger, Gabino; Agraït, Nicolás; Palacios, JJ; Pérez, Emilio M.; Castellanos-Gomez, Andres

    2017-01-01

    The fabrication of van der Waals heterostructures, artificial materials assembled by individual stacking of 2D layers, is among the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods, which are

  14. Augmented van der Waals Equations of State: SAFT-VR versus Yukawa Based van der Waals Equation

    Czech Academy of Sciences Publication Activity Database

    Nezbeda, Ivo; Melnyk, R.; Trokhymchuk, A.

    2011-01-01

    Roč. 309, č. 2 (2011), s. 174-178 ISSN 0378-3812 R&D Projects: GA AV ČR IAA400720710 Institutional research plan: CEZ:AV0Z40720504 Keywords : perturbation theory * SAFT-VR * augmented van der Waals Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.139, year: 2011

  15. Density functional study of the adsorption and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2

    DEFF Research Database (Denmark)

    Moses, Poul Georg; Mortensen, Jens Jørgen; Lundqvist, Bengt

    2009-01-01

    der Waals interactions are essential for binding energies on MoS2 surfaces and that DFT with a recently developed exchange-correlation functional (vdW-DF) accurately calculates the van der Waals energy. Values are calculated for the adsorption energies of butadiene, thiophene, benzothiophene, pyridine...

  16. Effect of van der Waals interactions on the structural and binding properties of GaSe

    Energy Technology Data Exchange (ETDEWEB)

    Sarkisov, Sergey Y., E-mail: sarkisov@mail.tsu.ru [Tomsk State University, Lenin Avenue 36, 634050 Tomsk (Russian Federation); Kosobutsky, Alexey V., E-mail: kosobutsky@kemsu.ru [Tomsk State University, Lenin Avenue 36, 634050 Tomsk (Russian Federation); Kemerovo State University, Krasnaya 6, 650043 Kemerovo (Russian Federation); Shandakov, Sergey D. [Kemerovo State University, Krasnaya 6, 650043 Kemerovo (Russian Federation)

    2015-12-15

    The influence of van der Waals interactions on the lattice parameters, band structure, elastic moduli and binding energy of layered GaSe compound has been studied using projector-augmented wave method within density functional theory. We employed the conventional local/semilocal exchange-correlation functionals and recently developed van der Waals functionals which are able to describe dispersion forces. It is found that application of van der Waals density functionals allows to substantially increase the accuracy of calculations of the lattice constants a and c and interlayer distance in GaSe at ambient conditions and under hydrostatic pressure. The pressure dependences of the a-parameter, Ga–Ga, Ga–Se bond lengths and Ga–Ga–Se bond angle are characterized by a relatively low curvature, while c(p) has a distinct downward bowing due to nonlinear shrinking of the interlayer spacing. From the calculated binding energy curves we deduce the interlayer binding energy of GaSe, which is found to be in the range 0.172–0.197 eV/layer (14.2–16.2 meV/Å{sup 2}). - Highlights: • Effects of van der Waals interactions are analyzed using advanced density functionals. • Calculations with vdW-corrected functionals closely agree with experiment. • Interlayer binding energy of GaSe is estimated to be 14.2–16.2 meV/Å{sup 2}.

  17. Dynamical screening of the van der Waals interaction between graphene layers.

    Science.gov (United States)

    Dappe, Y J; Bolcatto, P G; Ortega, J; Flores, F

    2012-10-24

    The interaction between graphene layers is analyzed combining local orbital DFT and second order perturbation theory. For this purpose we use the linear combination of atomic orbitals-orbital occupancy (LCAO-OO) formalism, that allows us to separate the interaction energy as the sum of a weak chemical interaction between graphene layers plus the van der Waals interaction (Dappe et al 2006 Phys. Rev. B 74 205434). In this work, the weak chemical interaction is calculated by means of corrected-LDA calculations using an atomic-like sp(3)d(5) basis set. The van der Waals interaction is calculated by means of second order perturbation theory using an atom-atom interaction approximation and the atomic-like-orbital occupancies. We also analyze the effect of dynamical screening in the van der Waals interaction using a simple model. We find that this dynamical screening reduces by 40% the van der Waals interaction. Taking this effect into account, we obtain a graphene-graphene interaction energy of 70 ± 5 meV/atom in reasonable agreement with the experimental evidence.

  18. Accurate van der Waals coefficients from density functional theory

    Science.gov (United States)

    Tao, Jianmin; Perdew, John P.; Ruzsinszky, Adrienn

    2012-01-01

    The van der Waals interaction is a weak, long-range correlation, arising from quantum electronic charge fluctuations. This interaction affects many properties of materials. A simple and yet accurate estimate of this effect will facilitate computer simulation of complex molecular materials and drug design. Here we develop a fast approach for accurate evaluation of dynamic multipole polarizabilities and van der Waals (vdW) coefficients of all orders from the electron density and static multipole polarizabilities of each atom or other spherical object, without empirical fitting. Our dynamic polarizabilities (dipole, quadrupole, octupole, etc.) are exact in the zero- and high-frequency limits, and exact at all frequencies for a metallic sphere of uniform density. Our theory predicts dynamic multipole polarizabilities in excellent agreement with more expensive many-body methods, and yields therefrom vdW coefficients C6, C8, C10 for atom pairs with a mean absolute relative error of only 3%. PMID:22205765

  19. Quark confinement potential and color Van der Waals force

    International Nuclear Information System (INIS)

    Zheng Yuming; Hua Daping; Liu Zuhua

    1985-01-01

    The color-analog Van der Waals force between two hadrons is studied by use of the coupling channel resonating group method in the framework of the Gaussian-type quark confinement potential. The problem of the boundary values for the two channel coupling differential equations is changed to the problem of the initial values. The equations are solved numerically by use of the Gear mehtod. The calculated results show that there is no color Van der Waals force between hadrons in the confinement potential model. This indicates that the confinement potential model not only can describe the internal structure of hadrons but also can be used to calculate the hadron-hadron interactions if the quark confinement potential is chosen properly

  20. Evidence for van der Waals adhesion in gecko setae

    OpenAIRE

    Autumn, Kellar; Sitti, Metin; Liang, Yiching A.; Peattie, Anne M.; Hansen, Wendy R.; Sponberg, Simon; Kenny, Thomas W.; Fearing, Ronald; Israelachvili, Jacob N.; Full, Robert J.

    2002-01-01

    Geckos have evolved one of the most versatile and effective adhesives known. The mechanism of dry adhesion in the millions of setae on the toes of geckos has been the focus of scientific study for over a century. We provide the first direct experimental evidence for dry adhesion of gecko setae by van der Waals forces, and reject the use of mechanisms relying on high surface polarity, including capillary adhesion. The toes of live Tokay geckos were highly hydrophobic, and adhered equally well ...

  1. Grippers Based on Opposing Van Der Waals Adhesive Pads

    Science.gov (United States)

    Parness, Aaron (Inventor); Kennedy, Brett A. (Inventor); Heverly, Matthew C (Inventor); Cutkosky, Mark R. (Inventor); Hawkes, Elliot Wright (Inventor)

    2016-01-01

    Novel gripping structures based on van der Waals adhesive forces are disclosed. Pads covered with fibers can be activated in pairs by opposite forces, thereby enabling control of the adhesive force in an ON or OFF state. Pads can be used in groups, each comprising a group of opposite pads. The adhesive structures enable anchoring forces that can resist adverse forces from different directions. The adhesive structures can be used to enable the operation of robots on surfaces of space vehicles.

  2. Calculations of the thermal expansion, cohesive energy and thermodynamic stability of a Van der Waals crystal - fullerene C60

    International Nuclear Information System (INIS)

    Zubov, V.I.; Tretiakov, N.P.; Teixeira Rabelo, J.N.; Sanchez Ortiz, J.F.

    1994-01-01

    The temperature dependence of the intermolecular distance and the cohesive energy in the high-temperature modification of C 60 solid fullerene was studied on basis of the correlative method of unsymmetrized self-consistent field. The central intermolecular potential of Girifalco and its approximation by Yakub were used. We conclude about the decisive role of anharmonic effects at high temperatures. The discrepancy between the calculated and experimental values of intermolecular distance does not exceed 0.8% on the whole temperature interval. The temperature of loss of thermodynamic stability was obtained (∼1915 K) and a possible melting temperature was estimated (∼1400 K). ((orig.))

  3. Resonance oscillations of nonreciprocal long-range van der Waals forces between atoms in electromagnetic fields

    Science.gov (United States)

    Sherkunov, Yury

    2018-03-01

    We study theoretically the van der Waals interaction between two atoms out of equilibrium with an isotropic electromagnetic field. We demonstrate that at large interatomic separations, the van der Waals forces are resonant, spatially oscillating, and nonreciprocal due to resonance absorption and emission of virtual photons. We suggest that the van der Waals forces can be controlled and manipulated by tuning the spectrum of artificially created random light.

  4. Coincident-site lattice matching during van der Waals epitaxy

    OpenAIRE

    Boschker, Jos E.; Galves, Lauren A.; Flissikowski, Timur; Lopes, Joao Marcelo J.; Riechert, Henning; Calarco, Raffaella

    2015-01-01

    Van der Waals (vdW) epitaxy is an attractive method for the fabrication of vdW heterostructures. Here Sb2Te3 films grown on three different kind of graphene substrates (monolayer epitaxial graphene, quasi freestanding bilayer graphene and the SiC (6?3???6?3)R30? buffer layer) are used to study the vdW epitaxy between two 2-dimensionally (2D) bonded materials. It is shown that the Sb2Te3 /graphene interface is stable and that coincidence lattices are formed between the epilayers and substrate ...

  5. Layered van der Waals crystals with hyperbolic light dispersion

    DEFF Research Database (Denmark)

    Gjerding, Morten Niklas; Petersen, R.; Pedersen, T.G.

    2017-01-01

    -infrared to the ultraviolet. Combined with the emerging field of van der Waals heterostructuring, we demonstrate how the hyperbolic properties can be further controlled by stacking different two-dimensional crystals opening new perspectives for atomic-scale design of photonic metamaterials. As an application, we identify...... candidates for Purcell factor control of emission from diamond nitrogen-vacancy centers.Natural hyperbolic materials retain the peculiar optical properties of traditional metamaterials whilst not requiring artificial structuring. Here, the authors perform a theoretical screening of a large class of natural...

  6. Capillary pressure of van der Waals liquid nanodrops

    Science.gov (United States)

    Tsekov, R.; Toshev, B. V.

    2012-04-01

    The dependence of the surface tension on a nanodrop radius is important for the new-phase formation process. It is demonstrated that the famous Tolman formula is not unique and the size-dependence of the surface tension can distinct for different systems. The analysis is based on a relationship between the surface tension and disjoining pressure in nanodrops. It is shown that the van der Waals interactions do not affect the new-phase formation thermodynamics since the effect of the disjoining pressure and size-dependent component of the surface tension cancel each other.

  7. Capillary pressure of van der Waals liquid nanodrops

    OpenAIRE

    Tsekov, R.; Toshev, B. V.

    2011-01-01

    The dependence of the surface tension on a nanodrop radius is important for the new-phase formation process. It is demonstrated that the famous Tolman formula is not unique and the size-dependence of the surface tension can distinct for different systems. The analysis is based on a relationship between the surface tension and disjoining pressure in nanodrops. It is shown that the van der Waals interactions do not affect the new-phase formation thermodynamics since the effect of the disjoining...

  8. Van der Waals phase transition in the framework of holography

    Directory of Open Access Journals (Sweden)

    Xiao-Xiong Zeng

    2017-01-01

    Full Text Available Phase structure of the quintessence Reissner–Nordström–AdS black hole is probed by the nonlocal observables such as holographic entanglement entropy and two point correlation function. Our result shows that, as the case of the thermal entropy, both the observables exhibit the Van der Waals-like phase transition. To reinforce this conclusion, we further check the equal area law for the first order phase transition and critical exponent of the heat capacity for the second order phase transition. We also discuss the effect of the state parameter on the phase structure of the nonlocal observables.

  9. Van der Waals phase transition in the framework of holography

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Xiao-Xiong, E-mail: xxzeng@itp.ac.cn [State School of Material Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Li-Fang, E-mail: lilf@itp.ac.cn [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China)

    2017-01-10

    Phase structure of the quintessence Reissner–Nordström–AdS black hole is probed by the nonlocal observables such as holographic entanglement entropy and two point correlation function. Our result shows that, as the case of the thermal entropy, both the observables exhibit the Van der Waals-like phase transition. To reinforce this conclusion, we further check the equal area law for the first order phase transition and critical exponent of the heat capacity for the second order phase transition. We also discuss the effect of the state parameter on the phase structure of the nonlocal observables.

  10. Cl-intercalated graphene on SiC: Influence of van der Waals forces

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

    The atomic and electronic structures of Cl-intercalated epitaxial graphene on SiC are studied by first-principles calculations. By increasing the Cl concentration, doping levels from n-type to slightly p-type are achieved on the SiC(0001) surface, while a wider range of doping levels is possible on the SiC(0001̄) surface. We find that the Cl atoms prefer bonding to the substrate rather than to the graphene. By varying the Cl concentration the doping level can be tailored. Consideration of van der Waals forces improves the distance between the graphene and the substrate as well as the binding energy, but it is not essential for the formation energy. For understanding the doping mechanism the introduction of non-local van der Waals contributions to the exchange correlation functional is shown to be essential. Copyright © EPLA, 2013.

  11. The van der Waals interactions in rare-gas dimers: the role of interparticle interactions.

    Science.gov (United States)

    Chen, Yu-Ting; Hui, Kerwin; Chai, Jeng-Da

    2016-01-28

    We investigate the potential energy curves of rare-gas dimers with various ranges and strengths of interparticle interactions (nuclear-electron, electron-electron, and nuclear-nuclear interactions). Our investigation is based on the highly accurate coupled-cluster theory associated with those interparticle interactions. For comparison, the performances of the corresponding Hartree-Fock theory, second-order Møller-Plesset perturbation theory, and density functional theory are also investigated. Our results reveal that when the interparticle interactions retain the long-range Coulomb tails, the nature of van der Waals interactions in the rare-gas dimers remains similar. By contrast, when the interparticle interactions are sufficiently short-range, the conventional van der Waals interactions in the rare-gas dimers completely disappear, yielding purely repulsive potential energy curves.

  12. Retardation-enhanced van der Waals force between thin metal films

    OpenAIRE

    Boström, Mathias; Sernelius, Bo

    2000-01-01

    We recently investigated the van der Waals force between thin metal films. Under certain conditions this force decrease with separation to a fractional power. In the present work we use optical data of metals and the zero-temperature Lifshitz formalism to demonstrate a retardation effect. The retarded attraction between thin metal films may be larger than the nonretarded attraction. This property is related to a comparatively weak retardation dependence of the energy that originates from the ...

  13. Evidence for van der Waals adhesion in gecko setae.

    Science.gov (United States)

    Autumn, Kellar; Sitti, Metin; Liang, Yiching A; Peattie, Anne M; Hansen, Wendy R; Sponberg, Simon; Kenny, Thomas W; Fearing, Ronald; Israelachvili, Jacob N; Full, Robert J

    2002-09-17

    Geckos have evolved one of the most versatile and effective adhesives known. The mechanism of dry adhesion in the millions of setae on the toes of geckos has been the focus of scientific study for over a century. We provide the first direct experimental evidence for dry adhesion of gecko setae by van der Waals forces, and reject the use of mechanisms relying on high surface polarity, including capillary adhesion. The toes of live Tokay geckos were highly hydrophobic, and adhered equally well to strongly hydrophobic and strongly hydrophilic, polarizable surfaces. Adhesion of a single isolated gecko seta was equally effective on the hydrophobic and hydrophilic surfaces of a microelectro-mechanical systems force sensor. A van der Waals mechanism implies that the remarkable adhesive properties of gecko setae are merely a result of the size and shape of the tips, and are not strongly affected by surface chemistry. Theory predicts greater adhesive forces simply from subdividing setae to increase surface density, and suggests a possible design principle underlying the repeated, convergent evolution of dry adhesive microstructures in gecko, anoles, skinks, and insects. Estimates using a standard adhesion model and our measured forces come remarkably close to predicting the tip size of Tokay gecko seta. We verified the dependence on size and not surface type by using physical models of setal tips nanofabricated from two different materials. Both artificial setal tips stuck as predicted and provide a path to manufacturing the first dry, adhesive microstructures.

  14. Analysis of van der waal equation near the critical point | Awuor ...

    African Journals Online (AJOL)

    The van der Waal equation of state is redefined in a functional manner that reveals some additional critical parameters and presents the ideal gas temperature as a lower limit to the van der Waal gas temperature. The law of corresponding states is also shown to apply to the lower limits of reduced temperatures.

  15. Anisotropic spheres with Van der Waals-type equation of state

    Indian Academy of Sciences (India)

    2014-07-02

    Jul 2, 2014 ... Abstract. We study static spherically symmetric space-time to describe relativistic compact ob- jects with anisotropic matter distribution and derive two classes of exact models to the Einstein–. Maxwell system with a modified Van der Waals equation of state. We motivate a Van der Waals-type equation of ...

  16. Density-functional calculation of van der Waals forces for free-electron-like surfaces

    DEFF Research Database (Denmark)

    Hult, E.; Hyldgaard, P.; Rossmeisl, Jan

    2001-01-01

    A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well as for the in......A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well...... as for the interaction between the surfaces themselves. The densities and static image-plane positions that are needed as input in the van der Waals functional are calculated self-consistently within density-functional theory using the generalized-gradient approximation, pseudopotentials, and plane waves. This study...

  17. The toluene-Ar complex: S0 and S1 van der Waals modes, changes to methyl rotation, and torsion-van der Waals vibration coupling

    Science.gov (United States)

    Gascooke, Jason R.; Lawrance, Warren D.

    2013-02-01

    The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are |V3(S1)| = 33.4 ± 1.0 cm-1, |V3(S0)| = 20.0 ± 1.0 cm-1, V6(S1) = -10.7 ± 1.0 cm-1, and V6(S0) = -1.7 ± 1.0 cm-1. The methyl rotor is also found to couple with van der Waals vibration; specifically, the m″ = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m″ = 1. The coupling constant is determined to be 1.9 cm-1, which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.

  18. Supersonic molecular beam electric resonance spectroscopy and van der Waals molecules

    International Nuclear Information System (INIS)

    Luftman, H.S.

    1982-09-01

    A supersonic molecular beam electric resonance (MBER) spectrometer was built to study the radiofrequency spectra of weakly bound gas phase van der Waals molecules. The instrument and its operating characteristics are described in detail. Sample mass spectra of Ar-ClF gas mixtures are also presented as an illustration of the synthesis of van der Waals molecules. The Stark focusing process for linear polar molecules is discussed and computer-simulated using both second order perturbation and variational methods. Experimental refocusing spectra of OCS and ClF are studied and compared with these trajectory calculations. Though quantitative fitting is poor, there are strong qualitative indicators that the central part of a supersonic beam consists of molecules with a significantly greater population in the lowest energy rotational states than generally assumed. Flop in as opposed to flop out resonance signals for OCS are also numerically predicted and observed. The theoretical properties of the MBER spectrum for linear molecules are elaborated upon with special emphasis on line shape considerations. MBER spectra of OCS and ClF under a variety of conditions are presented and discussed in context to these predictions. There is some uncertainty expressed both in our own modeling and in the manner complex MBER spectra have been analyzed in the past. Finally, an electrostatic potential model is used to quantitatively describe the class of van der Waals molecules Ar-MX, where MX is an alkali halide. Energetics and equilibrium geometries are calculated. The validity of using an electrostatic model to predict van der Waals bond properties is critically discussed

  19. Van der Waals equation of state revisited: importance of the dispersion correction.

    Science.gov (United States)

    de Visser, Sam P

    2011-04-28

    One of the most basic equations of state describing nonideal gases and liquids is the van der Waals equation of state, and as a consequence, it is generally taught in most first year undergraduate chemistry courses. In this work, we show that the constants a and b in the van der Waals equation of state are linearly proportional to the polarizability volume of the molecules in a gas or liquid. Using this information, a new thermodynamic one-parameter equation of state is derived that contains experimentally measurable variables and physics constants only. This is the first equation of state apart from the Ideal Gas Law that contains experimentally measurable variables and physics constants only, and as such, it may be a very useful and practical equation for the description of dilute gases and liquids. The modified van der Waals equation of state describes pV as the sum of repulsive and attractive intermolecular interaction energies that are represented by an exponential repulsion function between the electron clouds of the molecules and a London dispersion component, respectively. The newly derived equation of state is tested against experimental data for several gas and liquid examples, and the agreement is satisfactory. The description of the equation of state as a one-parameter function also has implications on other thermodynamic functions, such as critical parameters, virial coefficients, and isothermal compressibilities. Using our modified van der Waals equation of state, we show that all of these properties are a function of the molecular polarizability volume. Correlations of experimental data confirm the derived proportionalities.

  20. Physisorption of nucleobases on graphene: a comparative van der Waals study

    International Nuclear Information System (INIS)

    Le, Duy; Kara, Abdelkader; Rahman, Talat S; Schröder, Elsebeth; Hyldgaard, Per

    2012-01-01

    The physisorption of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) on graphene is studied using several variants of the density functional theory (DFT): the generalized gradient approximation with the inclusion of van der Waals interaction (vdW) based on the TS approach (Tkatchenko and Scheffer 2009 Phys. Rev. Lett. 102 073005) and our simplified version of this approach (here called sTS), the van der Waals density functional vdW-DF (Dion et al 2004 Phys. Rev. Lett. 92 246401) and vdW-DF2 (Lee et al 2010 Phys. Rev. B 82 081101), and DFT-D2 (Grimme 2006 J. Comput. Chem. 27 1787) and DFT-D3 (Grimme et al 2010 J. Chem. Phys. 132 154104) methods. The binding energies of nucleobases on graphene are found to be in the following order: G > A > T > C > U within TS, sTS, vdW-DF, and DFT-D2, and in the following order: G > A > T ∼ C > U within DFT-D3 and vdW-DF2. The binding separations are found to be different within different methods and in the following order: DFT-D2 < TS < DFT-D3 ∼ vdW-DF2 < vdW-DF. We also comment on the efficiency of combining the DFT-D approach and vdW-DF to study systems with van der Waals interactions.

  1. Physisorption of nucleobases on graphene: a comparative van der Waals study.

    Science.gov (United States)

    Le, Duy; Kara, Abdelkader; Schröder, Elsebeth; Hyldgaard, Per; Rahman, Talat S

    2012-10-24

    The physisorption of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) on graphene is studied using several variants of the density functional theory (DFT): the generalized gradient approximation with the inclusion of van der Waals interaction (vdW) based on the TS approach (Tkatchenko and Scheffer 2009 Phys. Rev. Lett. 102 073005) and our simplified version of this approach (here called sTS), the van der Waals density functional vdW-DF (Dion et al 2004 Phys. Rev. Lett. 92 246401) and vdW-DF2 (Lee et al 2010 Phys. Rev. B 82 081101), and DFT-D2 (Grimme 2006 J. Comput. Chem. 27 1787) and DFT-D3 (Grimme et al 2010 J. Chem. Phys. 132 154104) methods. The binding energies of nucleobases on graphene are found to be in the following order: G > A > T > C > U within TS, sTS, vdW-DF, and DFT-D2, and in the following order: G > A > T ~ C > U within DFT-D3 and vdW-DF2. The binding separations are found to be different within different methods and in the following order: DFT-D2 DFT-D3 ~ vdW-DF2 DFT-D approach and vdW-DF to study systems with van der Waals interactions.

  2. Isotope engineering of van der Waals interactions in hexagonal boron nitride

    Science.gov (United States)

    Vuong, T. Q. P.; Liu, S.; van der Lee, A.; Cuscó, R.; Artús, L.; Michel, T.; Valvin, P.; Edgar, J. H.; Cassabois, G.; Gil, B.

    2018-02-01

    Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes (10B and 11B) compared to those with the natural distribution of boron (20 at% 10B and 80 at% 11B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers in 10BN than in 11BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.

  3. Van Der Waals Friction: a Hamiltonian Test-Bed

    Science.gov (United States)

    Barton, Gabriel

    2012-07-01

    In the van der Waals regime (neglecting relativity and retardation), we find the power P generated by friction between two Drude-modelled dissipative half-spaces, at fixed separation and relative speed u, admitting only low u and low temperatures. This requires only elementary quantum mechanics; but the results can serve as partial checks on calculations in the fully retarded Casimir regime. They also raise questions regarding (i) the frequency-distribution of P; (ii) the status of predictions about Casimir forces generally, insofar as they feature parameters like conductivities with their empirical temperature-dependence; and (iii) calculations of heat transfer, insofar as they assume fluctuations in the two bodies to be uncorrelated.

  4. Layered van der Waals crystals with hyperbolic light dispersion

    DEFF Research Database (Denmark)

    Gjerding, Morten Niklas; Petersen, R.; Pedersen, T.G.

    2017-01-01

    candidates for Purcell factor control of emission from diamond nitrogen-vacancy centers.Natural hyperbolic materials retain the peculiar optical properties of traditional metamaterials whilst not requiring artificial structuring. Here, the authors perform a theoretical screening of a large class of natural......Compared to artificially structured hyperbolic metamaterials, whose performance is limited by the finite size of the metallic components, the sparse number of naturally hyperbolic materials recently discovered are promising candidates for the next generation of hyperbolic materials. Using first......-infrared to the ultraviolet. Combined with the emerging field of van der Waals heterostructuring, we demonstrate how the hyperbolic properties can be further controlled by stacking different two-dimensional crystals opening new perspectives for atomic-scale design of photonic metamaterials. As an application, we identify...

  5. Heterostructures based on inorganic and organic van der Waals systems

    Directory of Open Access Journals (Sweden)

    Gwan-Hyoung Lee

    2014-09-01

    Full Text Available The two-dimensional limit of layered materials has recently been realized through the use of van der Waals (vdW heterostructures composed of weakly interacting layers. In this paper, we describe two different classes of vdW heterostructures: inorganic vdW heterostructures prepared by co-lamination and restacking; and organic-inorganic hetero-epitaxy created by physical vapor deposition of organic molecule crystals on an inorganic vdW substrate. Both types of heterostructures exhibit atomically clean vdW interfaces. Employing such vdW heterostructures, we have demonstrated various novel devices, including graphene/hexagonal boron nitride (hBN and MoS2 heterostructures for memory devices; graphene/MoS2/WSe2/graphene vertical p-n junctions for photovoltaic devices, and organic crystals on hBN with graphene electrodes for high-performance transistors.

  6. Thermohydrodynamics of boiling in a van der Waals fluid.

    Science.gov (United States)

    Laurila, T; Carlson, A; Do-Quang, M; Ala-Nissila, T; Amberg, G

    2012-02-01

    We present a modeling approach that enables numerical simulations of a boiling Van der Waals fluid based on the diffuse interface description. A boundary condition is implemented that allows in and out flux of mass at constant external pressure. In addition, a boundary condition for controlled wetting properties of the boiling surface is also proposed. We present isothermal verification cases for each element of our modeling approach. By using these two boundary conditions we are able to numerically access a system that contains the essential physics of the boiling process at microscopic scales. Evolution of bubbles under film boiling and nucleate boiling conditions are observed by varying boiling surface wettability. We observe flow patters around the three-phase contact line where the phase change is greatest. For a hydrophilic boiling surface, a complex flow pattern consistent with vapor recoil theory is observed.

  7. Infrared hyperbolic metasurface based on nanostructured van der Waals materials

    Science.gov (United States)

    Li, Peining; Dolado, Irene; Alfaro-Mozaz, Francisco Javier; Casanova, Fèlix; Hueso, Luis E.; Liu, Song; Edgar, James H.; Nikitin, Alexey Y.; Vélez, Saül; Hillenbrand, Rainer

    2018-02-01

    Metasurfaces with strongly anisotropic optical properties can support deep subwavelength-scale confined electromagnetic waves (polaritons), which promise opportunities for controlling light in photonic and optoelectronic applications. We developed a mid-infrared hyperbolic metasurface by nanostructuring a thin layer of hexagonal boron nitride that supports deep subwavelength-scale phonon polaritons that propagate with in-plane hyperbolic dispersion. By applying an infrared nanoimaging technique, we visualize the concave (anomalous) wavefronts of a diverging polariton beam, which represent a landmark feature of hyperbolic polaritons. The results illustrate how near-field microscopy can be applied to reveal the exotic wavefronts of polaritons in anisotropic materials and demonstrate that nanostructured van der Waals materials can form a highly variable and compact platform for hyperbolic infrared metasurface devices and circuits.

  8. Flexible ferroelectric element based on van der Waals heteroepitaxy.

    Science.gov (United States)

    Jiang, Jie; Bitla, Yugandhar; Huang, Chun-Wei; Do, Thi Hien; Liu, Heng-Jui; Hsieh, Ying-Hui; Ma, Chun-Hao; Jang, Chi-Yuan; Lai, Yu-Hong; Chiu, Po-Wen; Wu, Wen-Wei; Chen, Yi-Chun; Zhou, Yi-Chun; Chu, Ying-Hao

    2017-06-01

    We present a promising technology for nonvolatile flexible electronic devices: A direct fabrication of epitaxial lead zirconium titanate (PZT) on flexible mica substrate via van der Waals epitaxy. These single-crystalline flexible ferroelectric PZT films not only retain their performance, reliability, and thermal stability comparable to those on rigid counterparts in tests of nonvolatile memory elements but also exhibit remarkable mechanical properties with robust operation in bent states (bending radii down to 2.5 mm) and cycling tests (1000 times). This study marks the technological advancement toward realizing much-awaited flexible yet single-crystalline nonvolatile electronic devices for the design and development of flexible, lightweight, and next-generation smart devices with potential applications in electronics, robotics, automotive, health care, industrial, and military systems.

  9. Multifunctional high-performance van der Waals heterostructures

    Science.gov (United States)

    Huang, Mingqiang; Li, Shengman; Zhang, Zhenfeng; Xiong, Xiong; Li, Xuefei; Wu, Yanqing

    2017-12-01

    A range of novel two-dimensional materials have been actively explored for More Moore and More-than-Moore device applications because of their ability to form van der Waals heterostructures with unique electronic properties. However, most of the reported electronic devices exhibit insufficient control of multifunctional operations. Here, we leverage the band-structure alignment properties of narrow-bandgap black phosphorus and large-bandgap molybdenum disulfide to realize vertical heterostructures with an ultrahigh rectifying ratio approaching 106 and on-off ratio up to 107. Furthermore, we design and fabricate tunable multivalue inverters, in which the output logic state and window of the mid-logic can be controlled by specific pairs of channel length and, most importantly, by the electric field, which shifts the band-structure alignment across the heterojunction. Finally, high gains over 150 are achieved in the inverters with optimized device geometries, showing great potential for future logic applications.

  10. Equilibrium shape of a suspended graphene sheet under electrostatic and van der Waals forces

    Science.gov (United States)

    Inui, Norio

    2018-03-01

    The equilibrium shape of a graphene sheet suspended over a silicon substrate with a narrow gap is investigated by introducing a continuum model. The displacement of the suspended graphene sheet, subject to electrostatic and van der Waals forces, was obtained by solving the equation of motion including the dissipation terms. The van der Waals force was calculated based on the quantum theory by considering the unique optical properties of graphene and their temperature dependence. The van der Waals force has a large effect on the equilibrium shape near the threshold value, below which a pull-in phenomenon occurs.

  11. On van der Waals-like forces in spontaneously broken supersymmetries

    International Nuclear Information System (INIS)

    Radescu, E.E.

    1982-12-01

    In spontaneously broken rigid supersymmetry, Goldstone fermion pair exchange should lead to a universal interaction between massive bodies uniquely fixed by the existing low energy theorem. The resulting van der Waals-like potential is shown to be V(r)=Mmπ -3 F -4 r -7 +O(r -8 ), where M,m are the masses of the interacting bodies while √F is the scale of the breaking. The change in the situation when the supersymmetry is promoted to a local one is briefly discussed. (author)

  12. Van der Waals interactions and photoelectric effect in noncommutative quantum mechanics

    International Nuclear Information System (INIS)

    Li Kang; Chamoun, N.

    2007-01-01

    We calculate the long-range Van der Waals force and the photoelectric cross section in a noncommutative setup. It is argued that non-commutativity effects could not be discerned for the Van der Waals interactions. The result for the photoelectric effect shows deviation from the usual commutative one, which in principle can be used to put bounds on the space-space non-commutativity parameter. (authors)

  13. Graphene Substrate for van der Waals Epitaxy of Layer-Structured Bismuth Antimony Telluride Thermoelectric Film.

    Science.gov (United States)

    Kim, Eun Sung; Hwang, Jae-Yeol; Lee, Kyu Hyoung; Ohta, Hiromichi; Lee, Young Hee; Kim, Sung Wng

    2017-02-01

    Graphene as a substrate for the van der Waals epitaxy of 2D layered materials is utilized for the epitaxial growth of a layer-structured thermoelectric film. Van der Waals epitaxial Bi 0.5 Sb 1.5 Te 3 film on graphene synthesized via a simple and scalable fabrication method exhibits good crystallinity and high thermoelectric transport properties comparable to single crystals. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Contribution of van der Waals forces to the plasticity of magnesium

    International Nuclear Information System (INIS)

    Ding, Zhigang; Liu, Wei; Li, Shuang; Zhang, Dalong; Zhao, Yonghao; Lavernia, Enrique J.; Zhu, Yuntian

    2016-01-01

    The accurate determination of stacking fault energies (SFE) and associated restoring forces is important for understanding plastic deformation, especially the dislocation emission and motion in metals. In this work, we use density-functional theory (DFT) calculations to, systematically study the all-dimension relaxed atomic models of Mg crystal slip, with a special focus on the “subslip modes” in prismatic and pyramidal slip systems. We find that slip systems with large interplanar distances are readily activated, which agrees well with experimental observations. Inclusion of the ubiquitous van der Waals (vdW) interactions results in lower generalized stacking fault energy curves. Remarkably, the unstable SFE value of pyramidal-II system is strongly reduced by up to 69 mJ/m 2 , and the related restoring stress is lowered by 0.74 GPa after taking into account the vdW energy. Our calculations indicate significant effect of vdW forces on the plasticity of Mg. - Graphical abstract: By using density-functional theory calculations, we systematically study the generalized stacking fault energy for pure Mg, and demonstrated pronounced contributions of van der Waals forces to the plasticity of Mg.

  15. Consistent van der Waals radii for the whole main group.

    Science.gov (United States)

    Mantina, Manjeera; Chamberlin, Adam C; Valero, Rosendo; Cramer, Christopher J; Truhlar, Donald G

    2009-05-14

    Atomic radii are not precisely defined but are nevertheless widely used parameters in modeling and understanding molecular structure and interactions. The van der Waals radii determined by Bondi from molecular crystals and data for gases are the most widely used values, but Bondi recommended radius values for only 28 of the 44 main-group elements in the periodic table. In the present Article, we present atomic radii for the other 16; these new radii were determined in a way designed to be compatible with Bondi's scale. The method chosen is a set of two-parameter correlations of Bondi's radii with repulsive-wall distances calculated by relativistic coupled-cluster electronic structure calculations. The newly determined radii (in A) are Be, 1.53; B, 1.92; Al, 1.84; Ca, 2.31; Ge, 2.11; Rb, 3.03; Sr, 2.49; Sb, 2.06; Cs, 3.43; Ba, 2.68; Bi, 2.07; Po, 1.97; At, 2.02; Rn, 2.20; Fr, 3.48; and Ra, 2.83.

  16. Rotational dissociation of impulsively aligned van der Waals complexes.

    Science.gov (United States)

    Søndergaard, Anders A; Zillich, Robert E; Stapelfeldt, Henrik

    2017-08-21

    The nonadiabatic alignment dynamics of weakly bound molecule-atom complexes, induced by a moderately intense 300 fs nonresonant laser pulse, is calculated by direct numerical solution of the time-dependent Schrödinger equation. Our method propagates the wave function according to the coupled channel equations for the complex, which can be done in a very efficient and stable manner out to large times. We present results for two van der Waal complexes, CS 2 -He and HCCH-He, as respective examples of linear molecules with large and small moments of inertia. Our main result is that at intensities typical of nonadiabatic alignment experiments, these complexes rapidly dissociate. In the case of the CS 2 -He complex, the ensuing rotational dynamics resembles that of isolated molecules, whereas for the HCCH-He complex, the detachment of the He atom severely perturbs and essentially quenches the subsequent rotational motion. At intensities of the laser pulse ≲2.0 × 10 12 W/cm 2 , it is shown that the molecule-He complex can rotate and align without breaking apart. We discuss the implications of our findings for recent experiments on iodine molecules solvated in helium nanodroplets.

  17. Spontaneous doping on high quality talc-graphene-hBN van der Waals heterostructures

    Science.gov (United States)

    Mania, E.; Alencar, A. B.; Cadore, A. R.; Carvalho, B. R.; Watanabe, K.; Taniguchi, T.; Neves, B. R. A.; Chacham, H.; Campos, L. C.

    2017-09-01

    Steady doping, added to its remarkable electronic properties, would make graphene a valuable commodity in the solar cell market, as energy power conversion could be substantially increased. Here we report a graphene van der Waals heterostructure which is able to spontaneously dope graphene (p-type) up to n ~ 2.2  ×  1013 cm-2 while providing excellent charge mobility (μ ~ 25 000 cm2 V-1 s-1). Such properties are achieved via deposition of graphene on atomically flat layered talc, a natural and abundant dielectric crystal. Raman investigation shows a preferential charge accumulation on graphene-talc van der Waals heterostructures, which are investigated through the electronic properties of talc/graphene/hBN heterostructure devices. These heterostructures preserve graphene’s good electronic quality, verified by the observation of quantum Hall effect at low magnetic fields (B  =  0.4 T) at T  =  4.2 K. In order to investigate the physical mechanisms behind graphene-on-talc p-type doping, we performed first-principles calculations of their interface structural and electronic properties. In addition to potentially improving solar cell efficiency, graphene doping via van der Waals stacking is also a promising route towards controlling the band gap opening in bilayer graphene, promoting a steady n or p type doping in graphene and, eventually, providing a new path to access superconducting states in graphene, predicted to exist only at very high doping.

  18. Adsorption of thiophene on transition metal surfaces with the inclusion of van der Waals effects

    Science.gov (United States)

    Malone, Walter; Matos, Jeronimo; Kara, Abdelkader

    2018-03-01

    We use density functional theory with the inclusion of the van der Waals interaction to study the adsorption of thiophene, C4H4S, on Pt, Rh, Pd, Au, and Ag (100) surfaces. The five van der Waals (vdW) inclusive functionals we employ are optB86b-vdW, optB88-vdW, optPBE-vdW, revPBE-vdW, and rPW86-vdW2. For comparison we also run calculations with the GGA- Perdew Burke and Ernzerhof (PBE) functional. We examine several adsorption sites with the plane of the molecule parallel or perpendicular to the surface. The most stable configuration on all metals was the site where the center of the thiophene lies over a 4-fold hollow site with the sulfur atom lying close to a top site. Furthermore, we examine several electronic and geometric properties of the adsorbate including charge transfer, modification of the d-band, adsorption energy, tilt angle, and adsorption height. For the coinage metals PBE gives the lowest adsorption energy. For reactive transition metal substrates, revPBE-vdW and rPW86-vdW2 give lower adsorption energies than PBE.

  19. Nonlocal van der Waals functionals: the case of rare-gas dimers and solids.

    Science.gov (United States)

    Tran, Fabien; Hutter, Jürg

    2013-05-28

    Recently, the nonlocal van der Waals (vdW) density functionals [M. Dion, H. Rydberg, E. Schröder, D. C. Langreth, and B. I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004)] have attracted considerable attention due to their good performance for systems where weak interactions are important. Since the physics of dispersion is included in these functionals, they are usually more accurate and show less erratic behavior than the semilocal and hybrid methods. In this work, several variants of the vdW functionals have been tested on rare-gas dimers (from He2 to Kr2) and solids (Ne, Ar, and Kr) and their accuracy compared to standard semilocal approximations, supplemented or not by an atom-pairwise dispersion correction [S. Grimme, J. Antony, S. Ehrlich, and H. Krieg, J. Chem. Phys. 132, 154104 (2010)]. An analysis of the results in terms of energy decomposition is also provided.

  20. Quantum Coulomb Systems: Recombination, Screening, and van der Waals Forces

    International Nuclear Information System (INIS)

    Alastuey, A.

    2009-01-01

    Under standard Earth conditions, and also in many astrophysical situations, the properties of matter result from the interplay between non-relativistic quantum mechanics and Coulomb interactions. In that context, the derivation of exact results for equilibrium properties of quantum Coulomb systems is of crucial importance. First, I briefly review rigorous proofs about either stability or limiting behaviours, as well as various asymptotic expansions specific to almost fully ionized situations. Then, I present the Feynman-Kac path integral representation which is the most efficient tool for dealing with both recombination and screening. Within that representation, the grand-canonical partition function for a system of quantum particles with two-body interactions is shown to be equal to its equivalent counterpart for a system of classical loops. Equilibrium quantities for the gas of loops are then represented by straightforward generalizations of standard Mayer diagrammatics. Because of the Coulomb-like long range of the two-body loop potential, every Mayer graph diverges. Such divergences are first removed via systematic chain resummations, which amount to introduce an effective potential φ, the quantum analogue of Debye potential. In a second step, the whole resumed diagrammatical series is exactly reorganized in terms of graphs where particle clusters are connected by bonds built with φ. The corresponding screened cluster representation is particularly useful for studying partially ionized gases, as illustrated by its application to hydrogen in the atomic regime. Exact asymptotic expansions for thermodynamics are derived beyond familiar Saha theory. Also, the screening of van der Waals forces between two hydrogen atoms by ionized protons and ionized electrons is shown to be only partial. (author)

  1. van der Waals Solids from Self-Assembled Nanoscale Building Blocks.

    Science.gov (United States)

    Choi, Bonnie; Yu, Jaeeun; Paley, Daniel W; Trinh, M Tuan; Paley, Maria V; Karch, Jessica M; Crowther, Andrew C; Lee, Chul-Ho; Lalancette, Roger A; Zhu, Xiaoyang; Kim, Philip; Steigerwald, Michael L; Nuckolls, Colin; Roy, Xavier

    2016-02-10

    Traditional atomic van der Waals materials such as graphene, hexagonal boron-nitride, and transition metal dichalcogenides have received widespread attention due to the wealth of unusual physical and chemical behaviors that arise when charges, spins, and vibrations are confined to a plane. Though not as widespread as their atomic counterparts, molecule-based two-dimensional (2D) layered solids offer significant benefits; their structural flexibility will enable the development of materials with tunable properties. Here we describe a layered van der Waals solid self-assembled from a structure-directing building block and C60 fullerene. The resulting crystalline solid contains a corrugated monolayer of neutral fullerenes and can be mechanically exfoliated. The absorption spectrum of the bulk solid shows an optical gap of 390 ± 40 meV that is consistent with thermal activation energy obtained from electrical transport measurement. We find that the dimensional confinement of fullerenes significantly modulates the optical and electronic properties compared to the bulk solid.

  2. Droplet spreading driven by van der Waals force: a molecular dynamics study

    KAUST Repository

    Wu, Congmin

    2010-07-07

    The dynamics of droplet spreading is investigated by molecular dynamics simulations for two immiscible fluids of equal density and viscosity. All the molecular interactions are modeled by truncated Lennard-Jones potentials and a long-range van der Waals force is introduced to act on the wetting fluid. By gradually increasing the coupling constant in the attractive van der Waals interaction between the wetting fluid and the substrate, we observe a transition in the initial stage of spreading. There exists a critical value of the coupling constant, above which the spreading is pioneered by a precursor film. In particular, the dynamically determined critical value quantitatively agrees with that determined by the energy criterion that the spreading coefficient equals zero. The latter separates partial wetting from complete wetting. In the regime of complete wetting, the radius of the spreading droplet varies with time as R(t) ∼ √t, a behavior also found in molecular dynamics simulations where the wetting dynamics is driven by the short-range Lennard-Jones interaction between liquid and solid. © 2010 IOP Publishing Ltd.

  3. Imaging of Interlayer Coupling in van der Waals Heterostructures Using a Bright-Field Optical Microscope.

    Science.gov (United States)

    Alexeev, Evgeny M; Catanzaro, Alessandro; Skrypka, Oleksandr V; Nayak, Pramoda K; Ahn, Seongjoon; Pak, Sangyeon; Lee, Juwon; Sohn, Jung Inn; Novoselov, Kostya S; Shin, Hyeon Suk; Tartakovskii, Alexander I

    2017-09-13

    Vertically stacked atomic layers from different layered crystals can be held together by van der Waals forces, which can be used for building novel heterostructures, offering a platform for developing a new generation of atomically thin, transparent, and flexible devices. The performance of these devices is critically dependent on the layer thickness and the interlayer electronic coupling, influencing the hybridization of the electronic states as well as charge and energy transfer between the layers. The electronic coupling is affected by the relative orientation of the layers as well as by the cleanliness of their interfaces. Here, we demonstrate an efficient method for monitoring interlayer coupling in heterostructures made from transition metal dichalcogenides using photoluminescence imaging in a bright-field optical microscope. The color and brightness in such images are used here to identify mono- and few-layer crystals and to track changes in the interlayer coupling and the emergence of interlayer excitons after thermal annealing in heterobilayers composed of mechanically exfoliated flakes and as a function of the twist angle in atomic layers grown by chemical vapor deposition. Material and crystal thickness sensitivity of the presented imaging technique makes it a powerful tool for characterization of van der Waals heterostructures assembled by a wide variety of methods, using combinations of materials obtained through mechanical or chemical exfoliation and crystal growth.

  4. Droplet spreading driven by van der Waals force: a molecular dynamics study

    International Nuclear Information System (INIS)

    Wu Congmin; Qian Tiezheng; Sheng Ping

    2010-01-01

    The dynamics of droplet spreading is investigated by molecular dynamics simulations for two immiscible fluids of equal density and viscosity. All the molecular interactions are modeled by truncated Lennard-Jones potentials and a long-range van der Waals force is introduced to act on the wetting fluid. By gradually increasing the coupling constant in the attractive van der Waals interaction between the wetting fluid and the substrate, we observe a transition in the initial stage of spreading. There exists a critical value of the coupling constant, above which the spreading is pioneered by a precursor film. In particular, the dynamically determined critical value quantitatively agrees with that determined by the energy criterion that the spreading coefficient equals zero. The latter separates partial wetting from complete wetting. In the regime of complete wetting, the radius of the spreading droplet varies with time as R(t)∼√t, a behavior also found in molecular dynamics simulations where the wetting dynamics is driven by the short-range Lennard-Jones interaction between liquid and solid.

  5. EDITORIAL: Van der Waals interactions in advanced materials, in memory of David C Langreth Van der Waals interactions in advanced materials, in memory of David C Langreth

    Science.gov (United States)

    Hyldgaard, Per; Rahman, Talat S.

    2012-10-01

    rationale for considering a more general switch to nonlocal functionals. Graziano et al note that the accuracy in the description of some soft layered systems like graphene and boron-nitride can be increased by changing the exchange description away from what was suggested in the original vdW-DF method. Hanke et al focused on the weak chemisorption of ethene on the various Cu facets that have an increasing degree of openness and provide a method for benchmarking through comparison with experimental observations. Finally, Björkman et al raise the question 'Are we van der Waals ready?' and proceed to test our readiness by benchmarking the performance of a range of vdW-aware methods for the group of 96 known layered structures. We have also included in this special issue one study of nonequilibrium transport which is linked to David's work in formal scattering theory [1, 2] and which observes that vdW forces (and possible generalizations to nonequilibrium transport conditions) will be of central importance in a richer computational characterization of molecular electronics under operational conditions. David was always keen to spearhead the development of tools that improved descriptions of nature and addressed actual experiments. We know that he was happy that DMP started the focused session on vdW and materials in 2011. We know that he would have thoroughly appreciated the articles in this special issue. He would have hoped, as we do, that materials theory may continue to learn how to tackle even more exciting experimental problems and that we may continue to deepen our understanding of materials and their functionality. Bibliography [1]Langreth D C 1976 1975 Nato Advanced Study Institute on Linear and Nonlinear Transport in Solids, Antwerben vol B17 (New York: Plenum) pp 3-32 [2]Langreth D C 1966 Friedel sum rule for Anderson's model of localized impurity states Phys. Rev. 150 516 [3]Langreth D C and Perdew J P 1975 The exchange-correlation energy of a metallic surface

  6. Out-of-plane heat transfer in van der Waals stacks through electron-hyperbolic phonon coupling

    Science.gov (United States)

    Tielrooij, Klaas-Jan; Hesp, Niels C. H.; Principi, Alessandro; Lundeberg, Mark B.; Pogna, Eva A. A.; Banszerus, Luca; Mics, Zoltán; Massicotte, Mathieu; Schmidt, Peter; Davydovskaya, Diana; Purdie, David G.; Goykhman, Ilya; Soavi, Giancarlo; Lombardo, Antonio; Watanabe, Kenji; Taniguchi, Takashi; Bonn, Mischa; Turchinovich, Dmitry; Stampfer, Christoph; Ferrari, Andrea C.; Cerullo, Giulio; Polini, Marco; Koppens, Frank H. L.

    2018-01-01

    Van der Waals heterostructures have emerged as promising building blocks that offer access to new physics, novel device functionalities and superior electrical and optoelectronic properties1-7. Applications such as thermal management, photodetection, light emission, data communication, high-speed electronics and light harvesting8-16 require a thorough understanding of (nanoscale) heat flow. Here, using time-resolved photocurrent measurements, we identify an efficient out-of-plane energy transfer channel, where charge carriers in graphene couple to hyperbolic phonon polaritons17-19 in the encapsulating layered material. This hyperbolic cooling is particularly efficient, giving picosecond cooling times for hexagonal BN, where the high-momentum hyperbolic phonon polaritons enable efficient near-field energy transfer. We study this heat transfer mechanism using distinct control knobs to vary carrier density and lattice temperature, and find excellent agreement with theory without any adjustable parameters. These insights may lead to the ability to control heat flow in van der Waals heterostructures.

  7. Interfacial adhesion between graphene and silicon dioxide by density functional theory with van der Waals corrections

    International Nuclear Information System (INIS)

    Gao, Wei; Liechti, Kenneth M; Huang, Rui; Xiao, Penghao; Henkelman, Graeme

    2014-01-01

    Interfacial adhesion between graphene and a SiO 2 substrate is studied by density functional theory (DFT) with dispersion corrections. The results demonstrate the van der Waals (vdW) interaction as the predominant mechanism at the graphene/SiO 2 interface. It is found that the interaction strength is strongly influenced by changes of the SiO 2 surface structures due to surface reactions with water. The adhesion energy is reduced when the reconstructed SiO 2 surface is hydroxylated, and further reduced when covered by a monolayer of adsorbed water molecules. Moreover, it is noted that vdW forces are required to accurately model the graphene/SiO 2 interface with DFT and that the adhesion energy is underestimated by empirical force fields commonly used in atomistic simulations. (paper)

  8. Rotational study on the van der Waals complex 1-chloro-1,1-difluoroethane-argon.

    Science.gov (United States)

    Wang, Juan; Chen, Junhua; Feng, Gang; Xia, Zhining; Gou, Qian

    2018-03-15

    The rotational spectrum of the van der Waals complex formed between 1-chloro-1,1-difluoroethane and argon has been investigated by using a pulsed jet Fourier transform microwave spectrometer. Only one set of rotational transitions belonging to the lowest energy conformer has been observed and assigned, although theoretical calculations suggest six stable conformers that might be observed. The observed conformer, according to the experimental evidence from two isotopologues ( 35 Cl and 37 Cl), adopts a configuration in which the argon atom is located, close to the CF 2 Cl top, between the CCF and CCCl planes (the dihedral angle ∠ArCCCl is 65.2°). The distance between argon atom and the center of mass of CH 3 CF 2 Cl is 3.949(2) Å. The dissociation energy, with pseudo diatomic approximation, is evaluated to be 2.4kJmol -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Mechanism of electron attachment to van der Waals clusters: Application to carbon dioxide clusters

    International Nuclear Information System (INIS)

    Tsukada, M.; Shima, N.; Tsuneyuki, S.; Kageshima, H.; Kondow, T.

    1987-01-01

    A theory on the attachment of very slow electrons to van der Waals clusters was developed on the basis of the electronic structure theory, and was applied to clarify the mechanism of the collisional electron transfer from a high-Rydberg atom to a CO 2 cluster. The strong coupled electron--phonon model is found to afford a reasonable mechanism of the attachment. The equilibrium geometry of (CO 2 )/sub N/ (2≤N≤13) clusters are determined and their vertical affinity levels are obtained by the DV-X α-transition state method. Using this information, as well as some plausible assumptions on the values of the coupling constants, the attachment cross section σ is evaluated as a function of the energy of the incident electron. The theory predicts the existence of the threshold cluster size for the attachment and a sharp decrease of σ with the energy, which are consistent with the experimental results

  10. Van-der-Waals interaction of atoms in dipolar Rydberg states

    Science.gov (United States)

    Kamenski, Aleksandr A.; Mokhnenko, Sergey N.; Ovsiannikov, Vitaly D.

    2018-02-01

    An asymptotic expression for the van-der-Waals constant C 6( n) ≈ -0.03 n 12 K p ( x) is derived for the long-range interaction between two highly excited hydrogen atoms A and B in their extreme Stark states of equal principal quantum numbers n A = n B = n ≫ 1 and parabolic quantum numbers n 1(2) = n - 1, n 2(1) = m = 0 in the case of collinear orientation of the Stark-state dipolar electric moments and the interatomic axis. The cubic polynomial K 3( x) in powers of reciprocal values of the principal quantum number x = 1/ n and quadratic polynomial K 2( y) in powers of reciprocal values of the principal quantum number squared y = 1/ n 2 were determined on the basis of the standard curve fitting polynomial procedure from the calculated data for C 6( n). The transformation of attractive van-der-Waals force ( C 6 > 0) for low-energy states n observed from the results of numerical calculations based on the second-order perturbation theory for the operator of the long-range interaction between neutral atoms. This transformation is taken into account in the asymptotic formulas (in both cases of p = 2, 3) by polynomials K p tending to unity at n → ∞ ( K p (0) = 1). The transformation from low- n attractive van-der-Waals force into high- n repulsive force demonstrates the gradual increase of the negative contribution to C 6( n) from the lower-energy two-atomic states, of the A(B)-atom principal quantum numbers n'A(B) = n-Δ n (where Δ n = 1, 2, … is significantly smaller than n for the terms providing major contribution to the second-order series), which together with the states of n″B(A) = n+Δ n make the joint contribution proportional to n 12. So, the hydrogen-like manifold structure of the energy spectrum is responsible for the transformation of the power-11 asymptotic dependence C 6( n) ∝ n 11of the low-angular-momenta Rydberg states in many-electron atoms into the power-12 dependence C 6( n) ∝ n 12 for the dipolar states of the Rydberg manifold.

  11. Understanding the nanoscale local buckling behavior of vertically aligned MWCNT arrays with van der Waals interactions.

    Science.gov (United States)

    Li, Yupeng; Kim, Hyung-ick; Wei, Bingqing; Kang, Junmo; Choi, Jae-boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-09-14

    The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect.

  12. A Componentwise Convex Splitting Scheme for Diffuse Interface Models with Van der Waals and Peng--Robinson Equations of State

    KAUST Repository

    Fan, Xiaolin

    2017-01-19

    This paper presents a componentwise convex splitting scheme for numerical simulation of multicomponent two-phase fluid mixtures in a closed system at constant temperature, which is modeled by a diffuse interface model equipped with the Van der Waals and the Peng-Robinson equations of state (EoS). The Van der Waals EoS has a rigorous foundation in physics, while the Peng-Robinson EoS is more accurate for hydrocarbon mixtures. First, the phase field theory of thermodynamics and variational calculus are applied to a functional minimization problem of the total Helmholtz free energy. Mass conservation constraints are enforced through Lagrange multipliers. A system of chemical equilibrium equations is obtained which is a set of second-order elliptic equations with extremely strong nonlinear source terms. The steady state equations are transformed into a transient system as a numerical strategy on which the scheme is based. The proposed numerical algorithm avoids the indefiniteness of the Hessian matrix arising from the second-order derivative of homogeneous contribution of total Helmholtz free energy; it is also very efficient. This scheme is unconditionally componentwise energy stable and naturally results in unconditional stability for the Van der Waals model. For the Peng-Robinson EoS, it is unconditionally stable through introducing a physics-preserving correction term, which is analogous to the attractive term in the Van der Waals EoS. An efficient numerical algorithm is provided to compute the coefficient in the correction term. Finally, some numerical examples are illustrated to verify the theoretical results and efficiency of the established algorithms. The numerical results match well with laboratory data.

  13. The hot pick-up technique for batch assembly of van der Waals heterostructures

    DEFF Research Database (Denmark)

    Pizzocchero, Filippo; Gammelgaard, Lene; Jessen, Bjarke Sørensen

    2016-01-01

    The assembly of individual two-dimensional materials into van der Waals heterostructures enables the construction of layered three-dimensional materials with desirable electronic and optical properties. A core problem in the fabrication of these structures is the formation of clean interfaces...... between the individual two-dimensional materials which would affect device performance. We present here a technique for the rapid batch fabrication of van der Waals heterostructures, demonstrated by the controlled production of 22 mono-, bi- and trilayer graphene stacks encapsulated in hexagonal boron...

  14. Electrostatics of electron-hole interactions in van der Waals heterostructures

    Science.gov (United States)

    Cavalcante, L. S. R.; Chaves, A.; Van Duppen, B.; Peeters, F. M.; Reichman, D. R.

    2018-03-01

    The role of dielectric screening of electron-hole interaction in van der Waals heterostructures is theoretically investigated. A comparison between models available in the literature for describing these interactions is made and the limitations of these approaches are discussed. A simple numerical solution of Poisson's equation for a stack of dielectric slabs based on a transfer matrix method is developed, enabling the calculation of the electron-hole interaction potential at very low computational cost and with reasonable accuracy. Using different potential models, direct and indirect exciton binding energies in these systems are calculated within Wannier-Mott theory, and a comparison of theoretical results with recent experiments on excitons in two-dimensional materials is discussed.

  15. Experiment and computation: a combined approach to study the van der Waals complexes

    Directory of Open Access Journals (Sweden)

    Surin L.A.

    2017-01-01

    Full Text Available A review of recent results on the millimetre-wave spectroscopy of weakly bound van der Waals complexes, mostly those which contain H2 and He, is presented. In our work, we compared the experimental spectra to the theoretical bound state results, thus providing a critical test of the quality of the M–H2 and M–He potential energy surfaces (PESs which are a key issue for reliable computations of the collisional excitation and de-excitation of molecules (M = CO, NH3, H2O in the dense interstellar medium. The intermolecular interactions with He and H2 play also an important role for high resolution spectroscopy of helium or para-hydrogen clusters doped by a probe molecule (CO, HCN. Such experiments are directed on the detection of superfluid response of molecular rotation in the He and p-H2 clusters.

  16. Jet-Cooled Infrared Laser Spectroscopy in the Umbrella νb{2} Vibration Region of NH_3: Improving the Potential Energy Surface Model of the NH_3-Ar Van Der Waals Complex

    Science.gov (United States)

    Asselin, Pierre; Jabri, Atef; Potapov, Alexey; Loreau, Jérome; van der Avoird, Ad

    2017-06-01

    Taking advantage of our sensitive laser spectrometer coupled to a pulsed slit jet, we recorded near the νb{2} vibration a series of rovibrational transitions of the NH_3-Ar van der Waals (vdW) complex. These transitions involve in the ground vibrational state several internal rotor states corresponding to the ortho{NH_3} and para{NH_3} spin modifications of the complex. They are labeled by Σ_{a}(j,k), Σ_{s}(j,k), Π_{a}(j,k) and Π_{s}(j,k) where Σ(K=0) and Π(K=1) indicate the projection K of the total rotational angular momentum J on the vdW axis, the superscripts s and a designate a symmetric or antisymmetric NH_3 inversion wave function, and j, k quantum numbers indicate the correlation between the internal-rotor state of the complex and the j, k rotational state of the free NH_3 monomer. Five bands have been identified, only one of which was partly observed before. They include transitions starting from the Σ_{a}(j=0 or j=1) state without any internal angular momentum, consequently they can be assigned from the band contour of a linear-molecule-like K=0, ΔJ=1 transition. The energies and splittings of the rovibrational levels of the νb{2}=1←0 spectrum derived from the analysis of the Π_{s}, Σ_{s}(j=1)← Σ_{a}(j=0), k=0 bands and mostly of the Σ_{s}, Π_{s} and Σ_{a}(j=1)←Σ_{a}(j=1), k=1 bands bring relevant information about the νb{2} dependence of the NH_3-Ar interaction, the rovibrational dynamics of the NH_3-Ar complex and provide a sensitive test of a recently developed 4D potential energy surface that includes explicitly its dependence on the umbrella motion. P. Asselin, Y. Berger, T. R. Huet, R. Motiyenko, L. Margulès, R. J. Hendricks, M. R. Tarbutt, S. Tokunaga, B. Darquié, PCCP 19, 4576 (2017), G. T. Fraser, A.S. Pine and W. A. Kreiner, J. Chem. Phys. 94, 7061 (1991). J. Loreau, J. Liévin, Y. Scribano and A. van der Avoird, J. Chem. Phys. 141, 224303 (2014).

  17. Kinetic Roughening and Material Optical Properties Influence on Van der Waals/Casimir Forces

    NARCIS (Netherlands)

    van Zwol, P. J.; Palasantzas, G.

    Atomic force microscopy measurements and force theory calculations using the Lifshitz theory show that van der Waals/Casimir dispersive forces have a strong dependence on surface roughness and material optical properties. It is found that at separations below 100 nm the roughness effect is

  18. Optical properties and kinetic roughening influence on dispersive casimir and van der Waals forces

    NARCIS (Netherlands)

    Palasantzas, G.; Svetovoy, Vitaly; van Zwol, P.J.

    2010-01-01

    Casimir and van der Waals dispersive forces between real material surfaces can be strongly influenced by surface roughness and the frequency dependent dielectric functions of the interacting materials. The Lifshitz theory allows calculations of these forces between two flat plates if the frequency

  19. Optical Properties and Kinetic Roughening Influence on Dispersive Casimir and van der Waals Forces

    NARCIS (Netherlands)

    Palasantzas, G.; Svetovoy, V. B.; Van Zwol, P. J.

    2010-01-01

    Casimir and van der Waals dispersive forces between real material surfaces can be strongly influenced by surface roughness and the frequency dependent dielectric functions of the interacting materials. The Lifshitz theory allows calculations of these forces between two flat plates if the frequency

  20. Far infrared study of the Argon-HCl van der Waals molecule

    NARCIS (Netherlands)

    Boom, E.W.; Frenkel, D.; Elsken, J. van der

    1977-01-01

    Results of far infrared measurements on the system HCl–Ar at low density and temperature are presented. Distinct spectral features are observed that must be attributed to Ar–HCl van der Waals molecules. Possible explanations of the observed spectra in terms of a simple picture of the internal motion

  1. Anisotropic spheres with Van der Waals-type equation of state

    Indian Academy of Sciences (India)

    2014-07-02

    Jul 2, 2014 ... viewed as a relativistic Fermi gas of quark at the extremes of densities necessary for colour deconfinement to ... nuclear forces mediated by multigluon exchange lead to a short-range force, which is considered to be in analogy with the effective Van der Waals force due to multiphoton exchange interaction ...

  2. Theoretical investigation of van der Waals forces between solid surfaces at nanoscales

    NARCIS (Netherlands)

    Kudryavtsev, Y.V.; Gelinck, E.R.M.; Fischer, H.R.

    2009-01-01

    A theoretical investigation of van der Waals forces acting between two solid silicon surfaces at separations from zero to approximately 20 nm is presented. We focused our efforts on the analysis of different factors that can cause deviations from the classical pressure-distance dependence p ∼ 1/D3.

  3. Low-Voltage Complementary Electronics from Ion-Gel-Gated Vertical Van der Waals Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yongsuk [SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 Korea; Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208 USA; Kang, Junmo [Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208 USA; Jariwala, Deep [Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208 USA; Kang, Moon Sung [Department of Chemical Engineering, Soongsil University, Seoul 156-743 Korea; Marks, Tobin J. [Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208 USA; Department of Chemistry, Northwestern University, Evanston IL 60208 USA; Hersam, Mark C. [Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208 USA; Department of Chemistry, Northwestern University, Evanston IL 60208 USA; Department of Electrical Engineering and Computer Science, Northwestern University, Evanston IL 60208 USA; Cho, Jeong Ho [SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 Korea; Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208 USA; School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746 Korea

    2016-03-22

    Low-voltage complementary circuits comprising n-type and p-type van der Waals heterojunction vertical field-effect transistors (VFETs) are demonstrated. The resulting VFETs possess high on-state current densities (>3000 A cm-2) and on/off current ratios (>104) in a narrow voltage window (<3 V).

  4. The van der Waals Equation of State and the Law of Corresponding States: A Spreadsheet Experiment

    NARCIS (Netherlands)

    Schaink, H.M.; Venema, P.

    2007-01-01

    In normal physical chemistry courses the student is told how the van der Waals equation works. The mathematics needed for making a Maxwell construction is difficult for the average chemistry student. This makes it difficult to show how the liquid-gas digram is obtained from the equation of state.

  5. Lithium ions in the van der Waals gap of Bi2Se3 single crystals

    Czech Academy of Sciences Publication Activity Database

    Bludská, Jana; Jakubec, Ivo; Karamazov, S.; Horák, Jaromír; Uher, C.

    2010-01-01

    Roč. 183, č. 12 (2010), s. 2813-2817 ISSN 0022-4596 Institutional research plan: CEZ:AV0Z40320502 Keywords : intercalation * van Der Waals gap * Bi2Se3 crystals Subject RIV: CG - Electrochemistry Impact factor: 2.261, year: 2010

  6. Van der Waals coefficients for alkali metal clusters and their size ...

    Indian Academy of Sciences (India)

    . 1000 atoms) easily, thereby allowing us to study the evolution of van der Waals coefficients with the size of the clusters. For details of the ETF method and its application to study alkali–metal cluster, we refer the reader to [9,10,27–29]. In the.

  7. Field Effect in Graphene-Based van der Waals Heterostructures: Stacking Sequence Matters

    DEFF Research Database (Denmark)

    Stradi, Daniele; Papior, Nick Rübner; Hansen, Ole

    2017-01-01

    Stacked van der Waals (vdW) heterostructures where semiconducting two-dimensional (2D) materials are contacted by overlaid graphene electrodes enable atomically thin, flexible electronics. We use first-principles quantum transport simulations of graphene-contacted MoS2 devices to show how the tra...

  8. Van der Waals coefficients for alkali metal clusters and their size

    Indian Academy of Sciences (India)

    In this paper we employ the hydrodynamic formulation of time-dependent density functional theory to obtain the van der Waals coefficients 6 and 8 of alkali metal clusters of various sizes including very large clusters. Such calculations become computationally very demanding in the orbital-based Kohn-Sham formalism, ...

  9. Density functional for van der Waals forces accounts for hydrogen bond in benchmark set of water hexamers

    DEFF Research Database (Denmark)

    Kelkkanen, Kari André; Lundqvist, Bengt; Nørskov, Jens Kehlet

    2009-01-01

    A recent extensive study has investigated how various exchange-correlation (XC) functionals treat hydrogen bonds in water hexamers and has shown traditional generalized gradient approximation and hybrid functionals used in density-functional (DF) theory to give the wrong dissociation-energy trend...... of low-lying isomers and van der Waals (vdW) dispersion forces to give key contributions to the dissociation energy. The question raised whether functionals that incorporate vdW forces implicitly into the XC functional predict the correct lowest-energy structure for the water hexamer and yield accurate...

  10. Quantum electrodynamics based on self-energy, without second quantization: The Lamb shift and long-range Casimir-Polder van der Waals forces near boundaries

    International Nuclear Information System (INIS)

    Barut, A.O.; Dowling, J.P.

    1986-12-01

    Using a previously formulated theory of quantum electrodynamics based on self-energy, we give a general method for computing the Lamb shift and related Casimir-Polder energies for a quantum system in the vicinity of perfectly conducting boundaries. Our results are exact and easily extendable to a full covariant relativistic form. As a particular example we apply the method to an atom near an infinite conducting plane, and we recover the standard QED results (which are known only in the dipole approximation) in a simple and straightforward manner. This is accomplished in the context of the new theory which is not second quantized and contains no vacuum fluctuations. (author)

  11. The role of van der Waals interactions in the adsorption of noble gases on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Chen, De-Li; Al-Saidi, W A; Johnson, J Karl

    2012-10-03

    Adsorption of noble gases on metal surfaces is determined by weak interactions. We applied two versions of the nonlocal van der Waals density functional (vdW-DF) to compute adsorption energies of Ar, Kr, and Xe on Pt(111), Pd(111), Cu(111), and Cu(110) metal surfaces. We have compared our results with data obtained using other density functional approaches, including the semiempirical vdW corrected DFT-D2. The vdW-DF results show considerable improvements in the description of adsorption energies and equilibrium distances over other DFTbased methods, giving good agreement with experiments. We have also calculated perpendicular vibrational energies for noble gases on the metal surfaces using vdWDF data and found excellent agreement with available experimental results. Our vdW-DF calculations show that adsorption of noble gases on low-coordination sites is energetically favored over high-coordination sites, but only by a few meV. Analysis of the 2-dimensional potential energy surface shows that the high-coordination sites are local maxima on the 2-dimensional potential energy surface and therefore unlikely to be observed in experiments, which provides an explanation of the experimental observations. The DFT-D2 approach with the standard parameterization was found to overestimate the dispersion interactions, and to give the wrong adsorption site preference for four of the nine systems we studied.

  12. Evaluation of a density functional with account of van der Waals forces using experimental data of H2 physisorption on Cu(111)

    DEFF Research Database (Denmark)

    Lee, Kyuho; Kelkkanen, Kari André; Berland, Kristian

    2011-01-01

    Detailed experimental data for physisorption potential-energy curves of H2 on low-indexed faces of Cu challenge theory. Recently, density-functional theory has been developed to also account for nonlocal correlation effects, including van der Waals forces. We show that one functional, denoted vd...

  13. Signatures of van der Waals binding: A coupling-constant scaling analysis

    Science.gov (United States)

    Jiao, Yang; Schröder, Elsebeth; Hyldgaard, Per

    2018-02-01

    The van der Waals (vdW) density functional (vdW-DF) method [Rep. Prog. Phys. 78, 066501 (2015), 10.1088/0034-4885/78/6/066501] describes dispersion or vdW binding by tracking the effects of an electrodynamic coupling among pairs of electrons and their associated exchange-correlation holes. This is done in a nonlocal-correlation energy term Ecnl, which permits density functional theory calculation in the Kohn-Sham scheme. However, to map the nature of vdW forces in a fully interacting materials system, it is necessary to also account for associated kinetic-correlation energy effects. Here, we present a coupling-constant scaling analysis, which permits us to compute the kinetic-correlation energy Tcnl that is specific to the vdW-DF account of nonlocal correlations. We thus provide a more complete spatially resolved analysis of the electrodynamical-coupling nature of nonlocal-correlation binding, including vdW attraction, in both covalently and noncovalently bonded systems. We find that kinetic-correlation energy effects play a significant role in the account of vdW or dispersion interactions among molecules. Furthermore, our mapping shows that the total nonlocal-correlation binding is concentrated to pockets in the sparse electron distribution located between the material fragments.

  14. Versatile van der Waals Density Functional Based on a Meta-Generalized Gradient Approximation

    Directory of Open Access Journals (Sweden)

    Haowei Peng

    2016-10-01

    Full Text Available A “best-of-both-worlds” van der Waals (vdW density functional is constructed, seamlessly supplementing the strongly constrained and appropriately normed (SCAN meta-generalized gradient approximation for short- and intermediate-range interactions with the long-range vdW interaction from rVV10, the revised Vydrov–van Voorhis nonlocal correlation functional. The resultant SCAN+rVV10 is the only vdW density functional to date that yields excellent interlayer binding energies and spacings, as well as intralayer lattice constants in 28 layered materials. Its versatility for various kinds of bonding is further demonstrated by its good performance for 22 interactions between molecules; the cohesive energies and lattice constants of 50 solids; the adsorption energy and distance of a benzene molecule on coinage-metal surfaces; the binding energy curves for graphene on Cu(111, Ni(111, and Co(0001 surfaces; and the rare-gas solids. We argue that a good semilocal approximation should (as SCAN does capture the intermediate-range vdW through its exchange term. We have found an effective range of the vdW interaction between 8 and 16 Å for systems considered here, suggesting that this interaction is negligibly small at the larger distances where it reaches its asymptotic power-law decay.

  15. Optoelectronic Properties of Van Der Waals Hybrid Structures: Fullerenes on Graphene Nanoribbons

    Science.gov (United States)

    Correa, Julián David; Orellana, Pedro Alejandro; Pacheco, Mónica

    2017-01-01

    The search for new optical materials capable of absorbing light in the frequency range from visible to near infrared is of great importance for applications in optoelectronic devices. In this paper, we report a theoretical study of the electronic and optical properties of hybrid structures composed of fullerenes adsorbed on graphene and on graphene nanoribbons. The calculations are performed in the framework of the density functional theory including the van der Waals dispersive interactions. We found that the adsorption of the C60 fullerenes on a graphene layer does not modify its low energy states, but it has strong consequences for its optical spectrum, introducing new absorption peaks in the visible energy region. The optical absorption of fullerenes and graphene nanoribbon composites shows a strong dependence on photon polarization and geometrical characteristics of the hybrid systems, covering a broad range of energies. We show that an external electric field across the nanoribbon edges can be used to tune different optical transitions coming from nanoribbon–fullerene hybridized states, which yields a very rich electro-absorption spectrum for longitudinally polarized photons. We have carried out a qualitative analysis on the potential of these hybrids as possible donor-acceptor systems in photovoltaic cells. PMID:28336904

  16. Optoelectronic Properties of Van Der Waals Hybrid Structures: Fullerenes on Graphene Nanoribbons.

    Science.gov (United States)

    Correa, Julián David; Orellana, Pedro Alejandro; Pacheco, Mónica

    2017-03-20

    The search for new optical materials capable of absorbing light in the frequency range from visible to near infrared is of great importance for applications in optoelectronic devices. In this paper, we report a theoretical study of the electronic and optical properties of hybrid structures composed of fullerenes adsorbed on graphene and on graphene nanoribbons. The calculations are performed in the framework of the density functional theory including the van der Waals dispersive interactions. We found that the adsorption of the C 60 fullerenes on a graphene layer does not modify its low energy states, but it has strong consequences for its optical spectrum, introducing new absorption peaks in the visible energy region. The optical absorption of fullerenes and graphene nanoribbon composites shows a strong dependence on photon polarization and geometrical characteristics of the hybrid systems, covering a broad range of energies. We show that an external electric field across the nanoribbon edges can be used to tune different optical transitions coming from nanoribbon-fullerene hybridized states, which yields a very rich electro-absorption spectrum for longitudinally polarized photons. We have carried out a qualitative analysis on the potential of these hybrids as possible donor-acceptor systems in photovoltaic cells.

  17. Optoelectronic Properties of Van Der Waals Hybrid Structures: Fullerenes on Graphene Nanoribbons

    Directory of Open Access Journals (Sweden)

    Julián David Correa

    2017-03-01

    Full Text Available The search for new optical materials capable of absorbing light in the frequency range from visible to near infrared is of great importance for applications in optoelectronic devices. In this paper, we report a theoretical study of the electronic and optical properties of hybrid structures composed of fullerenes adsorbed on graphene and on graphene nanoribbons. The calculations are performed in the framework of the density functional theory including the van der Waals dispersive interactions. We found that the adsorption of the C 60 fullerenes on a graphene layer does not modify its low energy states, but it has strong consequences for its optical spectrum, introducing new absorption peaks in the visible energy region. The optical absorption of fullerenes and graphene nanoribbon composites shows a strong dependence on photon polarization and geometrical characteristics of the hybrid systems, covering a broad range of energies. We show that an external electric field across the nanoribbon edges can be used to tune different optical transitions coming from nanoribbon–fullerene hybridized states, which yields a very rich electro-absorption spectrum for longitudinally polarized photons. We have carried out a qualitative analysis on the potential of these hybrids as possible donor-acceptor systems in photovoltaic cells.

  18. Nature and strength of bonding in a crystal of semiconducting nanotubes: van der Waals density functional calculations and analytical results

    DEFF Research Database (Denmark)

    Kleis, Jesper; Schröder, Elsebeth; Hyldgaard, Per

    2008-01-01

    for the nanotube-crystal binding energy can be approximated by a sum of nanotube-pair interactions when these are calculated in vdW-DR This observation suggests a framework for an efficient implementation of quantum-physical modeling of the carbon nanotube bundling in more general nanotube bundles, including...... nanotube yarn and rope structures.......The dispersive interaction between nanotubes is investigated through ab initio theory calculations and in an analytical approximation. A van der Waals density functional (vdW-DF) [M. Dion et al., Phys. Rev. Lett. 92, 246401 (2004)] is used to determine and compare the binding of a pair of nanotubes...

  19. Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure.

    Science.gov (United States)

    Hunt, B; Sanchez-Yamagishi, J D; Young, A F; Yankowitz, M; LeRoy, B J; Watanabe, K; Taniguchi, T; Moon, P; Koshino, M; Jarillo-Herrero, P; Ashoori, R C

    2013-06-21

    van der Waals heterostructures constitute a new class of artificial materials formed by stacking atomically thin planar crystals. We demonstrated band structure engineering in a van der Waals heterostructure composed of a monolayer graphene flake coupled to a rotationally aligned hexagonal boron nitride substrate. The spatially varying interlayer atomic registry results in both a local breaking of the carbon sublattice symmetry and a long-range moiré superlattice potential in the graphene. In our samples, this interplay between short- and long-wavelength effects resulted in a band structure described by isolated superlattice minibands and an unexpectedly large band gap at charge neutrality. This picture is confirmed by our observation of fractional quantum Hall states at ± 5/3 filling and features associated with the Hofstadter butterfly at ultrahigh magnetic fields.

  20. High External Quantum Efficiency in van der Waals Heterostructures for Ultrathin Photovoltaics

    Science.gov (United States)

    Wong, Joeson; Jariwala, Deep; Tat, Kevin; Tagliabue, Giulia; Davoyan, Artur; Sherrott, Michelle; Atwater, Harry

    High external radiative efficiency and high external quantum efficiency are prerequisites for an efficient photovoltaic cell. In transition metal dichalcogenides (TMDCs), previous work has demonstrated that near-unity external radiative efficiency is possible through superacid passivation. Yet, near-unity external quantum efficiency has remained elusive. In this work, we experimentally demonstrate that high external quantum efficiencies (>50%) are possible in vertical van der Waals heterostructures consisting of graphene, tungsten diselenide, and molybdenum disulfide, on metallic substrates. We achieve near-unity absorption in ultrathin (internal quantum efficiency, a measure of the carrier collection efficiency. Moreover, the internal quantum efficiency is shown to exhibit exciton resonances with peak efficiencies >70%. In summary, our results presented here will serve as design considerations and principles towards achieving near-unity external quantum efficiency in van der Waals materials.

  1. Bonding in Mercury-Alkali Molecules: Orbital-driven van der Waals Complexes

    Directory of Open Access Journals (Sweden)

    Dieter Cremer

    2008-06-01

    Full Text Available The bonding situation in mercury-alkali diatomics HgA (2Σ+ (A = Li, Na, K, Rb has been investigated employing the relativistic all-electron method Normalized Elimination of the Small Component (NESC, CCSD(T, and augmented VTZ basis sets. Although Hg,A interactions are typical of van der Waals complexes, trends in calculated De values can be explained on the basis of a 3-electron 2-orbital model utilizing calculated ionization potentials and the De values of HgA+(1Σ+ diatomics. HgA molecules are identified as orbital-driven van der Waals complexes. The relevance of results for the understanding of the properties of liquid alkali metal amalgams is discussed.

  2. Electrical and optical properties of SnS2/WSe2 van der Waals Heterojunction FETs

    Science.gov (United States)

    Zubair, Ahmad; Nourbakhsh, Amirhasan; Dresselhaus, Mildred; Palacios, Tomas

    Two dimensional crystals based on atomically thin films of transition metal dichalcogenides offer an exciting platform for various optoelectronic applications. Their unique crystal properties make them particularly attractive for van der Waals heterostructures which open up an additional degree of freedom to tailor the material properties into new physics and device applications. In this work, we explore, for the first time, the optoelectronic properties of van der Waals SnS2/WSe2 heterojunction. WSe2 is an ambipolar semiconductor while SnS2 is an n-type wide bandgap semiconductor. We use the pickup and dry transfer methods to fabricate SnS2/WSe2 heterojunction transistors (hetero-FETs). We observe negative differential transconductance in the SnS2/WSe2 hetero-FET. Also, the heterostructure couples strongly to incident light and shows high photovoltaic responsivity which can find applications in nano-devices such as photo-detectors and solar cells.

  3. Holographic Van der Waals-like phase transition in the Gauss–Bonnet gravity

    Energy Technology Data Exchange (ETDEWEB)

    He, Song, E-mail: hesong17@gmail.com [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, 14476 Golm (Germany); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Li-Fang, E-mail: lilf@itp.ac.cn [Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Zeng, Xiao-Xiong, E-mail: xxzeng@itp.ac.cn [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Material Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China)

    2017-02-15

    The Van der Waals-like phase transition is observed in temperature–thermal entropy plane in spherically symmetric charged Gauss–Bonnet–AdS black hole background. In terms of AdS/CFT, the non-local observables such as holographic entanglement entropy, Wilson loop, and two point correlation function of very heavy operators in the field theory dual to spherically symmetric charged Gauss–Bonnet–AdS black hole have been investigated. All of them exhibit the Van der Waals-like phase transition for a fixed charge parameter or Gauss–Bonnet parameter in such gravity background. Further, with choosing various values of charge or Gauss–Bonnet parameter, the equal area law and the critical exponent of the heat capacity are found to be consistent with phase structures in temperature–thermal entropy plane.

  4. Polymorphism and thermodynamic ground state of Silver fulminate studied from van der Waals density functional calculations

    OpenAIRE

    Yedukondalu, N.; Vaitheeswaran, G.

    2014-01-01

    Silver fulminate (AgCNO) is a primary explosive, which exists in two polymorphic phases namely orthorhombic (\\emph{Cmcm}) and trigonal (\\emph{R$\\bar{3}$}) forms at ambient conditions. In the present study, we have investigated the effect of pressure and temperature on relative phase stability of the polymorphs using planewave pseudopotential approaches based on Density Functional Theory (DFT). van der Waals interactions play a significant role in predicting the phase stability and they can be...

  5. Dynamic anomalies at the glass transition of the van der Waals glass tri-α-naphthylbenzene

    International Nuclear Information System (INIS)

    Bartsch, E.; Debus, O.; Fujara, F.; Kiebel, M.; Sillescu, H.; Petry, W.; Magill, J.H.

    1992-01-01

    The Debye-Waller factor of the van der Waals glass tri-α-naphthylbenzene, measured by high resolution incoherent quasielastic neutron scattering, shows a cusp at Tc = 407 ± 5 K signaling the existence of a critical instability as has been predicted by mode coupling theory to occur in supercooled glass forming liquids. At temperatures above Tc structural relaxation is observed to obey the time-temperature superposition principle. (orig.)

  6. Van der Waals bond in dimers: H2Ne, H2Ar, H2Kr

    International Nuclear Information System (INIS)

    Waaijer, M.

    1981-01-01

    The H 2 -inert gas dimers H 2 X, and particularly H 2 Ne, H 2 Ar and H 2 Kr, form the subject of this thesis and are loosely bound van der Waals complexes, which is reflected in the low number of bound states and the small anisotropic interaction. The H 2 X dimers studied are formed in a supersonic nozzle expansion, in which the internal energy is converted into the macroscopic flow energy, establishing an internal temperature drop to 3 K, which favours dimer formation. Because of this cooling the H 2 X dimers relax to the lowest rotational states. The hyperfine transitions have been measured using magnetic beam resonance and yield information about the isotropic as well as the anisotropic intermolecular potential in the range between the classical turning points and in the adjacent part of the repulsive branch. The sensitivity of the method is very high and slight changes in the intermolecular potential cause significant effects. The analysis of the measured hyperfine transitions incorporates all interacting states of the molecule, bound as well as unbound (continuum) states. For H 2 Ne, which is the best studied H 2 -inert gas system from the experimental point of view, the author succeeded in establishing an intermolecular potential, that provides a solid ground for comparison with future ab initio calculations. (Auth.)

  7. CO2 adsorption on the copper surfaces: van der Waals density functional and TPD studies

    Science.gov (United States)

    Muttaqien, Fahdzi; Hamamoto, Yuji; Hamada, Ikutaro; Inagaki, Kouji; Shiozawa, Yuichiro; Mukai, Kozo; Koitaya, Takanori; Yoshimoto, Shinya; Yoshinobu, Jun; Morikawa, Yoshitada

    2017-09-01

    We investigated the adsorption of CO2 on the flat, stepped, and kinked copper surfaces from density functional theory calculations as well as the temperature programmed desorption and X-ray photoelectron spectroscopy. Several exchange-correlation functionals have been considered to characterize CO2 adsorption on the copper surfaces. We used the van der Waals density functionals (vdW-DFs), i.e., the original vdW-DF (vdW-DF1), optB86b-vdW, and rev-vdW-DF2, as well as the Perdew-Burke-Ernzerhof (PBE) with dispersion correction (PBE-D2). We have found that vdW-DF1 and rev-vdW-DF2 functionals slightly underestimate the adsorption energy, while PBE-D2 and optB86b-vdW functionals give better agreement with the experimental estimation for CO2 on Cu(111). The calculated CO2 adsorption energies on the flat, stepped, and kinked Cu surfaces are 20-27 kJ/mol, which are compatible with the general notion of physisorbed species on solid surfaces. Our results provide a useful insight into appropriate vdW functionals for further investigation of related CO2 activation on Cu surfaces such as methanol synthesis and higher alcohol production.

  8. Fragmentation of neutral van der Waals clusters with visible laser light: A new variant of the Raman effect?

    International Nuclear Information System (INIS)

    Stamatovic, A.; Howorka, F.; Scheier, P.; Maerk, T.D.

    1989-01-01

    We have observed strong photodissociation (using visible laser light) of neutral van der Waals clusters (Ar, N 2 , O 2 , CO 2 , SO 2 , NH 3 ) produced by supersonic expansion and detected by electron ionization/mass spectrometer. Several tests were performed, all of them supporting this surprising discovery. We suggest that Raman induced photodissociation (RIP) is responsible for this phenomenon. This first observation of Raman induced photodissociation provides a new technique for the study of neutral van der Waals clusters. (orig.)

  9. van der Waals epitaxial ZnTe thin film on single-crystalline graphene

    Science.gov (United States)

    Sun, Xin; Chen, Zhizhong; Wang, Yiping; Lu, Zonghuan; Shi, Jian; Washington, Morris; Lu, Toh-Ming

    2018-01-01

    Graphene template has long been promoted as a promising host to support van der Waals flexible electronics. However, van der Waals epitaxial growth of conventional semiconductors in planar thin film form on transferred graphene sheets is challenging because the nucleation rate of film species on graphene is significantly low due to the passive surface of graphene. In this work, we demonstrate the epitaxy of zinc-blende ZnTe thin film on single-crystalline graphene supported by an amorphous glass substrate. Given the amorphous nature and no obvious remote epitaxy effect of the glass substrate, this study clearly proves the van der Waals epitaxy of a 3D semiconductor thin film on graphene. X-ray pole figure analysis reveals the existence of two ZnTe epitaxial orientational domains on graphene, a strong X-ray intensity observed from the ZnTe [ 1 ¯ 1 ¯ 2] ǁ graphene [10] orientation domain, and a weaker intensity from the ZnTe [ 1 ¯ 1 ¯ 2] ǁ graphene [11] orientation domain. Furthermore, this study systematically investigates the optoelectronic properties of this epitaxial ZnTe film on graphene using temperature-dependent Raman spectroscopy, steady-state and time-resolved photoluminescence spectroscopy, and fabrication and characterization of a ZnTe-graphene photodetector. The research suggests an effective approach towards graphene-templated flexible electronics.

  10. Accurate van der Waals force field for gas adsorption in porous materials.

    Science.gov (United States)

    Sun, Lei; Yang, Li; Zhang, Ya-Dong; Shi, Qi; Lu, Rui-Feng; Deng, Wei-Qiao

    2017-09-05

    An accurate van der Waals force field (VDW FF) was derived from highly precise quantum mechanical (QM) calculations. Small molecular clusters were used to explore van der Waals interactions between gas molecules and porous materials. The parameters of the accurate van der Waals force field were determined by QM calculations. To validate the force field, the prediction results from the VDW FF were compared with standard FFs, such as UFF, Dreiding, Pcff, and Compass. The results from the VDW FF were in excellent agreement with the experimental measurements. This force field can be applied to the prediction of the gas density (H 2 , CO 2 , C 2 H 4 , CH 4 , N 2 , O 2 ) and adsorption performance inside porous materials, such as covalent organic frameworks (COFs), zeolites and metal organic frameworks (MOFs), consisting of H, B, N, C, O, S, Si, Al, Zn, Mg, Ni, and Co. This work provides a solid basis for studying gas adsorption in porous materials. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  11. Underwater adhesion of abalone: The role of van der Waals and capillary forces

    International Nuclear Information System (INIS)

    Lin, A.Y.M.; Brunner, R.; Chen, P.Y.; Talke, F.E.; Meyers, M.A.

    2009-01-01

    The observation of the pedal foot of the red abalone Haliotis rufescens reveals the presence of micrometer-scaled setae terminating in nanometer-sized cylindrical fibrils, with some resemblance to those found on the gecko foot. Atomic force microscopy (AFM) pull-off force measurements on a single seta are compared with theoretical estimates for van der Waals attraction obtained through the Johnson-Kendall-Roberts (JKR) equation, approximately 600 nN, and show agreement. The use of the JKR equation is justified through an analysis of the shape of the fibril extremities (parabolic) as well as their diameter (∼200 nm). Measurements under varying humidity conditions indicate that additional capillary interactions play a role, since the pull-off force increases with humidity. It is proposed that both van der Waals and capillary forces play a role in the attachment mechanism of H. rufescens, effectively enabling suction to reach its theoretical limit. Bulk pull-off force measurements on entire live animals yield an average detachment stress of 115 kPa, consistent with theoretical estimates. The setae and nanoscale fibril terminations enable compliance to surfaces with a variety of roughnesses, effectively sealing the interface, in addition to providing capillary and van der Waals forces.

  12. Defect mediated van der Waals epitaxy of hexagonal boron nitride on graphene

    Science.gov (United States)

    Heilmann, M.; Bashouti, M.; Riechert, H.; Lopes, J. M. J.

    2018-04-01

    Van der Waals heterostructures comprising of hexagonal boron nitride and graphene are promising building blocks for novel two-dimensional devices such as atomically thin transistors or capacitors. However, demonstrators of those devices have been so far mostly fabricated by mechanical assembly, a non-scalable and time-consuming method, where transfer processes can contaminate the surfaces. Here, we investigate a direct growth process for the fabrication of insulating hexagonal boron nitride on high quality epitaxial graphene using plasma assisted molecular beam epitaxy. Samples were grown at varying temperatures and times and studied using atomic force microscopy, revealing a growth process limited by desorption at high temperatures. Nucleation was mostly commencing from morphological defects in epitaxial graphene, such as step edges or wrinkles. Raman spectroscopy combined with x-ray photoelectron measurements confirm the formation of hexagonal boron nitride and prove the resilience of graphene against the nitrogen plasma used during the growth process. The electrical properties and defects in the heterostructures were studied with high lateral resolution by tunneling current and Kelvin probe force measurements. This correlated approach revealed a nucleation apart from morphological defects in epitaxial graphene, which is mediated by point defects. The presented results help understanding the nucleation and growth behavior during van der Waals epitaxy of 2D materials, and point out a route for a scalable production of van der Waals heterostructures.

  13. Comparative DFT study of van der Waals complexes: rare-gas dimers, alkaline-earth dimers, zinc dimer, and zinc-rare-gas dimers.

    Science.gov (United States)

    Zhao, Yan; Truhlar, Donald G

    2006-04-20

    Recent interest in the application of density functional theory prompted us to test various functionals for the van der Waals interactions in the rare-gas dimers, the alkaline-earth metal dimers, zinc dimer, and zinc-rare-gas dimers. In the present study, we report such tests for 18 DFT functionals, including both some very recent functionals and some well-established older ones. We draw the following conclusions based on the mean errors in binding energies and complex geometries: (1) B97-1 gives the best performance for predicting the geometry of rare-gas dimers, whereas M05-2X and B97-1 give the best energetics for rare-gas dimers. (2) PWB6K gives the best performance for the prediction of the geometry of the alkaline-earth metal dimers, zinc dimers, and zinc-rare-gas dimers. M05-2X gives the best energetics for the metal dimers, whereas B97-1 gives the best energetics for the zinc-rare-gas dimers. (3) The M05 functional is unique in providing good accuracy for both covalent transition-metal dimers and van der Waals metal dimers. (4) The combined mean percentage unsigned error in geometries and energetics shows that M05-2X and MPWB1K are the overall best methods for the prediction of van der Waals interactions in metal and rare-gas van der Waals dimers.

  14. Tunable quasiparticle band gap in few-layer GaSe/graphene van der Waals heterostructures

    Science.gov (United States)

    Ben Aziza, Zeineb; Pierucci, Debora; Henck, Hugo; Silly, Mathieu G.; David, Christophe; Yoon, Mina; Sirotti, Fausto; Xiao, Kai; Eddrief, Mahmoud; Girard, Jean-Christophe; Ouerghi, Abdelkarim

    2017-07-01

    Two-dimensional (2D) materials have recently been the focus of extensive research. By following a similar trend as graphene, other 2D materials, including transition metal dichalcogenides (M X2 ) and metal mono-chalcogenides (MX), show great potential for ultrathin nanoelectronic and optoelectronic devices. Despite the weak nature of interlayer forces in semiconducting MX materials, their electronic properties are highly dependent on the number of layers. Using scanning tunneling microscopy and spectroscopy, we demonstrate the tunability of the quasiparticle energy gap of few-layered gallium selenide (GaSe) directly grown on a bilayer graphene substrate by molecular beam epitaxy. Our results show that the band gap is about 3.50 ± 0.05 eV for single-tetralayer, 3.00 ±0.05 eV for bi-tetralayer, and 2.30 ±0.05 eV for tri-tetralayer GaSe. This band-gap evolution of GaSe, particularly the shift of the valence band with respect to the Fermi level, was confirmed by angle-resolved photoemission spectroscopy (ARPES) measurements and our theoretical calculations. Moreover, we observed a charge transfer in the GaSe/graphene van der Waals (vdW) heterostructure using ARPES. These findings demonstrate the high impact on the GaSe electronic band structure and electronic properties that can be obtained by the control of 2D materials layer thickness and the graphene induced doping.

  15. Ab initio study of the Br(2P)-HBr van der Waals complex.

    Science.gov (United States)

    Toboła, R; Chałasiński, G; Kłos, J; Szcześniak, M M

    2009-05-14

    This study reports an ab initio characterization of a prereactive van der Waals complex between an open-shell atom Br((2)P) and a closed shell molecule HBr. The three adiabatic potential surfaces 1 (2)A('), 2 (2)A('), and 1 (2)A("), which result from the splitting of degenerate P state of Br are obtained from coupled cluster calculations. The coupling between same-symmetry states is calculated by multireference configuration-interaction method. A transformation to a diabatic representation and inclusion of the spin-orbit coupling effects on the interactions are also discussed. Bound states are calculated using an adiabatic bender model. The global minimum on the lowest adiabatic potential surface corresponds to a T-shaped geometry and has a well depth of D(e)=762.5 cm(-1) at R(e)=3.22 A. A secondary minimum occurs for a hydrogen-bonded geometry with D(e)=445.3 cm(-1) at R(e)=4.24 A. Upon inclusion of spin-orbit coupling the hydrogen-bonded minimum remains at the same depth, but the T-shaped minimum washes out to less than half of its spin-free value. The lowest bound state is localized in the linear minimum. The spin-orbit coupling plays a very important role in shaping of the potential energy surfaces of Br-HBr.

  16. Theoretical Study of the Pyridine-Helium van der Waals Complexes

    DEFF Research Database (Denmark)

    v, Hubert; Henriksen, Christian; Fernandez, Berta

    2015-01-01

    In this study we evaluate a high-level ab initio ground-state intermolecular potential-energy surface for the pyridine–He van der Waals complex, using the CCSD(T) method and Dunning’s augmented correlation consistent polarized valence double-ζ basis set extended with a set of 3s3p2d1f1g midbond...... functions. The potential is characterized by two symmetric global minima of −93.2 cm–1 that correspond to geometries where the distance between the helium atom and the pyridine center of mass is 3.105 Å and the angle with respect to the pyridine c rotational axis is 3.9°. Six local minima can be observed...... for geometries with the helium atom in the plane cotaining the pyridine molecule. To further analyze the nature of the intermolecular interactions in the complex, we use symmetry-adapted perturbation theory (SAPT). Additional consideration of the pyridine–He2 complex provides a better insight into many...

  17. Van der Waals-like behaviour of charged black holes and hysteresis in the dual QFTs

    Directory of Open Access Journals (Sweden)

    Mariano Cadoni

    2017-05-01

    Full Text Available Using the rules of the AdS/CFT correspondence, we compute the spherical analogue of the shear viscosity, defined in terms of the retarded Green function for the stress-energy tensor for QFTs dual to five-dimensional charged black holes of general relativity with a negative cosmological constant. We show that the ratio between this quantity and the entropy density, η˜/s, exhibits a temperature-dependent hysteresis. We argue that this hysteretic behaviour can be explained by the Van der Waals-like character of charged black holes, considered as thermodynamical systems. Under the critical charge, hysteresis emerges owing to the presence of two stable states (small and large black holes connected by a meta-stable region (intermediate black holes. A potential barrier prevents the equilibrium path between the two stable states; the system evolution must occur through the meta-stable region, and a path-dependence of η˜/s is generated.

  18. Size-tunable band alignment and optoelectronic properties of transition metal dichalcogenide van der Waals heterostructures

    Science.gov (United States)

    Zhao, Yipeng; Yu, Wangbing; Ouyang, Gang

    2018-01-01

    2D transition metal dichalcogenide (TMDC)-based heterostructures exhibit several fascinating properties that can address the emerging market of energy conversion and storage devices. Current achievements show that the vertical stacked TMDC heterostructures can form type II band alignment and possess significant optoelectronic properties. However, a detailed analytical understanding of how to quantify the band alignment and band offset as well as the optimized power conversion efficiency (PCE) is still lacking. Herein, we propose an analytical model to exhibit the PCEs of TMDC van der Waals (vdW) heterostructures and explore the intrinsic mechanism of photovoltaic conversion based on the detailed balance principle and atomic-bond-relaxation correlation mechanism. We find that the PCE of monolayer MoS2/WSe2 can be up to 1.70%, and that of the MoS2/WSe2 vdW heterostructures increases with thickness, owing to increasing optical absorption. Moreover, the results are validated by comparing them with the available evidence, providing realistic efficiency targets and design principles. Highlights • Both electronic and optoelectronic models are developed for vertical stacked MoS2/WSe2 heterostructures. • The underlying mechanism on size effect of electronic and optoelectronic properties for vertical stacked MoS2/WSe2 heterostructures is clarified. • The macroscopically measurable quantities and the microscopical bond identities are connected.

  19. Sliding Dynamics of Parallel Graphene Sheets: Effect of Geometry and Van Der Waals Interactions on Nano-Spring Behavior

    Directory of Open Access Journals (Sweden)

    Alessandro Crisafulli

    2018-03-01

    Full Text Available Graphene and carbon nanotubes are promising materials for nanoelectromechanical systems. Among other aspects, a proper understanding of the sliding dynamics of parallel graphene sheets or concentric nanotubes is of crucial importance for the design of nano-springs. Here, we analytically investigate the sliding dynamics between two parallel, rigid graphene sheets. In particular, the analysis focuses on configurations in which the distance between the sheets is kept constant and lower than the equilibrium interlayer spacing of graphite (unstable configurations. The aim is to understand how the interlayer force due to van der Waals interactions along the sliding direction changes with the geometrical characteristics of the configuration, namely size and interlayer spacing. Results show metastable equilibrium positions with completely faced sheets, namely a null force along the sliding direction, whereas net negative/positive forces arise when the sheets are approaching/leaving each other. This behavior resembles a molecular spring, being able to convert kinetic into potential energy (van der Waals potential, and viceversa. The amplitude of both storable energy and entrance/exit forces is found to be proportional to the sheet size, and inversely proportional to their interlayer spacing. This model could also be generalized to describe the behavior of configurations made of concentric carbon nanotubes, therefore allowing a rational design of some elements of carbon-based nanoelectromechanical systems.

  20. A review on data and predictions of water dielectric spectra for calculations of van der Waals surface forces.

    Science.gov (United States)

    Wang, Jianlong; Nguyen, Anh V

    2017-12-01

    Van der Waals forces are one of the important components of intermolecular, colloidal and surface forces governing many phenomena and processes. The latest examples include the colloidal interactions between hydrophobic colloids and interfaces in ambient (non-degassed) water in which dissolved gases and nanobubbles are shown to affect the van der Waals attractions significantly. The advanced computation of van der Waals forces in aqueous systems by the Lifshitz theory requires reliable data for water dielectric spectra. In this paper we review the available predictions of water dielectric spectra for calculating colloidal and surface van der Waals forces. Specifically, the available experimental data for the real and imaginary parts of the complex dielectric function of liquid water in the microwave, IR and UV regions and various corresponding predictions of the water spectra are critically reviewed. The data in the UV region are critical, but the available predictions are still based on the outdated data obtained in 1974 (for frequency only up to 25.5eV). We also reviewed and analysed the experimental data obtained for the UV region in 2000 (for frequency up to 50eV) and 2015 (for frequency up to 100eV). The 1974 and 2000 data require extrapolations to higher frequencies needed for calculating the van der Waals forces but remain inaccurate. Our analysis shows that the latest data of 2015 do not require the extrapolation and can be used to reliably calculate van der Waals forces. The most recent water dielectric spectra gives the (non-retarded) Hamaker constant, A=5.20×10 -20 J, for foam films of liquid water. This review provides the most updated and reliable water dielectric spectra to compute van der Waals forces in aqueous systems. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Nucleotide insertion initiated by van der Waals interaction during ...

    Indian Academy of Sciences (India)

    play any role for an obvious reason, but holes (positive charge carriers) can play a vital role in biomolecules as proven experimentally by Fujitsuka and Majima17 with respect to charge transfer in DNA. There are two formal proofs for the ionization energy approxima- tion. The first one is indirect and reads, HIET. (r,t) =.

  2. Origin of the size-dependence of the equilibrium van der Waals binding between nanostructures

    Science.gov (United States)

    Tao, Jianmin; Perdew, John P.; Tang, Hong; Shahi, Chandra

    2018-02-01

    Nanostructures can be bound together at equilibrium by the van der Waals (vdW) effect, a small but ubiquitous many-body attraction that presents challenges to density functional theory. How does the binding energy depend upon the size or number of atoms in one of a pair of identical nanostructures? To answer this question, we treat each nanostructure as a whole object, not as a collection of atoms. Our calculations start from an accurate static dipole polarizability for each considered nanostructure, and an accurate equilibrium center-to-center distance for the pair (the latter from experiment or from the vdW-DF-cx functional). We consider the competition in each term -C2k/d2k (k = 3, 4, 5) of the long-range vdW series for the interaction energy, between the size dependence of the vdW coefficient C2k and that of the 2kth power of the center-to-center distance d. The damping of these vdW terms can be negligible, but in any case, it does not affect the size dependence for a given term in the absence of non-vdW binding. To our surprise, the vdW energy can be size-independent for quasi-spherical nanoclusters bound to one another by vdW interaction, even with strong nonadditivity of the vdW coefficient, as demonstrated for fullerenes. We also show that, for low-dimensional systems, the vdW interaction yields the strongest size-dependence, in stark contrast to that of fullerenes. We illustrate this with parallel planar polycyclic aromatic hydrocarbons. The size dependences of other morphologies or bonding types lie between, as shown by sodium clusters.

  3. Van der Waals Epitaxy of GaSe/Graphene Heterostructure: Electronic and Interfacial Properties.

    Science.gov (United States)

    Ben Aziza, Zeineb; Henck, Hugo; Pierucci, Debora; Silly, Mathieu G; Lhuillier, Emmanuel; Patriarche, Gilles; Sirotti, Fausto; Eddrief, Mahmoud; Ouerghi, Abdelkarim

    2016-10-07

    Stacking two-dimensional materials in so-called van der Waals (vdW) heterostructures, like the combination of GaSe and graphene, provides the ability to obtain hybrid systems which are suitable to design optoelectronic devices. Here, we report the structural and electronic properties of the direct growth of multilayered GaSe by Molecular beam Epitaxy (MBE) on graphene. Reflection high-energy electron diffraction (RHEED) images exhibited sharp streaky features indicative of high quality GaSe layer produced via a vdW epitaxy. Micro-Raman spectroscopy showed that, after the vdW hetero-interface formation, the Raman signature of pristine graphene is preserved. However, the GaSe film tuned the charge density of graphene layer by shifting the Dirac point by about 80 meV toward lower binding energies, attesting an electron transfer from graphene to GaSe. Angle-resolved photoemission spectroscopy (ARPES) measurements showed that the maximum of the valence band of few layers of GaSe are located at the Γ point at a binding energy of about -0.73 eV relatively to the Fermi level (p-type doping). From the ARPES measurements, a hole effective mass defined along the ΓM direction and equal to about m*/m0 = -1.1 was determined. By coupling the ARPES data with high resolution X-ray photoemission spectroscopy (HR-XPS) measurements, the Schottky interface barrier height was estimated to be 1.2 eV. These findings allow deeper understanding of the interlayer interactions and the electronic structure of GaSe/graphene vdW heterostructure.

  4. Origin of the size-dependence of the equilibrium van der Waals binding between nanostructures.

    Science.gov (United States)

    Tao, Jianmin; Perdew, John P; Tang, Hong; Shahi, Chandra

    2018-02-21

    Nanostructures can be bound together at equilibrium by the van der Waals (vdW) effect, a small but ubiquitous many-body attraction that presents challenges to density functional theory. How does the binding energy depend upon the size or number of atoms in one of a pair of identical nanostructures? To answer this question, we treat each nanostructure as a whole object, not as a collection of atoms. Our calculations start from an accurate static dipole polarizability for each considered nanostructure, and an accurate equilibrium center-to-center distance for the pair (the latter from experiment or from the vdW-DF-cx functional). We consider the competition in each term -C 2k /d 2k (k = 3, 4, 5) of the long-range vdW series for the interaction energy, between the size dependence of the vdW coefficient C 2k and that of the 2kth power of the center-to-center distance d. The damping of these vdW terms can be negligible, but in any case, it does not affect the size dependence for a given term in the absence of non-vdW binding. To our surprise, the vdW energy can be size-independent for quasi-spherical nanoclusters bound to one another by vdW interaction, even with strong nonadditivity of the vdW coefficient, as demonstrated for fullerenes. We also show that, for low-dimensional systems, the vdW interaction yields the strongest size-dependence, in stark contrast to that of fullerenes. We illustrate this with parallel planar polycyclic aromatic hydrocarbons. The size dependences of other morphologies or bonding types lie between, as shown by sodium clusters.

  5. Multimodal Nonlinear Optical Imaging of MoS₂ and MoS₂-Based van der Waals Heterostructures.

    Science.gov (United States)

    Li, Dawei; Xiong, Wei; Jiang, Lijia; Xiao, Zhiyong; Golgir, Hossein Rabiee; Wang, Mengmeng; Huang, Xi; Zhou, Yunshen; Lin, Zhe; Song, Jingfeng; Ducharme, Stephen; Jiang, Lan; Silvain, Jean-Francois; Lu, Yongfeng

    2016-03-22

    van der Waals layered structures, notably the transitional metal dichalcogenides (TMDs) and TMD-based heterostructures, have recently attracted immense interest due to their unique physical properties and potential applications in electronics, optoelectronics, and energy harvesting. Despite the recent progress, it is still a challenge to perform comprehensive characterizations of critical properties of these layered structures, including crystal structures, chemical dynamics, and interlayer coupling, using a single characterization platform. In this study, we successfully developed a multimodal nonlinear optical imaging method to characterize these critical properties of molybdenum disulfide (MoS2) and MoS2-based heterostructures. Our results demonstrate that MoS2 layers exhibit strong four-wave mixing (FWM), sum-frequency generation (SFG), and second-harmonic generation (SHG) nonlinear optical characteristics. We believe this is the first observation of FWM and SFG from TMD layers. All three kinds of optical nonlinearities are sensitive to layer numbers, crystal orientation, and interlayer coupling. The combined and simultaneous SHG/SFG-FWM imaging not only is capable of rapid evaluation of crystal quality and precise determination of odd-even layers but also provides in situ monitoring of the chemical dynamics of thermal oxidation in MoS2 and interlayer coupling in MoS2-graphene heterostructures. This method has the advantages of versatility, high fidelity, easy operation, and fast imaging, enabling comprehensive characterization of van der Waals layered structures for fundamental research and practical applications.

  6. VUV spectroscopy of rare gas van der Waals dimers

    International Nuclear Information System (INIS)

    Dehmer, P.M.; Pratt, S.T.

    1982-01-01

    We have undertaken a systematic study of the photoionization spectra of the homonuclear and heteronuclear rare gas dimers in order to better understand the nature of the bonding in the Rydberg states adnd ions of these molecules. We have obtained results for Ar 2 , Kr 2 , Xe 2 , NeAr, NeKr, NeXe, ArKr, ArXe, and KrXe. Of the remaining dimer species (Ne 2 and the Herare gas dimers), only Ne 2 has been studied using photoionization mass spectrometry. The results of the present series of experiments provide information both on the excited states of the neutral dimers and on the ground and excited states of the dimer ions. Using the data obtained in these measurements, we are able to compile for the first time a nearly complete list of ground state dissociation energies for the homonuclear and heteronuclear rare gas dimer ions. Somewhat less complete results are obtained for the excited states of these species. The observed trends in binding energy provide an excellent example of the systematic changes that occur as a result of changes in atomic orbital energies, polarizability, and internuclear distance, and these trends can be explained qualitatively in terms of simple molecular orbital theory

  7. Excitons in van der Waals Heterostructures: A theoretical study

    DEFF Research Database (Denmark)

    Latini, Simone

    in a generalized hydrogenic model to compute exciton binding energies in isolated, supported, or encapsulated 2D semiconductors. The non-locality of the dielectric screening is inherently included in our method and we can successfully describe the non-hydrogenic Rydberg series of low-dimensional systems......)electronics devices, e.g. light emitting diodes, solar cells, ultra-fast photodetectors, transistors etc., have been successfully fabricated. It is well established that for isolated 2D semiconductors and vdWHs the optical response is governed by excitonic effects. While it is understood that the reduced amount...... limitations of standard ab-initio methods. In this thesis first-principles models that overcome the limitations of standard ab-initio techniques are developed for the description of dielectric, electronic and excitonic properties in isolated 2D materials and vdWHs. The main contribution is a multi...

  8. Silicene on MoS2: role of the van der Waals interaction

    KAUST Repository

    Jiajie Zhu,

    2015-10-13

    We demonstrate for silicene on MoS2 substrate the limitations of the predictive power of first principles calculations based on van der Waals density functional theory. Only the optB86b-vdW functional is found to give reasonable agreement with experimental results on structural properties, while for all other investigated functionals the interlayer interaction is underestimated or the charge redistribution at the interface is not described correctly so that the predicted electronic structure is qualitatively wrong. © 2015 IOP Publishing Ltd.

  9. Atomically thin resonant tunnel diodes built from synthetic van der Waals heterostructures

    KAUST Repository

    Lin, Yu-Chuan

    2015-06-19

    Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, atomically thin, multi-junction heterostructures by combining graphene with the monolayer transition-metal dichalcogenides: molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2). The realization of MoS2–WSe2–graphene and WSe2–MoS2–graphene heterostructures leads to resonant tunnelling in an atomically thin stack with spectrally narrow, room temperature negative differential resistance characteristics.

  10. Interlayer coupling effects on Schottky barrier in the arsenene-graphene van der Waals heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Congxin, E-mail: xiacongxin@htu.edu.cn; Xue, Bin; Wang, Tianxing; Peng, Yuting [Department of Physic, Henan Normal University, Xinxiang 453007 (China); Jia, Yu [School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China)

    2015-11-09

    The electronic characteristics of arsenene-graphene van der Waals (vdW) heterostructures are studied by using first-principles methods. The results show that a linear Dirac-like dispersion relation around the Fermi level can be quite well preserved in the vdW heterostructures. Moreover, the p-type Schottky barrier (0.18 eV) to n-type Schottky barrier (0.31 eV) transition occurs when the interlayer distance increases from 2.8 to 4.5 Å, which indicates that the Schottky barrier can be tuned effectively by the interlayer distance in the vdW heterostructures.

  11. Olefin-borane "van der Waals complexes": intermediates in frustrated Lewis pair addition reactions.

    Science.gov (United States)

    Zhao, Xiaoxi; Stephan, Douglas W

    2011-08-17

    The nature of the borane-olefin interactions that take place prior to frustrated Lewis pair addition reactions has been probed employing a Lewis acidic borane tethered to a vinyl group through an alkyl chain. (1)H{(19)F} HOESY spectral data obtained at -50 °C demonstrated the spatial proximity of the boryl and vinyl groups and computational data support the initial formation of a van der Waals borane-olefin complex. Such species serve as intermediates undergoing facile addition reactions with phosphine bases to afford cyclic zwitterionic products.

  12. Nucleon-nucleon interaction with quark exchanges and prediction to colour van der Waals potential

    International Nuclear Information System (INIS)

    Osman, A.

    1985-11-01

    The nucleon-nucleon interaction is considered by including the colour nucleon clusters. The nucleon-nucleon system is treated as a six-quark system. The obtained local potentials reduce the short-range repulsion. The resulted nucleon-nucleon potential by using a quark-quark potential well agrees with the central-force potentials. The phase shifts calculated by using these local potentials are in good agreement with those obtained from other methods. Introducing the quark-quark potential in the nucleon-nucleon interaction, leads to a colour van der Waals potential very strong compared with that predicted by experiments. (author)

  13. Spectroscopic Signatures for Interlayer Coupling in MoS2-WSe2 van der Waals Stacking

    Science.gov (United States)

    2014-09-07

    REPORT NUMBER 19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE NUMBER Pullickel Ajayan Ming -Hui Chiu, Ming -Yang Li, Wengjing Zhang, Wei-Ting Hsu, Wen...2014 C 2014 American Chemical Society Spectroscopic Signatures for Interlayer Coupling in MoS2WSe2 van der Waals Stacking Ming -Hui Chiu,†,X Ming -Yang...www.acsnano.org 9655 7. Jones, A. M.; Yu, H.; Ghimire, N. J.; Wu, S.; Aivazian, G.; Ross, J. S.; Zhao, B.; Yan, J.; Mandrus, D. G.; Xiao , D.; et al. Optical

  14. Multicomponent van der Waals equation of state: Applications in nuclear and hadronic physics

    Science.gov (United States)

    Vovchenko, Volodymyr; Motornenko, Anton; Alba, Paolo; Gorenstein, Mark I.; Satarov, Leonid M.; Stoecker, Horst

    2017-10-01

    A generalization of the quantum van der Waals equation of state for a multicomponent system in the grand-canonical ensemble is proposed. The model includes quantum statistical effects and allows us to specify the parameters characterizing repulsive and attractive forces for each pair of particle species. The model is applied to the description of asymmetric nuclear matter and also for mixtures of interacting nucleons and nuclei. Applications of the model to the equation of state of an interacting hadron resonance gas are discussed.

  15. Virtual Resonance and Frequency Difference Generation by van der Waals Interaction

    Science.gov (United States)

    Tetard, L.; Passian, A.; Eslami, S.; Jalili, N.; Farahi, R. H.; Thundat, T.

    2011-05-01

    The ability to explore the interior of materials for the presence of inhomogeneities was recently demonstrated by mode synthesizing atomic force microscopy [L. Tetard, A. Passian, and T. Thundat, Nature Nanotech. 5, 105 (2009).NNAABX1748-338710.1038/nnano.2009.454]. Proposing a semiempirical nonlinear force, we show that difference frequency ω- generation, regarded as the simplest synthesized mode, occurs optimally when the force is tuned to van der Waals form. From a parametric study of the probe-sample excitation, we show that the predicted ω- oscillation agrees well with experiments. We then introduce the concept of virtual resonance to show that probe oscillations at ω- can efficiently be enhanced.

  16. Ionization and fragmentation of isomeric van der Waals complexes embedded in helium nanodroplets

    Science.gov (United States)

    Lewis, William K.; Lindsay, C. Michael; Miller, Roger E.

    2008-11-01

    The ionization and charge transfer processes, which occur when a doped helium droplet undergoes electron impact, are studied for droplets doped with van der Waals complexes with various structures and electrostatic moments. The mass spectra of the two isomers of hydrogen cyanide complexed with either cyanoacetylene or acetylene in helium droplets were obtained using optically selected mass spectrometry, and show that the structure of the complex has a large effect on the fragmentation pattern. The resulting fragmentation pattern is consistent with an ionization process in which charge steering strongly influences the site of initial ionization. The observed dissociation products may also be subject to caging by the helium matrix.

  17. A Fractionally Ionic Approach to Polarizability and van der Waals Many-Body Dispersion Calculations.

    Science.gov (United States)

    Gould, Tim; Lebègue, Sébastien; Ángyán, János G; Bučko, Tomáš

    2016-12-13

    By explicitly including fractionally ionic contributions to the polarizability of a many-component system, we are able to significantly improve on previous atom-wise many-body van der Waals approaches with essentially no extra numerical cost. For nonionic systems, our method is comparable in accuracy to existing approaches. However, it offers substantial improvements in ionic solids, e.g., producing better polarizabilities by over 65% in some cases. It has particular benefits for two-dimensional transition metal dichalcogenides and interactions of H 2 with modified coronenes, ionic systems of nanotechnological interest. It thus offers an efficient improvement on existing approaches, valid for a wide range of systems.

  18. Polymorphism and thermodynamic ground state of silver fulminate studied from van der Waals density functional calculations

    Science.gov (United States)

    Yedukondalu, N.; Vaitheeswaran, G.

    2014-06-01

    Silver fulminate (AgCNO) is a primary explosive, which exists in two polymorphic phases, namely, orthorhombic (Cmcm) and trigonal (Rbar{3}) forms at ambient conditions. In the present study, we have investigated the effect of pressure and temperature on relative phase stability of the polymorphs using planewave pseudopotential approaches based on Density Functional Theory (DFT). van der Waals interactions play a significant role in predicting the phase stability and they can be effectively captured by semi-empirical dispersion correction methods in contrast to standard DFT functionals. Based on our total energy calculations using DFT-D2 method, the Cmcm structure is found to be the preferred thermodynamic equilibrium phase under studied pressure and temperature range. Hitherto Cmcm and Rbar{3} phases denoted as α- and β-forms of AgCNO, respectively. Also a pressure induced polymorphic phase transition is seen using DFT functionals and the same was not observed with DFT-D2 method. The equation of state and compressibility of both polymorphic phases were investigated. Electronic structure and optical properties were calculated using full potential linearized augmented plane wave method within the Tran-Blaha modified Becke-Johnson potential. The calculated electronic structure shows that α, β phases are indirect bandgap insulators with a bandgap values of 3.51 and 4.43 eV, respectively. The nature of chemical bonding is analyzed through the charge density plots and partial density of states. Optical anisotropy, electric-dipole transitions, and photo sensitivity to light of the polymorphs are analyzed from the calculated optical spectra. Overall, the present study provides an early indication to experimentalists to avoid the formation of unstable β-form of AgCNO.

  19. Effect of adding Te to layered GaSe crystals to increase the van der Waals bonding force

    Science.gov (United States)

    Tanabe, Tadao; Zhao, Shu; Sato, Yohei; Oyama, Yutaka

    2017-10-01

    The interplanar binding strength of layered GaSe1-xTex crystals was directly measured using a tensile testing machine. The GaSe1-xTex crystals were grown by a low temperature liquid phase solution method under a controlled Se vapor pressure. The stoichiometry-controlled GaSe1-xTex crystal has the ɛ-polytype structure of GaSe, where the Te atoms are substituted for some of the Se atoms in the GaSe crystal. The effect of adding Te on the bonding strength between the GaSe layers was determined from direct measurements of the van der Waals bonding energy. The bonding energy was increased from 0.023 × 106 N/m2 for GaSe to 0.16 × 106 N/m2 for GaSe1-xTex (x = 0.106).

  20. Long-Range van der Waals Correction to a Semilocal Density Functional: The Tail Need Not Wag the Dog

    Science.gov (United States)

    Perdew, John P.

    The SCAN (strongly constrained and appropriately normed) meta-generalized gradient approximation satisfies all 17 exact constraints that a semilocal functional can. Without being fitted to any bonded system, it correctly describes most kinds of bonding, including intermediate-range van der Waals (vdW) interaction. It can be supplemented [3.4] with a long-range vdW correction such as D3 or rVV10, which have the flexibility to exclude any intermediate-range contribution. Accurate results are found for free molecules, for molecules weakly bound to metal surfaces, and for interlayer binding energies of layered materials. Despite being a pair-interaction model, the rVV10 correction to SCAN also gives a random-phase-approximation-like long-range contribution to the binding energy curve for graphene on a nickel surface. Supported by DOE BES and NSF DMR.

  1. From the Cover: Evidence for van der Waals adhesion in gecko setae

    Science.gov (United States)

    Autumn, Kellar; Sitti, Metin; Liang, Yiching A.; Peattie, Anne M.; Hansen, Wendy R.; Sponberg, Simon; Kenny, Thomas W.; Fearing, Ronald; Israelachvili, Jacob N.; Full, Robert J.

    2002-09-01

    Geckos have evolved one of the most versatile and effective adhesives known. The mechanism of dry adhesion in the millions of setae on the toes of geckos has been the focus of scientific study for over a century. We provide the first direct experimental evidence for dry adhesion of gecko setae by van der Waals forces, and reject the use of mechanisms relying on high surface polarity, including capillary adhesion. The toes of live Tokay geckos were highly hydrophobic, and adhered equally well to strongly hydrophobic and strongly hydrophilic, polarizable surfaces. Adhesion of a single isolated gecko seta was equally effective on the hydrophobic and hydrophilic surfaces of a microelectro-mechanical systems force sensor. A van der Waals mechanism implies that the remarkable adhesive properties of gecko setae are merely a result of the size and shape of the tips, and are not strongly affected by surface chemistry. Theory predicts greater adhesive forces simply from subdividing setae to increase surface density, and suggests a possible design principle underlying the repeated, convergent evolution of dry adhesive microstructures in gecko, anoles, skinks, and insects. Estimates using a standard adhesion model and our measured forces come remarkably close to predicting the tip size of Tokay gecko seta. We verified the dependence on size and not surface type by using physical models of setal tips nanofabricated from two different materials. Both artificial setal tips stuck as predicted and provide a path to manufacturing the first dry, adhesive microstructures.

  2. Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.

    Science.gov (United States)

    Vaara, Juha; Hanni, Matti; Jokisaari, Jukka

    2013-03-14

    Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation.

  3. Effect of van der Waals interaction on the properties of SnS2 layered semiconductor

    International Nuclear Information System (INIS)

    Seminovski, Y.; Palacios, P.; Wahnón, P.

    2013-01-01

    Nowadays, dispersion correction applied on layered semiconductors is a topic of interest. Among the known layered semiconductors, SnS 2 polytypes are wide gap semiconductors with a van der Waals interaction between their layers, which could form good materials to be used in photovoltaic applications. The present work gives an approach to the SnS 2 geometrical and electronic characterization using an empirical dispersion correction added to the Perdew–Burke–Ernzerhof functional and subsequent actualization of the electronic charge density using the screened hybrid Heyd–Scuseria–Ernzerhof functional using a density functional code. The obtained interlayer distance and band-gap are in good agreement with experimental values when van der Waals dispersion forces are included. - Highlights: ► Tin disulphide (SnS 2 ) has been calculated using density functional theory methods. ► A dispersion correction was also applied for two different SnS 2 polytypes. ► Geometrical parameters and band-gaps were obtained using both approaches. ► Our calculations give a good agreement of the computed band gap with experiment

  4. Application of the van der Waals equation of state to polymers .4. Correlation and prediction of lower critical solution temperatures for polymer solutions

    DEFF Research Database (Denmark)

    Goncalves, Ana Saraiva; Kontogeorgis, Georgios; Harismiadis, Vassilis I.

    1996-01-01

    and has been successfully used for the prediction of upper critical solution temperatures for various binary polymer solutions. In this work, we demonstrate and explain some of the problems which cubic equations of state exhibit in describing the lower critical solution behavior for polymer solutions......The van der Waals equation of state is used for the correlation and the prediction of the lower critical solution behavior or mixtures including a solvent and a polymer. The equation of state parameters for the polymer are estimated from experimental volumetric data at low pressures. The equation...... of state parameters for the solvent are estimated via the classical Soave method, i.e. using the critical properties and a generalized equation for the energy parameter. When extended to mixtures, the van der Waals one-fluid mixing rules along with the Berthelot combining rule for the molecular cross...

  5. Using the van der Waals broadening of spectral atomic lines to measure the gas temperature of an argon-helium microwave plasma at atmospheric pressure

    International Nuclear Information System (INIS)

    Munoz, J.; Dimitrijevic, M.S.; Yubero, C.; Calzada, M.D.

    2009-01-01

    The applications of plasmas generated with gas mixtures have become increasingly common in different scientific and technological fields. In order to understand the advantages of these discharges, for instance in chemical analysis, it is necessary to know the gas temperature (T g , kinetic energy of the heavy particles) since it has a great influence on the atomization reactions of the molecules located in the discharge, along with the dependence of the reaction rate on this parameter. The ro-vibrational emission spectra of the molecular species are usually used to measure the gas temperature of a discharge at atmospheric pressure although under some experimental conditions, these are difficult to detect. In such cases, the gas temperature can be determined from the van der Waals broadening of the emitted atomic spectral lines related to this parameter. The method proposed is based on the van der Waals broadening taking into account two perturbers

  6. WSe2/MoS2 and MoTe2/SnSe2 van der Waals heterostructure transistors with different band alignment

    Science.gov (United States)

    Li, Chao; Yan, Xiao; Song, Xiongfei; Bao, Wenzhong; Ding, Shijin; Zhang, David Wei; Zhou, Peng

    2017-10-01

    Heterostructure field-effect transistors (hetero-FETs) are experimentally demonstrated, consisting of van der Waals heterostructure channels based on a 2D semiconductor. By optimally selecting the band alignment of the heterostructure channels, different output characteristics of the hetero-FETs were achieved. In atomically thin WSe2/MoS2 hetero-FET with staggered energy band, the oscillating transfer characteristic and negative transconductance were realized. With near-broken-gap alignment in the MoTe2/SnSe2 heterostructure channel, a superior reverse-biased current was obtained in the hetero-FETs, which can be analyzed as typical tunneling current. Our study on the hetero-FET-based atomically thin van der Waals heterostructure channel, provides significant inspiration and reference to novel heterostructure FETs.

  7. Ab initio van der waals interactions in simulations of water alter structure from mainly tetrahedral to high-density-like

    DEFF Research Database (Denmark)

    Møgelhøj, Andreas; Kelkkanen, Kari André; Wikfeldt, K Thor

    2011-01-01

    The structure of liquid water at ambient conditions is studied in ab initio molecular dynamics simulations in the NVE ensemble using van der Waals (vdW) density-functional theory, i.e., using the new exchange-correlation functionals optPBE-vdW and vdW-DF2, where the latter has softer nonlocal...... protocol could cause the deviation. An O-O PCF consisting of a linear combination of 70% from vdW-DF2 and 30% from low-density liquid water, as extrapolated from experiments, reproduces near-quantitatively the experimental O-O PCF for ambient water. This suggests the possibility that the new functionals...... shows some resemblance with experiment for high-density water ( Soper , A. K. and Ricci , M. A. Phys. Rev. Lett. 2000 , 84 , 2881 ), but not directly with experiment for ambient water. Considering the accuracy of the new functionals for interaction energies, we investigate whether the simulation...

  8. Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals.

    Science.gov (United States)

    Ambrosio, Francesco; Miceli, Giacomo; Pasquarello, Alfredo

    2015-12-28

    We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H(+)/H2 level defining the standard hydrogen electrode, the OH(-)/OH(∗) level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH(∗) level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in

  9. Electronic Properties and Device Applications of van-der-Waals Thin Films

    Science.gov (United States)

    Renteria, Jacqueline de Dios

    Successful exfoliation of graphene and discoveries of its unique electrical and thermal properties have motivated searches for other quasi two-dimensional (2D) materials with interesting properties. The layered van der Waals materials can be cleaved mechanically or exfoliated chemically by breaking the relatively weak bonding between the layers. In this dissertation research I addressed a special group of inorganic van der Waals materials -- layered transition metal dichalcogenides (MX2, where M=Mo, W, Nb, Ta or Ti and X=S, Se or Te). The focus of the investigation was electronic properties of thin films of TaSe2 and MoS2 and their device applications. In the first part of the dissertation, I describe the fabrication and performance of all-metallic three-terminal devices with the TaSe2 thin-film conducting channel. The layers of 2H-TaSe2 were exfoliated mechanically from single crystals grown by the chemical vapor transport method. It was established that devices with nanometer-scale thickness channels exhibited strongly non-linear current-voltage characteristics, unusual optical response, and electrical gating at room temperature. It was found that the drain-source current in thin-film 2H-TaSe2--Ti/Au devices reproducibly shows an abrupt transition from a highly resistive to a conductive state, with the threshold tunable via the gate voltage. Such current-voltage characteristics can be used, in principle, for implementing radiation-hard all-metallic logic circuits. In the second part of the dissertation, I describe the fabrication, electrical testing and measurements of the low-frequency 1/f noise in three-terminal devices with the MoS2 thin-film channel (f is the frequency). Analysis of the experimental data allowed us to distinguish channel and contact noise contributions for both as fabricated and aged devices. The noise characteristics of MoS 2--Ti/Au devices are in agreement with the McWhorter model description. The latter is contrary to what is observed in

  10. Electronic structure, lattice dynamics, and optical properties of a novel van der Waals semiconductor heterostructure: InGaSe2

    Science.gov (United States)

    Ibarra-Hernández, Wilfredo; Elsayed, Hannan; Romero, Aldo H.; Bautista-Hernández, Alejandro; Olguín, Daniel; Cantarero, Andrés

    2017-07-01

    There is a growing interest in the property dependence of transition metal dichalcogenides as a function of the number of layers and formation of heterostructures. Depending on the stacking, doping, edge effects, and interlayer distance, the properties can be modified, which opens the door to novel applications that require a detailed understanding of the atomic mechanisms responsible for those changes. In this work, we analyze the electronic properties and lattice dynamics of a heterostructure constructed by simultaneously stacking InSe layers and GaSe layers bounded by van der Waals forces. We have assumed the same space group of GaSe, P 6 ¯m 2 as it becomes the lower energy configuration for other considered stackings. The structural, vibrational, and optical properties of this layered compound have been calculated using density functional theory. The structure is shown to be energetically, thermally, and elastically stable, which indicates its possible chemical synthesis. A correlation of the theoretical physical properties with respect to its parent compounds is extensively discussed. One of the most interesting properties is the low thermal conductivity, which indicates its potential use in thermolectric applications. Additionally, we discuss the possibility of using electronic gap engineering methods, which can help us to tune the optical emission in a variable range close to that used in the field of biological systems (NIR). Finally, the importance of considering properly van der Waals dispersion in layered materials has been emphasized as included in the exchange correlation functional. As for the presence of atoms with important spin-orbit coupling, relativistic corrections have been included.

  11. First-principles study of van der Waals interactions and lattice mismatch at MoS2/metal interfaces

    NARCIS (Netherlands)

    Farmanbar Gelepordsari, M.; Brocks, G.

    2016-01-01

    We explore the adsorption of MoS 2 on a range of metal substrates by means of first-principles density functional theory calculations. Including van der Waals forces in the density functional is essential to capture the interaction between MoS 2 and a metal surface, and obtain reliable interface

  12. Ab initio determination of polarizabilities and van der Waals coefficients of Li atoms using the relativistic coupled-cluster method

    NARCIS (Netherlands)

    Wansbeek, L. W.; Sahoo, B. K.; Timmermans, R. G. E.; Das, B. P.; Mukherjee, D.

    We report on a technique to determine the van der Waals coefficients of lithium (Li) atoms based on relativistic coupled-cluster theory. These quantities are determined using the imaginary parts of the scalar dipole and quadrupole polarizabilities, which are evaluated using an approach that we have

  13. Influence of van der Waals forces on the adsorption structure of benzene on silicon studied using density functional theory

    DEFF Research Database (Denmark)

    Johnston, Karen; Kleis, Jesper; Lundqvist, Bengt

    2008-01-01

    Two different adsorption configurations of benzene on the Si(001)-(2×1) surface, the tight-bridge and butterfly structures, were studied using density functional theory. Several exchange and correlation functionals were used, including the recently developed van der Waals density functional (vd...

  14. Formation and physical characteristics of van der Waals molecules, cations, and anions: Estimates of complete basis set values

    Czech Academy of Sciences Publication Activity Database

    Zahradník, Rudolf; Šroubková, Libuše

    2005-01-01

    Roč. 104, č. 1 (2005), s. 52-63 ISSN 0020-7608 Institutional research plan: CEZ:AV0Z40400503 Keywords : intermolecular complexes * van der Waals species * ab initio calculations * complete basis set values * estimates Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.192, year: 2005

  15. Direction-specific van der Waals attraction between rutile TiO 2 nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xin; He, Yang; Sushko, Maria L.; Liu, Jia; Luo, Langli; De Yoreo, James J.; Mao, Scott X.; Wang, Chongmin; Rosso, Kevin M.

    2017-04-27

    Mutual lattice orientations dictate the types and magnitudes of forces between crystalline particles. When lattice polarizability is anisotropic, the van der Waals dispersion attraction can, in principle, contribute to this direction dependence. Here we report direct measurement of this attraction between rutile nanocrystals, as a function of their mutual orientation and surface hydration extent. At tens of nanometers of separation the attraction is weak and shows no dependence on azimuthal alignment nor surface hydration. At separations of approximately one hydration layer the attraction is strongly dependent on azimuthal alignment, and systematically decreases as intervening water density increases. Measured forces are in close agreement with predictions from Lifshitz theory, and show that dispersion forces are capable of generating a torque between particles interacting in solution and between grains in materials.

  16. Production Methods of Van der Waals Heterostructures Based on Transition Metal Dichalcogenides

    Directory of Open Access Journals (Sweden)

    Haimei Qi

    2018-01-01

    Full Text Available Two dimensional (2D materials have gained significant attention since the discovery of graphene in 2004. Layered transition metal dichalcogenides (TMDs have become the focus of 2D materials in recent years due to their wide range of chemical compositions and a variety of properties. These TMDs layers can be artificially integrated with other layered materials into a monolayer (lateral or a multilayer stack (vertical heterostructures. The resulting heterostructures provide new properties and applications beyond their component 2D atomic crystals and many exciting experimental results have been reported during the past few years. In this review, we present the various synthesis methods (mechanical exfoliation, physical vapor transport, chemical vapor deposition, and molecular beam epitaxy method on van der Waals heterostructures based on different TMDs as well as an outlook for future research.

  17. Effect of van der Waals interactions on the stability of SiC polytypes

    Energy Technology Data Exchange (ETDEWEB)

    Kawanishi, Sakiko, E-mail: s-kawa@tagen.tohoku.ac.jp; Mizoguchi, Teruyasu [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2016-05-07

    Density functional theory calculations with a correction of the long-range dispersion force, namely, the van der Waals (vdW) force, are performed for SiC polytypes. The lattice parameters are in good agreement with those obtained from the experiments. Furthermore, the stability of the polytypes in the experiments, which show 3C-SiC as the most stable, is reproduced by the present calculations. The effects of the vdW force on the electronic structure and the stability of polytypes are discussed. We observe that the vdW interaction is more sensitive to the cubic site than the hexagonal site. Thus, the influence of the vdW force increases with decreasing the hexagonality of the polytype, which results in the confirmation that the most stable polytype is 3C-SiC.

  18. Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates

    Directory of Open Access Journals (Sweden)

    Han Huang

    2016-09-01

    Full Text Available Two dimensional atomic crystals, like grapheme (G and molybdenum disulfide (MoS2, exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA, and dioctylbenzothienobenzothiophene (C8-BTBT and layered substrates (G, MoS2 and hexagonal boron nitride (h-BN. The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed.

  19. Two-Dimensional Semiconductor Optoelectronics Based on van der Waals Heterostructures

    Directory of Open Access Journals (Sweden)

    Jae Yoon Lee

    2016-10-01

    Full Text Available Two-dimensional (2D semiconductors such as transition metal dichalcogenides (TMDCs and black phosphorous have drawn tremendous attention as an emerging optical material due to their unique and remarkable optical properties. In addition, the ability to create the atomically-controlled van der Waals (vdW heterostructures enables realizing novel optoelectronic devices that are distinct from conventional bulk counterparts. In this short review, we first present the atomic and electronic structures of 2D semiconducting TMDCs and their exceptional optical properties, and further discuss the fabrication and distinctive features of vdW heterostructures assembled from different kinds of 2D materials with various physical properties. We then focus on reviewing the recent progress on the fabrication of 2D semiconductor optoelectronic devices based on vdW heterostructures including photodetectors, solar cells, and light-emitting devices. Finally, we highlight the perspectives and challenges of optoelectronics based on 2D semiconductor heterostructures.

  20. Impact of momentum mismatch on 2D van der Waals tunnel field-effect transistors

    Science.gov (United States)

    Cao, Jiang; Logoteta, Demetrio; Pala, Marco G.; Cresti, Alessandro

    2018-02-01

    We numerically investigate electron quantum transport in 2D van der Waals tunnel field-effect-transistors in the presence of lateral momentum mismatch induced by lattice mismatch or rotational misalignment between the two-dimensional layers. We show that a small momentum mismatch induces a threshold voltage shift without altering the subthreshold swing. On the contrary, a large momentum mismatch produces significant potential variations and ON-current reduction. Short-range scattering, such as that due to phonons or system edges, enables momentum variations, thus enhancing interlayer tunneling. The coupling of electrons with acoustic phonons is shown to increase the ON current without affecting the subthreshold swing. In the case of optical phonons, the ON-current increase is accompanied by a subthreshold swing degradation due to the inelastic nature of the scattering.

  1. Tunable Schottky contacts in the antimonene/graphene van der Waals heterostructures

    Science.gov (United States)

    Li, Wei; Wang, Xinlian; Dai, Xianqi

    2017-03-01

    Electronic structures modulation in the antimonene/graphene van der Waals(vdW) heterostructure with an external electric field(Eext) are investigated by density functional theory calculations. It is demonstrated that weak vdW interactions dominate between antimonene and graphene with their intrinsic electronic properties preserved. Furthermore, the vertical Eext can control not only the Schottky barrier but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the antimonene/graphene interface. Meanwhile, the negative Eext can shifts the Dirac point of graphene above the Fermi level, resulting in p-type doping in graphene because electrons can easily transfer from the Dirac point of graphene to the conduction band of antimonene. The present study would open a new avenue for application of ultrathin antimonene/graphene heterostructures in future nano- and optoelectronics.

  2. Tuning the Schottky barrier in the arsenene/graphene van der Waals heterostructures by electric field

    Science.gov (United States)

    Li, Wei; Wang, Tian-Xing; Dai, Xian-Qi; Wang, Xiao-Long; Ma, Ya-Qiang; Chang, Shan-Shan; Tang, Ya-Nan

    2017-04-01

    Using density functional theory calculations, we investigate the electronic properties of arsenene/graphene van der Waals (vdW) heterostructures by applying external electric field perpendicular to the layers. It is demonstrated that weak vdW interactions dominate between arsenene and graphene with their intrinsic electronic properties preserved. We find that an n-type Schottky contact is formed at the arsenene/graphene interface with a Schottky barrier of 0.54 eV. Moreover, the vertical electric field can not only control the Schottky barrier height but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the interface. Tunable p-type doping in graphene is achieved under the negative electric field because electrons can transfer from the Dirac point of graphene to the conduction band of arsenene. The present study would open a new avenue for application of ultrathin arsenene/graphene heterostructures in future nano- and optoelectronics.

  3. Is there a Difference in Van Der Waals Interactions between Rare Gas Atoms Adsorbed on Metallic and Semiconducting Single-Walled Carbon Nanotubes?

    Energy Technology Data Exchange (ETDEWEB)

    Chen, De-Li [Univ. of Pittsburgh, PA (United States). Dept. of Chemical and Petroleum Engineering; Mandeltort, Lynn [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Chemistry; Saidi, Wissam A. [Univ. of Pittsburgh, PA (United States). Dept. of Chemical and Petroleum Engineering; Yates, John T. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Chemistry; Cole, Milton W. [Pennsylvania State Univ., University Park, PA (United States). Dept of Physics; Johnson, J. Karl [Univ. of Pittsburgh, PA (United States). Dept. of Chemical and Petroleum Engineering; National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

    2013-03-01

    Differences in polarizabilities of metallic (M) and semiconducting (S) single-walled carbon nanotubes (SWNTs) might give rise to differences in adsorption potentials. We show from experiments and van der Waals-corrected density functional theory (DFT) that binding energies of Xe adsorbed on M- and S-SWNTs are nearly identical. Temperature programmed desorption of Xe on purified M- and S-SWNTs give similar peak temperatures, indicating that desorption kinetics and binding energies are independent of the type of SWNT. Binding energies computed from vdW-corrected DFT are in good agreement with experiments.

  4. Characterization of van der Waals type bimodal,- lambda,- meta- and spinodal phase transitions in liquid mixtures, solid suspensions and thin films.

    Science.gov (United States)

    Rosenholm, Jarl B

    2018-03-01

    The perfect gas law is used as a reference when selecting state variables (P, V, T, n) needed to characterize ideal gases (vapors), liquids and solids. Van der Waals equation of state is used as a reference for models characterizing interactions in liquids, solids and their mixtures. Van der Waals loop introduces meta- and unstable states between the observed gas (vapor)-liquid P-V transitions at low T. These intermediate states are shown to appear also between liquid-liquid, liquid-solid and solid-solid phase transitions. First-order phase transitions are characterized by a sharp discontinuity of first-order partial derivatives (P, S, V) of Helmholtz and Gibbs free energies. Second-order partial derivatives (K T , B, C V , C P , E) consist of a static contribution relating to second-order phase transitions and a relaxation contribution representing the degree of first-order phase transitions. Bimodal (first-order) and spinodal (second-order) phase boundaries are used to separate stable phases from metastable and unstable phases. The boundaries are identified and quantified by partial derivatives of molar Gibbs free energy or chemical potentials with respect to P, S, V and composition (mole fractions). Molecules confined to spread Langmuir monolayers or adsorbed Gibbs monolayers are characterized by equation of state and adsorption isotherms relating to a two-dimensional van der Waals equation of state. The basic work of two-dimensional wetting (cohesion, adsorption, spreading, immersion), have to be adjusted by a horizontal surface pressure in the presence of adsorbed vapor layers. If the adsorption is extended to liquid films a vertical surface pressure (Π) may be added to account for the lateral interaction, thus restoring PV = ΠAh dependence of thin films. Van der Waals attraction, Coulomb repulsion and structural hydration forces contribute to the vertical surface pressure. A van der Waals type coexistence of ordered (dispersed) and disordered

  5. Density, structure, and dynamics of water: the effect of van der Waals interactions.

    Science.gov (United States)

    Wang, Jue; Román-Pérez, G; Soler, Jose M; Artacho, Emilio; Fernández-Serra, M-V

    2011-01-14

    It is known that ab initio molecular dynamics (AIMD) simulations of liquid water at ambient conditions, based on the generalized gradient approximation (GGA) to density functional theory (DFT), with commonly used functionals fail to produce structural and diffusive properties in reasonable agreement with experiment. This is true for canonical, constant temperature simulations where the density of the liquid is fixed to the experimental density. The equilibrium density, at ambient conditions, of DFT water has recently been shown by Schmidt et al. [J. Phys. Chem. B, 113, 11959 (2009)] to be underestimated by different GGA functionals for exchange and correlation, and corrected by the addition of interatomic pair potentials to describe van der Waals (vdW) interactions. In this contribution we present a DFT-AIMD study of liquid water using several GGA functionals as well as the van der Waals density functional (vdW-DF) of Dion et al. [Phys. Rev. Lett. 92, 246401 (2004)]. As expected, we find that the density of water is grossly underestimated by GGA functionals. When a vdW-DF is used, the density improves drastically and the experimental diffusivity is reproduced without the need of thermal corrections. We analyze the origin of the density differences between all the functionals. We show that the vdW-DF increases the population of non-H-bonded interstitial sites, at distances between the first and second coordination shells. However, it excessively weakens the H-bond network, collapsing the second coordination shell. This structural problem is partially associated to the choice of GGA exchange in the vdW-DF. We show that a different choice for the exchange functional is enough to achieve an overall improvement both in structure and diffusivity.

  6. Lithium ions in the van der Waals gap of Bi2Se3 single crystals

    International Nuclear Information System (INIS)

    Bludska, J.; Jakubec, I.; Karamazov, S.; Horak, J.; Uher, C.

    2010-01-01

    Insertion/extraction of lithium ions into/from Bi 2 Se 3 crystals was investigated by means of cyclic voltammetry. The process of insertion is reflected in the appearance of two bands on voltammograms at ∼1.7 and ∼1.5 V, corresponding to the insertion of Li + ions into octahedral and tetrahedral sites of the van der Waals gap of these layered crystals. The process of extraction of Li + ions from the gap results in the appearance of four bands on the voltammograms. The bands 1 and 2 at ∼2.1 and ∼2.3 V correspond to the extraction of a part of Li + guest ions from the octahedral and tetrahedrals sites and this extraction has a character of a reversible intercalation/deintercalation process. A part of Li + ions is bound firmly in the crystal due to the formation of negatively charged clusters of the (LiBiSe 2 .Bi 3 Se 4 - ) type. A further extraction of Li + ions from the van der Waals gap is associated with the presence of bands 3 and 4 placed at ∼2.5 and ∼2.7 V on the voltammograms as their extraction needs higher voltage due to the influence of negative charges localized on these clusters. -- Graphical abstract: Insertion/extraction of lithium ions into/from Bi 2 Se 3 layered crystals was investigated by cyclic voltammetry. The extraction of Li + results in the appearance of four bands on the voltammograms. The first two bands have a character of a reversible process. A part of Li + ions is bound firmly in the crystal due to the formation of negatively charged clusters of the (LiBiSe 2 .Bi 3 Se 4 - ) type. Their extraction needs higher voltage due to the negative charge. Display Omitted

  7. Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

    Science.gov (United States)

    Huang, Bevin; Clark, Genevieve; Navarro-Moratalla, Efrén; Klein, Dahlia R.; Cheng, Ran; Seyler, Kyle L.; Zhong, Ding; Schmidgall, Emma; McGuire, Michael A.; Cobden, David H.; Yao, Wang; Xiao, Di; Jarillo-Herrero, Pablo; Xu, Xiaodong

    2017-06-01

    Since the discovery of graphene, the family of two-dimensional materials has grown, displaying a broad range of electronic properties. Recent additions include semiconductors with spin-valley coupling, Ising superconductors that can be tuned into a quantum metal, possible Mott insulators with tunable charge-density waves, and topological semimetals with edge transport. However, no two-dimensional crystal with intrinsic magnetism has yet been discovered; such a crystal would be useful in many technologies from sensing to data storage. Theoretically, magnetic order is prohibited in the two-dimensional isotropic Heisenberg model at finite temperatures by the Mermin-Wagner theorem. Magnetic anisotropy removes this restriction, however, and enables, for instance, the occurrence of two-dimensional Ising ferromagnetism. Here we use magneto-optical Kerr effect microscopy to demonstrate that monolayer chromium triiodide (CrI3) is an Ising ferromagnet with out-of-plane spin orientation. Its Curie temperature of 45 kelvin is only slightly lower than that of the bulk crystal, 61 kelvin, which is consistent with a weak interlayer coupling. Moreover, our studies suggest a layer-dependent magnetic phase, highlighting thickness-dependent physical properties typical of van der Waals crystals. Remarkably, bilayer CrI3 displays suppressed magnetization with a metamagnetic effect, whereas in trilayer CrI3 the interlayer ferromagnetism observed in the bulk crystal is restored. This work creates opportunities for studying magnetism by harnessing the unusual features of atomically thin materials, such as electrical control for realizing magnetoelectronics, and van der Waals engineering to produce interface phenomena.

  8. 2D halide perovskite-based van der Waals heterostructures: contact evaluation and performance modulation

    Science.gov (United States)

    Guo, Yaguang; Saidi, Wissam A.; Wang, Qian

    2017-09-01

    Halide perovskites and van der Waals (vdW) heterostructures are both of current interest owing to their novel properties and potential applications in nano-devices. Here, we show the great potential of 2D halide perovskite sheets (C4H9NH3)2PbX4 (X  =  Cl, Br and I) that were synthesized recently (Dou et al 2015 Science 349 1518-21) as the channel materials contacting with graphene and other 2D metallic sheets to form van der Waals heterostructures for field effect transistor (FET). Based on state-of-the-art theoretical simulations, we show that the intrinsic properties of the 2D halide perovskites are preserved in the heterojunction, which is different from the conventional contact with metal surfaces. The 2D halide perovskites form a p-type Schottky barrier (Φh) contact with graphene, where tunneling barrier exists, and a negative band bending occurs at the lateral interface. We demonstrate that the Schottky barrier can be turned from p-type to n-type by doping graphene with nitrogen atoms, and a low-Φh or an Ohmic contact can be realized by doping graphene with boron atoms or replacing graphene with other high-work-function 2D metallic sheets such as ZT-MoS2, ZT-MoSe2 and H-NbS2. This study not only predicts a 2D halide perovskite-based FETs, but also enhances the understanding of tuning Schottky barrier height in device applications.

  9. Jet-Cooled High Resolution Infrared Spectroscopy of Small Van Der Waals SF_6 Clusters

    Science.gov (United States)

    Asselin, Pierre; Boudon, Vincent; Potapov, Alexey; Bruel, Laurent; Gaveau, Marc-André; Mons, Michel

    2016-06-01

    Using a pulsed slit nozzle multipass absorption spectrometer with a tunable quantum cascade laser we investigated van der Waals clusters involving sulfur hexafluoride in the spectral range near the νb{3} stretching vibration. Different sized homo-complexes were generated in a planar supersonic expansion with typically 0,5 % SF_6 diluted in 6 bar He. Firstly, several rotationally resolved parallel and perpendicular bands of (SF_6)_2, at 934,0 and 956,1 wn (#1 structure) in agreement with Takami et al. but also one band at 933,6 wn (#2 structure) never observed previously, were analyzed in light of a recent theoretical study predicting three nearly isoenergetic isomers of D2d, C2h and C_2 symmetry for the dimer. Furthermore, some broader bands were detected around 938 and 964 wn and assigned to (SF_6)_3 and (SF_6)_4 clusters on the grounds of concentration effects and/or ab initio calculations. Lastly, with 0,5 % rare gas Rg (Rg = Ne, Ar, Kr and Xe) added to the SF_6:He gas mixture, a series of van der Waals (SF_6)_2-Rg hetero-trimers were observed, which display a remarkable linear dependence of the vibrational shift with the polarizability of the rare gas atom provided that the initial SF_6 dimer structure is #2 . In the same time no transitions belonging to the binary complexes SF_6-Rg were found near the νb{3} monomer band. This result suggests a complex thermodynamics within the pulsed supersonic expansion leading to the preponderance of (SF_6)_2-Rg clusters over SF_6-Rg binary systems. R. D. Urban and M. Takami, J. Chem. Phys. 103, 9132 (1995). T. Vazhappily, A. Marjolin and K. D. Jordan, J. Phys. Chem. B, DOI: 10.1021/acs.jpcb.5b09419 (2015).

  10. Single Photon Ionization Mass Spectroscopy of Hydrogen Bonded and van der Waals Cluster Systems Using a Capillary Discharge Soft X-Ray Laser

    Science.gov (United States)

    Heinbuch, S.; Dong, F.; Bernstein, E. R.; Rocca, J. J.

    We report the first use of a soft x-ray laser in photochemistry studies. A 46.9 nm capillary discharge soft x-ray laser was used to study hydrogen bonded and van der Waals cluster systems. The study of van der Waals cluster formation and growth in the gas phase can contribute to the understanding of solvation processes, solvation dynamics, and the nucleation and growth of small clusters. The comparative investigation of water, methanol, and ammonia clusters is of importance because these clusters demonstrate a wide range of van der Waals interactions and hydrogen bonding: water clusters are very strongly and dominantly hydrogen bonded; methanol clusters somewhat less so; and ammonia clusters perhaps not at all. Sulfur dioxide is the major contributor to acid rain and a generator of soot. The process of SO2 and water forming acid rain has been studied for some time in order to determine the atmospheric mechanism for this environmental issue. Carbon dioxide is the major gas phase pollutant responsible for the "green house effect" of the atmosphere. Many experiments employing supersonic expansion coupled with mass spectroscopic detection have been conducted in order to study monomeric and clustered structure and behavior of each of these systems. Spectroscopic and photochemical properties of the systems should be related to cluster structure. However, one of the most serious problems in the investigation of the distribution of neutral hydrogen-bonded and van der Waals clusters is the fragmentation or the intra-cluster ion-molecule reactions to the protonated cluster ions. Electron Impact (EI) ionization usually suffers considerably from fragmentation of parent cluster ions on account of the large excess energies during the ionization process. Multiphoton ionization (MPI) processes result in the predissociation of the neutral clusters before ionization. Single photon ionization is a more "gentle" way to study hydrogen-bonded and Van der Waals clusters since less

  11. Binding mechanisms of DNA/RNA nucleobases adsorbed on graphene under charging: first-principles van der Waals study

    Science.gov (United States)

    Gürel, Hikmet Hakan; Salmankurt, Bahadır

    2017-06-01

    Graphene is a 2D material that has attracted much attention due to its outstanding properties. Because of its high surface area and unique chemical and physical properties, graphene is a good candidate for biological applications. For this reason, a deep understanding of the mechanism of interaction of graphene with biomolecules is required. In this study, theoretical investigation of van der Waals effects has been conducted using density functional theory. Here we show that the order of the binding energies of five nucleobases with graphene is G  >  A  >  T  >  C  >   U. This trend is in good agreement with most of the theoretical and experimental data. Also, the effects of charging on the electronic and structural properties of the graphene-nucleubase systems are studied for the first time. We show that the binding energy can be changed by adding or removing an electron from the system. The results presented in this work provide fundamental insights into the quantum interactions of DNA with carbon-based nanostructures and will be useful for developments in biotechnology and nanotechnology.

  12. Significant decrease in thermal conductivity of multi-walled carbon nanotube induced by inter-wall van der Waals interactions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xue; Zhou, Wu-Xing, E-mail: wuxingzhou@hnu.edu.cn; Chen, Xue-Kun; Liu, Yue-Yang; Chen, Ke-Qiu, E-mail: keqiuchen@hnu.edu.cn

    2016-05-06

    The thermal transport properties of multi-walled carbon nanotubes (MWCNTs) were investigated by using non-equilibrium molecular dynamics simulation. The results show that the thermal conductivity of MWCNTs decreases significantly comparing to that of single-walled carbon nanotubes (SWCNTs) due to the inter-wall van der Waals interactions. The more interesting is a fact that the thermal conductance of MWCNTs is significantly greater than the thermal conductance summation of each SWCNTs. This is because the thermal conductance of a carbon nanotube protected by an outer tube is much larger than that of one that is not protected. Moreover, we also studied the thermal flux distribution of MWCNTs, and found that the outer tube plays a dominant role in heat energy transfer. - Highlights: • Significant decrease in thermal conductivity of multi-walled carbon nanotube induced by inter-wall interactions. • The thermal conductivity of the inner tube is increased significantly due to protected by outer tube. • The outer tube plays a dominant role in heat energy transfer in multi-walled carbon nanotube.

  13. Hybrid, Gate-Tunable, van der Waals p–n Heterojunctions from Pentacene and MoS 2

    Energy Technology Data Exchange (ETDEWEB)

    Jariwala, Deep [Department of Materials Science and Engineering and ‡Department of; Howell, Sarah L. [Department of Materials Science and Engineering and ‡Department of; Chen, Kan-Sheng [Department of Materials Science and Engineering and ‡Department of; Kang, Junmo [Department of Materials Science and Engineering and ‡Department of; Sangwan, Vinod K. [Department of Materials Science and Engineering and ‡Department of; Filippone, Stephen A. [Department of Materials Science and Engineering and ‡Department of; Turrisi, Riccardo [Department of Materials Science and Engineering and ‡Department of; Marks, Tobin J. [Department of Materials Science and Engineering and ‡Department of; Lauhon, Lincoln J. [Department of Materials Science and Engineering and ‡Department of; Hersam, Mark C. [Department of Materials Science and Engineering and ‡Department of

    2015-12-18

    The recent emergence of a wide variety of two-dimensional (2D) materials has created new opportunities for device concepts and applications. In particular, the availability of semiconducting transition metal dichalcogenides, in addition to semimetallic graphene and insulating boron nitride, has enabled the fabrication of “all 2D” van der Waals heterostructure devices. Furthermore, the concept of van der Waals heterostructures has the potential to be significantly broadened beyond layered solids. For example, molecular and polymeric organic solids, whose surface atoms possess saturated bonds, are also known to interact via van der Waals forces and thus offer an alternative for scalable integration with 2D materials. Here, we demonstrate the integration of an organic small molecule p-type semiconductor, pentacene, with a 2D n-type semiconductor, MoS2. The resulting p–n heterojunction is gate-tunable and shows asymmetric control over the antiambipolar transfer characteristic. In addition, the pentacene/MoS2 heterojunction exhibits a photovoltaic effect attributable to type II band alignment, which suggests that MoS2 can function as an acceptor in hybrid solar cells.

  14. Multiple critical points and liquid-liquid equilibria from the van der Waals like equations of state

    International Nuclear Information System (INIS)

    Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor

    2008-01-01

    The principal aim of this work is a comprehensive analysis of the phase diagram of water via the van der Waals like equations of state (EoSs) which are considered as superpositions of repulsive and attractive forces. We test more extensively the modified van der Waals EoS (MVDW) proposed by Skibinski et al (2004 Phys. Rev. E 69 061206) and refine this model by introducing instead of the classical van der Waals repulsive term a very accurate hard sphere EoS over the entire stable and metastable regions (Liu 2006 Preprint cond-mat/0605392). It was detected that the simplest form of MVDW EoS displays a complex phase behavior, including three critical points, and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). Moreover the experimentally observed (Mallamace et al 2007 Proc. Natl Acad. Sci. USA 104 18387) anomalous behavior of the density of water in the deeply supercooled region (a density minimum) is reproduced by the MWDW EoS. An improvement of the repulsive part does not change the topological picture of the phase behavior of water in the wide range of thermodynamic variables. The new parameters set for second and third critical points are recognized by thorough analysis of experimental data for the loci of thermodynamic response function extrema

  15. Multiple critical points and liquid-liquid equilibria from the van der Waals like equations of state

    Energy Technology Data Exchange (ETDEWEB)

    Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor [Thermodynamics Department, Academy of Refrigeration, 65082 Odessa (Ukraine)

    2008-06-18

    The principal aim of this work is a comprehensive analysis of the phase diagram of water via the van der Waals like equations of state (EoSs) which are considered as superpositions of repulsive and attractive forces. We test more extensively the modified van der Waals EoS (MVDW) proposed by Skibinski et al (2004 Phys. Rev. E 69 061206) and refine this model by introducing instead of the classical van der Waals repulsive term a very accurate hard sphere EoS over the entire stable and metastable regions (Liu 2006 Preprint cond-mat/0605392). It was detected that the simplest form of MVDW EoS displays a complex phase behavior, including three critical points, and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). Moreover the experimentally observed (Mallamace et al 2007 Proc. Natl Acad. Sci. USA 104 18387) anomalous behavior of the density of water in the deeply supercooled region (a density minimum) is reproduced by the MWDW EoS. An improvement of the repulsive part does not change the topological picture of the phase behavior of water in the wide range of thermodynamic variables. The new parameters set for second and third critical points are recognized by thorough analysis of experimental data for the loci of thermodynamic response function extrema.

  16. Recent progress in predicting structural and electronic properties of organic solids with the van der Waals density functional

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Susumu, E-mail: shou@sci.u-ryukyu.ac.jp [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan); Okuma, Koji; Inaoka, Takeshi [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan); Hamada, Ikutaro, E-mail: Hamada.Ikutaro@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan)

    2015-10-01

    Highlights: • Review of theoretical studies on organic solids with the density-functional methods. • van der Waals (vdW)-inclusive methods to predict cohesive properties of oligoacenes. • A variant of the vdW density functional describes the structures accurately. • The molecular configuration and conformation crucially affects the band dispersion. - Abstract: We review recent studies on electronic properties of the organic solids with the first-principles electronic structure methods, with the emphasis on the roles of the intermolecular van der Waals (vdW) interaction in electronic properties of the organic semiconductors. After a brief summary of the recent vdW inclusive first-principle theoretical methods, we discuss their performance in predicting cohesive properties of oligoacene crystals as examples of organic crystals. We show that a variant of the van der Waals density functional describes structure and energetics of organic crystals accurately. In addition, we review our recent study on the zinc phthalocyanine crystal and discuss the importance of the intermolecular distance and orientational angle in the band dispersion. Finally, we draw some general conclusions and the future perspectives.

  17. Direct observation of interlayer hybridization and Dirac relativistic carriers in graphene/MoS₂ van der Waals heterostructures.

    Science.gov (United States)

    Diaz, Horacio Coy; Avila, José; Chen, Chaoyu; Addou, Rafik; Asensio, Maria C; Batzill, Matthias

    2015-02-11

    Artificial heterostructures assembled from van der Waals materials promise to combine materials without the traditional restrictions in heterostructure-growth such as lattice matching conditions and atom interdiffusion. Simple stacking of van der Waals materials with diverse properties would thus enable the fabrication of novel materials or device structures with atomically precise interfaces. Because covalent bonding in these layered materials is limited to molecular planes and the interaction between planes are very weak, only small changes in the electronic structure are expected by stacking these materials on top of each other. Here we prepare interfaces between CVD-grown graphene and MoS2 and report the direct measurement of the electronic structure of such a van der Waals heterostructure by angle-resolved photoemission spectroscopy. While the Dirac cone of graphene remains intact and no significant charge transfer doping is detected, we observe formation of band gaps in the π-band of graphene, away from the Fermi-level, due to hybridization with states from the MoS2 substrate.

  18. Novel electronic properties of 2D MoS2/TiO2 van der Waals heterostructure

    Science.gov (United States)

    Li, Yanhua; Cai, Congzhong; Sun, Baoguang; Chen, Jianjun

    2017-10-01

    Two different exchange-correlation functionals with van der Waals correction are employed to investigate the electronic properties of 2D {MoS}}2/{TiO}}2 heterostructure with a special configuration of Moiré pattern. It is found that, for both PBE and HSE06 functional, the new van der Waals heterostructure that consists of monolayer {MoS}}2 and 2D lepidocrocite-type {TiO}}2 exhibits a type-II band alignment between the {MoS}}2 and {TiO}}2 layers, and the electronic structures of monolayer {MoS}}2 and 2D {TiO}}2 are well retained in their respective layers due to a weak interlaminar coupling, which indicates that the new heterostructure may have potential applications in many fields such as photocatalysis, photoelectric devices, solar cells, etc. Furthermore, a novel design scheme based on the new 2D {MoS}}2/{TiO}}2 van der Waals heterostructure is proposed for a solar cell, and the corresponding power conversion efficiency is estimated to be about 8%.

  19. Van der Waals potentials between metal clusters and helium atoms obtained with density functional theory and linear response methods

    International Nuclear Information System (INIS)

    Liebrecht, M.

    2014-01-01

    The importance of van der Waals interactions in many diverse research fields such as, e. g., polymer science, nano--materials, structural biology, surface science and condensed matter physics created a high demand for efficient and accurate methods that can describe van der Waals interactions from first principles. These methods should be able to deal with large and complex systems to predict functions and properties of materials that are technologically and biologically relevant. Van der Waals interactions arise due to quantum mechanical correlation effects and finding appropriate models an numerical techniques to describe this type of interaction is still an ongoing challenge in electronic structure and condensed matter theory. This thesis introduces a new variational approach to obtain intermolecular interaction potentials between clusters and helium atoms by means of density functional theory and linear response methods. It scales almost linearly with the number of electrons and can therefore be applied to much larger systems than standard quantum chemistry techniques. The main focus of this work is the development of an ab-initio method to account for London dispersion forces, which are purely attractive and dominate the interaction of non--polar atoms and molecules at large distances. (author) [de

  20. van der Waals torque and force between anisotropic topological insulator slabs

    Science.gov (United States)

    Lu, Bing-Sui

    2018-01-01

    We investigate the character of the van der Waals (vdW) torque and force between two coplanar and dielectrically anisotropic topological insulator (TI) slabs separated by a vacuum gap in the nonretardation regime, where the optic axes of the slabs are each perpendicular to the normal direction to the slab-gap interface and also generally differently oriented from each other. We find that in addition to the magnetoelectric coupling strength, the anisotropy can also influence the sign of the vdW force, viz., a repulsive vdW force can become attractive if the anisotropy is increased sufficiently. In addition, the vdW force oscillates as a function of the angular difference between the optic axes of the TI slabs, being most repulsive/least attractive (least repulsive/most attractive) for angular differences that are integer (half-integer) multiples of π . Our third finding is that the vdW torque for TI slabs is generally weaker than that for ordinary dielectric slabs. Our work provides an instance in which the vector potential appears in a calculation of the vdW interaction for which the limit is nonretarded or static.

  1. van der Waals Interactions in Hadron Resonance Gas: From Nuclear Matter to Lattice QCD.

    Science.gov (United States)

    Vovchenko, Volodymyr; Gorenstein, Mark I; Stoecker, Horst

    2017-05-05

    An extension of the ideal hadron resonance gas (HRG) model is constructed which includes the attractive and repulsive van der Waals (VDW) interactions between baryons. This VDW-HRG model yields the nuclear liquid-gas transition at low temperatures and high baryon densities. The VDW parameters a and b are fixed by the ground state properties of nuclear matter, and the temperature dependence of various thermodynamic observables at zero chemical potential are calculated within the VDW-HRG model. Compared to the ideal HRG model, the inclusion of VDW interactions between baryons leads to a qualitatively different behavior of second and higher moments of fluctuations of conserved charges, in particular in the so-called crossover region T∼140-190  MeV. For many observables this behavior resembles closely the results obtained from lattice QCD simulations. This hadronic model also predicts nontrivial behavior of net-baryon fluctuations in the region of phase diagram probed by heavy-ion collision experiments. These results imply that VDW interactions play a crucial role in the thermodynamics of hadron gas. Thus, the commonly performed comparisons of the ideal HRG model with the lattice and heavy-ion data may lead to misconceptions and misleading conclusions.

  2. van der Waals epitaxy of CdS thin films on single-crystalline graphene

    Science.gov (United States)

    Sun, Xin; Lu, Zonghuan; Xie, Weiyu; Wang, Yiping; Shi, Jian; Zhang, Shengbai; Washington, Morris A.; Lu, Toh-Ming

    2017-04-01

    van der Waals epitaxy (vdWE) of three-dimensional CdS thin films on both single-crystalline graphene/Cu(111)/spinel(111) and single-crystalline graphene/SiO2/Si substrates is achieved via thermal evaporation. X-ray and electron backscatter diffraction pole figures reveal that the CdS films are a Wurtzite structure with a weak epitaxy on graphene and accompanied with a fiber texture background. The epitaxial alignment between CdS and graphene is observed to be an unusual non-parallel epitaxial relationship with a 30° rotation between the unit vectors of CdS and graphene. A geometrical model based on the minimization of superlattice area mismatch is employed to calculate possible interface lattice arrangement. It is found that the 30° rotation between CdS and graphene is indeed the most probable interface epitaxial lattice alignment. The vdWE of CdS on graphene, transferrable to arbitrary substrates, may represent a step forward for the growth of quality CdS thin films on arbitrary substrates through a graphene buffer.

  3. Thermal stability and thermal conductivity of phosphorene in phosphorene/graphene van der Waals heterostructures.

    Science.gov (United States)

    Pei, Qing-Xiang; Zhang, Xiaoliang; Ding, Zhiwei; Zhang, Ying-Yan; Zhang, Yong-Wei

    2017-07-14

    Phosphorene, a new two-dimensional (2D) semiconducting material, has attracted tremendous attention recently. However, its structural instability under ambient conditions poses a great challenge to its practical applications. A possible solution for this problem is to encapsulate phosphorene with more stable 2D materials, such as graphene, forming van der Waals heterostructures. In this study, using molecular dynamics simulations, we show that the thermal stability of phosphorene in phosphorene/graphene heterostructures can be enhanced significantly. By sandwiching phosphorene between two graphene sheets, its thermally stable temperature is increased by 150 K. We further study the thermal transport properties of phosphorene and find surprisingly that the in-plane thermal conductivity of phosphorene in phosphorene/graphene heterostructures is much higher than that of the free-standing one, with a net increase of 20-60%. This surprising increase in thermal conductivity arises from the increase in phonon group velocity and the extremely strong phonon coupling between phosphorene and the graphene substrate. Our findings have an important meaning for the practical applications of phosphorene in nanodevices.

  4. Non-additivity of molecule-surface van der Waals potentials from force measurements

    Science.gov (United States)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-11-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  5. Non-additivity of molecule-surface van der Waals potentials from force measurements.

    Science.gov (United States)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F Stefan

    2014-11-26

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  6. Tunable band gaps in graphene/GaN van der Waals heterostructures

    International Nuclear Information System (INIS)

    Huang, Le; Kang, Jun; Li, Yan; Li, Jingbo; Yue, Qu

    2014-01-01

    Van der Waals (vdW) heterostructures consisting of graphene and other two-dimensional materials provide good opportunities for achieving desired electronic and optoelectronic properties. Here, we focus on vdW heterostructures composed of graphene and gallium nitride (GaN). Using density functional theory, we perform a systematic study on the structural and electronic properties of heterostructures consisting of graphene and GaN. Small band gaps are opened up at or near the Γ point of the Brillouin zone for all of the heterostructures. We also investigate the effect of the stacking sequence and electric fields on their electronic properties. Our results show that the tunability of the band gap is sensitive to the stacking sequence in bilayer-graphene-based heterostructures. In particular, in the case of graphene/graphene/GaN, a band gap of up to 334 meV is obtained under a perpendicular electric field. The band gap of bilayer graphene between GaN sheets (GaN/graphene/graphene/GaN) shows similar tunability, and increases to 217 meV with the perpendicular electric field reaching 0.8 V Å  − 1 . (paper)

  7. Approximate scheme for calculating van der Waals interactions between finite cylindrical volume elements.

    Science.gov (United States)

    Jaiswal, Ravi P; Beaudoin, Stephen P

    2012-06-05

    A successful approach to calculating van der Waals (vdW) forces between irregular bodies is to divide the bodies into small cylindrical volume elements and integrate the vdW interactions between opposing elements. In this context it has been common to use Hamaker's expression for parallel plates to approximate the vdW interactions between the opposing elements. This present study shows that Hamaker's vdW expression for parallel plates does not accurately describe the vdW interactions for co-axial cylinders having a ratio of cylinder radius to separation distance (R/D) of 10 or less. This restricts the systems that can be simulated using this technique and explicitly excludes consideration of topographical or compositional variations at the nanoscale for surfaces that are in contact or within a few nm of contact. To address this limitation, approximate analytical expressions for nonretarded vdW forces between finite cylinders in different orientations are derived and are shown to produce a high level of agreement with forces calculated using full numerical solutions of the corresponding Hamaker's equations. The expressions developed here allow accurate calculation of vdW forces in systems where particles are in contact or within a few nm of contact with surfaces and the particles and/or surfaces have heterogeneous nanoscale morphology or composition. These calculations can be performed at comparatively low computational cost compared to the full numerical solution of Hamaker's equations.

  8. Fluctuations of the van der Waals attraction force between macroscopic bodies

    Energy Technology Data Exchange (ETDEWEB)

    Kogan, A. S. (Aleksandr Semenovich)

    2003-01-01

    The tliccry of the fluctuations of the van der Waals (vdW) attractive force between macroscopic bodies is developed. A general equation for the spectral density of the fluctuating surface Maxwell stress (force per unit mea.) in va,cuurn nea,r the surface of a body is derived under the assumption that, inside the bodies, the random La.ngevin sources of the electric and magnetic fields (charges, polarizations, currents) are Gaussian. This spectral density of stress is an integral over frequencies of a sum of terms each of which is a product of Fourier amplitudes of two field components' correlation functions. For metallic bodies, the contribution of free electrons to the vdW force (at frequencies up to the frequency of electron scattering) is calculated. This contribution to the force and its noise grows with temperature. Application of noiseless voltage to two interacting metals across the vacuum gap between them generates an additional force noise. This additional noise is proportional to the volta.ge squared and to the spectral density of the random electric field at the frequency of noise measurement. The theoretical qualitative conclusions are in good agreement with experirncnts.

  9. Pauli Repulsion Versus van der Waals: Interaction of Indenocorannulene with a Cu(111) Surface.

    Science.gov (United States)

    Zoppi, Laura; Stöckl, Quirin; Mairena, Anaïs; Allemann, Oliver; Siegel, Jay S; Baldridge, Kim K; Ernst, Karl-Heinz

    2018-01-18

    Modification of metal electrode surfaces with functional organic molecules is an important step toward organic electronics. The interaction of the buckybowl indenocorannulene with a Cu(111) surface and the two-dimensional self-assembly on the same surface was studied by means of scanning tunneling microscopy and dispersion-enabled density functional theory. Based on the conjecture of maximizing van der Waals interaction with the surface one would expect the indeno group to be aligned parallel to the surface. Theoretical investigations predict a nonparallel arrangement with the benzo ring of the indeno group located higher above the surface than the bowl rim connected to the indeno group. This adsorbate geometry is due to strong electronic interaction between molecule and surface, including substantial Pauli repulsion. The long-range ordered monolayer shows differences for two molecules of the unit cell in scanning tunneling microscopy contrast, suggesting either different polar alignments, and therefore a different tilt of the indeno group, or occupation of different adsorption sites.

  10. Flexible Multiferroic Bulk Heterojunction with Giant Magnetoelectric Coupling via van der Waals Epitaxy.

    Science.gov (United States)

    Amrillah, Tahta; Bitla, Yugandhar; Shin, Kwangwoo; Yang, Tiannan; Hsieh, Ying-Hui; Chiou, Yu-You; Liu, Heng-Jui; Do, Thi Hien; Su, Dong; Chen, Yi-Chun; Jen, Shien-Uang; Chen, Long-Qing; Kim, Kee Hoon; Juang, Jenh-Yih; Chu, Ying-Hao

    2017-06-27

    Magnetoelectric nanocomposites have been a topic of intense research due to their profound potential in the applications of electronic devices based on spintronic technology. Nevertheless, in spite of significant progress made in the growth of high-quality nanocomposite thin films, the substrate clamping effect still remains a major hurdle in realizing the ultimate magnetoelectric coupling. To overcome this obstacle, an alternative strategy of fabricating a self-assembled ferroelectric-ferrimagnetic bulk heterojunction on a flexible muscovite via van der Waals epitaxy is adopted. In this study, we investigated the magnetoelectric coupling in a self-assembled BiFeO 3 (BFO)-CoFe 2 O 4 (CFO) bulk heterojunction epitaxially grown on a flexible muscovite substrate. The obtained heterojunction is composed of vertically aligned multiferroic BFO nanopillars embedded in a ferrimagnetic CFO matrix. Moreover, due to the weak interaction between the flexible substrate and bulk heterojunction, the interface is incoherent and, hence, the substrate clamping effect is greatly reduced. The phase-field simulation model also complements our results. The magnetic and electrical characterizations highlight the improvement in magnetoelectric coupling of the BFO-CFO bulk heterojunction. A magnetoelectric coupling coefficient of 74 mV/cm·Oe of this bulk heterojunction is larger than the magnetoelectric coefficient reported earlier on flexible substrates. Therefore, this study delivers a viable route of fabricating a remarkable magnetoelectric heterojunction and yet flexible electronic devices that are robust against extreme conditions with optimized performance.

  11. Van der Waals enhancement of optical atom potentials via resonant coupling to surface polaritons.

    Science.gov (United States)

    Kerckhoff, Joseph; Mabuchi, Hideo

    2009-08-17

    Contemporary experiments in cavity quantum electrodynamics (cavity QED) with gas-phase neutral atoms rely increasingly on laser cooling and optical, magneto-optical or magnetostatic trapping methods to provide atomic localization with sub-micron uncertainty. Difficult to achieve in free space, this goal is further frustrated by atom-surface interactions if the desired atomic placement approaches within several hundred nanometers of a solid surface, as can be the case in setups incorporating monolithic dielectric optical resonators such as microspheres, microtoroids, microdisks or photonic crystal defect cavities. Typically in such scenarios, the smallest atom-surface separation at which the van der Waals interaction can be neglected is taken to be the optimal localization point for associated trapping schemes, but this sort of conservative strategy generally compromises the achievable cavity QED coupling strength. Here we suggest a new approach to the design of optical dipole traps for atom confinement near surfaces that exploits strong surface interactions, rather than avoiding them, and present the results of a numerical study based on (39)K atoms and indium tin oxide (ITO). Our theoretical framework points to the possibility of utilizing nanopatterning methods to engineer novel modifications of atom-surface interactions. (c) 2009 Optical Society of America

  12. An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows

    International Nuclear Information System (INIS)

    Pantano, C.; Saurel, R.; Schmitt, T.

    2017-01-01

    Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-known pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. As a result, the combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement.

  13. Stabilization of thin liquid films by repulsive van der waals force

    KAUST Repository

    Li, Erqiang

    2014-05-13

    Using high-speed video recording of bubble rise experiments, we study the stability of thin liquid films trapped between a rising bubble and a surfactant-free liquid-liquid meniscus interface. Using different combinations of nonpolar oils and water that are all immiscible, we investigate the extent to which film stability can be predicted by attractive and repulsive van der Waals (vdW) interactions that are indicated by the relative magnitude of the refractive indices of the liquid combinations, for example, water (refractive index, n = 1.33), perfluorohexane (n = 1.23), and tetradecane (n = 1.43). We show that, when the film-forming phase was oil (perfluorohexane or tetradecane), the stability of the film could always be predicted from the sign of the vdW interaction, with a repulsive vdW force resulting in a stable film and an attractive vdW force resulting in film rupture. However, if aqueous electrolyte is the film-forming bulk phase between the rising air bubble and the upper oil phase, the film always ruptured, even when a repulsive vdW interaction was predicted. We interpret these results as supporting the hypothesis that a short-ranged hydrophobic attraction determines the stability of the thin water film formed between an air phase and a nonpolar oil phase. © 2014 American Chemical Society.

  14. Mobility Engineering in Vertical Field Effect Transistors Based on Van der Waals Heterostructures.

    Science.gov (United States)

    Shin, Yong Seon; Lee, Kiyoung; Kim, Young Rae; Lee, Hyangsook; Lee, I Min; Kang, Won Tae; Lee, Boo Heung; Kim, Kunnyun; Heo, Jinseong; Park, Seongjun; Lee, Young Hee; Yu, Woo Jong

    2018-03-01

    Vertical integration of 2D layered materials to form van der Waals heterostructures (vdWHs) offers new functional electronic and optoelectronic devices. However, the mobility in vertical carrier transport in vdWHs of vertical field-effect transistor (VFET) is not yet investigated in spite of the importance of mobility for the successful application of VFETs in integrated circuits. Here, the mobility in VFET of vdWHs under different drain biases, gate biases, and metal work functions is first investigated and engineered. The traps in WSe 2 are the main source of scattering, which influences the vertical mobility and three distinct transport mechanisms: Ohmic transport, trap-limited transport, and space-charge-limited transport. The vertical mobility in VFET can be improved by suppressing the trap states by raising the Fermi level of WSe 2 . This is achieved by increasing the injected carrier density by applying a high drain voltage, or decreasing the Schottky barrier at the graphene/WSe 2 and metal/WSe 2 junctions by applying a gate bias and reducing the metal work function, respectively. Consequently, the mobility in Mn vdWH at +50 V gate voltage is about 76 times higher than the initial mobility of Au vdWH. This work enables further improvements in the VFET for successful application in integrated circuits. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Electric-field tunable electronic structure in WSe2/arsenene van der Waals heterostructure

    Science.gov (United States)

    Zhang, Fang; Li, Wei; Dai, Xianqi

    2017-04-01

    The electronic properties of WSe2/arsenene van der Waals (vdW) heterostructure with an external electric field (Eext) are investigated by density functional theory (DFT). It is demonstrated that the WSe2/arsenene heterobilayer is a type-II vdW heterostructure, and thus electrons and holes are spatially separated. The WSe2/arsenene heterobilayer undergoes a transition from semiconductor to metal when subjected to an Eext. The positive and negative Eext have different effects on the band gap due to the spontaneous electric polarization in WSe2/arsenene heterostructure. The variation of band edges as a function of Eext provides further insight to the linear variation of the band gap. Moreover, the WSe2/arsenene vdW heterostructure experiences transitions from type-II to type-I and then from type-I to type-II with an increasing negative Eext. The present study would open a new avenue for application of ultrathin WSe2/arsenene heterobilayer in future nano- and optoelectronics.

  16. Van der Waals interactions between planar substrate and tubular lipid membranes undergoing pearling instability

    Science.gov (United States)

    Valchev, G. S.; Djondjorov, P. A.; Vassilev, V. M.; Dantchev, D. M.

    2017-10-01

    In the current article we study the behavior of the van der Waals force between a planar substrate and an axisymmetric bilayer lipid membrane undergoing pearling instability, caused by uniform hydrostatic pressure difference. To do so, the recently suggested "surface integration approach" is used, which can be considered a generalization of the well known and widely used Derjaguin approximation. The static equilibrium shape after the occurrence of the instability is described in the framework of Helfrich's spontaneous curvature model. Some specific classes of exact analytical solutions to the corresponding shape equation are considered, and the components of the respective position vectors given in terms of elliptic integrals and Jacobi elliptic functions. The mutual orientation between the interacting objects is chosen such that the axis of revolution of the distorted cylinder be parallel to the plane bounding the substrate. Based on the discussed models and approaches we made some estimations for the studied force in real experimentally realizable systems, thus showing the possibility of pearling as an useful technique for reduction of the adhesion in variety of industrial processes using lipid membranes as carriers.

  17. Two-dimensional laser induced fluorescence spectroscopy of van der Waals complexes: fluorobenzene-Ar(n) (n = 1,2).

    Science.gov (United States)

    Gascooke, Jason R; Alexander, Ula N; Lawrance, Warren D

    2012-04-07

    The technique of two-dimensional laser induced fluorescence (2D-LIF) spectroscopy has been used to observe the van der Waals complexes fluorobenzene-Ar and fluorobenzene-Ar(2) in the region of their S(1)-S(0) electronic origins. The 2D-LIF spectral images reveal a number of features assigned to the van der Waals vibrations in S(0) and S(1). An advantage of 2D-LIF spectroscopy is that the LIF spectrum associated with a particular species may be extracted from an image. This is illustrated for fluorobenzene-Ar. The S(1) van der Waals modes observed in this spectrum are consistent with previous observations using mass resolved resonance enhanced multiphoton ionisation techniques. For S(0), the two bending modes previously observed using a Raman technique were observed along with three new levels. These agree exceptionally well with ab initio calculations. The Fermi resonance between the stretch and bend overtone has been analysed in both the S(0) and S(1) states, revealing that the coupling is stronger in S(0) than in S(1). For fluorobenzene-Ar(2) the 2D-LIF spectral image reveals the S(0) symmetric stretch van der Waals vibration to be 35.0 cm(-1), closely matching the value predicted based on the fluorobenzene-Ar van der Waals stretch frequency. Rotational band contour analysis has been performed on the fluorobenzene-Ar 0(0)(0) transition to yield a set of S(1) rotational constants A' = 0.05871 ± 0.00014 cm(-1), B' = 0.03803 ± 0.00010 cm(-1), and C' = 0.03103 ± 0.00003 cm(-1). The rotational constants imply that in the S(1) 0(0) level the Ar is on average 3.488 Å from the fluorobenzene centre of mass and displaced from it towards the centre of the ring at an angle of ~6° to the normal. The rotational contour for fluorobenzene-Ar(2) was predicted using rotational constants calculated on the basis of the fluorobenzene-Ar geometry and compared with the experimental contour. The comparison is poor which, while due in part to expected saturation effects, suggests

  18. Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures

    Science.gov (United States)

    Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

    2016-01-01

    As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices. PMID:27553787

  19. A combining rule calculation of the ground state van der Waals potentials of the mercury rare-gas complexes.

    Science.gov (United States)

    Sheng, X W; Li, P; Tang, K T

    2009-05-07

    The ground state van der Waals potentials of the Hg-RG (RG = He,Ne,Ar,Kr,Xe) systems are generated by the Tang-Toennies potential model. The parameters of the model are calculated from the potentials of the homonuclear mercury and rare-gas dimers with combining rules. The predicted spectroscopic parameters for these mercury rare-gas complexes are in good agreement with available experimental values, except for Hg-He. In the repulsive and potential well regions, the predicted potential energy curves agree with the available experimental hybrid potentials, but they differ in the long range part of the potential. On the other hand, the present potentials are in agreement with the ab initio CCSD(T) calculations in the long range part of the potential, but there are some differences in the short repulsive regions. According to the present theory, the reduced potential curves of these five systems, including Hg-He, are almost identical to each other. This reduced potential curve can also describe, within a few percent, the five reduced potentials obtained from the ab initio CCSD(T) calculations. These reduced potentials have a potential bowl that is wider than that of the rare-gas dimers, but narrower than the mercury dimer.

  20. VAN DER WAALS MIXING RULES FOR THE REDLICH-KWONG EQUATION OF STATE. APPLICATION FOR SUPERCRITICAL SOLUBILITY MODELING

    Directory of Open Access Journals (Sweden)

    Ratnawati Ratnawati

    2012-02-01

    Full Text Available A solid-supercritical fluid system is highly asymmetric in terms of the size and energy differences of the components. The key point in extending a cubic equation of state to such system is on the choice of proper mixing rules. New mixing rules for the Redlich-Kwong equation of state are developed. The developement is based on the statistical-mechanical theory of the van der Waals mixing rules. The Redlich Kwong equation of state with the proposed mixing rules along with the original ones is used to predict solubilities of solids in supercritical fluid. The prediction is done with kij equal zero, as well as with optimized kij.  The results show superiority of the proposed mixing rules over the original ones. For most of the systems considered, the proposed mixing rules with the kij equal zero are closer to the experimental data than the original ones do. For 28 systems with 521 data points taken from various sources, the original and the proposed mixing rules give the overall AAD of 13.4%, while the original mixing rules give 45.9%.

  1. Modulation of interfacial electronic properties in PbI2 and BN van der Waals heterobilayer via external electric field

    Science.gov (United States)

    Ma, Yaqiang; Zhao, Xu; Niu, Mengmeng; Dai, Xianqi; Li, Wei; Wang, Xiaolong; Zhao, Mingyu; Wang, Tianxing; Tang, Yanan

    2017-07-01

    The interfacial electronic properties of PbI2 and BN van der Waals (vdW) heterobilayer are explored by using density functional theory (DFT) method. An intrinsic type-II heterostructure with a wide bandgap is demonstrated. The spatial separation of the lowest energy electron-hole pairs can be actualised and make PbI2/BN heterostructure as a good candidate for applications in optoelectronics and solar cell. A simulation of Efield is actualized to modify its electronic properties. Band alignment converts from type-II to type-I heterostructure separated by a forward voltage with the value of about 0.07 V/Å. Three regions implying different Efield-sensitive properties are obtained from the variations of bandgap with Efield. The charge redistribution with an Efield is mainly on the surface of PbI2 and BN layers as well as the amount of electrons depends on the strength of Efield. In addition, the PbI2/BN heterobilayer exhibits more outstanding optical conductivity capability. Our results could bring forward a new perspective on sensor and shed light on the design of novel nano- and optoelectronics based on the PbI2/BN vdW heterostructure.

  2. Quasi van der Waals epitaxy of copper thin film on single-crystal graphene monolayer buffer

    Science.gov (United States)

    Lu, Zonghuan; Sun, Xin; Washington, Morris A.; Lu, Toh-Ming

    2018-03-01

    Quasi van der Waals epitaxial growth of face-centered cubic Cu (~100 nm) thin films on single-crystal monolayer graphene is demonstrated using thermal evaporation at an elevated substrate temperature of 250 °C. The single-crystal graphene was transferred to amorphous (glass) and crystalline (quartz) SiO2 substrates for epitaxy study. Raman analysis showed that the thermal evaporation method had minimal damage to the graphene lattice during the Cu deposition. X-ray diffraction and electron backscatter diffraction analyses revealed that both Cu films are single-crystal with (1 1 1) out-of-plane orientation and in-plane Σ3 twin domains of 60° rotation. The crystallinity of the SiO2 substrates has a negligible effect on the Cu crystal orientation during the epitaxial growth, implying the strong screening effect of graphene. We also demonstrate the epitaxial growth of polycrystalline Cu on a commercial polycrystalline monolayer graphene consisting of two orientation domains offset 30° to each other. It confirms that the crystal orientation of the epitaxial Cu film follows that of graphene, i.e. the Cu film consists of two orientation domains offset 30° to each other when deposited on polycrystalline graphene. Finally, on the contrary to the report in the literature, we show that the direct current and radio frequency flip sputtering method causes significant damage to the graphene lattice during the Cu deposition process, and therefore neither is a suitable method for Cu epitaxial growth on graphene.

  3. Calculated carrier mobility of h-BN/γ-InSe/h-BN van der Waals heterostructures

    Science.gov (United States)

    Kang, P.; Michaud-Rioux, V.; Kong, X.-H.; Yu, G.-H.; Guo, H.

    2017-12-01

    Recent experiments reported excellent transport properties of two-dimensional (2D) van der Waals (vdW) heterostructures made of atomically thin InSe layers encapsulated by two hBN capping layers (ISBN). The carrier mobility of the ISBN films exceeded μ ˜ 1.2× {{10}4} \\text{c}{{\\text{m}}2} {{\\text{V}}-1} {{\\text{s}}-1} at low temperature, much higher than that of pristine InSe films. It has been puzzling why the relatively inert hBN capping layer could so drastically enhance mobility of the ISBN composite. Using a state-of-the-art first principles method, we have calculated phonon limited carrier mobility of 18 different ISBN films and 6 pristine InSe films with different thicknesses, the largest system containing 2212 atoms. The hBN capping layer significantly alters the elastic stiffness coefficient as compared with pure InSe—thus the acoustic phonons in the ISBN composite—giving rise to the observed large mobility of ISBN films. Of the 18 calculated ISBN films, the ones with no strain at the hBN/InSe interface possess the highest electron mobility, reaching 4340~\\text{c}{{\\text{m}}2}~{{\\text{V}}-1}~{{\\text{s}}-1} at room temperature, which could easily go over {{10}4}~\\text{c}{{\\text{m}}2}~{{\\text{V}}-1}~{{\\text{s}}-1} at low temperatures. We conclude that the mechanical properties of the composite 2D vdW ISBN material play the crucial role for inducing the large carrier mobility, a principle that could be applied to many other 2D vdW heterostructures.

  4. Combining density functional and incremental post-Hartree-Fock approaches for van der Waals dominated adsorbate-surface interactions: Ag2/graphene

    International Nuclear Information System (INIS)

    Lara-Castells, María Pilar de; Mitrushchenkov, Alexander O.; Stoll, Hermann

    2015-01-01

    A combined density functional (DFT) and incremental post-Hartree-Fock (post-HF) approach, proven earlier to calculate He-surface potential energy surfaces [de Lara-Castells et al., J. Chem. Phys. 141, 151102 (2014)], is applied to describe the van der Waals dominated Ag 2 /graphene interaction. It extends the dispersionless density functional theory developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] by including periodic boundary conditions while the dispersion is parametrized via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. Starting with the elementary cluster unit of the target surface (benzene), continuing through the realistic cluster model (coronene), and ending with the periodic model of the extended system, modern ab initio methodologies for intermolecular interactions as well as state-of-the-art van der Waals-corrected density functional-based approaches are put together both to assess the accuracy of the composite scheme and to better characterize the Ag 2 /graphene interaction. The present work illustrates how the combination of DFT and post-HF perspectives may be efficient to design simple and reliable ab initio-based schemes in extended systems for surface science applications

  5. Combining density functional and incremental post-Hartree-Fock approaches for van der Waals dominated adsorbate-surface interactions: Ag2/graphene.

    Science.gov (United States)

    de Lara-Castells, María Pilar; Mitrushchenkov, Alexander O; Stoll, Hermann

    2015-09-14

    A combined density functional (DFT) and incremental post-Hartree-Fock (post-HF) approach, proven earlier to calculate He-surface potential energy surfaces [de Lara-Castells et al., J. Chem. Phys. 141, 151102 (2014)], is applied to describe the van der Waals dominated Ag2/graphene interaction. It extends the dispersionless density functional theory developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] by including periodic boundary conditions while the dispersion is parametrized via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. Starting with the elementary cluster unit of the target surface (benzene), continuing through the realistic cluster model (coronene), and ending with the periodic model of the extended system, modern ab initio methodologies for intermolecular interactions as well as state-of-the-art van der Waals-corrected density functional-based approaches are put together both to assess the accuracy of the composite scheme and to better characterize the Ag2/graphene interaction. The present work illustrates how the combination of DFT and post-HF perspectives may be efficient to design simple and reliable ab initio-based schemes in extended systems for surface science applications.

  6. Combining density functional and incremental post-Hartree-Fock approaches for van der Waals dominated adsorbate-surface interactions: Ag{sub 2}/graphene

    Energy Technology Data Exchange (ETDEWEB)

    Lara-Castells, María Pilar de, E-mail: Pilar.deLara.Castells@csic.es [Instituto de Física Fundamental (C.S.I.C.), Serrano 123, E-28006 Madrid (Spain); Mitrushchenkov, Alexander O. [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France); Stoll, Hermann [Institut für Theoretische Chemie, Universität Stuttgart, D-70550 Stuttgart (Germany)

    2015-09-14

    A combined density functional (DFT) and incremental post-Hartree-Fock (post-HF) approach, proven earlier to calculate He-surface potential energy surfaces [de Lara-Castells et al., J. Chem. Phys. 141, 151102 (2014)], is applied to describe the van der Waals dominated Ag{sub 2}/graphene interaction. It extends the dispersionless density functional theory developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] by including periodic boundary conditions while the dispersion is parametrized via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. Starting with the elementary cluster unit of the target surface (benzene), continuing through the realistic cluster model (coronene), and ending with the periodic model of the extended system, modern ab initio methodologies for intermolecular interactions as well as state-of-the-art van der Waals-corrected density functional-based approaches are put together both to assess the accuracy of the composite scheme and to better characterize the Ag{sub 2}/graphene interaction. The present work illustrates how the combination of DFT and post-HF perspectives may be efficient to design simple and reliable ab initio-based schemes in extended systems for surface science applications.

  7. Size effects in van der Waals clusters studied by spin and angle-resolved electron spectroscopy and multi-coincidence ion imaging

    International Nuclear Information System (INIS)

    Rolles, D; Pesic, Z D; Zhang, H; Bilodeau, R C; Bozek, J D; Berrah, N

    2007-01-01

    We have studied the valence and inner-shell photoionization of free rare-gas clusters by means of angle and spin resolved photoelectron spectroscopy and momentum resolving electron-multi-ion coincidence spectroscopy. The electron measurements probe the evolution of the photoelectron angular distribution and spin polarization parameters as a function of photon energy and cluster size, and reveal a strong cluster size dependence of the photoelectron angular distributions in certain photon energy regions. In contrast, the spin polarization parameter of the cluster photoelectrons is found to be very close to the atomic value for all covered photon energies and cluster sizes. The ion imaging measurements, which probe the fragmentation dynamics of multiply charged van der Waals clusters, also exhibit a pronounced cluster size dependence

  8. Hybrid van der Waals p-n Heterojunctions based on SnO and 2D MoS2

    KAUST Repository

    Wang, Zhenwei

    2016-08-30

    A p-type oxide/2D hybrid van der Waals p-n heterojunction is demonstrated for the first time between SnO (tin monoxide) (the p-type oxide) and 2D MoS2 (molybdenum disulfide), showing an ideality factor of 2 and rectification ratio up to 10(4) . The reported heterojunction is gate-tunable with typical anti-ambipolar transfer characteristics. Surface potential mapping is performed and a current model for such a heterojunction is proposed.

  9. Connection between fragility, mean-squared displacement and shear modulus in two van der Waals bonded glass-forming liquids

    DEFF Research Database (Denmark)

    Hansen, Henriette Wase; Frick, Bernhard; Hecksher, Tina

    2017-01-01

    The temperature dependence of the high-frequency shear modulus measured in the kHz range is compared with the mean-squared displacement measured in the nanosecond range for the two van der Waals bonded glass-forming liquids cumene and 5-polyphenyl ether. This provides an experimental test...... for the assumption connecting two versions of the shoving model for the non-Arrhenius temperature dependence of the relaxation time in glass formers. The two versions of the model are also tested directly and both are shown to work well for these liquids....

  10. All-carbon vertical van der Waals heterostructures: Non-destructive functionalization of graphene for electronic applications

    OpenAIRE

    Woszczyna, Miroslaw; Winter, Andreas; Grothe, Miriam; Willunat, Annika; Wundrack, Stefan; Stosch, Rainer; Weimann, Thomas; Ahlers, Franz; Turchanin, Andrey

    2014-01-01

    We present a route to non-destructive functionalization of graphene via assembly of vertical all-carbon van der Waals heterostructures. To this end, we employ singlelayer graphene (SLG) sheets grown by low-pressure methane CVD on Cu foils and large-area dielectric ~1 nm thick amino-terminated carbon nanomembranes (NH2-CNMs) generated by electron-beam-induced crosslinking of aromatic self-assembled monolayers. We encapsulate SLG sheets on oxidized silicon wafers with NH2-CNMs via mechanical st...

  11. Graphene-supported small transition-metal clusters: A density functional theory investigation within van der Waals corrections

    Science.gov (United States)

    Rêgo, Celso R. C.; Tereshchuk, Polina; Oliveira, Luiz N.; Da Silva, Juarez L. F.

    2017-06-01

    Transition-metal nanoparticles adsorbed on graphene are of great interest due to the unique catalytic and magnetic properties resulting from nanoparticles-graphene interactions. Comparison between the physical properties of such systems and those of the same nanoparticles in the gas phase is especially important. Here we report a systematic density functional investigation of the structural, energetic, and magnetic properties of small Nin, Pdn, and Ptn clusters, comprising from n =1 to 6 atoms, in the gas phase and adsorbed on a graphene monolayer. Our results show that the Ni adatom binds to the graphene hollow site, with -1.47 -meV adsorption energy, while Pd and Pt prefer the bridge sites, with -1.14 - and -1.62 -meV adsorption energies, respectively. This difference is determined by a competition between quantum and classical forces. Ni2 and Pt2 dimers bind perpendicularly on hollow and bridge sites, respectively, while Pd2 lies parallel to the graphene sheet, with each adatom on a bridge site. For larger TMn (TM = Ni , Pd , Pt ; n =3 -6 ) clusters, either two or three atoms bind to bridge graphene sites. In almost all cases the adsorbed clusters retain their gas-phase structures. The exceptions are Ni5 and Pt4, which acquire more compact structures with effective coordination number 12 and 19 % larger than in the gas phase, respectively. As the number of atoms grows, the cluster binds more weakly to the graphene, while its binding energy mounts up. Van der Waals corrections to the plain density functional theory (DFT) total energy raise the adsorption energy, but leave the cluster structure unchanged, in the gas phase or upon adsorption. Bader charge analysis shows that adsorption causes minor charge redistribution: the TM atoms bound to C atoms become positively charged, while the remaining metal atoms acquire negative charge. We have derived an approximate analytical expression for the local densities of states for the d orbitals of Ni , Pd , and Pt adatoms

  12. Van der Waals heterojunction diode composed of WS2 flake placed on p-type Si substrate

    Science.gov (United States)

    Aftab, Sikandar; Farooq Khan, M.; Min, Kyung-Ah; Nazir, Ghazanfar; Afzal, Amir Muhammad; Dastgeer, Ghulam; Akhtar, Imtisal; Seo, Yongho; Hong, Suklyun; Eom, Jonghwa

    2018-01-01

    P–N junctions represent the fundamental building blocks of most semiconductors for optoelectronic functions. This work demonstrates a technique for forming a WS2/Si van der Waals junction based on mechanical exfoliation. Multilayered WS2 nanoflakes were exfoliated on the surface of bulk p-type Si substrates using a polydimethylsiloxane stamp. We found that the fabricated WS2/Si p–n junctions exhibited rectifying characteristics. We studied the effect of annealing processes on the performance of the WS2/Si van der Waals p–n junction and demonstrated that annealing improved its electrical characteristics. However, devices with vacuum annealing have an enhanced forward-bias current compared to those annealed in a gaseous environment. We also studied the top-gate-tunable rectification characteristics across the p–n junction interface in experiments as well as density functional theory calculations. Under various temperatures, Zener breakdown occurred at low reverse-bias voltages, and its breakdown voltage exhibited a negative coefficient of temperature. Another breakdown voltage was observed, which increased with temperature, suggesting a positive coefficient of temperature. Therefore, such a breakdown can be assigned to avalanche breakdown. This work demonstrates a promising application of two-dimensional materials placed directly on conventional bulk Si substrates.

  13. A van der Waals DFT study of PtH{sub 2} systems absorbed on pristine and defective graphene

    Energy Technology Data Exchange (ETDEWEB)

    López-Corral, Ignacio [Instituto de Química del Sur (INQUISUR), UNS-CONICET, Av. Alem 1253, B8000 Bahía Blanca (Argentina); Departamento de Química, Universidad Nacional del Sur, Av. Alem 1253, B8000 Bahía Blanca (Argentina); Piriz, Sebastián; Faccio, Ricardo [Centro NanoMat/DETEMA, Facultad de Química, Universidad de la República, Montevideo (Uruguay); Centro Interdisciplinario de Nanotecnología, Química y Física de Materiales (CINQUIFIMA), Facultad de Química, Universidad de la República, Montevideo (Uruguay); Juan, Alfredo, E-mail: cajuan@uns.edu.ar [Instituto de Física del Sur (IFISUR), UNS-CONICET, Av. Alem 1253, B8000 Bahía Blanca (Argentina); Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000 Bahía Blanca (Argentina); Avena, Marcelo [Instituto de Química del Sur (INQUISUR), UNS-CONICET, Av. Alem 1253, B8000 Bahía Blanca (Argentina); Departamento de Química, Universidad Nacional del Sur, Av. Alem 1253, B8000 Bahía Blanca (Argentina)

    2016-09-30

    Highlights: • We performed DFT calculations including van der Waals interactions. • Kubas-type Pt-H2 complex is stable on defective graphene. • Carbon vacancy decreases the reactivity of the metal decoration. • The interaction between σ-H and π-C states favors the Kubas-type complex. - Abstract: We used a density functional that incorporates van der Waals interactions to study hydrogen adsorption onto Pt atoms attached to carbon-vacancies on graphene layers, considering molecular and dissociated hydrogen-platinum coordination structures. PtH{sub 2} complexes adsorbed on several sites of pristine graphene were also studied for comparison. Our results indicate that both a Kubas-type dihydrogen complex and a classic hydride without H−H bond are the preferential PtH{sub 2} systems on the vacancy site of graphene. In contrast, the Kubas complex is unstable onto pristine graphene and the hydride is obtained at all adsorption sites. Our simulations suggest that the C-vacancy decreases the reactivity of the metal decoration, allowing a non-dissociative hydrogen adsorption. The H{sub 2} molecule is oriented almost perpendicular to the outermost C−Pt bond, interacting also with the graphene surface through σ-H and π-C states. This stabilization of the Kubas-type complex could play a very important role for hydrogen storage in Pt-decorated carbon adsorbents with vacancies.

  14. A van der Waals DFT study of PtH2 systems absorbed on pristine and defective graphene

    International Nuclear Information System (INIS)

    López-Corral, Ignacio; Piriz, Sebastián; Faccio, Ricardo; Juan, Alfredo; Avena, Marcelo

    2016-01-01

    Highlights: • We performed DFT calculations including van der Waals interactions. • Kubas-type Pt-H2 complex is stable on defective graphene. • Carbon vacancy decreases the reactivity of the metal decoration. • The interaction between σ-H and π-C states favors the Kubas-type complex. - Abstract: We used a density functional that incorporates van der Waals interactions to study hydrogen adsorption onto Pt atoms attached to carbon-vacancies on graphene layers, considering molecular and dissociated hydrogen-platinum coordination structures. PtH 2 complexes adsorbed on several sites of pristine graphene were also studied for comparison. Our results indicate that both a Kubas-type dihydrogen complex and a classic hydride without H−H bond are the preferential PtH 2 systems on the vacancy site of graphene. In contrast, the Kubas complex is unstable onto pristine graphene and the hydride is obtained at all adsorption sites. Our simulations suggest that the C-vacancy decreases the reactivity of the metal decoration, allowing a non-dissociative hydrogen adsorption. The H 2 molecule is oriented almost perpendicular to the outermost C−Pt bond, interacting also with the graphene surface through σ-H and π-C states. This stabilization of the Kubas-type complex could play a very important role for hydrogen storage in Pt-decorated carbon adsorbents with vacancies.

  15. Van der Waals molecular dimers (He2)2 in solutions of the quantum liquids He3-He II

    International Nuclear Information System (INIS)

    Bashkin, E.P.

    1980-01-01

    Bound states of a pair of impurity He 3 quasiparticles produced as a result of van der Waals attraction at the free surface, in thin films, in narrow capillaries and at vortex filaments in superfluid He 4 are investigated. The contribution of bound states to the thermodynamics of the solution becomes predominant on lowering of the temperature. The inelastic absorption coefficient of first sound due to decay of the bound state in the field of an acoustic wave is calculated. For a system of impurity excitations in narrow capillaries or vortex filaments the existence of a resonance singularity (at a frequency corresponding to the threshold for bound state splitting) is predicted for which the absorption coefficient for monochromatic sound becomes infinite. The gas-liquid phase transition temperature and superfluid transition temperature are calculated for a Bose system of van der Waals (He 3 ) 2 pairs at the surface or in thin He II films. It is shown that the superfluid transition temperature may be of the order of 35 mK

  16. Effect of van der Waals interaction on the properties of SnS{sub 2} layered semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Seminovski, Y. [Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpt. TEAT, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Palacios, P., E-mail: pablo.palacios@upm.es [Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpt. FyQATA, EIAE, Universidad Politécnica de Madrid, Pz. Cardenal Cisneros, 3, 28040 Madrid (Spain); Wahnón, P. [Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpt. TEAT, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)

    2013-05-01

    Nowadays, dispersion correction applied on layered semiconductors is a topic of interest. Among the known layered semiconductors, SnS{sub 2} polytypes are wide gap semiconductors with a van der Waals interaction between their layers, which could form good materials to be used in photovoltaic applications. The present work gives an approach to the SnS{sub 2} geometrical and electronic characterization using an empirical dispersion correction added to the Perdew–Burke–Ernzerhof functional and subsequent actualization of the electronic charge density using the screened hybrid Heyd–Scuseria–Ernzerhof functional using a density functional code. The obtained interlayer distance and band-gap are in good agreement with experimental values when van der Waals dispersion forces are included. - Highlights: ► Tin disulphide (SnS{sub 2}) has been calculated using density functional theory methods. ► A dispersion correction was also applied for two different SnS{sub 2} polytypes. ► Geometrical parameters and band-gaps were obtained using both approaches. ► Our calculations give a good agreement of the computed band gap with experiment.

  17. Film Thickness Formation in Nanoscale due to Effects of Elastohydrodynamic, Electrostatic and Surface force of Solvation and Van der Waals

    Directory of Open Access Journals (Sweden)

    M.F. Abd Al-Samieh

    2017-03-01

    Full Text Available The mechanism of oil film with a thickness in the nanoscale is discussed in this paper. A polar lubricant of propylene carbonate is used as the intervening liquid between contiguous bodies in concentrated contacts. A pressure caused by the hydrodynamic viscous action in addition to double layer electrostatic force, Van der Waals inter-molecular forces, and solvation pressure due to inter-surface forces is considered in calculating the ultrathin lubricating films. The numerical solution has been carried out, using the Newton-Raphson iteration technique, applied for the convergence of the hydrodynamic pressure. The results show that, at separations beyond about five molecular diameters of the intervening liquid, the formation of a lubricant film thickness is governed by combined effects of viscous action and surface force of an attractive Van der Waals force and a repulsive double layer force. At smaller separations below about five molecular diameters of the intervening liquid, the effect of solvation force is dominant in determining the oil film thickness

  18. Using the van der Waals broadening of the spectral atomic lines to measure the gas temperature of an argon microwave plasma at atmospheric pressure

    International Nuclear Information System (INIS)

    Yubero, C.; Dimitrijevic, M.S.; Garcia, M.C.; Calzada, M.D.

    2007-01-01

    The ro-vibrational emission spectra of the molecular species are usually used to measure the gas temperature of a discharge at atmospheric pressure. However, under some experimental conditions, it is difficult to detect them. In order to overcome this difficulty and obtain the temperature, there are methods based on the relation between the gas temperature and the van der Waals broadening of argon atomic spectral lines with a Stark contribution negligible. In this work, we propose a method based on this relation but for lines with a Stark broadening comparable with the van der Waals one

  19. Revisiting van der Waals like behavior of f(R AdS black holes via the two point correlation function

    Directory of Open Access Journals (Sweden)

    Jie-Xiong Mo

    2017-05-01

    Full Text Available Van der Waals like behavior of f(R AdS black holes is revisited via two point correlation function, which is dual to the geodesic length in the bulk. The equation of motion constrained by the boundary condition is solved numerically and both the effect of boundary region size and f(R gravity are probed. Moreover, an analogous specific heat related to δL is introduced. It is shown that the T−δL graphs of f(R AdS black holes exhibit reverse van der Waals like behavior just as the T−S graphs do. Free energy analysis is carried out to determine the first order phase transition temperature T⁎ and the unstable branch in T−δL curve is removed by a bar T=T⁎. It is shown that the first order phase transition temperature is the same at least to the order of 10−10 for different choices of the parameter b although the values of free energy vary with b. Our result further supports the former finding that charged f(R AdS black holes behave much like RN-AdS black holes. We also check the analogous equal area law numerically and find that the relative errors for both the cases θ0=0.1 and θ0=0.2 are small enough. The fitting functions between log⁡|T−Tc| and log⁡|δL−δLc| for both cases are also obtained. It is shown that the slope is around 3, implying that the critical exponent is about 2/3. This result is in accordance with those in former literatures of specific heat related to the thermal entropy or entanglement entropy.

  20. THz absorption spectrum of the CO2–H2O complex: Observation and assignment of intermolecular van der Waals vibrations

    DEFF Research Database (Denmark)

    Andersen, Jonas; Heimdal, J.; Wallin Mahler Andersen, Denise

    2014-01-01

    Terahertz absorption spectra have been recorded for the weakly bound CO2–H2O complex embedded in cryogenic neon matrices at 2.8 K. The three high-frequency van der Waals vibrational transitions associated with out-of-plane wagging, in-plane rocking, and torsional motion of the isotopic H2O subunit...

  1. Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform

    DEFF Research Database (Denmark)

    Cui, Xu; Lee, Gwan-Hyoung; Kim, Young Duck

    2015-01-01

    scattering, we have developed here a van der Waals heterostructure device platform where MoS2 layers are fully encapsulated within hexagonal boron nitride and electrically contacted in a multi-terminal geometry using gate-tunable graphene electrodes. Magneto-transport measurements show dramatic improvements...

  2. Spectroscopic Signatures for Interlayer Coupling in MoS 2 –WSe 2 van der Waals Stacking

    KAUST Repository

    Chiu, Ming-Hui

    2014-09-23

    Stacking of MoS2 and WSe2 monolayers is conducted by transferring triangular MoS2 monolayers on top of WSe2 monolayers, all grown by chemical vapor deposition (CVD). Raman spectroscopy and photoluminescence (PL) studies reveal that these mechanically stacked monolayers are not closely coupled, but after a thermal treatment at 300 degrees C, it is possible to produce van der Waals solids consisting of two interacting transition metal dichalcogenide (TMD) monolayers. The layer-number sensitive Raman out-of-plane mode A(1g)(2) for WSe2 (309 cm(-1)) is found sensitive to the coupling between two TMD monolayers. The presence of interlayer excitonic emissions and the changes in other intrinsic Raman modes such as E \\'\\' for MoS2 at 286 cm(-1) and A(1g)(2) for MoS2 at around 463 cm(-1) confirm the enhancement of the interlayer coupling.

  3. Semiempirical calculation of van der Waals coefficients for alkali-metal and alkaline-earth-metal atoms

    International Nuclear Information System (INIS)

    Mitroy, J.; Bromley, M.W.J.

    2003-01-01

    The van der Waals coefficients, C 6 , C 8 , and C 10 for the alkali-metal (Li, Na, K, and Rb) and alkaline-earth-metal (Be, Mg, Ca, and Sr) atoms are estimated by a combination of ab initio and semiempirical methods. Polarizabilities and atom-wall coefficients are given as a diagnostic check, and the lowest order nonadiabatic dispersion coefficient, D 8 and the three-body coefficient, C 9 are also presented. The dispersion coefficients are in agreement with the available relativistic many-body perturbation theory calculations. The contribution from the core was included by using constrained sum rules involving the core polarizability and Hartree-Fock expectation values to estimate the f-value distribution

  4. Electronic structure of transferred graphene/h-BN van der Waals heterostructures with nonzero stacking angles by nano-ARPES.

    Science.gov (United States)

    Wang, Eryin; Chen, Guorui; Wan, Guoliang; Lu, Xiaobo; Chen, Chaoyu; Avila, Jose; Fedorov, Alexei V; Zhang, Guangyu; Asensio, Maria C; Zhang, Yuanbo; Zhou, Shuyun

    2016-11-09

    In van der Waals heterostructures, the periodic potential from the Moiré superlattice can be used as a control knob to modulate the electronic structure of the constituent materials. Here we present a nanoscale angle-resolved photoemission spectroscopy (nano-ARPES) study of transferred graphene/h-BN heterostructures with two different stacking angles of 2.4° and 4.3° respectively. Our measurements reveal six replicas of graphene Dirac cones at the superlattice Brillouin zone (SBZ) centers. The size of the SBZ and its relative rotation angle to the graphene BZ are in good agreement with Moiré superlattice period extracted from atomic force microscopy (AFM) measurements. Comparison to the epitaxial graphene/h-BN with 0° stacking angles suggests that the interaction between graphene and h-BN decreases with increasing stacking angle.

  5. Van der Waals epitaxial growth of MoS2 on SiO2/Si by chemical vapor deposition

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

    Recently, single layer MoS2 with a direct band gap of 1.9 eV has been proposed as a candidate for two dimensional nanoelectronic devices. However, the synthetic approach to obtain high-quality MoS2 atomic thin layers is still problematic. Spectroscopic and microscopic results reveal that both single layers and tetrahedral clusters of MoS2 are deposited directly on the SiO2/Si substrate by chemical vapor deposition. The tetrahedral clusters are mixtures of 2H- and 3R-MoS2. By ex situ optical analysis, both the single layers and tetrahedral clusters can be attributed to van der Waals epitaxial growth. Due to the similar layered structures we expect the same growth mechanism for other transition-metal disulfides by chemical vapor deposition. © 2013 The Royal Society of Chemistry.

  6. Bandgap engineering in van der Waals heterostructures of blue phosphorene and MoS{sub 2}: A first principles calculation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.Y. [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Si, M.S., E-mail: sims@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Peng, S.L. [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Zhang, F. [Key Lab of Photovoltaic Materials of Henan Province, Henan University, Kaifeng 475001 (China); Wang, Y.H.; Xue, D.S. [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2015-11-15

    Blue phosphorene (BP) was theoretically predicted to be thermally stable recently. Considering its similar in-layer hexagonal lattice to MoS{sub 2}, MoS{sub 2} could be an appropriate substrate to grow BP in experiments. In this work, the van der Waals (vdW) heterostructures are constructed by stacking BP on top of MoS{sub 2}. The thermal stability and electronic structures are evaluated based on first principles calculations with vdW-corrected exchange-correlation functional. The formation of the heterostructures is demonstrated to be exothermic and the most stable stacking configuration is confirmed. The heterostructures BP/MoS{sub 2} preserve both the properties of BP and MoS{sub 2} but exhibit relatively narrower bandgaps due to the interlayer coupling effect. The band structures can be further engineered by applying external electric fields. An indirect–direct bandgap transition in bilayer BP/MoS{sub 2} is demonstrated to be controlled by the symmetry property of the built-in electric dipole fields. - Graphical abstract: An indirect-direct band gap transition occurs in van der Waals heterostructure of MoS{sub 2}/BP under external electric fields which is demonstrated to be controlled by the symmetry of the built-in electric dipole fields. - Highlights: • The stacking of heterostructures of BP/MoS{sub 2} is demonstrated to be exothermic. • This suggests that it is possible to grow BP using MoS{sub 2} as the substrate. • The band structures of the heterostructures are exploited. • It realizes an indirect–direct gap transition under external electric fields. • The symmetry of the built-in electric dipole fields controls such gap transition.

  7. Application of Solution-blown 20-50 nm Nanofibers in Filtration of Nanoparticles: The Efficient van der Waals Collectors

    Science.gov (United States)

    Sinha-Ray, Sumit; Sinha-Ray, Suman; Yarin, Alexander; Pourdeyhimi, Behnam

    2015-11-01

    Filtration efficiency of commercially available filter media with fiber/pore sizes on the scale of 10 μm can be dramatically increased by adding a layer of ultrafine supersonically-blown 20-50 nm nanofibers. Different commercial filters were modified with (i) electrospun nanofibers alone, (ii) solution-blown 20-50 nm alone, and (iii) the dual coating with electrospun nanofibers deposited first and the solution-blown 20-50 nm nanofibers deposited on top of them. Detailed observations of nanoparticle removal revealed that the above-mentioned modified filters, especially those with the dual nanofiber coating with the 20-50 nm nanofibers deposited on top, are the most effective in removing the below-200 nm Cu nanoparticles/clusters from aqueous suspensions, in particular at the lowest concentrations of 0.2-0.5 ppm. The theory developed in the present work dealing with convective transport of nanoparticles in the fluid flow along with diffusion of nanoparticles and the van der Waals attraction explains and describes how the smallest solution-blown nanofibers introduce a novel physical mechanism of nanoparticle interception (the attractive van der Waals forces) and become significantly more efficient collectors compared to the larger electrospun nanofibers. The theory also elucidates the morphology of the nanoparticle clusters being accumulated at the smallest nanofiber surfaces, including the clusters growing at the windward side, or in some cases also on the leeward side of a nanofiber. This work is supported by the Nonwovens Cooperative Research Center (NCRC), grant No. 12-144SB.

  8. The influence of van der Waals forces on the state of water in the shallow subsurface of Mars

    Science.gov (United States)

    Möhlmann, Diedrich T. F.

    2008-05-01

    Microscopic liquid layers of water can evolve via adsorption on grain and mineral surfaces at and in the soil of the surface of Mars. The upper parts of these layers will start to freeze at temperatures clearly below the freezing point of bulk water (freezing point depression). A sandwich structure with layers of ice (top), liquid water (in between) and mineral surface (bottom) can evolve. The properties of the interfacial water (of adsorption water and premelted ice) on grain surfaces are described by a sandwich-model of a layer of liquid-like adsorption water between the adsorbing mineral surface layer and an upper ice layer. It is shown that the thickness or number of mono-layers of the interfacial water (of adsorption water and premelted ice) depends on temperature and atmospheric relative humidity. The derived equations for the sandwich model fit well to a known phenomenological relation between thickness of the liquid layer and relative humidity, and can be a tool to estimate or to determine for appropriate materials Hamaker's constant for van der Waals interactions on grains and in porous media. The curvature of grain surfaces is shown to have no remarkable effects for particles in the μm-range and larger. The application of these equations to thermo-physical conditions on Mars shows that the thickness of frost-layers, which can evolve over several hours on cooling surface parts of Mars, is typically of the order or a few tenths of one millimeter or less. This is in agreement with observations. Furthermore, an equation is derived, which relates the freezing point depression for van der Waals force governed interfacial water to the value of the Hamaker constant, to the latent heat of solidification, to the mass density of water ice, and to the thickness of the liquid-like layer. Again, this equation fits well to a known phenomenological relation between freezing point depression and thickness of the liquid-like layer. The derived equation shows that the

  9. Application of mixed-mode, solid-phase extraction in environmental and clinical chemistry. Combining hydrogen-bonding, cation-exchange and Van der Waals interactions

    Science.gov (United States)

    Mills, M.S.; Thurman, E.M.; Pedersen, M.J.

    1993-01-01

    Silica- and styrene-divinylbenzene-based mixed-mode resins that contain C8, C18 and sulphonated cation-exchange groups were compared for their efficiency in isolation of neutral triazine compounds from water and of the basic drug, benzoylecgonine, from urine. The triazine compounds were isolated by a combination of Van der Waals and hydrogen-bonding interactions, and benzoylecgonine was isolated by Van der Waals interactions and cation exchange. All analytes were eluted with a polar organic solvent contaning 2% ammonium hydroxide. Larger recoveries (95%) were achieved on copolymerized mixed-mode resins where C18 and sulfonic acid are in closer proximity than on 'blended' mixed-mode resins (60-70% recovery).

  10. Substrate induced tuning of compressive strain and phonon modes in large area MoS2 and WS2 van der Waals epitaxial thin films

    Science.gov (United States)

    Sahu, Rajib; Radhakrishnan, Dhanya; Vishal, Badri; Negi, Devendra Singh; Sil, Anomitra; Narayana, Chandrabhas; Datta, Ranjan

    2017-07-01

    Large area MoS2 and WS2 van der Waals epitaxial thin films with control over number of layers including monolayer is grown by pulsed laser deposition utilizing slower growth kinetics. The films grown on c-plane sapphire show stiffening of A1g and E12g phonon modes with decreasing number of layers for both MoS2 and WS2. The observed stiffening translate into the compressive strain of 0.52% & 0.53% with accompanying increase in fundamental direct band gap to 1.74 and 1.68 eV for monolayer MoS2 and WS2, respectively. The strain decays with the number of layers. HRTEM imaging directly reveals the nature of atomic registry of van der Waals layers with the substrate and the associated compressive strain. The results demonstrate a practical route to stabilize and engineer strain for this class of material over large area device fabrication.

  11. Bifurcations of new multi soliton solutions of the van der Waals normal form for fluidized granular matter via six different methods

    Directory of Open Access Journals (Sweden)

    Dianchen Lu

    Full Text Available In this article, we study one of the most popular models in nature and also industrial which is the van der Waals normal form for the fluidized granular matter. Understanding of static and dynamic property for these kinds of the models is very important in many aspects of industrial from pharmaceuticals to civil engineering and also some basic physical phenomena like those studied in geophysics. This model explains the phase separation phenomenon. We apply six different methods for this model to obtained the traveling and solitary wave solutions. We make the comparison between obtained solutions with each of them and also with obtained solutions with different methods. Keywords: The van der Waals normal form for fluidized granular matter, Modified simple equation method, The improved mapping approach and variable separation method, Traveling wave solutions, Solitary wave solutions, Mathematical physics

  12. Understanding the role of vibrations, exact exchange, and many-body van der Waals interactions in the cohesive properties of molecular crystals

    Science.gov (United States)

    Reilly, Anthony M.; Tkatchenko, Alexandre

    2013-07-01

    The development and application of computational methods for studying molecular crystals, particularly density-functional theory (DFT), is a large and ever-growing field, driven by their numerous applications. Here we expand on our recent study of the importance of many-body van der Waals interactions in molecular crystals [A. M. Reilly and A. Tkatchenko, J. Phys. Chem. Lett. 4, 1028 (2013), 10.1021/jz400226x], with a larger database of 23 molecular crystals. Particular attention has been paid to the role of the vibrational contributions that are required to compare experiment sublimation enthalpies with calculated lattice energies, employing both phonon calculations and experimental heat-capacity data to provide harmonic and anharmonic estimates of the vibrational contributions. Exact exchange, which is rarely considered in DFT studies of molecular crystals, is shown to have a significant contribution to lattice energies, systematically improving agreement between theory and experiment. When the vibrational and exact-exchange contributions are coupled with a many-body approach to dispersion, DFT yields a mean absolute error (3.92 kJ/mol) within the coveted "chemical accuracy" target (4.2 kJ/mol). The role of many-body dispersion for structures has also been investigated for a subset of the database, showing good performance compared to X-ray and neutron diffraction crystal structures. The results show that the approach employed here can reach the demanding accuracy of crystal-structure prediction and organic material design with minimal empiricism.

  13. Ionic Intercalation in Two-Dimensional van der Waals Materials: In Situ Characterization and Electrochemical Control of the Anisotropic Thermal Conductivity of Black Phosphorus.

    Science.gov (United States)

    Kang, Joon Sang; Ke, Ming; Hu, Yongjie

    2017-03-08

    Two-dimensional van der Waals materials have shown novel fundamental properties and promise for wide applications. Here, we report for the first time an experimental demonstration of the in situ characterization and highly reversible control of the anisotropic thermal conductivity of black phosphorus. We develop a novel platform based on lithium ion batteries that integrates ultrafast optical spectroscopy and electrochemical control to investigate the interactions between lithium ions and the lattices of the black phosphorus electrode. We discover a strong dependence of the thermal conductivity on battery charge states (lithium concentrations) during the discharge/charge process. The thermal conductivity of black phosphorus is reversibly tunable over a wide range of 2.45-3.86, 62.67-85.80, and 21.66-27.58 W·m -1 ·K -1 in the cross-plan, zigzag, and armchair directions, respectively. The modulation in thermal conductivity is attributed to phonon scattering introduced by the ionic intercalation in between the interspacing layers and shows anisotropic phonon scattering mechanism based on semiclassical model. At the fully discharged state (x ∼ 3 in Li x P), a dramatic reduction of thermal conductivity by up to 6 times from that of the pristine crystal has been observed. This study provides a unique approach to explore the fundamental energy transport involving lattices and ions in the layered structures and may open up new opportunities in controlling energy transport based on novel operation mechanisms and the rational design of nanostructures.

  14. Investigating the effect of Casimir and van der Waals attractions on the electrostatic pull-in instability of nano-actuators

    International Nuclear Information System (INIS)

    Soroush, R; Koochi, A; Haddadpour, H; Kazemi, A S; Noghrehabadi, A; Abadyan, M

    2010-01-01

    This paper investigates the effect of dispersion (van der Waals and Casimir) forces on the pull-in instability of cantilever nano-actuators by considering their range of application. Adomian decomposition is introduced to obtain an analytical solution of the distributed parameter model. Dispersion forces decrease the pull-in deflection and voltage of a nano-actuator. However, the fringing field increases the pull-in deflection while decreasing the pull-in voltage of the actuator. The minimum initial gap and the detachment length of the actuator that does not stick to the substrate due to van der Waals and Casimir attractions were determined. Furthermore, the proposed approach is capable of determining the stress distribution of the actuator at the onset of instability. It is seen that Casimir and van der Waals attractions effectively reduce the maximum value of stress resultants at the onset of instability. The results indicate that Adomian decomposition is a reliable method for simulating nano-structures at submicrometer ranges.

  15. Layer-dependent electronic properties of phosphorene-like materials and phosphorene-based van der Waals heterostructures.

    Science.gov (United States)

    Huang, Y C; Chen, X; Wang, C; Peng, L; Qian, Q; Wang, S F

    2017-06-29

    Black phosphorus is a layered semiconducting allotrope of phosphorus with high carrier mobility. Its monolayer form, phosphorene, is an extremely fashionable two-dimensional material which has promising potential in transistors, optoelectronics and electronics. However, phosphorene-like analogues, especially phosphorene-based heterostructures and their layer-controlled electronic properties, are rarely systematically investigated. In this paper, the layer-dependent structural and electronic properties of phosphorene-like materials, i.e., mono- and few-layer MXs (M = Sn, Ge; X = S, Se), are first studied via first-principles calculations, and then the band edge position of these MXs as well as mono- and few-layer phosphorene are aligned. It is revealed that van der Waals heterostructures with a Moiré superstructure formed by mutual coupling among MXs and among MXs and few-layer phosphorene are able to show type-I or type-II characteristics and a I-II or II-I transition can be induced by adjusting the number of layers. Our work is expected to yield a new family of phosphorene-based semiconductor heterostructures with tunable electronic properties through altering the number of layers of the composite.

  16. A semi-floating gate memory based on van der Waals heterostructures for quasi-non-volatile applications.

    Science.gov (United States)

    Liu, Chunsen; Yan, Xiao; Song, Xiongfei; Ding, Shijin; Zhang, David Wei; Zhou, Peng

    2018-04-09

    As conventional circuits based on field-effect transistors are approaching their physical limits due to quantum phenomena, semi-floating gate transistors have emerged as an alternative ultrafast and silicon-compatible technology. Here, we show a quasi-non-volatile memory featuring a semi-floating gate architecture with band-engineered van der Waals heterostructures. This two-dimensional semi-floating gate memory demonstrates 156 times longer refresh time with respect to that of dynamic random access memory and ultrahigh-speed writing operations on nanosecond timescales. The semi-floating gate architecture greatly enhances the writing operation performance and is approximately 10 6 times faster than other memories based on two-dimensional materials. The demonstrated characteristics suggest that the quasi-non-volatile memory has the potential to bridge the gap between volatile and non-volatile memory technologies and decrease the power consumption required for frequent refresh operations, enabling a high-speed and low-power random access memory.

  17. Nuclear molecular halo: the ubiquitous occurrence of van der Waals molecular states near threshold in molecular, nuclear and particle physics

    International Nuclear Information System (INIS)

    Gai, Moshe

    1999-01-01

    The observation of large E1 strength near threshold in the electromagnetic dissociation of 11 Li poses a fundamental question: Is the large E1 strength due to the threshold or is it due to a low lying E1 state? Such molecular cluster states were observed in 18 O and in several nuclei near the drip line. We discuss the nature of the threshold effect as well as review the situation in Molecular (and Particle Physics) where such Molecular States are observed near the dissociation limit. We suggest that the situation in 11 Li is reminiscent of the argon-benzene molecule where the argon atom is loosely bound by a polarization (van der Waals) mechanism and thus leads to a very extended object lying near the dissociation limit. Such states are also suggested to dominate the structure of mesons [α 0 (980), f 0 (975)] and baryons [λ(1405)] with proposed Kaon molecular structure (Dalitz) near threshold. The inspection of such states throughout Physics allows us to gain insight into this phenomenon and suggest that a new collective Molecular Dipole Degree of Freedom plays a major role in the structure of hadrons (halo nuclei, mesons and baryons), and that quantitative tools such as the E1 Molecular Sum Rule are useful for elucidating the nature of the observed low lying E1 strength in halo nuclei. (author)

  18. A van der Waals DFT study of PtH2 systems absorbed on pristine and defective graphene

    Science.gov (United States)

    López-Corral, Ignacio; Piriz, Sebastián; Faccio, Ricardo; Juan, Alfredo; Avena, Marcelo

    2016-09-01

    We used a density functional that incorporates van der Waals interactions to study hydrogen adsorption onto Pt atoms attached to carbon-vacancies on graphene layers, considering molecular and dissociated hydrogen-platinum coordination structures. PtH2 complexes adsorbed on several sites of pristine graphene were also studied for comparison. Our results indicate that both a Kubas-type dihydrogen complex and a classic hydride without Hsbnd H bond are the preferential PtH2 systems on the vacancy site of graphene. In contrast, the Kubas complex is unstable onto pristine graphene and the hydride is obtained at all adsorption sites. Our simulations suggest that the C-vacancy decreases the reactivity of the metal decoration, allowing a non-dissociative hydrogen adsorption. The H2 molecule is oriented almost perpendicular to the outermost Csbnd Pt bond, interacting also with the graphene surface through σ-H and π-C states. This stabilization of the Kubas-type complex could play a very important role for hydrogen storage in Pt-decorated carbon adsorbents with vacancies.

  19. Rigorous analysis of Casimir and van der Waals forces on a silicon nano-optomechanical device actuated by optical forces.

    Science.gov (United States)

    Rodrigues, Janderson R; Gusso, Andre; Rosa, Felipe S S; Almeida, Vilson R

    2018-02-22

    Nano-optomechanical devices have enabled a lot of interesting scientific and technological applications. However, due to their nanoscale dimensions, they are vulnerable to the action of Casimir and van der Waals (dispersion) forces. This work presents a rigorous analysis of the dispersion forces on a nano-optomechanical device based on a silicon waveguide and a silicon dioxide substrate, surrounded by air and driven by optical forces. The dispersion forces are calculated using a modified Lifshitz theory with experimental optical data and validated by means of a rigorous 3D FDTD simulation. The mechanical nonlinearity of the nanowaveguide is taken into account and validated using a 3D FEM simulation. The results show that it is possible to attain a no pull-in critical point due to only the optical forces; however, the dispersion forces usually impose a pull-in critical point to the device and establish a minimal initial gap between the waveguide and the substrate. Furthermore, it is shown that the geometric nonlinearity effect may be exploited in order to avoid or minimize the pull-in and, therefore, the device collapse.

  20. Unified many-body approach to van der Waals interactions based on semi-local polarizability functional

    Science.gov (United States)

    Hermann, Jan; Scheffler, Matthias; Tkatchenko, Alexandre

    Electromagnetic coupling of charge fluctuations leads to van der Waals (vdW) attraction in systems ranging from metal nanoparticles to dielectric materials. In this regard, broadly applicable and accurate description of vdW interactions in complex materials is an elusive and unsolved puzzle. Many promising approaches model various subsets of this general problem, but are limited in scope by the underlying parametrization (atomic models), in accuracy due to missing many-body interactions (nonlocal density functionals), or in efficiency by working with virtual orbital space (e.g., random-phase approximation). Here, we present a unifying method that combines key elements from different theories and accurately describes vdW interactions in covalent, ionic, and metallic systems. In particular, we employ a semi-local polarizability functional of the electron density and its gradient to parametrize material response and its coupling within the many-body dispersion framework, and demonstrate the generality of the method on binding in molecular dimers and crystals, carbon-based nanomaterials, oxides, and salts, as well as on adsorption of molecules on metal surfaces. Our approach allows consistent modelling of a wide spectrum of materials as well as hybrid materials with mixed bond types.

  1. Hybrid van der Waals SnO/MoS2 Heterojunctions for Thermal and Optical Sensing Applications

    KAUST Repository

    Wang, Zhenwei

    2017-11-10

    Emerging van der Waals heterojunctions (vdWH) containing 2D materials have shown exciting functionalities that surpass those of traditional devices based on bulk materials. In this Communication, a report on the properties of a 2D sulfide/oxide hybrid vdWH based on n-type molybdenum disulfide (MoS2) and p-type tin monoxide (SnO) is presented, with promising rectification, thermal-sensing, and photosensing performance. Specifically, the hybrid SnO/MoS2 vdWH shows static rectification ratio of 2 × 102 with ideality factor of 2.3, and can operate at 100 Hz with good stability. The vdWH shows good temperature stability with reversible and reproducible current levels up to 110 °C, indicating its potential for thermal sensing applications. The sensitivity of current variation is calculated to be 0.0144 dec °C−1. Finally, maximum responsivity of 8.17 mA W−1 and external quantum efficiency of 2.14% have been achieved in photovoltaic measurements. The results suggest that MoS2–SnO hybrid vdWH are promising for various sensing applications.

  2. Rearrangement of van der Waals stacking and formation of a singlet state at T = 90 K in a cluster magnet

    Energy Technology Data Exchange (ETDEWEB)

    Sheckelton, John P.; Plumb, Kemp W.; Trump, Benjamin A.; Broholm, Collin L.; McQueen, Tyrel M.

    2017-01-01

    Insulating Nb3Cl8 is a layered chloride consisting of two-dimensional triangular layers of Seff = 1/2 Nb3Cl13 clusters at room temperature. Magnetic susceptibility measurement show a sharp, hysteretic drop to a temperature independent value below T = 90 K. Specific heat measurements show that the transition is first order, with ΔS ≈ 5 J K-1 mol-1 f.u.-1, and a low temperature T-linear contribution originating from defect spins. Neutron and X-ray diffraction show a lowering of symmetry from trigonal P[3 with combining macron]m1 to monoclinic C2/m symmetry, with a change in layer stacking from –AB–AB– to –AB'–BC'–CA'– and no observed magnetic order. This lowering of symmetry and rearrangement of successive layers evades geometric magnetic frustration to form a singlet ground state. It is the lowest temperature at which a change in stacking sequence is known to occur in a van der Waals solid, occurs in the absence of orbital degeneracies, and suggests that designer 2-D heterostructures may be able to undergo similar phase transitions.

  3. Piezotronic effect in 1D van der Waals solid of elemental tellurium nanobelt for smart adaptive electronics

    Science.gov (United States)

    Gao, Shengjie; Wang, Yixiu; Wang, Ruoxing; Wu, Wenzhuo

    2017-10-01

    Emerging technologies in wearable systems demand that functional devices can adaptively interact with the human body, where mechanical stimuli are ubiquitous and abundant. However, the electrical manipulation of charge carriers underpins the operations of state-of-the-art devices, and the effective control of interfacial energetics for charge carriers by the dynamic mechanical stimuli is still a relatively unexplored degree of freedom for semiconductor nanodevices. Piezotronic effect in nanostructured piezoelectric semiconductors offers exciting opportunities in addressing the above challenges. Here we report the first experimental exploration of piezotronic effect in 1D van der Waals solid of p-type tellurium nanobelt and systematically investigate the strain-gated charge carriers transport properties. The strain-induced polarization charges at the [10\\bar{1}0] surfaces of Te nanobelt can modulate the electronic transport through the interfacial effect on the Schottky contacts and the volumetric effect on the conducting channel. The competing phenomenon between interfacial and volumetric effects has been studied for the first time in piezotronics. Our research allows the access to a broad range of characterization and application of Te nanomaterials for piezotronics and could guide the future study of piezotronic effect in other materials. This progress in piezotronics, together with emerging methods for deterministic production and assembly of nanomaterials, leads to compelling opportunities for research from basic studies of piezoelectricity and semiconductor properties in functional nanomaterials to the development of ‘smarter’ electronics and optoelectronics.

  4. Schottky barrier tuning of the graphene/SnS2 van der Waals heterostructures through electric field

    Science.gov (United States)

    Zhang, Fang; Li, Wei; Ma, Yaqiang; Dai, Xianqi

    2018-03-01

    Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. The effects of external electric field (Eext) on the electronic structures of monolayer SnS2 with graphene hybrid heterobilayers are studied by using the first-principle calculations. It is demonstrated that the intrinsic electronic properties of SnS2 and graphene are quite well preserved due to the weak van der Waals (vdW) interactions. We find that the n-type Schottky contacts with the significantly small Schottky barrier are formed at the graphene/SnS2 interface. In the graphene/SnS2 heterostructure, the vertical Eext can control not only the Schottky barriers (n-type and p-type) but also contact types (Schottky contact or Ohmic contact) at the interface. The present study would open a new avenue for application of ultrathin graphene/SnS2 heterostructures in future nano- and optoelectronics.

  5. van der Waals Interactions and Hadron Resonance Gas: Role of resonance widths modeling on conserved charges fluctuations

    Science.gov (United States)

    Vovchenko, Volodymyr; Alba, Paolo; Gorenstein, Mark I.; Stoecker, Horst

    2018-02-01

    The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons - the QvdW-HRG model - is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for χBQ11/χB2, effects of the QvdW interactions essentially cancel out. It is found that the inclusion of the finite resonance widths leads to an improved description of χB2, but it also leads to a worse description of χBQ11/χB2, as compared to the lattice data. On the other hand, inclusion of the extra, unconfirmed baryons into the hadron list leads to a simultaneous improvement in the description of both observables.

  6. Quantitative relationships for the prediction of the vapor pressure of some hydrocarbons from the van der Waals molecular surface

    Directory of Open Access Journals (Sweden)

    Olariu Tudor

    2015-01-01

    Full Text Available A quantitative structure - property relationship (QSPR modeling of vapor pressure at 298.15 K, expressed as log (VP / Pa was performed for a series of 84 hydrocarbons (63 alkanes and 21 cycloalkanes using the van der Waals (vdW surface area, SW/Å2, calculated by the Monte Carlo method, as the molecular descriptor. The QSPR model developed from the subset of 63 alkanes (C1-C16, deemed as the training set, was successfully used for the prediction of the log (VP / Pa values of the 21 cycloalkanes, which was the external prediction (test subset. A QSPR model was also developed for a series composed of all 84 hydrocarbons. Both QSPR models were statistically tested for their ability to fit the data and for prediction. The results showed that the vdW molecular surface used as molecular descriptor (MD explains the variance of the majority of the log (VP / Pa values in this series of 84 hydrocarbons. This MD describes very well the intermolecular forces that hold neutral molecules together. The clear physical meaning of the molecular surface values, SW/Å2, could explain the success of the QSPR models obtained with a single structural molecular descriptor.

  7. MoS2/Rubrene van der Waals Heterostructure: Toward Ambipolar Field-Effect Transistors and Inverter Circuits.

    Science.gov (United States)

    He, Xuexia; Chow, WaiLeong; Liu, Fucai; Tay, BengKang; Liu, Zheng

    2017-01-01

    2D transition metal dichalcogenides are promising channel materials for the next-generation electronic device. Here, vertically 2D heterostructures, so called van der Waals solids, are constructed using inorganic molybdenum sulfide (MoS 2 ) few layers and organic crystal - 5,6,11,12-tetraphenylnaphthacene (rubrene). In this work, ambipolar field-effect transistors are successfully achieved based on MoS 2 and rubrene crystals with the well balanced electron and hole mobilities of 1.27 and 0.36 cm 2 V -1 s -1 , respectively. The ambipolar behavior is explained based on the band alignment of MoS 2 and rubrene. Furthermore, being a building block, the MoS 2 /rubrene ambipolar transistors are used to fabricate CMOS (complementary metal oxide semiconductor) inverters that show good performance with a gain of 2.3 at a switching threshold voltage of -26 V. This work paves a way to the novel organic/inorganic ultrathin heterostructure based flexible electronics and optoelectronic devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Efficient band structure modulations in two-dimensional MnPSe3/CrSiTe3 van der Waals heterostructures

    Science.gov (United States)

    Pei, Qi; Wang, Xiaocha; Zou, Jijun; Mi, Wenbo

    2018-05-01

    As a research upsurge, van der Waals (vdW) heterostructures give rise to numerous combined merits and novel applications in nanoelectronics fields. Here, we systematically investigate the electronic structure of MnPSe3/CrSiTe3 vdW heterostructures with various stacking patterns. Then, particular attention of this work is paid on the band structure modulations in MnPSe3/CrSiTe3 vdW heterostructures via biaxial strain or electric field. Under a tensile strain, the relative band edge positions of heterostructures transform from type-I (nested) to type-II (staggered). The relocation of conduction band minimum also brings about a transition from indirect to direct band gap. Under a compressive strain, the electronic properties change from semiconducting to metallic. The physical mechanism of strain-dependent band structure may be ascribed to the shifts of the energy bands impelled by different superposition of atomic orbitals. Meanwhile, our calculations manifest that band gap values of MnPSe3/CrSiTe3 heterostructures are insensitive to the electric field. Even so, by applying a suitable intensity of negative electric field, the band alignment transition from type-I to type-II can also be realized. The efficient band structure modulations via external factors endow MnPSe3/CrSiTe3 heterostructures with great potential in novel applications, such as strain sensors, photocatalysis, spintronic and photoelectronic devices.

  9. Reactivity of phosphorene with a 3d element trioxide (CrO3) considering van der Waals molecular interactions: a DFT-D2 study.

    Science.gov (United States)

    Rubio-Pereda, Pamela; Cocoletzi, Gregorio H

    2017-02-01

    First-principle calculations are performed to investigate the interaction between clean black phosphorene and the CrO 3 molecule which is known to be a powerful oxidizer and a suspected carcinogen. Van der Waals forces are included in all calculations through empirical corrections. Energetics studies are first done to determine the structural stability. Then charge density, Löwdin population analysis and electronic states are evaluated. Results show that the CrO 3 molecule, with an acceptor electron character, is chemisorbed on the phosphorene surface inducing minimal geometrical distortions, however, after adsorption, a partial charge gradient is produced between the P atoms located at the phosphorene upper and lower planes. Furthermore, variations on the CrO 3 concentration causes different interaction strengths. At high concentrations of adsorbed CrO 3 molecules, the interaction with the surface becomes stronger due to an increased steric effect between neighboring molecules. Nevertheless, this effect along with the geometrical distortions produced on the phosphorene structure, due to the large number of molecules adsorbed, leads to a decrement on the adsorption energy. It is expected that the reported results may render phosphorene as a promising material for application as a gas sensor.

  10. Origin of n-type conductivity in two-dimensional InSe: In atoms from surface adsorption and van der Waals gap

    Science.gov (United States)

    Wang, Hui; Shi, Jun-jie; Huang, Pu; Ding, Yi-min; Wu, Meng; Cen, Yu-lang; Yu, Tongjun

    2018-04-01

    Recently, two-dimensional (2D) InSe nanosheet becomes a promising material for electronic and optoelectronic nano-devices due to its excellent electron transport, wide bandgap tunability and good metal contact. The inevitable native point defects are essential in determining its characteristics and device performance. Here we investigate the defect formation energy and thermodynamic transition levels for the most important native defects and clarify the physical origin of n-type conductivity in unintentionally doped 2D InSe by using the powerful first-principles calculations. We find that both surface In adatom and Se vacancy are the key defects, and the In adatom, donated 0.65 electrons to the host, causes the n-type conductivity in monolayer InSe under In-rich conditions. For bilayer or few-layer InSe, the In interstitial within the van der Waals gap, transferred 0.68 electrons to InSe, is found to be the most stable donor defect, which dominates the n-type character. Our results are significant for understanding the defect nature of 2D InSe and improving the related nano-device performance.

  11. Analysis of van der waal equation near the critical point | Boyo ...

    African Journals Online (AJOL)

    This model has been utilized to determine the free energy of mixing, concentration fluctuations in the long wavelength limit Scc (0), the Warren Crowley short-range order parameter, heat of mixing, entropy of mixing and diffusion coefficient. From these thermodynamic quantities we find that Na-Cs exhibits strong deviation ...

  12. Band structure engineering in van der Waals heterostructures via dielectric screening: the GΔW method

    DEFF Research Database (Denmark)

    Winther, Kirsten Trøstrup; Thygesen, Kristian Sommer

    2017-01-01

    renormalization of a 2D material embedded in an arbitrary vdWH. The method evaluates the change in the GW self-energy of the 2D material from the change in the screened Coulomb interaction. The latter is obtained using the quantum-electrostatic heterostructure (QEH) model. We benchmark the GΔW method against full...

  13. Analysis of van der waal equation near the critical point | Boyo ...

    African Journals Online (AJOL)

    We report detailed thermodynamic properties of Na in molten Na-Cs alloys obtained by using the simple theoretical model of Heterocordination. This model has been utilized to determine the free energy of mixing, concentration fluctuations in the long wavelength limit Scc (0), the Warren Crowley short-range order ...

  14. Accurate treatment of nanoelectronics through improved description of van der Waals Interactions

    DEFF Research Database (Denmark)

    Kelkkanen, Kari André

    -dimensional extent of the surface and favors adsorption sites close to the surface, while the Pauli repulsion keeps the adsorbate away. Impurities, like an adatom or an adsorbed pyramid, pushes the adsorbate away from surface, giving a reduction of the attraction due to vdW forces. In this way the vdW force varies...... functionals. DFT calculations are performed for water dimer and hexamer, and for liquid water. Calculations on four low-energetic isomers of the water hexamer show that the vdW-DF accurately determines the energetic trend on these small clusters. How- ever, the dissociation-energy values with the vd...

  15. Regular approach for generating van der Waals Cs coefficients to arbitrary orders

    International Nuclear Information System (INIS)

    Ovsiannikov, Vitali D; Mitroy, J

    2006-01-01

    A completely general formalism is developed to describe the energy E disp = Σ s C s /R s of dispersion interaction between two atoms in spherically symmetric states. Explicit expressions are given up to the tenth order of perturbation theory for the dispersion energy E disp and dispersion coefficients C s . The method could, in principle, be used to derive the expressions for any s while including all contributing orders of perturbation theory for asymptotic interaction between two atoms. The theory is applied to the calculation of the complete series up to s = 30 for two hydrogen atoms in their ground state. A pseudo-state series expansion of the two-atom Green function gives rapid convergence of the series for radial matrix elements. The numerical values of C s are computed up to C 30 to a relative accuracy of 10 -7 or better. The dispersion coefficients for the hydrogen-antihydrogen interaction are obtained from the H-H coefficients by simply taking the absolute magnitude of C s

  16. Infrared photodissociation of van der Waals complexes selectively prepared by molecular beam scattering

    Science.gov (United States)

    Buck, U.; Huisken, Friedrich; Lauenstein, Ch.; Pertsch, Thomas; Sroka, R.

    1988-02-01

    Infrared photodissociation experiments were carried out on (C2H4)n-clusters, which were prepared according to their size by scattering them from a helium beam. The ethylene clusters were dissociated upon absorption of a CO2-laser photon by exciting the nu-7 mode of the monomer. Since an appreciable amount of energy is transferred to the cluster during the collision, the laser photons interact with internally cold or hot clusters depending on whether the interaction is before or after the collision center. The frequency and fluence dependences of the photodissociation cross sections were measured for cold and hot clusters from n=2 to n=6. The spectra of the cold clusters show the same shape and line width for all cluster sizes investigated, while those of the hot clusters are characterized by large variations in shape and line width. The very structured dimer spectrum is explained by the excitation of hot bands.

  17. Spectroscopic features of the low-lying electronic states of some sodium-helium and potassium-helium van der Waals systems

    Science.gov (United States)

    Chattopadhyay, Anjan

    2011-08-01

    Configuration interaction studies on MHe and MHe2 (where M = Na, K) systems have revealed several interesting characteristics in the properties of their low-lying electronic states. Binding energy values of the 12Π1/2, 3/2 states in MHe systems are found to be lower than the values of 12Πu (1/2, 3/2) states in the He-M-He systems by a margin of more than 200 cm-1, indicating better exciplex stabilities of the latter systems. Excited states of the other variety of the linear MHe2 (M-He-He) systems are almost repulsive. The characteristic energy barrier of the first excited spin-orbit state of alkali metal-helium systems is found to be only 15 cm-1 in KHe and 19 cm-1 in He-K-He. For the Na*He and K*He exciplexes, predicted radiative lifetime values of 18.5 ns and 29.8 ns, respectively, are in excellent agreement with the experimental values. The red-tail portions of their emission bands are contributed by M*He2 exciplexes with relatively high radiative lifetimes. The repulsive excited state of 2Σ+1/2 (or 2Σ+g,1/2) symmetry in these van der Waals systems is likely to play an important role in the pumping of the blue side of the ns2S1/2 → np2P3/2 transition, which eventually may give rise to the np2P1/2 → ns2S1/2 lasing transition.

  18. Light-Triggered Ternary Device and Inverter Based on Heterojunction of van der Waals Materials.

    Science.gov (United States)

    Shim, Jaewoo; Jo, Seo-Hyeon; Kim, Minwoo; Song, Young Jae; Kim, Jeehwan; Park, Jin-Hong

    2017-06-27

    Multivalued logic (MVL) devices/circuits have received considerable attention because the binary logic used in current Si complementary metal-oxide-semiconductor (CMOS) technology cannot handle the predicted information throughputs and energy demands of the future. To realize MVL, the conventional transistor platform needs to be redesigned to have two or more distinctive threshold voltages (V TH s). Here, we report a finding: the photoinduced drain current in graphene/WSe 2 heterojunction transistors unusually decreases with increasing gate voltage under illumination, which we refer to as the light-induced negative differential transconductance (L-NDT) phenomenon. We also prove that such L-NDT phenomenon in specific bias ranges originates from a variable potential barrier at a graphene/WSe 2 junction due to a gate-controllable graphene electrode. This finding allows us to conceive graphene/WSe 2 -based MVL logic circuits by using the I D -V G characteristics with two distinctive V TH s. Based on this finding, we further demonstrate a light-triggered ternary inverter circuit with three stable logical states (ΔV out of each state <0.05 V). Our study offers the pathway to substantialize MVL systems.

  19. Thermodynamics of hydrogen bonding and van der Waals interactions of organic solutes in solutions of imidazolium based ionic liquids: “Structure-property” relationships

    International Nuclear Information System (INIS)

    Varfolomeev, Mikhail A.; Khachatrian, Artashes A.; Akhmadeev, Bulat S.; Solomonov, Boris N.

    2016-01-01

    Highlights: • Solution enthalpies of organic solutes in imidazolium based ionic liquids were measured. • van der Waals interactions scale of imidazolium based ionic liquids was proposed. • Enthalpies of solvation of organic solutes in ionic liquids were determined. • Hydrogen bond enthalpies of organic solutes with ionic liquids were calculated. • Relationships between structure of ionic liquids and thermochemical data were obtained. - Abstract: In the present work thermochemistry of intermolecular interactions of organic compounds in solutions of imidazolium based ionic liquids (ILs) has been studied using solution calorimetry method. Enthalpies of solution at infinite dilution of non-polar (alkanes, aromatic hydrocarbons) and polar (alcohols, amides, and etc.) organic solutes in two ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium trifluoromethanesulfonate were measured at 298.15 K. The scale of van der Waals interactions of imidazolium based ILs has been proposed on the basis of solution enthalpies of n-alkanes in their media. The effect of the cation and anion structure of ILs on the enthalpies of solvation was analyzed. Enthalpies of hydrogen bonding of organic solutes with imidazolium based ILs were determined. It has been shown that these values are close to zero for proton acceptor solutes. At the same time, enthalpies of hydrogen bonding of proton donor solutes with ionic liquids are increased depending the anion: tetrafluoroborate ≈ bis(trifluoromethylsulfonyl)imide < 2-(2-methoxyethoxy)ethyl sulfate < trifluoromethanesulfonate. Enthalpies of van der Waals interactions and hydrogen bonding in the solutions of imidazolium based ionic liquids were compared with the same data for molecular solvents.

  20. Bifurcations of new multi soliton solutions of the van der Waals normal form for fluidized granular matter via six different methods

    Science.gov (United States)

    Lu, Dianchen; Seadawy, Aly R.; Khater, Mostafa M. A.

    In this article, we study one of the most popular models in nature and also industrial which is the van der Waals normal form for the fluidized granular matter. Understanding of static and dynamic property for these kinds of the models is very important in many aspects of industrial from pharmaceuticals to civil engineering and also some basic physical phenomena like those studied in geophysics. This model explains the phase separation phenomenon. We apply six different methods for this model to obtained the traveling and solitary wave solutions. We make the comparison between obtained solutions with each of them and also with obtained solutions with different methods.

  1. Effect of temperature and density fluctuations on the spatially heterogeneous dynamics of glass-forming Van der Waals liquids under high pressure.

    Science.gov (United States)

    Koperwas, K; Grzybowski, A; Grzybowska, K; Wojnarowska, Z; Sokolov, A P; Paluch, M

    2013-09-20

    In this Letter, we show how temperature and density fluctuations affect the spatially heterogeneous dynamics at ambient and elevated pressures. By using high-pressure experimental data for van der Waals liquids, we examine contributions of the temperature and density fluctuations to the dynamics heterogeneity. We show that the dynamic heterogeneity decreases significantly with increasing pressure at a constant structural relaxation time (isochronal condition), while the broadening of the relaxation spectrum remains constant. This observation questions the relationship between spectral broadening and dynamic heterogeneity.

  2. Representation of phase equilibria and densities for complex systems using a van der Waals volume translated equation of state with a UNIFAC mixing rule

    Directory of Open Access Journals (Sweden)

    Osvaldo Chiavone-Filho

    2014-09-01

    Full Text Available This work investigated the applicability of the van der Waals cubic equation of state (EoS with volume translation (vdWt, using the modified Huron-Vidal (MHV2 mixing rule with the UNIFAC (UNIQUAC Functional Activity Coefficients model for describing phase equi-librium and density data for a series of complex systems over wide ranges of temperature (T and pressure (P. Some limitations were identified in the prediction of the experimental data collected, e.g., systems with highly associating components, but in general, the EoS vdWt+MHV was able to satisfactorily represent both phase equilibrium and volumetric behavior.

  3. Behavior of quasinormal modes and Van der Waals-like phase transition of charged AdS black holes in massive gravity

    Energy Technology Data Exchange (ETDEWEB)

    Zou, De-Cheng; Yue, Ruihong [Yangzhou University, Center for Gravitation and Cosmology, College of Physical Science and Technology, Yangzhou (China); Liu, Yunqi [Huazhong University of Science and Technology, School of Physics, Wuhan (China)

    2017-06-15

    In this work, we utilize the quasinormal modes (QNMs) of a massless scalar perturbation to probe the Van der Waals-like small and large black holes (SBH/LBH) phase transition of charged topological Anti-de Sitter (AdS) black holes in four-dimensional massive gravity. We find that the signature of this SBH/LBH phase transition is detected in the isobaric as well as in the isothermal process. This further supports the idea that the QNMs can be an efficient tool to investigate the thermodynamical phase transition. (orig.)

  4. Generation of “bastard” molecular ions from van der Waals clusters: Arn(C2Cl4)m+ ions, suspected interlopers in collection of solar neutrinos

    OpenAIRE

    Buelow, S. J.; Worsnop, D. R.; Herschbach, D. R.

    1981-01-01

    Gaseous molecular ions containing argon and perchlorethylene, Arn(C2Cl4)m+ in which n ≥ 1-29 and m ≥ 1-4, are produced by electron bombardment of van der Waals clusters formed by expanding an Ar/C2Cl4 mixture through a supersonic nozzle. Previous attempts to observe such ions in a high-pressure mass spectrometer were not successful, as with many other (“bastard”) ions that similarly lack a stable chemically bound neutral parent molecule. This is probably due to dissociation induced by the lar...

  5. Lennard-Jones parameters for small diameter carbon nanotubes and water for molecular mechanics simulations from van der Waals density functional calculations.

    Science.gov (United States)

    Kaukonen, M; Gulans, A; Havu, P; Kauppinen, E

    2012-03-05

    Lennard-Jones (LJ) parameters are derived for classical nonpolarizable force fields for carbon nanotubes (CNTs) and for CNT-water interaction from van der Waals (vdW) enhanced density functional calculations. The new LJ parameters for carbon-carbon interactions are of the same order as those previously used in the literature but differ significantly for CNT-water interactions. This may partially originate from the fact that in addition to pure vdW interactions the polarization and other quantum mechanics effects are embedded into the LJ-potential. Copyright © 2012 Wiley Periodicals, Inc.

  6. Symmetry-adapted perturbation theory based on unrestricted Kohn-Sham orbitals for high-spin open-shell van der Waals complexes.

    Science.gov (United States)

    Hapka, Michał; Żuchowski, Piotr S; Szczęśniak, Małgorzata M; Chałasiński, Grzegorz

    2012-10-28

    Two open-shell formulations of the symmetry-adapted perturbation theory are presented. They are based on the spin-unrestricted Kohn-Sham (SAPT(UKS)) and unrestricted Hartree-Fock (SAPT(UHF)) descriptions of the monomers, respectively. The key reason behind development of SAPT(UKS) is that it is more compatible with density functional theory (DFT) compared to the previous formulation of open-shell SAPT based on spin-restricted Kohn-Sham method of Żuchowski et al. [J. Chem. Phys. 129, 084101 (2008)]. The performance of SAPT(UKS) and SAPT(UHF) is tested for the following open-shell van der Waals complexes: He···NH, H(2)O···HO(2), He···OH, Ar···OH, Ar···NO. The results show an excellent agreement between SAPT(UKS) and SAPT(ROKS). Furthermore, for the first time SAPT based on DFT is shown to be suitable for the treatment of interactions involving Π-state radicals (He···OH, Ar···OH, Ar···NO). In the interactions of transition metal dimers ((3)Σ(u)(+))Au(2) and ((13)Σ(g)(+))Cr(2) we show that SAPT is incompatible with the use of effective core potentials. The interaction energies of both systems expressed instead as supermolecular UHF interaction plus dispersion from SAPT(UKS) result in reasonably accurate potential curves.

  7. Investigation of the range of validity of the pairwise summation method applied to the calculation of the surface roughness correction to the van der Waals force

    Science.gov (United States)

    Gusso, André; Burnham, Nancy A.

    2016-09-01

    It has long been recognized that stochastic surface roughness can considerably change the van der Waals (vdW) force between interacting surfaces and particles. However, few analytical expressions for the vdW force between rough surfaces have been presented in the literature. Because they have been derived using perturbative methods or the proximity force approximation the expressions are valid when the roughness correction is small and for a limited range of roughness parameters and surface separation. In this work, a nonperturbative approach, the effective density method (EDM) is proposed to circumvent some of these limitations. The method simplifies the calculations of the roughness correction based on pairwise summation (PWS), and allows us to derive simple expressions for the vdW force and energy between two semispaces covered with stochastic rough surfaces. Because the range of applicability of PWS and, therefore, of our results, are not known a priori, we compare the predictions based on the EDM with those based on the multilayer effective medium model, whose range of validity can be defined more properly and which is valid when the roughness correction is comparatively large. We conclude that the PWS can be used for roughness characterized by a correlation length of the order of its rms amplitude, when this amplitude is of the order of or smaller than a few nanometers, and only for typically insulating materials such as silicon dioxide, silicon nitride, diamond, and certain glasses, polymers and ceramics. The results are relevant for the correct modeling of systems where the vdW force can play a significant role such as micro and nanodevices, for the calculation of the tip-sample force in atomic force microscopy, and in problems involving adhesion.

  8. Modulation of interfacial electronic properties in PbI{sub 2} and BN van der Waals heterobilayer via external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yaqiang [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Zhao, Xu, E-mail: zhaoxu@htu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Niu, Mengmeng [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Dai, Xianqi, E-mail: xqdai@htu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); School of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Li, Wei [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Wang, Xiaolong [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); State Key Laboratory of Information Photonics and Optical Communication, Beijing University Posts and Telecommunications, Beijing 100876 (China); Zhao, Mingyu; Wang, Tianxing [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Tang, Yanan [School of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China)

    2017-07-31

    Highlights: • An atomically type-II heterobilayer which is suitable for optoelectronics and solar cell with wide bandgap was formed. • The charge redistribution is mainly on the surface and the amount of electrons depends on the strength of E{sub field}. • The bandgaps varying with E{sub field} can be divided into three ranges indicating different E{sub field}-sensitive which may possess potential in sensor. • Increasing the E{sub field} upon 0.07 V/Å, the band alignment converts from type-II to type-I heterojunction. - Abstract: The interfacial electronic properties of PbI{sub 2} and BN van der Waals (vdW) heterobilayer are explored by using density functional theory (DFT) method. An intrinsic type-II heterostructure with a wide bandgap is demonstrated. The spatial separation of the lowest energy electron-hole pairs can be actualised and make PbI{sub 2}/BN heterostructure as a good candidate for applications in optoelectronics and solar cell. A simulation of E{sub field} is actualized to modify its electronic properties. Band alignment converts from type-II to type-I heterostructure separated by a forward voltage with the value of about 0.07 V/Å. Three regions implying different E{sub field}-sensitive properties are obtained from the variations of bandgap with E{sub field}. The charge redistribution with an E{sub field} is mainly on the surface of PbI{sub 2} and BN layers as well as the amount of electrons depends on the strength of E{sub field}. In addition, the PbI{sub 2}/BN heterobilayer exhibits more outstanding optical conductivity capability. Our results could bring forward a new perspective on sensor and shed light on the design of novel nano- and optoelectronics based on the PbI{sub 2}/BN vdW heterostructure.

  9. Trends on band alignments: Validity of Anderson's rule in SnS2- and SnSe2-based van der Waals heterostructures

    Science.gov (United States)

    Koda, Daniel S.; Bechstedt, Friedhelm; Marques, Marcelo; Teles, Lara K.

    2018-04-01

    Van der Waals (vdW) heterostructures are promising candidates for building blocks in novel electronic and optoelectronic devices with tailored properties, since their electronic action is dominated by the band alignments upon their contact. In this work, we analyze 10 vdW heterobilayers based on tin dichalcogenides by first-principles calculations. Structural studies show that all systems are stable, and that commensurability leads to smaller interlayer distances. Using hybrid functional calculations, we derive electronic properties and band alignments for all the heterosystems and isolated two-dimensional (2D) crystals. Natural band offsets are derived from calculated electron affinities and ionization energies of 11 freestanding 2D crystals. They are compared with band alignments in true heterojunctions, using a quantum mechanical criterion, and available experimental data. For the hBN/SnSe 2 system, we show that hBN suffers an increase in band gap, while leaving almost unchanged the electronic properties of SnSe2. Similarly, MX2 (M = Mo, W; X = S, Se) over SnX2 preserve the natural discontinuities from each side of the heterobilayer. Significant charge transfer occurs in junctions with graphene, which becomes p-doped and forms an Ohmic contact with SnX2. Zirconium and hafnium dichalcogenides display stronger interlayer interactions, leading to larger shifts in band alignments with tin dichalcogenides. Significant orbital overlap is found, which creates zero conduction band offset systems. The validity of the Anderson electron affinity rule is discussed. Failures of this model are traced back to interlayer interaction, band hybridization, and quantum dipoles. The systematic work sheds light on interfacial engineering for future vdW electronic and optoelectronic devices.

  10. Influence of the van der Waals interaction in the dissociation dynamics of N{sub 2} on W(110) from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Gondre, L. [Institut UTINAM-CNRS UMR 6213, Université de Franche-Comté, 16 Route de Gray, 25030 Besançon Cedex (France); Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Juaristi, J. I. [Departamento de Física de Materiales, Facultad de Químicas (UPV/EHU), Apartado 1072, 20080 Donostia-San Sebastián (Spain); Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián (Spain); Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Blanco-Rey, M. [Departamento de Física de Materiales, Facultad de Químicas (UPV/EHU), Apartado 1072, 20080 Donostia-San Sebastián (Spain); Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Díez Muiño, R.; Alducin, M. [Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián (Spain); Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain)

    2015-02-21

    Using ab initio molecular dynamics (AIMD) calculations, we investigate the role of the van der Waals (vdW) interaction in the dissociative adsorption of N{sub 2} on W(110). Hitherto, existing classical dynamics calculations performed on six-dimensional potential energy surfaces based on density functional theory (DFT), and the semi-local PW91 and RPBE [Hammer et al. Phys. Rev. B 59, 7413 (1999)] exchange-correlation functionals were unable to fully describe the dependence of the initial sticking coefficient on the molecular beam incidence conditions as found in experiments. N{sub 2} dissociation on W(110) was shown to be very sensitive not only to short molecule-surface distances but also to large distances where the vdW interaction, not included in semilocal-DFT, should dominate. In this work, we perform a systematic study on the dissociative adsorption using a selection of existing non-local functionals that include the vdW interaction (vdW-functionals). Clearly, the inclusion of the non-local correlation term contributes in all cases to correct the unrealistic energy barriers that were identified in the RPBE at large molecule-surface distances. Among the tested vdW-functionals, the original vdW-DF by Dion et al. [Phys. Rev. Lett. 92, 246401 (2004)] and the ulterior vdW-DF2 give also an adequate description of the N{sub 2} adsorption energy and energy barrier at the transition state, i.e., of the properties that are commonly used to verify the quality of any exchange-correlation functional. However, the results of our AIMD calculations, which are performed at different incidence conditions and hence extensively probe the multi-configurational potential energy surface of the system, do not seem as satisfactory as the preliminary static analysis suggested. When comparing the obtained dissociation probabilities with existing experimental data, none of the used vdW-functionals seems to provide altogether an adequate description of the N{sub 2}/W(110) interaction at

  11. Ab initio and semi-empirical van der Waals study of graphene-boron nitride interaction from a molecular point of view.

    Science.gov (United States)

    Caciuc, Vasile; Atodiresei, Nicolae; Callsen, Martin; Lazić, Predrag; Blügel, Stefan

    2012-10-24

    We have performed a systematic semi-empirical and ab initio van der Waals study to investigate the bonding mechanism of benzene (C(6)H(6)), triazine (C(3)N(3)H(3)) and borazine (B(3)N(3)H(6)) adsorbed on graphene and a single boron nitride (BN) sheet. The two semi-empirical approaches used to include the van der Waals (vdW) interactions in our density functional theory (DFT) calculations suggest that the strength of the molecule-surface interaction corresponds to a strong physisorption with no net charge transfer between the molecules and the corresponding substrates. This observation is strengthened by the use of first-principles non-local correlation vdW-DF functionals which provide a sound physical basis to include vdW interactions in DFT calculations. In particular we have employed two flavors of vdW-DF functionals which enabled us to determine the role of the non-local correlation effects in the molecule-surface bonding mechanism which cannot be assessed by using only semi-empirical vdW methods. Our study also reveals that the strength of the molecule-surface interaction can be influenced by the electronegativity of the B, C and N atoms.

  12. Probing the Interlayer Exciton Physics in a MoS2/MoSe2/MoS2 van der Waals Heterostructure.

    Science.gov (United States)

    Baranowski, M; Surrente, A; Klopotowski, L; Urban, J M; Zhang, N; Maude, D K; Wiwatowski, K; Mackowski, S; Kung, Y C; Dumcenco, D; Kis, A; Plochocka, P

    2017-10-11

    Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of interlayer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe 2 /WSe 2 heterostructures. Here we report on the observation of long-lived interlayer exciton emission in a MoS 2 /MoSe 2 /MoS 2 trilayer van der Waals heterostructure. The interlayer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power, and temperature dependence of the interlayer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long-lived valley polarization of interlayer exciton. Intriguingly, the interlayer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the interlayer exciton emission.

  13. Many-body study of van der Waals interaction involving lithium and rare-gas atoms and its contribution to hyperfine shifts

    International Nuclear Information System (INIS)

    Rao, B.K.; Das, T.P.

    1982-01-01

    Using linked cluster many-body perturbation theory, the frequency-dependent dipole polarizabilities a(ω) has been calculated for the lithium atom. The value of a(ω) at the static limit (169.04 a 0 3 ) matches well with other available theoretical values and experimental results. These values have been used to calculate the van der Waals constants for interactions of lithium, helium and neon atoms. The values of the van der Waals constants for dipole-dipole interaction in atomic units are -22.9, -44.8, -1465.8, 184950.0, 2011.8, 3896.5, 30.3, 59.0 and 115.1 for Li-He, Li-Ne, Li-Li, Li-Li-Li, Li-Li-He, Li-Li-Ne, Li-He-He, Li-He-Ne and Li-Ne-Ne interactions respectively. Obtaining the suitable response functions for lithium and helium atoms, the long range contribution to Δa(r)/a 0 in the study of fractional frequency shift in hyperfine pressure and temperature shift measurements is obtained as -541 atomic units. (author)

  14. Influence of van der Waals contact forces on the deformation mechanics of thin flexible membranes assembled from metallic or semiconducting single-wall carbon nanotubes

    Science.gov (United States)

    Hobbie, Erik K.; Harris, John; Iyer, Swathi; Huh, Ji Yeon; Fagan, Jeffrey A.; Hudson, Steven D.; Stafford, Christopher M.

    2011-03-01

    Thin membranes of single-wall carbon nanotubes (SWCNTs) assembled from either metallic or semiconducting SWCNTs are subjected to the compressive strains imposed by a stretched elastic substrate, and the mechanical characteristics of the membranes are inferred from the topography of the wrinkling instability that emerges. By depositing comparable films on quartz, we also use optical (UV-Vis-NIR) absorption spectroscopy to compute the effective London dispersion spectra of the purified materials, and from these we compute the attractive part of the van der Waals potential between nanotubes of identical electronic type as a function of separation and relative orientation. We find significant differences in the strength and shape of the contact potential depending on electronic type, which in turn are evident in the modulus and yield strain measured from the deformation of the films. Supported by the NSF through CMMI-0969155 and the DOE through DE-FG36-08GO88160.

  15. Effect of van der Waals interaction on energetics and transport properties of a single anthracene molecule adsorbed or confined inside a carbon nanotube

    Science.gov (United States)

    Debbichi, L.; Dappe, Y. J.; Alouani, M.

    2012-01-01

    The energetics and transport properties of a single aromatic molecule (C14H10) in interaction with a metallic single-walled carbon nanotube (SWCNT) have been studied using state-of-the-art density functional calculations. In both adsorption and encapsulation configurations, we show that the fundamental importance of the weak van der Waals (vdW) interactions is to stabilize the position of the molecule. These interactions have been treated through the ab initio linear combination of atomic orbitals (LCAO-S2) method including the vdW weak interactions. Moreover, we show that the electric conductance of the SWCNT, calculated within a nonequilibrium Green's-function formalism, is very sensitive to the position of the molecule with respect to the nanotube. The change of the conductance is explained in terms of charge transfer strength between the nanotube and the molecule.

  16. Sequence-specific recognition of DNA by phenanthrenequinone diimine complexes of rhodium(III): importance of steric and van der Waals interactions.

    Science.gov (United States)

    Sitlani, A; Barton, J K

    1994-10-11

    The importance of steric and van der Waals interactions in the sequence-specific recognition of DNA by [Rh(phi)]3+ complexes has been explored through the synthesis and application of a series of Rh(phi)3+ (phi: 9,10-phenanthrenequinone diimine) derivatives. [Rh(phi)]3+ complexes intercalate in the major groove of DNA via the phi ligand and promote strand scission in the presence of UV light. The complexes reported here are derivatives of the parent molecules [Rh(phi)2bpy]3+ and [Rh(bpy)2phi]3+ (bpy: 2,2'-bipyridyl). The [Rh(phi)]3+ complexes have comparable photoefficiencies; therefore, their different photocleavage patterns on 32P-end-labeled DNA fragments reflect their unique sequence-specific recognition characteristics. The shapes of the [Rh(phi)]3+ complexes are found to govern DNA recognition and reaction. Importantly and generally, the more sterically bulky complexes, containing methyl or phenyl groups on the ancillary ligands, cleave DNA at a subset of sequences recognized by their parent molecules. [Rh-(diphenylbpy)2phi]3+ specifically targets the site 5'-CTCTAGAG-3'. Furthermore, chiral discrimination in site selectivity is observed; the different isomers target different sites. delta- and lambda-[Rh(5,5'-dimethylbpy)2phi]3+ cleave specifically at sites that are defined by the consensus sequences 5'-C-T-N-G-3' and 5'-A-C/G-T-C/G-3', respectively. The sequence selectivities may be understood on the basis of both negative steric clashes and positive van der Waals interactions between methyl groups on the metal complex and thymine methyl groups in the DNA major groove.

  17. Photochemistry of xenon-halogen Van der Waals complexes (X2 = Cl2, Br2, I2): evidence for the intermediate states in the (Xe-X2)*→ XeX* + X reaction

    International Nuclear Information System (INIS)

    Boivineau, Michel

    1987-01-01

    This research thesis addresses the reactivity of excited states of xenon-halogen Van der Waals complexes (Cl 2 , Br 2 , I 2 ) submitted to a multi-photonic excitation. The objective of this study is, by means of a specific experimental approach, to highlight the R*+ X 2 *- to better understand the reaction mechanism, and to study the reactivity of rare gas/halogen systems depending on the halogen nature. After having reported a bibliographical study on each studied system, the author describes the experimental system, reports and discusses experimental results obtained on the different complex systems (chlorine-, bromine- or iodine-based). He finally comments a possible and original application of these works in the development of an excimer laser with a new active medium (the rare gas/halogen Van der Waals complex) which would allow a continuous operation and an easy discharge production [fr

  18. Including screening in van der Waals corrected density functional theory calculations: The case of atoms and small molecules physisorbed on graphene

    International Nuclear Information System (INIS)

    Silvestrelli, Pier Luigi; Ambrosetti, Alberto

    2014-01-01

    The Density Functional Theory (DFT)/van der Waals-Quantum Harmonic Oscillator-Wannier function (vdW-QHO-WF) method, recently developed to include the vdW interactions in approximated DFT by combining the quantum harmonic oscillator model with the maximally localized Wannier function technique, is applied to the cases of atoms and small molecules (X=Ar, CO, H 2 , H 2 O) weakly interacting with benzene and with the ideal planar graphene surface. Comparison is also presented with the results obtained by other DFT vdW-corrected schemes, including PBE+D, vdW-DF, vdW-DF2, rVV10, and by the simpler Local Density Approximation (LDA) and semilocal generalized gradient approximation approaches. While for the X-benzene systems all the considered vdW-corrected schemes perform reasonably well, it turns out that an accurate description of the X-graphene interaction requires a proper treatment of many-body contributions and of short-range screening effects, as demonstrated by adopting an improved version of the DFT/vdW-QHO-WF method. We also comment on the widespread attitude of relying on LDA to get a rough description of weakly interacting systems

  19. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure.

    Science.gov (United States)

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H; Khondaker, Saiful I; Choi, Wonbong; Jung, Yeonwoong

    2016-05-05

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm(2)) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials.

  20. Research Update: Van-der-Waals epitaxy of layered chalcogenide Sb2Te3 thin films grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Isom Hilmi

    2017-05-01

    Full Text Available An attempt to deposit a high quality epitaxial thin film of a two-dimensionally bonded (layered chalcogenide material with van-der-Waals (vdW epitaxy is of strong interest for non-volatile memory application. In this paper, the epitaxial growth of an exemplary layered chalcogenide material, i.e., stoichiometric Sb2Te3 thin films, is reported. The films were produced on unreconstructed highly lattice-mismatched Si(111 substrates by pulsed laser deposition (PLD. The films were grown by vdW epitaxy in a two-dimensional mode. X-ray diffraction measurements and transmission electron microscopy revealed that the films possess a trigonal Sb2Te3 structure. The single atomic Sb/Te termination layer on the Si surface was formed initializing the thin film growth. This work demonstrates a straightforward method to deposit vdW-epitaxial layered chalcogenides and, at the same time, opens up the feasibility to fabricate chalcogenide vdW heterostructures by PLD.

  1. Free volume from positron lifetime and pressure-volume-temperature experiments in relation to structural relaxation of van der Waals molecular glass-forming liquids.

    Science.gov (United States)

    Dlubek, G; Shaikh, M Q; Rätzke, K; Paluch, M; Faupel, F

    2010-06-16

    Positron annihilation lifetime spectroscopy (PALS) is employed to characterize the temperature dependence of the free volume in two van der Waals liquids: 1, 1'-bis(p-methoxyphenyl)cyclohexane (BMPC) and 1, 1'-di(4-methoxy-5-methylphenyl)cyclohexane (BMMPC). From the PALS spectra analysed with the routine LifeTime9.0, the size (volume) distribution of local free volumes (subnanometer size holes), its mean, [v(h)], and mean dispersion, σ(h), were calculated. A comparison with the macroscopic volume from pressure-volume-temperature (PV T) experiments delivered the hole density and the specific hole free volume and a complete characterization of the free volume microstructure in that sense. These data are used in correlation with structural (α) relaxation data from broad-band dielectric spectroscopy (BDS) in terms of the Cohen-Grest and Cohen-Turnbull free volume models. An extension of the latter model allows us to quantify deviations between experiments and theory and an attempt to systematize these in terms of T(g) or of the fragility. The experimental data for several fragile and less fragile glass formers are involved in the final discussion. It was concluded that, for large differences in the fragility of different glass formers, the positron lifetime mirrors clearly the different character of these materials. For small differences in the fragility, additional properties like the character of bonds and chemical structure of the material may affect size, distribution and thermal behaviour of the free volume.

  2. Rotational spectra of the Xe-(H2O)2 van der Waals trimer: xenon as a probe of electronic structure and dynamics.

    Science.gov (United States)

    Wen, Qing; Jäger, Wolfgang

    2007-03-22

    Rotational spectra of three isotopomers of the Xe-(H2O)2 van der Waals trimer were recorded using a pulsed-nozzle, Fourier transform microwave spectrometer. Nine [nine, four] a-type and twelve [eleven, seven] b-type transitions were measured for the 132Xe-(H2O)2 [129Xe-(H2O)2, 131Xe-(H2O)2] isotopomer. The determined rotational and centrifugal distortion constants were used to extract information about the structure and vibrational motions of the complex. The nuclear quadrupole hyperfine structures due to the 131Xe (nuclear spin quantum number I=3/2) nucleus were also detected. The large value of the off-diagonal nuclear quadrupole coupling constant chiab in particular provides detailed insight into the electronic environment of the xenon atom and the orientations of the water molecules within the complex. An effective structure that best reproduces the experimental 131Xe nuclear quadrupole coupling constants is rationalized by ab initio calculations. An overall goal of this line of work is to determine how the successive solvation of a xenon atom with water molecules affects the xenon electron distribution and its intermolecular interactions. The results may provide molecular level interpretations of 129Xe NMR data from, for example, imaging experiments.

  3. A kinetic Monte Carlo simulation method of van der Waals epitaxy for atomistic nucleation-growth processes of transition metal dichalcogenides.

    Science.gov (United States)

    Nie, Yifan; Liang, Chaoping; Cha, Pil-Ryung; Colombo, Luigi; Wallace, Robert M; Cho, Kyeongjae

    2017-06-07

    Controlled growth of crystalline solids is critical for device applications, and atomistic modeling methods have been developed for bulk crystalline solids. Kinetic Monte Carlo (KMC) simulation method provides detailed atomic scale processes during a solid growth over realistic time scales, but its application to the growth modeling of van der Waals (vdW) heterostructures has not yet been developed. Specifically, the growth of single-layered transition metal dichalcogenides (TMDs) is currently facing tremendous challenges, and a detailed understanding based on KMC simulations would provide critical guidance to enable controlled growth of vdW heterostructures. In this work, a KMC simulation method is developed for the growth modeling on the vdW epitaxy of TMDs. The KMC method has introduced full material parameters for TMDs in bottom-up synthesis: metal and chalcogen adsorption/desorption/diffusion on substrate and grown TMD surface, TMD stacking sequence, chalcogen/metal ratio, flake edge diffusion and vacancy diffusion. The KMC processes result in multiple kinetic behaviors associated with various growth behaviors observed in experiments. Different phenomena observed during vdW epitaxy process are analysed in terms of complex competitions among multiple kinetic processes. The KMC method is used in the investigation and prediction of growth mechanisms, which provide qualitative suggestions to guide experimental study.

  4. Charge Transfer Effects in Naturally Occurring van der Waals Heterostructures (PbSe )1.16(TiSe2 )m (m =1 , 2)

    Science.gov (United States)

    Yao, Q.; Shen, D. W.; Wen, C. H. P.; Hua, C. Q.; Zhang, L. Q.; Wang, N. Z.; Niu, X. H.; Chen, Q. Y.; Dudin, P.; Lu, Y. H.; Zheng, Y.; Chen, X. H.; Wan, X. G.; Feng, D. L.

    2018-03-01

    van der Waals heterostructures (VDWHs) exhibit rich properties and thus has potential for applications, and charge transfer between different layers in a heterostructure often dominates its properties and device performance. It is thus critical to reveal and understand the charge transfer effects in VDWHs, for which electronic structure measurements have proven to be effective. Using angle-resolved photoemission spectroscopy, we studied the electronic structures of (PbSe )1.16(TiSe2 )m (m =1 , 2), which are naturally occurring VDWHs, and discovered several striking charge transfer effects. When the thickness of the TiSe2 layers is halved from m =2 to m =1 , the amount of charge transferred increases unexpectedly by more than 250%. This is accompanied by a dramatic drop in the electron-phonon interaction strength far beyond the prediction by first-principles calculations and, consequently, superconductivity only exists in the m =2 compound with strong electron-phonon interaction, albeit with lower carrier density. Furthermore, we found that the amount of charge transferred in both compounds is nearly halved when warmed from below 10 K to room temperature, due to the different thermal expansion coefficients of the constituent layers of these misfit compounds. These unprecedentedly large charge transfer effects might widely exist in VDWHs composed of metal-semiconductor contacts; thus, our results provide important insights for further understanding and applications of VDWHs.

  5. van der Waals interactions govern C-β-d-glucopyranosyl triazoles' nM inhibitory potency in human liver glycogen phosphorylase.

    Science.gov (United States)

    Kantsadi, Anastassia L; Stravodimos, George A; Kyriakis, Efthimios; Chatzileontiadou, Demetra S M; Solovou, Theodora G A; Kun, Sándor; Bokor, Éva; Somsák, László; Leonidas, Demetres D

    2017-07-01

    3-(C-Glucopyranosyl)-5aryl-1,2,4-triazoles with an aryl moiety larger than phenyl have been shown to have strong inhibitory potency (K i values in the range of upper nM) for human liver glycogen phosphorylase (hlGP), a pharmacologically relevant target for diabetes type 2. In this study we investigate in a comparative manner the inhibitory effect of the above triazoles and their respective imidazoles on hlGPa. Kinetic studies show that the imidazole derivatives are 6-8 times more potent than their corresponding triazoles. We also seek to answer how the type of the aryl moiety affects the potency in hlGPa, and by determination of the crystal structure of rmGPb in complex with the triazole derivatives the structural basis of their inhibitory efficacy is also elucidated. Our studies revealed that the van der Waals interactions between the aryl moiety and residues in a hydrophobic pocket within the active site are mainly responsible for the variations in the potency of these inhibitors. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Interlayer Trions in the MoS2/WS2 van der Waals Heterostructure

    DEFF Research Database (Denmark)

    Deilmann, Thorsten; Thygesen, Kristian Sommer

    2018-01-01

    theoretical footing. Our calculations predict the existence of bound interlayer trions below the neutral interlayer excitons. We obtain binding energies of 18/28 meV for the positive/negative interlayer trions with both electrons/holes located on the same layer. In contrast, a negligible binding energy...

  7. A new model approach for the near-critical point region: 1. Construction of the generalized van der Waals equation of state.

    Science.gov (United States)

    Lee, Sukbae; Jeon, Joonhyeon; Kim, Wonsoo; Chair, Tong-Seek

    2008-12-11

    To date, it has been considered that all classical equations of state (EOS) have failed to describe the properties of fluids near the critical region, where the density fluctuations have a significant influence on fluid properties. In this paper, we suggest a newly constructed equation for fluid states, the generalized van der Waals (GvdW) EOS with the highly simplified Dieterici's form P = [RT/(V - b)] - a(b/V)c by a new model potential construction describing intermolecular interactions. On the basis of the model potential construction, it is shown that the a, b, and c parameters have physical interpretations as an internal pressure, a void volume, and a dimensionless value that represents an inharmonic intermolecular cell potential, respectively. As an illustration of our model approach, we initially apply it to near the critical point (cp) region, where all classical EOS descriptions have been incorporated with experimental thermodynamic data, and we obtain a table of three parameters for 12 pure normal fluids, which precisely describes thermodynamic critical values. On the basis of the basic relations between pressure and volume at the critical point, we express the corresponding EOS in terms of the c parameter, and by this means, we also obtain a theoretical vapor-liquid equilibrium (VLE) line, which closely coincides with the experimental data for several pure normal fluids near the critical region. As a result, we show that thermodynamic properties near the critical region can be described analytically by only three parameters. In addition, to validate our EOS for the temperature-differential derivatives, we show that the calculated isochoric heat capacity (Cv) of saturated argon closely coincides with the experimental data. Moreover, the possibility of a precise description with respect to the entire fluid region is also argued, in terms of the physical cases from the triple point to the ideal gas region.

  8. Moiré-pattern interlayer potentials in van der Waals materials in the random-phase approximation

    Science.gov (United States)

    Leconte, Nicolas; Jung, Jeil; Lebègue, Sébastien; Gould, Tim

    2017-11-01

    Stacking-dependent interlayer interactions are important for understanding the structural and electronic properties in incommensurable two-dimensional material assemblies where long-range moiré patterns arise due to small lattice constant mismatch or twist angles. Here we study the stacking-dependent interlayer coupling energies between graphene (G) and hexagonal boron nitride (BN) homo- and heterostructures using high-level random-phase approximation (RPA) ab initio calculations. Our results show that although total binding energies within LDA and RPA differ substantially by a factor of 200%-400%, the energy differences as a function of stacking configuration yield nearly constant values with variations smaller than 20%, meaning that LDA estimates are quite reliable. We produce phenomenological fits to these energy differences, which allows us to calculate various properties of interest including interlayer spacing, sliding energetics, pressure gradients, and elastic coefficients to high accuracy. The importance of long-range interactions (captured by RPA but not LDA) on various properties is also discussed. Parametrizations for all fits are provided.

  9. Structure and bonding studies of ClX-C 2H 4 (X = H or Br) van der Waals complexes

    Science.gov (United States)

    Lin, Zhenyang; Bytheway, Ian

    1995-07-01

    High-quality ab initio calculations at the MP n ( n = 2, 3 or 4) levels for the π-donor complex formed by HCl and ethene, and the recently characterized ClBr-ethene complex are presented. Interaction energies were calculated with the inclusion of both basis-set superposition error and zero-point energy corrections, resulting in values of about 1 kcal mol -1 for both complexes. The total charge densities for both complexes yielded molecular graphs indicative of the weak binding in these molecules, and correspondingly, calculated charges showed that the XCl moiety has an overall slightly negative charge, while the ethene moiety is slightly positive. Analysis of the Laplacian of the charge density showed that the geometry of the ClBr- C 2H 4 complex may be understood in terms of the VSEPR model as an example of an AXYE 3 molecule.

  10. MICMOC/MICMOS: Photochemistry of van der Waals solids and the rise of the organic molecular complexity

    Directory of Open Access Journals (Sweden)

    Sergeant d’Hendecourt L. Le

    2014-02-01

    Full Text Available Ices of well-known composition are widely observed in molecular clouds out of which stars, planets and debris (asteroids, comets will form. These ices are naturally subjected to energy input in the form of UV photons and charged cosmic particles which are able to start a very rich radical chemistry in the solid state. These phenomena are simulated in the MICMOC experiment which focuses on the possible prebiotic significance of the organic residues that are formed at room temperature. Further than MICMOC, we propose a general prospective of the evolution of this experiment toward the concept of non-directed experiments that may allow simulating the very first steps from the inanimate molecular world to selective pathways toward self-replicating autocatalytic and heterotrophic molecules that could be considered, for a physicist a template for “minimal” life.

  11. New models for intermolecular repulsion and their application to Van Der Waals complexes and crystals of organic molecules

    International Nuclear Information System (INIS)

    Tsui, H.H.Y.

    2001-01-01

    Model intermolecular potentials are required for simulations of molecules in the gas, liquid, or solid phase. The widely used isotropic atom-atom model potentials are empirically fitted and based on the assumptions of transferability, combining rules and that atoms in molecules are spherical. This thesis develops a non-empirical method of modelling repulsion by applying the overlap model, which we show as a general non-empirical method of deriving repulsion potentials for a specific molecule. In this thesis, the repulsion parameters for an exponential atom-atom model potential are obtained from the ab initio charge density of a small organic molecule by making the assumption that the repulsion is proportional to the overlap of a pair of molecules. The proportionality constant is fixed by a limited number of intermolecular perturbation theory (IMPT) calculations. To complete the model potential, the electrostatic interaction is represented by a distributed multipole analysis, and the Slater-Kirkwood formula is used for the dispersion. These non-empirical potentials can reproduce experimental crystal structure when applied to crystal structure prediction of an oxyboryl derivative. A detailed study on further improving the overlap model was carried out for phenol-water, by including other minor intermolecular contributions of charge-transfer and penetration. High quality ab initio calculations on the complex were performed for use in comparison. To compare with experimental data, diffusion Monte Carlo simulations were performed with the potential, so that the effects of anharmonic zero-point motion on structure and energy of the system are included. When the system is too large for an IMPT calculation, the proportionality constant can be determined empirically by fitting the cell volume as shown in our study of crystal structures of chlorothalonil. This is used with an anisotropic repulsion model that has been derived for Cl and N atoms in chlorothalonil. This model

  12. Rotational distributions following van der Waals molecule dissociation: comparison between experiment and theory for benzene-Ar.

    Science.gov (United States)

    Sampson, Rebecca K; Bellm, Susan M; McCaffery, Anthony J; Lawrance, Warren D

    2005-02-15

    The translational energy release distribution for dissociation of benzene-Ar has been measured and, in combination with the 6(1)(0) rotational contour of the benzene product observed in emission, used to determine the rotational J,K distribution of 0(0) benzene products formed during dissociation from 6(1). Significant angular momentum is transferred to benzene on dissociation. The 0(0) rotational distribution peaks at J=31 and is skewed to low K:Javerage=27, (K)average=10.3. The average angle between the total angular momentum vector and the unique rotational axis is determined to be 68 degrees. This indicates that benzene is formed tumbling about in-plane axes rather than in a frisbeelike motion, consistent with Ar "pushing off" benzene from an off-center position above or below the plane. The J distribution is very well reproduced by angular momentum model calculations based on an equivalent rotor approach [A. J. McCaffery, M. A. Osborne, R. J. Marsh, W. D. Lawrance, and E. R. Waclawik, J. Chem. Phys. 121, 1694 (2004)], indicating that angular momentum constraints control the partitioning of energy between translation and rotation. Calculations for p-difluorobenzene-Ar suggest that the equivalent rotor model can provide a reasonable prediction of both J and K distributions in prolate (or near prolate) tops when dissociation leads to excitation about the unique, in-plane axis. Calculations for s-tetrazine-Ar require a small maximum impact parameter to reproduce the comparatively low J values seen for the s-tetrazine product. The three sets of calculations show that the maximum impact parameter is not necessarily equal to the bond length of the equivalent rotor and must be treated as a variable parameter. The success of the equivalent rotor calculations argues that angular momentum constraints control the partitioning between rotation and translation of the products.

  13. Adsorption of Organic Molecules to van der Waals Materials: Comparison of Fluorographene and Fluorographite with Graphene and Graphite.

    Science.gov (United States)

    Karlický, František; Otyepková, Eva; Lo, Rabindranath; Pitoňák, Michal; Jurečka, Petr; Pykal, Martin; Hobza, Pavel; Otyepka, Michal

    2017-03-14

    Understanding strength and nature of noncovalent binding to surfaces imposes significant challenge both for computations and experiments. We explored the adsorption of five small nonpolar organic molecules (acetone, acetonitrile, dichloromethane, ethanol, ethyl acetate) to fluorographene and fluorographite using inverse gas chromatography and theoretical calculations, providing new insights into the strength and nature of adsorption of small organic molecules on these surfaces. The measured adsorption enthalpies on fluorographite range from -7 to -13 kcal/mol and are by 1-2 kcal/mol lower than those measured on graphene/graphite, which indicates higher affinity of organic adsorbates to fluorographene than to graphene. The dispersion-corrected functionals performed well, and the nonlocal vdW DFT functionals (particularly optB86b-vdW) achieved the best agreement with the experimental data. Computations show that the adsorption enthalpies are controlled by the interaction energy, which is dominated by London dispersion forces (∼70%). The calculations also show that bonding to structural features, like edges and steps, as well as defects does not significantly increase the adsorption enthalpies, which explains a low sensitivity of measured adsorption enthalpies to coverage. The adopted Langmuir model for fitting experimental data enabled determination of adsorption entropies. The adsorption on the fluorographene/fluorographite surface resulted in an entropy loss equal to approximately 40% of the gas phase entropy.

  14. Molecular beam epitaxy of quasi-freestanding transition metal disulphide monolayers on van der Waals substrates: a growth study

    Science.gov (United States)

    Hall, Joshua; Pielić, Borna; Murray, Clifford; Jolie, Wouter; Wekking, Tobias; Busse, Carsten; Kralj, Marko; Michely, Thomas

    2018-04-01

    Based on an ultra-high vacuum compatible two-step molecular beam epitaxy synthesis with elemental sulphur, we grow clean, well-oriented, and almost defect-free monolayer islands and layers of the transition metal disulphides MoS2, TaS2 and WS2. Using scanning tunneling microscopy and low energy electron diffraction we investigate systematically how to optimise the growth process, and provide insight into the growth and annealing mechanisms. A large band gap of 2.55 eV and the ability to move flakes with the scanning tunneling microscope tip both document the weak interaction of MoS2 with its substrate consisting of graphene grown on Ir(1 1 1). As the method works for the synthesis of a variety of transition metal disulphides on different substrates, we speculate that it could be of great use for providing hitherto unattainable high quality monolayers of transition metal disulphides for fundamental spectroscopic investigations.

  15. Cálculo do Volume Molar de um Gás de van der Waals em SCILAB: o Método Newton-Raphson na Resolução de um Problema Físico-Químico

    Directory of Open Access Journals (Sweden)

    Diogenes Filho

    2014-07-01

    Full Text Available The use of software in chemical calculations is a constant reality in both laboratories as well as in simulation processes of chemical transformations. Around addition, this publication discusses the use of the computer program in Scilab problems of chemical origin, especially in the case of calculating the molar volume of gas van der Waals forces. Discussions on the results of the use of this program with a view to the tools available for the calculation of a polynomial provide satisfactory conclusions on the use of mathematical methods in Physical Chemistry, especially the Newton-Raphson method.

  16. Advanced Communication and Control Solutions of Distributed Energy Resources (DER)

    Energy Technology Data Exchange (ETDEWEB)

    Asgeirsson, Haukur; Seguin, Richard; Sherding, Cameron; de Bruet, Andre, G.; Broadwater, Robert; Dilek, Murat

    2007-01-10

    This report covers work performed in Phase II of a two phase project whose objective was to demonstrate the aggregation of multiple Distributed Energy Resources (DERs) and to offer them into the energy market. The Phase I work (DE-FC36-03CH11161) created an integrated, but distributed, system and procedures to monitor and control multiple DERs from numerous manufacturers connected to the electric distribution system. Procedures were created which protect the distribution network and personnel that may be working on the network. Using the web as the communication medium for control and monitoring of the DERs, the integration of information and security was accomplished through the use of industry standard protocols such as secure SSL,VPN and ICCP. The primary objective of Phase II was to develop the procedures for marketing the power of the Phase I aggregated DERs in the energy market, increase the number of DER units, and implement the marketing procedures (interface with ISOs) for the DER generated power. The team partnered with the Midwest Independent System Operator (MISO), the local ISO, to address the energy market and demonstrate the economic dispatch of DERs in response to market signals. The selection of standards-based communication technologies offers the ability of the system to be deployed and integrated with other utilities’ resources. With the use of a data historian technology to facilitate the aggregation, the developed algorithms and procedures can be verified, audited, and modified. The team has demonstrated monitoring and control of multiple DERs as outlined in phase I report including procedures to perform these operations in a secure and safe manner. In Phase II, additional DER units were added. We also expanded on our phase I work to enhance communication security and to develop the market model of having DERs, both customer and utility owned, participate in the energy market. We are proposing a two-part DER energy market model--a utility

  17. van't Hoff-van der Waals osmotic pressure and energy transformers

    OpenAIRE

    Zener, Clarence; Levenson, William

    1983-01-01

    We find the van't Hoff relations between osmotic pressure, freezing point depression, and boiling point elevation provide a clue on how, by using salt solutions, one may lower the cost of extracting power from low-grade heat sources. In particular, the ratio of 7 between the heat of evaporation and the heat of freezing of pure water suggests a chemical system that raises 7-fold the temperature difference between heat source and heat sink, while decreasing by the same factor the heat flux. Hea...

  18. In silico carbon molecular beam epitaxial growth of graphene on the h-BN substrate: carbon source effect on van der Waals epitaxy

    Science.gov (United States)

    Lee, Jonghoon; Varshney, Vikas; Park, Jeongho; Farmer, Barry L.; Roy, Ajit K.

    2016-05-01

    Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon molecular beam epitaxy (CMBE) techniques using solid carbon sublimation have reported relatively poor quality of the graphene. In this article, the CMBE growth of graphene on the h-BN substrate is numerically studied in order to identify the effect of the carbon source on the quality of the graphene film. The carbon molecular beam generated by the sublimation of solid carbon source materials such as graphite and glassy carbon is mostly composed of atomic carbon, carbon dimers and carbon trimers. Therefore, the graphene film growth becomes a complex process involving various deposition characteristics of a multitude of carbon entities. Based on the study of surface adsorption and film growth characteristics of these three major carbon entities comprising graphite vapour, we report that carbon trimers convey strong traits of vdW epitaxy prone to high quality graphene growth, while atomic carbon deposition is a surface-reaction limited process accompanied by strong chemisorption. The vdW epitaxial behaviour of carbon trimers is found to be substantial enough to nucleate and develop into graphene like planar films within a nanosecond of high flux growth simulation, while reactive atomic carbons tend to impair the structural integrity of the crystalline h-BN substrate upon deposition to form an amorphous interface between the substrate and the growing carbon film. The content of reactive atomic carbons in the molecular beam is suspected to be the primary cause of low quality graphene reported in the literature. A possible optimization of the molecular beam composition towards the synthesis of better quality graphene films is suggested.Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon

  19. DFT investigation on two-dimensional GeS/WS2 van der Waals heterostructure for direct Z-scheme photocatalytic overall water splitting

    Science.gov (United States)

    Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Huang, Baibiao

    2018-03-01

    Recently, extensive attention has been paid to the direct Z-scheme systems for photocatalytic water splitting where carriers migrate directly between the two semiconductors without a redox mediator. In the present work, the electronic structure and related properties of two-dimensional (2D) van de Waals (vdW) GeS/WX2 (X = O, S, Se, Te) heterojunction are systematically investigated by first-principles calculations. Our results demonstrate that, the GeS/WS2 heterojunction could form a direct Z-scheme system for photocatalytic water splitting, whereas the GeS/WX2 (X = O, Se, Te) can't, because of their respective unsuitable electronic structures. For the GeS/WS2 heterojunction, the GeS and WS2 monolayers serve as photocatalysts for the hydrogen evolution reactionand oxygen evolution reaction, respectively. The internal electric field induced by the electron transfer at the interface can promote the separation of photo-generated charge carriers and formation of the interface Z-scheme electron transfer. Remarkably, the designed GeS/WS2 heterojunction not only enhances the hydrogen production activity of GeS and the oxygen production ability of WS2 but also improves the light absorption of the two monolayers by reducing the band gaps. Moreover, it is found that narrowing the interlayer distance could enhance the internal electric field, improving the photocatalytic ability of the vdW heterojunction. This work provides fundamental insights for further design and preparation of emergent metal dichalcogenide catalysts, beneficial for the development in clean energy.

  20. Distributed Energy Resource (DER) Cybersecurity Standards

    Energy Technology Data Exchange (ETDEWEB)

    Saleem, Danish [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Johnson, Jay [Sandia National Laboratories

    2017-11-08

    This presentation covers the work that Sandia National Laboratories and National Renewable Energy Laboratory are doing for distributed energy resource cybersecurity standards, prepared for NREL's Annual Cybersecurity & Resilience Workshop on October 9-10, 2017.

  1. The role of the anionic and cationic pt sites in the adsorption site preference of water and ethanol on defected Pt4/Pt(111) substrates: A density functional theory investigation within the D3 van der waals corrections

    Science.gov (United States)

    Seminovski, Yohanna; Amaral, Rafael C.; Tereshchuk, Polina; Da Silva, Juarez L. F.

    2018-01-01

    Platinum (Pt) atoms in the bulk face-centered cubic structure have neutral charge because they are equivalent by symmetry, however, in clean Pt surfaces, the effective charge on Pt atoms can turn slightly negative (anionic) or positive (cationic) while increasing substantially in magnitude for defected (low-coordinated) Pt sites. The effective charge affect the adsorption properties of molecular species on Pt surfaces and it can compete in importance with the coupling of the substrate-molecule electronic states. Although several studies have been reported due to the importance of Pt for catalysis, our understanding of the role played by low-coordinated sites is still limited. Here, we employ density functional theory within the Perdew-Burke-Ernzerhof exchange-correlation functional and the D3 van der Waals (vdW) correction to investigate the role of the cationic and anionic Pt sites on the adsorption properties of ethanol and water on defected Pt4/Pt(111) substrates. Four substrates were carefully selected, namely, two two-dimensional (2D) Pt4 configurations (2D-strand and 2D-island) and two tri-dimensional (3D) Pt4 (3D-fcc and 3D-hcp), to understand the role of coordination, effective charge, and coupling of the electronic states in the adsorption properties. From the Bader charge analysis, we identified the cationic and anionic sites among the Pt atoms exposed to the vacuum region in the Pt4/Pt(111) substrates. We found that ethanol and water bind via the anionic O atoms to the low-coordinated defected Pt sites of the substrates, where the angle PtOH is nearly 100° for most configurations. In the 3D-fcc or 3D-hcp defected configurations, the lowest-coordinated Pt atoms are anionic, hence, those Pt sites are not preferable for the adsorption of O atoms. The charge transfer from water and ethanol to the Pt substrates has similar magnitude for all cases, which implies similar Coulomb contribution to the adsorption energy. Moreover, we found a correlation of the

  2. Basics of energy policy; Grundlagen der Energiepolitik

    Energy Technology Data Exchange (ETDEWEB)

    Reiche, D. (ed.)

    2005-07-01

    This book displays basics of German and international energy policy. It explains the subject area for newcomers like students as well as for experts from industry, sciences or journalism and is intended to be a valuable source of information and helpfull reference book. It is made purposely in a way to be read section-wise. How is the state of development of special energy sources as coal, wind power or tidal and wave power respectively? Which actors operate in energy policy, what instruments of energy policy can be used by the legislator? The book is supposed to answer those questions. It was tried to achieve a high level of readability and useability by structuring and the use of many pictures and tables. (orig./uke)

  3. The intercombination Cd line 326.1 nm and van der Waals potential coefficients {Delta}C{sub 6}{sup 0}and{Delta}C{sub 6}{sup 1} for pure Cd and Cd-inert gas systems

    Energy Technology Data Exchange (ETDEWEB)

    Roston, G.D., E-mail: Gamal_daniel@yahoo.com [Department of Physics, Faculty of Science, Alexandria University, Alexandria (Egypt); Helmi, M.S. [Department of Physics, Faculty of Science, Alexandria University, Alexandria (Egypt)

    2009-03-30

    The absorption profiles of the Cd 326.1 nm line for pure Cd and Cd-inert gases (Xe, Kr, Ar, Ne and He) have been carefully studied from the line center to 700 cm{sup -1} in the red wing using a high resolution double beam spectrometer. The density of Cd was about 5.108 x 10{sup 18} atoms cm{sup -3}. The temperature dependences of the red wings of these profiles were analysed in the frame work of the Unified Frank Condon (UFC) treatment of pressure broadening of spectral lines developed by Szudy and Baylis. The van der Waals potential coefficient differences {Delta}C{sub 6}{sup 0} and {Delta}C{sub 6}{sup 1} between the ground {sup 1}0{sup +} state and the two excited states {sup 3}0{sup +} and {sup 3}1 were obtained using Kuhn's law.

  4. The climate protection contribution of the German Energy Transition; Der Klimaschutzbeitrag der deutschen Energiewende

    Energy Technology Data Exchange (ETDEWEB)

    Erdmann, Georg [TU Berlin (Germany). Fachgebiet Energiesysteme

    2017-04-15

    Energy Transition has already led to changes in the energy landscape and will continue to initiate changes. However, it also raises questions that need to be answered: What are the objectives to be achieved by 2020, what are the objectives of a more or less threatening failure? Which instruments and measures have proved to be helpful, which to be (largely) ineffective? What caused the likely heterogeneous goal fulfillment? What are the relevant exogenous causes, which are characterized by the fact that the national energy policy can not have any influence on it? And what are the endogenous causes, which lead to concrete indications of a necessary re-control of the energy transition? Obviously, the answers to these questions are relevant not only from a historical perspective, but also for the question of how the energy tansition will be successfully continued in the 2020-2030 period, and how possible failures can be avoided or at least reduced. [German] Die Energiewende hat bereits heute zu Umbruechen in der Energielandschaft gefuehrt und wird auch weiter Veraenderungen anstossen. Dennoch wirft sie auch Fragen auf, die beantwortet werden wollen: Welche Ziele duerften bis zum Jahr 2020 erreicht werden, bei welchen Zielen droht eine mehr oder weniger starke Verfehlung? Welche Instrumente und Massnahmen haben sich als hilfreich erwiesen, welche als (weitgehend) wirkungslos? Worauf ist die voraussichtlich heterogene Zielerfuellung zurueckzufuehren? Was sind die dafuer massgebenden exogenen Ursachen, die dadurch gekennzeichnet sind, dass die nationale Energiepolitik darauf grundsaetzlich keinen Einfluss nehmen kann? Und was sind die endogenen Ursachen, woraus sich konkrete Hinweise auf ein erforderliches Nachsteuern der Energiewende ergeben? Offensichtlich sind die Antworten auf diese Fragen nicht nur aus historischer Perspektive relevant, sondern auch fuer die Frage, wie die Energiewende im Zeitraum 2020 bis 2030 erfolgreich weitergefuehrt und wie allfaellige

  5. Review of Integration of Distributed Energy Resources (DERs) into Power Systems

    DEFF Research Database (Denmark)

    Wu, Qiuwei; Xu, Zhao

    2011-01-01

    state‐of‐the‐art DER integration concepts  relations existing DER integration concepts to the EV system The power balancing challenges of power systems brought by high penetration of intermittent DER have been discussed, especially the wind power integration in the Danish context. The relevance...... of the integration of electric vehicles (EVs) to the DER integration concepts have been analyzed as well based on the energy storage potential of EVs.   Two main concepts for DER integration, virtual power plant (VPP) and microgrids, are described and a comparison of the two concepts have been done. The comparison......An overview of the integration of distributed energy resources (DER) into power systems has been presented in this report. Different aspects of integration of DER into power systems have been reviewed and discussed which are listed below.    needs of DER integration into power systems  various...

  6. Practical guide to more efficient use of energy in industry; Praxisleitfaden zur Foerderung der rationellen Energieverwendung in der Industrie

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-09-04

    Starting with an easily digestible explanation of fundamental concepts and terms in the field of energy and its applications, as well as the related thermodynamic principles and processes, the second chapter explains the system of energy and exergy. Chapters 3 and 4 give a comprehensive picture of current technologies and processes in energy generation and engineering, from energy applications for process heat generation through to power plants and combined and heat and power systems, fuel cells and energy generation from renewable primary sources, discussing related aspects of interest such as energy and pollutant emissions, and economic aspects. Chapter 5 is devoted to counselling and guidance for corporate energy engineering analysis and enhancement. Chapters 6 and 7 round up the comprehensive information addressing the legal aspects of procedures for licensing of energy generation and conversion systems, and the various financing instruments and schemes available for projects intended to promote more efficient use of energy. (orig./CB) [Deutsch] Ausgehend von einer anschaulichen Beschreibung grundlegender Energiebegriffe und thermodynamischer Zusammenhaenge wird im zweiten Kapitel in klarer Weise das Zusammenspiel zwischen Energie und Exergie dargestellt. Aufbauend auf diesen grundlegenden Hinweisen bieten die Kapitel 3 und 4 eine weitreichende Uebersicht der gegenwaertig zur Verfuegung stehenden Prozess- und Energietechniken. Ausgehend von Techniken zur Prozesswaermebereitstellung spannt sich der Bogen ueber Kraftanlagen und Kraft-Waerme-Kopplungssysteme bis hin zu Brennstoffzellen und regenerativen Energietechniken, wobei der Schwerpunkt der Betrachtungen auf Energie- und Emissionsaspekte sowie wirtschaftliche Randbedingungen gelegt wurde. Kapitel 5 gibt Hinweise zur Vorbereitung und Durchfuehrung energietechnischer Beratungen und Analysen auf betrieblicher Ebene. Im Anschluss an den technischen Teil dieses Leitfadens folgt in Kapitel 6 eine Erlaeuterung der

  7. Geothermics - energy for the future. Proceedings; Geothermie - Energie der Zukunft. Tagungsband

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-01

    The proceedings volume of the 4th Geothermal Congress, held in Constance in 1996, comprises 74 papers on the following subjects: 1. Practical applications of hydrogeothermal resources; 2. Hot dry rock; 3. Geothermal heat pumps; 4; Economic aspects of geothermal energy. (AKF) [Deutsch] Der Tagungsband zur 4. Geothermischen Fachtagung 1996 in Konstanz enthaelt 74 Beitraege, die sich mit den folgenden Schwerpunkten befassen: 1. Praktische Anwendungen der Hydrogeothermie; 2. Hot-dry-rock; 3. Oberflaechennahe/untiefe Geothermie; 4. Geothermie und wirtschaftliche Fragen. (AKF)

  8. Energy policy in a direct democracy; Die Politik der Energie in der direkten Demokratie

    Energy Technology Data Exchange (ETDEWEB)

    Leuenberger, M

    2007-07-01

    This comprehensive article, written by Moritz Leuenberger, Swiss Federal Councillor for the Environment, Traffic, Energy and Communications, takes a look at the energy perspectives for Switzerland and various new and revised laws and regulations in the energy area. The author criticises the reduction of complex interactions between climate, market and international interdependencies down to oversimplified questions such as 'atomic power: yes or no' or 'gas-fired power stations: yes or no'. The ceaseless political discussion in Switzerland is criticised. The author discusses three energy and climate-relevant political dossiers: The Swiss Energy Law, the Law on Electricity Supply and the duty on carbon dioxide emissions. Also, the energy perspectives published by the Swiss Federal Office of Energy and questions concerning nuclear wastes are discussed in detail.

  9. New results for the formation of a muoniated radical in the Mu + Br2 system: a van der Waals complex or evidence for vibrational bonding in Br-Mu-Br?

    Science.gov (United States)

    Fleming, Donald G; Cottrell, Stephen P; McKenzie, Iain; Macrae, Roderick M

    2012-08-21

    New evidence is presented for the observation of a muoniated radical in the Mu + Br(2) system, from μSR longitudinal field (LF) repolarisation studies in the gas phase, at Br(2) concentrations of 0.1 bar in a Br(2)/N(2) mixture at 300 K and at 10 bar total pressure. The LF repolarisation curve, up to a field of 4.5 kG, reveals two paramagnetic components, one for the Mu atom, formed promptly during the slowing-down process of the positive muon, with a known Mu hyperfine coupling constant (hfcc) of 4463 MHz, and one for a muoniated radical formed by fast Mu addition. From model fits to the Br(2)/N(2) data, the radical component is found to have an unusually high muon hfcc, assessed to be ∼3300 MHz with an overall error due to systematics expected to exceed 10%. This high muon hfcc is taken as evidence for the observation of either the Br-Mu-Br radical, and hence of vibrational bonding in this H[combining low line]-L[combining low line]-H[combining low line] system, or of a MuBr(2) van der Waals complex formed in the entrance channel. Preliminary ab initio electronic structure calculations suggest the latter is more likely but fully rigorous calculations of the effect of dynamics on the hfcc for either system have yet to be carried out.

  10. The contribution of wind energy to electric power generation; Der Beitrag der Windenergie zur Stromerzeugung

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    The conference discussed the following five subjects: (1) Status and perspectives of wind power in Germany and Japan; (2) Grid connection of wind power systems; (3) Wind power and electric power supply; (4) Future fields of application, technical perspectives; (5) Panel discussion. [German] Der Tagungsband beinhaltet Beitraege in fuenf Bloecken, die die folgenden Ueberschriften haben: (1) Stand und Perspektiven der Windenergienutzung in Deutschland und Japan; (2) Netzintegration von Windenergieanlagen; (3) Windenergie in der elektrischen Energieversorgung; (4) zukuenftige Anwendungsfelder, technische Perspektiven sowie (5) Paneldiskussion. (AKF)

  11. Use of hydrogeothermal energy to support traditional heat supply systems; Nutzung der Energie von geothermalen Gewaessern zur Unterstuetzung der traditionellen Waermeversorgungssysteme

    Energy Technology Data Exchange (ETDEWEB)

    Kabat, M.; Nowak, W.; Sobanski, R. [Technische Univ., Szczecin (Poland)

    1997-12-01

    In the Szczecin Region, there are considerable resources of geothermal waters with temperatures from about 30 to 120 C. The authors present in their paper, on the example of selected urban centres, a possibility of utilising geothermal energy for modernisation of traditional heating systems. Among others, the idea of using geothermal energy in combination with conventional heat and power plants has been discussed and the geothermal heating system in Pyrzyce commissioned in February 1996 has been presented. (orig.) [Deutsch] In der Woiwodschaft-Szczecin sind betraechtliche Vorraete der geothermalen Gewaesser mit den Temperaturen von 30 bis ca. 120 C vorhanden. Im vorliegenden Referat stellen die Autoren am Beispiel einiger staedtischer Gebiete die Moeglichkeit, die geothermale Energie zur Modernisierung der traditionellen Waermeversorgungssysteme zu nutzen. Unter anderem wurde das Nutzungskonzept der geothermalen Waermequelle gekopplelt mit konventionellen Heizkraftwerken beschrieben und das im Februar 1996 in Betrieb genommene geothermale Waermeversorgungssysteme in Pyrzyce praesentiert. (orig.)

  12. Status of the energy transition and important fields of action; Stand der Energiewende und wichtige Handlungsfelder

    Energy Technology Data Exchange (ETDEWEB)

    Loeschel, Andreas [Muenster Univ. (Germany); Erdmann, Georg [Technische Univ. Berlin (Germany); Staiss, Frithjof [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg, Stuttgart (Germany); Ziesing, Hans-Joachim [AG Energiebilanzen e.V. (AGEB), Berlin (Germany)

    2017-12-15

    The energy concept of September 2010 and the exit from nuclear energy in August 2011 represent a long-term strategy of Germany's energy policy with ambitious goals. Since 2011, an independent commission of four energy experts has been advising the Federal Government in this process. It presents annual opinions on the progress of the energy transition, which review the implementation of the energy concept, including its objectives, with a view to ensuring a secure, economic and environmentally sound supply of energy in order to be able to follow up where necessary. The statements are attached to the Federal Government's annual monitoring reports on the energy transition and forwarded to the Bundestag. In order to support the upcoming political discussions on the effective and efficient further development of the energy transition, the expert commission would like to give an up-to-date, fact-based overview of the current state of the implementation of the energy transition with the help of an energy transition traffic light in this article. [German] Das Energiekonzept vom September 2010 und der Kernenergieausstieg vom August 2011 stellen eine Langfriststrategie der Energiepolitik Deutschlands mit ambitionierten Zielsetzungen dar. Seit dem Jahr 2011 steht der Bundesregierung in diesem Prozess eine unabhaengige Kommission aus vier Energieexperten beratend zur Seite. Sie legt jaehrliche Stellungnahmen zum Fortschritt der Energiewende vor, mit denen die Umsetzung des Energiekonzepts einschliesslich der darin enthaltenen Ziele mit Blick auf eine sichere, wirtschaftliche und umweltvertraegliche Energieversorgung ueberprueft wird, um bei Bedarf nachsteuern zu koennen. Die Stellungnahmen werden den jaehrlichen Monitoring-Berichten der Bundesregierung zur Energiewende beigefuegt und dem Bundestag zugeleitet. Um die anstehenden politischen Diskussionen zur effektiven und effizienten Weiterentwicklung der Energiewende zu unterstuetzen, moechte die Expertenkommission

  13. Secondary geochemical reactions in hydrothermal energy harnessing; Geochemische Folgereaktionen bei der hydrogeothermalen Energiegewinnung

    Energy Technology Data Exchange (ETDEWEB)

    Kuehn, M.

    1996-12-01

    This thesis is in six parts: description of geothermal energy harnessing, analytics, geochemical-thermodynamic modellings, experimental investigations, discussion of results, summary. (HW) [Deutsch] Die vorliegende Dissertationsschrift gliedert sich in 6 Teile: - Beschreibung der geothermischen Energienutzung - Analytik - geochemische-thermodynamische Modellierungen - experimentelle Untersuchungen - Diskussion der Ergebnisse - Zusammenfassung. (HW)

  14. Interlayer Excitons and Band Alignment in MoS2/hBN/WSe2 van der Waals Heterostructures

    DEFF Research Database (Denmark)

    Latini, Simone; Winther, Kirsten Trøstrup; Olsen, Thomas

    2017-01-01

    of bilayer MoS2/WSe2 with and without intercalated hBN layers, finding excellent agreement with experimental photoluminescence spectra. A comparison to density functional theory calculations demonstrates the crucial role of self-energy and electron-hole interaction effects....... of incommensurate vdWHs. The method combines our quantum electrostatic heterostructure (QEH) model for obtaining the dielectric function with the many-body GW approximation and a generalized 2D Mott-Wannier exciton model. We calculate the level alignment together with intra- and interlayer exciton binding energies...

  15. Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m.

    Science.gov (United States)

    Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

    2006-10-21

    Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2-1.5) x 10(4) s(-1) for cluster sizes of 5CO2-H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.

  16. Misfit-layered Bi1.85 Sr2 Co1.85 O7.7-δ for the hydrogen evolution reaction: beyond van der Waals heterostructures.

    Science.gov (United States)

    Chua, Chun Kiang; Sofer, Zdeněk; Jankovský, Ondřej; Pumera, Martin

    2015-03-16

    Recent research on stable 2D nanomaterials has led to the discovery of new materials for energy-conversion and energy-storage applications. A class of layered heterostructures known as misfit-layered chalcogenides consists of well-defined atomic layers and has previously been applied as thermoelectric materials for use as high-temperature thermoelectric batteries. The performance of such misfit-layered chalcogenides in electrochemical applications, specifically the hydrogen evolution reaction, is currently unexplored. Herein, a misfit-layered chalcogenide consisting of CoO2 layers interleaved with an SrO-BiO-BiO-SrO rock-salt block and having the formula Bi1.85 Sr2 Co1.85 O7.7-δ is synthesized and examined for its structural and electrochemical properties. The hydrogen-evolution performance of misfit-layered Bi1.85 Sr2 Co1.85 O7.7-δ , which has an overpotential of 589 mV and a Tafel slope of 51 mV per decade, demonstrates the promising potential of misfit-layered chalcogenides as electrocatalysts instead of classical carbon. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Optimizing Distributed Energy Resources and building retrofits with the strategic DER-CAModel

    International Nuclear Information System (INIS)

    Stadler, M.; Groissböck, M.; Cardoso, G.; Marnay, C.

    2014-01-01

    Highlights: • We model strategic investment decisions for distributed energy resources and passive measures. • Compare the demonstrated mixed integer optimization model with other existing tools. • Describe the mathematical formulation of the tool. • Demonstrate the capabilities at an Austrian University building. • Show the trade-off between cost and CO 2 reduction and report on the optimal investment decisions. - Abstract: The pressuring need to reduce the import of fossil fuels as well as the need to dramatically reduce CO 2 emissions in Europe motivated the European Commission (EC) to implement several regulations directed to building owners. Most of these regulations focus on increasing the number of energy efficient buildings, both new and retrofitted, since retrofits play an important role in energy efficiency. Overall, this initiative results from the realization that buildings will have a significant impact in fulfilling the 20/20/20-goals of reducing the greenhouse gas emissions by 20%, increasing energy efficiency by 20%, and increasing the share of renewables to 20%, all by 2020. The Distributed Energy Resources Customer Adoption Model (DER-CAM) is an optimization tool used to support DER investment decisions, typically by minimizing total annual costs or CO 2 emissions while providing energy services to a given building or microgrid site. This paper shows enhancements made to DER-CAM to consider building retrofit measures along with DER investment options. Specifically, building shell improvement options have been added to DER-CAM as alternative or complementary options to investments in other DER such as PV, solar thermal, combined heat and power, or energy storage. The extension of the mathematical formulation required by the new features introduced in DER-CAM is presented and the resulting model is demonstrated at an Austrian Campus building by comparing DER-CAM results with and without building shell improvement options. Strategic

  18. A study of van der Waals complexes of 1,2-dichloroethane in paraffin oil by FTIR spectroscopy and ab initio calculations.

    Science.gov (United States)

    Fishman, A I; Noskov, A I; Aminova, R M; Skochilov, R A

    2015-02-05

    Weak molecular interactions of 1,2-dichloroethane dissolved in paraffin oil were investigated by FTIR spectroscopy. Occurrence of isosbestic points in the spectra along with the factor analysis showed that DCE⋯DCE dimers are formed in solutions at DCE concentrations between 7 and 15 vol.%. It was found that both trans and gauche conformers are involved in the complexation, forming a tg-dimer. From the spectra collected at 200-222 K, the complexation enthalpy was determined: -4.2±0.4 kcal mol(-1). The equilibrium geometry of tg-dimer and the vibrational frequencies were determined from the density functional calculations performed at B3LYP/6-311++G(d,p) and 6-31G(d,p) levels. The C-C bonds of the two molecules involved in tg-dimers were found to be oriented nearly perpendicular to each other. The complexation energy calculated using 6-31G(d,p) and 6-311++G(d,p) basis sets was found to be -1.59 and -1.52 kcal mol(-1), respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. The contributions of sociology and politology to energy practice; Der Beitrag der Soziologie und der Politologie fuer die Energiepraxis

    Energy Technology Data Exchange (ETDEWEB)

    Gloor, D.; Meier, H. [cultur prospectiv, Zurich (Switzerland)

    1996-02-01

    In the present investigation, the position of research in the field of sociology and politology in the area of energy politics is presented and the additional research requirement is explained. In order to demonstrate the possible usefulness of the social science knowledge in the energy world, the report was also discussed at a workshop with scientists and energy experts. (author) figs., tabs., refs.

  20. Communal energy management. Integrated heat supply systems for buildings owned by the city of Altenburg; Kommunales Energiemanagement. Waermeverbundsysteme der Gebaeudeleittechnik der Stadt Altenburg

    Energy Technology Data Exchange (ETDEWEB)

    Paul, A.

    1999-03-01

    The city of Altenburg intended to reduce the investment, energy and operating cost of administrative buildings and schools. Apart from economically efficient power supply, emission reduction was another declared goal. This was achieved by integrated heat supply system and a centralized DDC facility management system. The solution combines high availability with user-friendliness, and the systems reflect the latest state of the art. [Deutsch] Die Stadt Altenburg suchte Wege, die Investitions-, Energie- und Betriebskosten fuer Verwaltungsgebaeude und Schulen zu senken. Neben der wirtschaftlichen Waermeversorgung war ein weiteres Ziel, die hohen Emissionswerte, besonders im inneren Stadtgebiet zu mindern. Die realisierten Waermeverbundsysteme und die zentrale DDC-Gebaeudeleittechnik der Stadt Altenburg gewaehrleisten dies. Die Loesung sichert ausserdem eine hohe Versorgungssicherheit mit Anwendungskomfort. Die Anpassung der Systeme an den jeweiligen Stand der Umweltanforderung und der Technik sind sehr gut gegeben. (orig./MSK)

  1. Stationary battery storage of energy transition a central component; Stationaere Batteriespeicher der Energiewende eine zentrale Komponente

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, Matthias; Lux, Stephan [Fraunhofer-Institut fuer Solare Energiesysteme ISE, Freiburg (Germany)

    2017-01-15

    In a regenerative energy system with strong fluctuations in electricity production, the importance of short-term storage is increasing - on the one hand, in order to optimal need-oriented use of the energy supply, on the other hand, at any time to ensure a high network quality. The present overview of stationary battery storage shows how important it will be especially in the area of larger storage facilities with direct link to regenerative power plants, as a district storage or in the industry. [German] In einem regenerativen Energiesystem mit starken Fluktuationen der Stromproduktion nimmt die Bedeutung der Kurzzeitspeicherung zu - einerseits, um das Energieangebot bedarfsgerecht optimal zu nutzen, andererseits, um zu jedem Zeitpunkt eine hohe Netzqualitaet zu gewaehrleisten. Der vorliegende Ueberblick ueber stationaere Batteriespeicher zeigt, wie wichtig vor allem der Bereich groesserer Speicher in direkter Koppelung mit regenerativen Kraftwerken, als Quartiersspeicher oder im Gewerbe sein wird.

  2. What costs the development of renewable energies in power generation actually?; Was kostet der Ausbau erneuerbarer Energien in der Stromerzeugung tatsaechlich?

    Energy Technology Data Exchange (ETDEWEB)

    Nitsch, Joachim

    2013-03-30

    Additional costs of the energy transition can only be termed when the present state of the power system is considered as a benchmark for future raised previous achievements. An energy policy that has an effective climate protection goal, must endeavor to change the market design of the energy market so as to align the price signals at the expense of those technologies that are able to provide energy without emissions and significant use of fossil resources. The derivable overall economic benefits of energy transition is significant. This is illustrated by the example of the differential cost for the annex of renewable energies in the electricity sector. A further development of renewable energy sources in combination with an effective electricity market design leads to an overall economic benefit of around 460 billion Euros in 2050. [German] Von zusaetzlichen Kosten der Energiewende kann nur gesprochen werden, wenn der heutige Zustand des Energiesystems als Massstab fuer zukuenftig aufzubringende Vorleistungen betrachtet wird. Eine Energiewende, die einen effektiven Klimaschutz zum Ziel hat, muss jedoch bestrebt sein, das Marktdesign des Energiemarkts so zu veraendern, dass sich die Preissignale an den Kosten derjenigen Technologien ausrichten, die in der Lage sind, Energie emissionsfrei und ohne wesentliche Inanspruchnahme fossiler Ressourcen bereitzustellen. Der daraus ableitbare gesamtwirtschaftliche Nutzen der Energiewende ist erheblich. Es wird hier am Beispiel der Differenzkosten des Zubaus erneuerbarer Energien im Stromsektor erlaeutert. Ein konsequenter weiterer Erneuerbare Energien-Zubau in Kombination mit einem effektiven Strommarktdesign fuehrt zu einem gesamtwirtschaftlichen Nutzen von rund 460 Mrd. Euro im Jahr 2050.

  3. Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces.

    Science.gov (United States)

    Valchev, Galin; Dantchev, Daniel

    2017-08-01

    We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The latter arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar one-component fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab and between two spherical colloid particles. We do that using general scaling arguments and mean-field-type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential μ. The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the so-called (+,+) boundary conditions. On the other hand, the core region of the slab and the particles influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters, the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T, μ, or L, in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding

  4. Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

    Science.gov (United States)

    Valchev, Galin; Dantchev, Daniel

    2017-08-01

    We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The latter arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar one-component fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab and between two spherical colloid particles. We do that using general scaling arguments and mean-field-type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential μ . The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the so-called (+,+) boundary conditions. On the other hand, the core region of the slab and the particles influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters, the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , μ , or L , in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding

  5. Energy conservation potentials in the countries of Central and Eastern Europe - an expose of theses; Die Energiespeicherpotentiale in den Laendern Mittel- und Osteuropas - eine Darstellung der Thesen

    Energy Technology Data Exchange (ETDEWEB)

    Riesner, W. [Hochschule fuer Technik, Wirtschaft und Sozialwesen Zittau/Goerlitz FH, Zittau (Germany)

    1996-07-01

    The report compares western and eastern Europe in terms of their supply with fossil energy, the development of their primary and end-use energy consumption, and the development of their gross power generation. The technical state of energy conversion plants and electrothermal power plants, Russia`s energy conservation potential, and the efficacy of measures for enhancing electric energy efficiency in the Ukraine are described. Finally, a comparison of energy input coefficients and energy costs between the old and new federal states of Germany is made. (DG) [Deutsch] Bezueglich der Versorgung mit fossiler Energie, der Entwicklung des Primaer- und Endenergieverbrauchs und der Entwicklung der Brutto-Stromerzeugung werden West- und Osteuropa miteinander verglichen. Der technische Stand der Energieumwandlungsanlagen und der Elektrowaermeanlagen sowie das Energieeinsparungspotential in Russland und die Effektivitaet von Massnahmen zur Elektroenergieeffizienzsteigerung in der Ukraine werden dargestellt. Schliesslich erfolgt ein Vergleich der Energieintensitaets- und Energiekosten zwischen den alten und neuen Bundeslaendern der BRD. (DG)

  6. Enskog and van der Waals play hockey

    NARCIS (Netherlands)

    Cutchis, Protagoras; Beijeren, H. van; Dorfman, J.R.

    1977-01-01

    We consider the mean free path of a hockey puck in a system of other pucks on an air table, and show how the simple low-density kinetic-theory value for this mean free path can be extended to higher densities. This approach is connected both with the Enskog theory of the transport properties of

  7. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    D)> HBr (0.83 D) > HI (0.45 D) [8]. Hence, these molecules can and do induce a dipole moment in the rare gas atoms when the two interact. The induced dipole moment is proportional to the inducing field E and the proportionality constant is the polariz- ability, i.e., μ i. = αE. However, as mentioned above, dispersion.

  8. Molecule Matters van der Waals Molecules

    Indian Academy of Sciences (India)

    Admin

    Experimental and theoretical results for ... Group 8. During my student days, the group number was equal to the number of electrons in the s and p orbitals in the outermost shell. Helium could have caused some confusion ... and pointed out that the constant a depends on the intermolecular potential (which controls the.

  9. Excitons in van der Waals heterostructures

    DEFF Research Database (Denmark)

    Latini, Simone; Olsen, Thomas; Thygesen, Kristian Sommer

    2015-01-01

    -dimensional (2D) excitons is still lacking. Here we provide a critical assessment of a widely used 2D hydrogenic exciton model, which assumes a dielectric function of the form epsilon(q) = 1 + 2 pi alpha q, and we develop a quasi-2D model with a much broader applicability. Within the quasi-2D picture, electrons...

  10. The solar way out of the energy trap for industrial society. Der Sonnenweg aus der Energiefalle der Industriegesellschaft

    Energy Technology Data Exchange (ETDEWEB)

    Hopfmann, J.

    1994-01-01

    The first part of this book presents the different variations of solar energy utilisation. All countries of the world are in a position to cover their energy demand by a sensible combination of different solar technologies. This is a chance for industrialised countries to pursue environmentally benign, qualitative economic growth. The second part of the book inquires into the antiecological and antisocial energy policy of the countries of the industrialised world. The energy prices are only so low because the exploitation of nature is not being paid for. The third part of the book arrives at the conclusion that the energy squander practised by industrial society is an act against the evolution of the concerns. All systems brought forth by cosmic evolution tend to bind as much energy as possible and release the minimum possible of bound energy. It is therefore an entropic duty of humanity to use solar energy. The fourth part of the book analyses the economic side of the energy problem. The deliberations focus on the inclusion of the reproduction costs entailed by the consumption of nature in the price of the goods traded in the free market. The reproduction costs entailed by the consumption of nature must be paid in any case. If they are not included in the cost price of the goods, they will reappear multiplied as rehabilitation costs in the subsequent economic process. A social and ecological market economy must therefore take the consumption of all production factors into account in determining the prices of its goods. (orig./UA)

  11. Energy and the future: Sustainable methods of energy use from passive architecture to fusion. Lectures; Energie und Zukunft: Zukunftsweisende Methoden der Energienutzung vom Passivhaus bis zur Fusion. Vortraege

    Energy Technology Data Exchange (ETDEWEB)

    Nahm, W.; Schultze, K. [eds.

    1998-12-31

    In the run-up to the Kyoto conference, there is far-reaching agreement that the world energy industry needs to be reconstructed by the middle of the next century if a climate catastrophe is to be avoided. But how this goal can be reached is controversial. The risks involved are described in contributions concerned with German energy policy, the insurance sector, and scenarios for mitigating carbon dioxides on the basis of the Ikarus model. But the focus of this annual report of DPG`s task force Energy is on reports on longer-term technologies and methods. Two papers describe the state of the art of fusion research. In the conventional energy sector, high-efficiency absorption-type refrigerators and thermal engines, and fuel conservation through low-cost passive architecture are dealt with inter alia. Other lectures report on the state of solar energy utilization and process chains in the hydrogen-based economy. Five papers are individually listed in the Energy database. (orig.) [Deutsch] Im Vorfeld der Konferenz von Kyoto besteht weitgehende Einigkeit, dass die Weltenergiewirtschaft bis zur Mitte des naechsten Jahrhunderts umgestaltet werden muss, um eine Klimakatastrophe zu verhindern. Der Weg dahin ist umstritten. Seine Risiken kommen in Beitraegen zur deutschen Energiepolitik, zur Versicherungswirtschaft und zu Szenarien der Minderung der CO{sub 2}-Emissionen auf der Basis des Ikarus-Modells zum Ausdruck. Im Mittelpunkt des Jahresbandes des Arbeitskreises Energie der DPG stehen diesmal jedoch Berichte ueber laengerfristig angelegte Technologien und Methoden. Zwei Beitraege berichten ueber den Stand der Fusionsforschung. Im konventionellen Bereich geht es u.a. um hocheffiziente Absorptionsmaschinen zur Versorgung mit Kaelte und Waerme und um die Brennstoffeinsparung durch kostenguenstige Passivhaeuser. Andere Vortraege berichten ueber den Stand der Nutzung der Sonnenenergie und Prozessketten in der Wasserstoffwirtschaft. Fuer die Datenbank Energy wurden fuenf

  12. SOLID-DER. Reaching large-scale integration of Distributed Energy Resources in the enlarged European electricity market

    International Nuclear Information System (INIS)

    Van Oostvoorn, F.; Ten Donkelaar, M.

    2007-05-01

    The integration of DER (distributed energy resources) in the European electricity networks has become a key issue for energy producers, network operators, policy makers and the R and D community. In some countries it created already a number of challenges for the stability of the electricity supply system, thereby creating new barriers for further expansion of the share of DER in supply. On the other hand in many Member States there exists still a lack of awareness and understanding of the possible benefits and role of DER in the electricity system, while environmental goals and security of supply issues ask more and more for solutions that DER could provide in the future. The project SOLID-DER, a Coordination Action, will assess the barriers for further integration of DER, overcome both the lack of awareness of benefits of DER solutions and fragmentation in EU R and D results by consolidating all European DER research activities and report on its common findings. In particular awareness of DER solutions and benefits will be raised in the new Member States, thereby addressing their specific issues and barriers and incorporate them in the existing EU DER R and D community. The SOLID-DER Coordination Action will run from November 2005 to October 2008

  13. New structure of the boundary conditions of energy law and communalisation of electricity supply; Neuordnung der energierechtlichen Rahmenbedingungen und Kommunalisierung der Elektrizitaetsversorgung

    Energy Technology Data Exchange (ETDEWEB)

    Lang, G.

    1993-06-01

    Points relating to economic policy in the German energy policy are shaped not only by national and supranational legislative powers, but also to a large extent by the local authorities. The areas under local authority are set out at a country level, illustrating a further development of the ``Germany law governing local authorities`` in 1935. Many areas have not hesitated to use their powers in establishing their own supply utilities. The communalisation of the energy supply brings it once again to the forefront of discussions; it represents strengthened founding opportunities as well as the decentralisation of the power plant structure. This study aims to illustrate and provide an economic interpretation of the fourth and fifth regulations on hindrances to competition against the background of the present intervention system and current market structure of the energy sector (chapter 2 and 3). Further to that, the improvements of local authority`s opportunities to construct their own electricity production capacity in the new framework are explored, and the likely economic consequences (chapter 4). A summary and evaluation of the results is given in chapter 5. (UA) [Deutsch] Wirtschaftspolitische Weichenstellungen in der Energiepolitik werden in der BRD nicht nur von den nationalen und supranationalen Gesetzgebungsinstanzen, sonder in sehr hohem Ausmass auch von den Kommunen gepraegt. Der ordnungspolitische Handlungsspielraum der Kommunen wird dabei von den Gemeindeordnungen der jeweiligen Bundeslaender festgelegt, die eine Fortentwicklung der ``Deutschen Gemeindeordnung`` von 1935 darstellen. Viele Gemeinden haben nicht gezoegert, diese Handlungsmoeglichkeiten insbesondere durch die Gruendung von eigenen Versorgungsunternehmen auszunuetzen. Die Kommunalisierung der Energieversorgung steht jetzt wieder im Mittelpunkt vieler Diskussionen, wobei nicht nur eine verstaerkte Gruendungsaktivitaet als solche, sondern darueber hinaus eine Dezentralisierung der

  14. Assessment of (mu)grid distributed energy resource potential using DER-CAM and GIS

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, Jennifer L.; Marnay, Chris; Bartholomew, Emily; Ouaglal, Boubekeur; Siddiqui, Afzal S.; LaCommare, Kristina S.H.

    2002-01-01

    This report outlines an approach to assess the local potential for deployment of distributed energy resources (DER), small power-generation installations located close to the point where the energy they produce will be consumed. Although local restraints, such as zoning, building codes, and on-site physical barriers are well-known frustrations to DER deployment, no analysis method has been developed to address them within a broad economic analysis framework. The approach developed here combines established economic optimization techniques embedded in the Distributed Energy Resource Customer Adoption Model (DER-CAM) with a geographic information system (GIS) analysis of local land-use constraint. An example case in the San Diego area is developed from a strictly customer perspective, based on the premise that future development of DER may take the form of microgrids ((mu)Grids) under the control of current utility customers. Beginning with assumptions about which customer combinations h ave complementary energy loads, a GIS was used to locate specific neighborhoods in the San Diego area with promising customer combinations. A detailed energy analysis was conducted for the commercial/residential area chosen covering both electrical and heat energy requirements. Under various scenarios, different combinations of natural gas reciprocating engines were chosen by DER-CAM, ranging in size from 25 kW to 500 kW, often with heat recovery or absorption cooling. These generators typically operate throughout the day and are supplemented by purchased electricity during late-night and early-morning hours, when utility time-of-use prices are lowest. Typical (mu)Grid scenarios displaced about 80 percent of their annual gas heat load through CHP. Self-generation together with absorption cooling dramatically reduce electricity purchases, which usually only occur during nighttime hours.

  15. Geothermal energy in the Emden museum building; Geothermie am Beispiel der Kunsthalle Emden

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, W. [AETNA Energiesysteme, Wildau (Germany); Gebauer, F. [Ingenieurgesellscahft IGG mbH, Lilienthal (Germany); Stuekerjuergen, R. [STUEWA Konrad Stuekerjuergen GmbH, Rietberg (Germany)

    2001-07-01

    The new museum building at Emden was equipped with air humidifiers and dehumidifiers. However, international museum standards require stable room climates especially for foreign exhibits. For this reason, a high-efficiency air conditioning system was installed which integrates electric heat pumps and geothermal energy. [German] Die Ausstellungsraeume der Kunsthalle Emden wurden bei ihrem Neubau lediglich mit Raumluftbe- und -entfeuchtergeraeten ausgestattet. Der internationale Museumsstandard verlangt aus konservatorischen Gesichtspunkten jedoch stabile klimatische Raumverhaeltnisse, die vor allem bei Fremdexponaten erforderlich sind. Eine hochleistungsfaehige Klimaanlage konnte nun installiert werden, in die Elektrowaermepumpen mit Erdwaermesonden zur Einsparung von Primaerenergie eingebunden sind. (orig.)

  16. Connecting Distributed Energy Resources to the Grid: Their Benefits to the DER Owner etc.

    Energy Technology Data Exchange (ETDEWEB)

    Poore, WP

    2003-07-09

    The vision of the Distributed Energy Research Program (DER) program of the U.S. Department of Energy (DOE) is that the United States will have the cleanest and most efficient and reliable energy system in the world by maximizing the use of affordable distributed energy resources. Electricity consumers will be able to choose from a diverse number of efficient, cost-effective, and environmentally friendly distributed energy options and easily connect them into the nation's energy infrastructure while providing benefits to their owners and other stakeholders. The long-term goal of this vision is that DER will achieve a 20% share of new electric capacity additions in the United States by 2010, thereby helping to make the nation's electric power generation and delivery system more efficient, reliable, secure, clean, economical, and diverse in terms of fuel use (oil, natural gas, solar, hydroelectric, etc.) and prime mover resource (solar, wind, gas turbines, etc.). Near- and mid-term goals are to develop new technologies for implementing and operating DER and address barriers associated with DER usage and then to reduce costs and emissions and improve the efficiency and reliability of DER. Numerous strategies for meeting these goals have been developed into a research, development, and demonstration (RD&D) program that supports generation and delivery systems architecture, including modeling and simulation tools. The benefits associated with DER installations are often significant and numerous. They almost always provide tangible economic benefits, such as energy savings or transmission and distribution upgrade deferrals, as well as intangible benefits, such as power quality improvements that lengthen maintenance or repair intervals for power equipment. Also, the benefits routinely are dispersed among end users, utilities, and the public. For instance, an end user may use the DER to reduce their peak demand and save money due to lower demand charges. Reduced

  17. Energy research in Switzerland; Energieforschung in der Schweiz

    Energy Technology Data Exchange (ETDEWEB)

    Buchs, M.; Luetolf, I.; Schorer, M

    2002-07-01

    This brochure takes a look at energy research in Switzerland, and contains a foreword from the director of the Swiss Federal Office of Energy (SFOE), an interview with the president of the Swiss Energy Research Commission and a total of 12 articles on energy research-related topics. These include the expectations placed on energy research by politics, industry's point of view, figures on energy research in the nineties, financing aspects, international co-operation, solar technology, geothermal energy, fuel cells, sensible building for the future, nuclear fusion and socio-economical fundamentals. Private energy research is also focused on with examples of products produced by innovative small and medium-sized companies in Switzerland.

  18. Sustained energy supply under globalisation and liberalisation conditions; Nachhaltige Energieversorgung unter den Bedingungen der Globalisierung und Liberalisierung

    Energy Technology Data Exchange (ETDEWEB)

    Hempelmann, Rolf [Enquete-Kommission des Deutschen Bundestags, Berlin (Germany)

    2002-06-06

    The major challenge at the threshold of this century is to structure the energy supply in the sense of sustained development. The Committee of Enquiry of the Federal German Parliament 'Sustained energy supply under globalisation and liberalisation conditions' is developing medium to long-term concepts in this respect. Analysis of the boundary conditions of future energy policy shows that the consequences of future enrichment of climatic gases in the atmosphere and no longer the availability and productiveness of the energy deposits could become the limiting factor. Following the analysis of the technological and non-technological future potentials for sustained energy supply the Committee of Enquiry is currently working on the formulation of strategies for the energy industry transformation process. (orig.) [German] An der Schwelle dieses Jahrhunderts stellt sich die grosse Herausforderung, die Energieversorgung im Sinne einer nachhaltigen Entwicklung zu strukturieren. Die Enquete-Kommission des Deutschen Bundestags 'Nachhaltige Energieversorgung unter den Bedingungen der Globalisierung und Liberalisierung' entwickelt hierzu mittel- bis laengerfristige Konzepte. Die Analyse der Rahmenbedingungen kuenftiger Energiepolitik zeigt, dass die Folgen einer weiteren Anreicherung von Klimagasen in der Atmosphaere und nicht mehr die Verfuegbarkeit und Ergiebigkeit der Energielagerstaetten zum limitierenden Faktor werden koennten. Nach der Analyse der technologischen und nicht-technologischen Zukunftspotentiale fuer eine nachhaltige Energieversorgung arbeitet die Enquete-Kommission derzeit an der Formulierung von Strategien fuer den energiewirtschaftlichen Transformationsprozess. Vortrag gehalten auf der GVSt-Konferenz 'Kohle - Energie fuer die Zukunft' anlaesslich der E-World of Energy am 14. Februar 2002. (orig.)

  19. On the genesis and accuracy of the energy consumption data of the housing industry; Zur Genese und Genauigkeit der Energieverbrauchsdaten der Wohnungswirtschaft

    Energy Technology Data Exchange (ETDEWEB)

    Vogler, Ingrid [GdW Bundesverband deutscher Wohnungs- und Immobilienunternehmen e.V., Berlin (Germany)

    2016-08-01

    Only the measured power consumption can show us whether commitment and investments in energy efficiency have been successful. We can expect before as much as we want (and expect we must, because otherwise no viable concept comes about). But only the measured consumption shows whether the plan ws successfully. This depends on the final energy, where the system losses and the type of use are included. What use is the best energy saving concept, if despite large investments of energy consumption will not fall as planned? The housing industry recorded since 2007 every two years energy consumption data, presented at the annual press conferences and published in ''Data and Trends''. The following explains, what data is collected, how the characteristic value is formed and how accurate the results are. [German] Nur der gemessene Energieverbrauch kann uns zeigen, ob Engagement und Investitionen in Energieeffizienz erfolgreich waren. Wir koennen vorher rechnen so viel wir wollen (und rechnen muessen wir, weil sonst kein tragfaehiges Konzept zustande kommt). Aber erst der gemessene Verbrauch zeigt, ob der Plan erfolgreich war. Dabei kommt es auf die Endenergie an, d.h. die Systemverluste und die Art der Nutzung sind enthalten. Was nutzt das beste Energieeinsparkonzept, wenn trotz hoher Investitionen der Energieverbrauch nicht wie geplant sinkt? Die Wohnungswirtschaft erfasst seit 2007 alle zwei Jahre Energieverbrauchsdaten, die anlaesslich der Jahrespressekonferenzen vorgestellt und in ''Daten und Trends'' veroeffentlicht werden. Im Folgenden wird erlaeutert, welche Daten erfasst werden, wie die Kennwertbildung erfolgt und wie genau die Ergebnisse sind.

  20. Role for Distributed Energy Resources (DER) in the Digital Economy

    Energy Technology Data Exchange (ETDEWEB)

    Key, Thomas S [Electric Power Research Institute (EPRI)

    2007-11-01

    A large, and growing, part of the Nation's economy either serves or depends upon the information technology industry. These high-tech or "digital" enterprises are characterized by a dependence on electronic devices, need for completely reliable power supply, and intolerance to any power quality problems. In some cases these enterprises are densely populated with electronic loads and have very high energy usage per square foot. Serving these enterprises presents both electric power and equipment cooling challenges. Traditional electric utilities are often hard-pressed to deliver power that meets the stringent requirements of digital customers, and the economic and social consequences of a service quality or reliability problem can be large. New energy delivery and control options must be developed to effectively serve a digital economy. This report explores how distributed energy resources, partnerships between utility and customer to share the responsibility for service quality, innovative facility designs, higher energy efficiencies and waste-heat utilization can be coupled to meet the needs of a growing digital economy.

  1. Solar energy systems in modernized buildings; Solarenergienutzung bei der Sanierung von Gebaeuden

    Energy Technology Data Exchange (ETDEWEB)

    Voss, K. [Fraunhofer-Inst. fuer Solare Energiesysteme, Freiburg (Germany). Gruppe Solares Bauen

    1998-02-01

    The statistics of residential buildings in Germany is of extraordinary distinctness: About 70% of the houses are more than 25 years old and the construction rate is about 1% per annum. In most neighbouring European countries the situation is similar. Predictions show that almost 60% of the building stock of the year 2020 is already erected today. The conclusions: The present building stock is essential for the burden of the environment not only today but also tomorrow. Measures saving energy and protecting the climate must include the already existing houses. Solar concepts especially suited for the renovation of old housing should be more promoted. Technically mature products, architecturally and economically attractive and integrated concepts and convincing examples of practical applications are prerequisites for successful advances into this direction. (orig.) [Deutsch] Die statistische Analyse des Bestands an Wohngebaeuden in Deutschland spricht eine deutliche Sprache: Rund 70% der Gebaeude sind aelter als 25 Jahre; die Neubaurate liegt um 1% pro Jahr. In den meisten europaeischen Nachbarlaendern ist die Situation vergleichbar. Eine Hochrechnung auf das Jahr 2020 belegt, dass schon heute knapp 60% des dann vorliegenden Gebaeudebestands existieren. Fazit: Der Gebaeudebestand von heute bestimmt die Umweltbelastung von heute und morgen. Massnahmen zur Energieeinsparung und fuer einen wirkungsvollen Klimaschutz muessen vordringlich am Gebaeudebestand ansetzen. Unter dem Blickwinkel einer Verbreitung der Solartechnik ist offensichtlich, dass Solarkonzepten, die speziell an die Belange der Sanierung im Bestand angepasst sind, eine grosse Bedeutung zukommt. Voraussetzungen fuer einen erfolgreichen Weg in diesen Markt sind technisch ausgereifte Produkte, architektonisch und wirtschaftlich attraktive Gesamtkonzepte sowie ueberzeugende Beispiele aus der Praxis. (orig.)

  2. Energy-oriented and structural modernisation of industrial large-panel buildings, type ``Hoyerswerda``; Energetische und bautechnische Sanierung von industriellen Wohnbauten der Wohnbauserie Typ ``Hoyerswerda``

    Energy Technology Data Exchange (ETDEWEB)

    Loeber, H.; Derlig, R. [Hochschule fuer Technik, Wirtschaft und Sozialwesen Zittau/Goerlitz, Zittau (Germany); Sprenger, S. [Wohnungsgenossenschaft Hoyerswerda e.G. (Germany)

    1997-12-31

    The condition of the building prior to redevelopment is described with the following regards: layout of the building, construction material specifications and layers of structural components, condition of the thermally insulating shell of the building and condition of its technical equipment. Executed modernization measures are discussed. Heat energy consumption before and after modernization is compared and put in relation to external temperature. Finally, area-specific heat energy consumption and ventilation are discussed in detail. Information as to the cost of modernization rounds off the report. (MSK.) [Deutsch] Der Gebaeudezustand vor der Sanierung wird in folgenden Punkten beschrieben: Bausystem, Baustoffdaten und Schichtaufbau der Bauteile, Bauzustand der waermedaemmenden Gebaeudehuelle sowie Bauzustand der technischen Gebaeudeausruestung. Die Sanierungsmassnahmen werden erlaeutert. Der Heiwaermeverbrauch vor und nach der Sanierung wird verglichen und in Beziehung zur Aussentemperatur gesetzt. Ausserdem werden der flaechenspezifische Heizwaermeverbrauch und die Wohnungslueftung naeher erlaeutert. Angaben zu den Sanierungskosten schliessen den Bericht ab.

  3. Ecological valuation of mechanic-biological waste treatment and waste combustion on the basis of energy balances and air pollutant balances; Oekologische Bewertung der mechanisch-biologischen Restabfallbehandlung und der Muellverbrennung auf Basis von Energie- und Schadgasbilanzen

    Energy Technology Data Exchange (ETDEWEB)

    Wallmann, R.

    1999-04-01

    The work aims at an ecological valuation of air pollutant emissions and energy consumption as particularly relevant aspects of waste treatment and waste combustion plants, based on new scientific results, in order to draw up ecological budgets and make system comparisons in waste treatment. The target set is particularly effectively achieved by the following: documentation and scientific derivation of relevant boundary conditions, careful surveying and data processing for the purpose of making up an ecological budget, and objective valuation and interpretation of results. The high transparency of the methodics should be emphasized. They make the results obtained conclusive and verifiable. (orig.) [Deutsch] Ziel der vorliegenden Arbeit ist die oekologische Bewertung der besonders relevanten Aspekte Abluftemissionen und Energieverbrauch von MBA und MVA auf Basis aktueller Forschungsergebnisse als Grundlage fuer Oekobilanzen und Systemvergleiche zur Restabfallbehandlung. Diese Zielvorgabe wird durch die Dokumentation und wissenschaftliche Herleitung relevanter Rahmenbedingungen, sorgfaeltige Erhebung und Aufbereitung der Daten unter Gesichtspunkten der Erstellung einer Oekobilanz und letztendlich aufgrund der objektiven Bewertung und Interpretation der Ergebnisse im besonderen Masse erreicht. Besonders hervorzuheben hierbei ist die hohe Transparenz bei der methodischen Vorgehensweise. Die ermittelten Ergebnisse sind somit nachvollziehbar und ueberpruefbar. (orig.)

  4. Evaluating the implementation of the energy consumption labelling ordinance. Executive summary; Evaluierung zur Umsetzung der Energieverbrauchskennzeichnungsverordnung (EnVKV). Kurzfassung des Abschlussberichts

    Energy Technology Data Exchange (ETDEWEB)

    Schlomann, B.; Eichhammer, W.; Gruber, E.; Kling, N.; Mannsbart, W.; Stoeckle, F.

    2001-03-01

    The main objective of the study was to examine the present degree of compliance with the Energy Consumption Labelling Ordinance for large household appliances in Germany in an empirical inventory. Concrete proposals to improve the degree of compliance with Directive among manufacturers and retailers were to be elaborated based on this inventory and the analysis of possible deficiencies in implementation and and their causes. A further objective of the study was to examine whether there was an increase in the share of appliance sales in the highest efficiency classes, so as to be able to judge the success of the measures provided in the Directive in accordance with the underlying energy and environmental objective of further reducing energy consumption in households. Furthermore, experience of other European countries in implementing the EU Directive was to be considered. (orig./CB) [German] Die wesentliche Zielsetzung der Untersuchung war es, den bisherigen Befolgungsgrad der Energieverbrauchskennzeichnungsverordnung fuer Haushaltsgrossgeraete in Deutschland mittels einer empirischen Bestandsaufnahme zu pruefen. Ausgehend von dieser Bestandsaufnahme und der Analyse moeglicher Umsetzungsdefizite und ihrer Ursachen sollten konkrete Vorschlaege zur Verbesserung des Befolgungsgrades der Verordnung bei Herstellern und im Handel erarbeitet werden. Als weitere Zielsetzung war auch der Aspekt einer Erhoehung des Anteils der verkauften Geraete in den sparsamsten Effizienzklassen zu beruecksichtigen bei der Beurteilung des Erfolgs der Massnahmen im Sinne der energie- und umweltpolitischen Zielsetzung, den Energieverbrauch in Haushalten weiter zu vermindern. Die Erfahrungen anderer europaeischer Laender bei der Umsetzung der EU-Richtlinie sollten dabei beruecksichtigt werden. (orig./CB)

  5. The great transformation of global energy supply. Central messages of the world energy congress; Die Grosse Transformation der Weltenergieversorgung. Zentrale Botschaften des World Energy Congress

    Energy Technology Data Exchange (ETDEWEB)

    Schiffer, Hans-Wilhelm [World Energy Council, London (United Kingdom). World Energy Resources

    2016-12-15

    The 23rd World Energy Congress, held in Istanbul from October 9 to 13, 2016, brought together some 4500 delegates from around the world. It is the world's largest international energy conference held every three years by the World Energy Council in changing world regions. The congress was a unique opportunity to present a comprehensive view of current and long-term global energy issues. [German] Der 23. Weltenergie-Kongress, veranstaltet vom 9. bis 13.10.2016 in Istanbul, brachte etwa 4500 Delegierte aus der ganzen Welt zusammen. Es ist die weltweit groesste internationale Energiekonferenz, die alle drei Jahre vom World Energy Council in wechselnden Weltregionen ausgerichtet wird. Mit dem Kongress wurde die einzigartige Gelegenheit wahrgenommen, einen umfassenden Blick sowohl auf die aktuellen als auch auf die langfristig global relevanten Energiethemen zu richten.

  6. Concepts for `superior process control` in the energy industry; Konzepte fuer die uebergeordnete Prozessfuehrung in der Energiewirtschaft

    Energy Technology Data Exchange (ETDEWEB)

    Doellen, U.C. von

    1996-12-01

    The work concerns the task of control described as dispatching of extensive energy supply and distribution networks. Due to the special contractual situation, there are special long-term targets in firms, which must be achieved in addition to the extensive operational tasks of control and monitoring of the networks. The concepts introduced in the work offer a framework for a target-orientated design of computer-aided menus for this superior process control in the energy industry. (orig./GL) [Deutsch] Die Arbeit betrachtet die als Dispatching bezeichnete Aufgabe der Fuehrung ausgedehnter Energieversorgungs- und verteilungsnetze. Aus den speziellen Vertragssituationen ergeben sich in den Unternehmen besondere, langfristige Zielvorgaben an die mit der Betriebsfuehrung beauftragen Operateure, die zusaetzlich zu den umfangreichen operativen Aufgaben der Fuehrung und Ueberwachung der Netze zu erreichen sind. Die in der Arbeit vorgestellten Konzepte bieten den Rahmen fuer einen zielgerichteten Entwurf rechnergestuetzter Hilfsmittel fuer diese uebergeordnete Prozessfuehrung in der Energiewirtschaft. Das erstellte Gesamtsystem wird abschliessend zur Loesung einer konkreten, energiewirtschaftlichen Problemstellung eingesetzt. Die entwickelte Anwendungsloesung wird als Hilfsmittel fuer die technische und vertragliche Optimierung im Dispatching eingesetzt. Wesentliche Zielsetzung ist ein technisch und wirtschaftlich optimaler Einsatz von Energiespeichern zur Deckung von Spitzenlasten. (orig./GL)

  7. Future of the gas industry. Energy carriers instead of power source?; Zukunft der Gaswirtschaft. Energietraeger statt Energiequelle?

    Energy Technology Data Exchange (ETDEWEB)

    Bothe, David; Janssen, Matthias; Riechmann, Christoph [Frontier Economics, Koeln (Germany)

    2017-03-15

    For a long time, natural gas was considered as an ideal bridge technology for the energy transition because of the relatively low CO{sub 2} content. With increasing decarbonisation of electricity generation by renewable energies and the associated political vision of a far-reaching electrification of energy applications, in particular in the heat sector, the gas sector is, however, threatened to be overtaken by the renewables. This creates increasing uncertainty for business models and investments in the natural gas sector itself, but also potentially high macroeconomic costs of the energy transition. It can be shown that such a development is not unavoidable if the gas sector succeeds in using the existing possibilities cleverly. Thereby the continued use of existing gas infrastructure plays a central role. For use of the opportunities, however, a paradigm shift in politics, regulation and natural gas sector is necessary, whose key points are developed in this article. [German] Lange wurde Gas aufgrund des relativ geringen C0{sub 2}-Gehalts als ideale Brueckentechnologie fuer die Energiewende gehandelt. Mit zunehmender Dekarbonisierung der Stromerzeugung durch erneuerbare Energien und der damit verbundenen politischen Vision einer weitreichenden Elektrifizierung von Energieanwendungen insbesondere im Waermesektor droht die Gaswirtschaft allerdings von den Erneuerbaren ueberholt zu werden. Das schafft zunehmende Unsicherheit fuer Geschaeftsmodelle und Investitionen im Gassektor selbst, aber auch potenziell hohe gesamtwirtschaftliche Kosten der Energiewende. Es laesst sich zeigen, dass eine solche Entwicklung nicht unabwendbar ist, wenn es der Gaswirtschaft gelingt, die vorhandenen Moeglichkeiten clever zu nutzen. Dabei spielt der fortgesetzte Gebrauch der bereits vorhandenen Gasinfrastruktur die zentrale Rolle. Zur Nutzung der Chancen ist aber ein Paradigmenwechsel in Politik, Regulierung und Gaswirtschaft notwendig, dessen Eckpunkte in diesem Artikel entwickelt

  8. The role of the alkali and chalcogen atoms on the stability of the layered chalcogenide [Formula: see text] (A  =  alkali-metal; M  =  metal-cations; Q  =  chalcogen) compounds: a density functional theory investigation within van der Waals corrections.

    Science.gov (United States)

    Besse, Rafael; Da Silva, Juarez L F

    2017-01-25

    There is a great interest to design two-dimensional (2D) chalcogenide materials, however, our atomistic understanding of the major physical parameters that drive the formation of 2D or three-dimensional (3D) chalcogenides is far from satisfactory, in particular, for complex quaternary systems. To address this problem, we selected a set of quaternary 2D and 3D chalcogenide compounds, namely, [Formula: see text] (A  =  Li, K, Cs; Q  =  S, Se, Te), which were investigated by density functional theory calculations within van der Waals (vdW) corrections. Employing experimental crystal structures and well designed crystal modifications, we found that the average atomic radius of the alkali-metal, A, and chalcogen, Q, species play a crucial role in the stability of the 2D structures. For example, the 2D structures are energetically favored for smaller [Formula: see text] and larger [Formula: see text] average atomic radius, while 3D structures are favored at intermediate average atomic radius. Those results are explained in terms of strain minimization and Coulomb repulsion of the anionic species in the structure framework. Furthermore, the equilibrium lattice parameters are in excellent agreement with experimental results. Thus, the present insights can help in the design of stable quartenary 2D chalcogenide compounds.

  9. Infuence of the amount of energy at the outlet of elbow suction pipes on the results of efficiency measurements in water turbines; Der Einfluss der Energiehoehe am Austritt von Ellbogen-Saugrohren auf das Ergebnis von Wirkungsgradmessungen an Wasserturbinen

    Energy Technology Data Exchange (ETDEWEB)

    Geromiller, W. [Sulzer-Escher Wyss GmbH, Ravensburg (Germany); Feyrer, R. [Stuttgart Univ. (Germany). Inst. fuer Stroemungsmechanik und Hydraulische Stroemungsmaschinen

    1994-12-31

    These studies on flow conditions in and following a Kaplan elbow suction pipe were commissioned by the company Sulzer-Escher Wyss. The measured speed distribution in the outlet cross-section of the suction pipe deviates strongly from the mean speed and shows maxima of speed along the vertical external walls. The energy calculated from the measured speeds exceeds the value calculated according to the IEC guidelines from the mean speed at full load by a factor of two to three. The resulting additional losses are taken into account by the guaranteed efficiencies. Since, according to IEC, the energy at the outlet is always calculated with the same proportion of speed energy from the mean value, the results of the efficiency measurement depend on the magnitude of the water table above the suction pipe. Because of this dependence and with a view to higher measuring accuracy, pressure measurement in the outlet cross-section of the suction pipe is to be preferred to water table measurement. (orig./AKF) [Deutsch] Im Auftrag der Firma Sulzer-Escher Wyss wurden Untersuchungen der Stroemungsverhaeltnisse in und nach einem Kaplan-Ellbogensaugrohr durchgefuehrt. Die gemessene Geschwindigkeitsverteilung im Saugrohraustrittsquerschnitt weicht sehr stark von der mittleren Geschwindigkeit ab und weist die Geschwindigkeitsmaxima entlang den vertikalen Aussenwaenden auf. Die aus den gemessenen Geschwindigkeiten berechnete Energie uebertrifft den gemaess IEC-Richtlinien aus der mittleren Geschwindigkeit berechneten Wert bei Vollast um den Faktor zwei bis drei. Diese daraus resultierenden Zusatzverluste sind in den abgegebenen Wirkungsgradgarantien enthalten. Da laut IEC die Energie am Austritt immer mit dem gleichen Anteil der Geschwindigkeitsenergie aus dem Mittelwert gerechnet wird, sind die Ergebnisse der Wirkungsgradmessung von der Groesse der Saugrohrueberdeckung abhaengig. Wegen dieser Abhaengigkeit von der Saugrohrueberdeckung und wegen einer besseren Messgenauigkeit ist die

  10. Potential and possibilities of supplying energy from biomass and biogas; Potentiale und Moeglichkeiten der Energiebereitstellung durch Biomasse und Biogas

    Energy Technology Data Exchange (ETDEWEB)

    Sonnenberg, H. [Bundesforschungsanstalt fuer Landwirtschaft, Braunschweig (Germany). Inst. fuer Betriebstechnik; Weiland, P.; Ahlgrimm, H.J. [Bundesforschungsanstalt fuer Landwirtschaft (FAL), Braunschweig (Germany). Inst. fuer Technologie

    1998-06-01

    Agriculture`s potential contribution to the energy supply of the ``town of the future`` through the conversion of biomass to energy, including biogas production, is a rather modest one. Supposing that the share of total renewable energy in Germany`s primary energy demand rises to approximately 4%, then the proportion of biomass from biotic raw materials especially produced for the purpose will at the most make up an eighth of this amount. Beyond this, biomass is burdened with other drawbacks such as low supply efficiency, limited availability, and weather-dependent reliability. On the other hand, biomass is well suited for conversion to solid, liquid, and gaseous fuels, including inexpensive ones with low energy density (solid fuels), mostly used for stationary heating applications, as well as more expensive ones such as liquid fuels with a high energy density for mobile applications in the automotive sector. Thanks to its capacity to regenerate, biomass is an inexhaustible resource. Moreover, its natural life cycle has a small impact on the environment. [Deutsch] Der Beitrag, den die Landwirtschaft durch energetische Nutzung von Biomasse, z.B. auch mit der Erzeugung von Biogas, zur Energieversorgung der `Stadt der Zukunft` leisten kann, nimmt sich bescheiden aus. Wird erwartet, dass innerhalb des naechsten Jahrzehnts der Anteil regenerativer Energien insgesamt auf etwa 4% des Primaerenergie-Verbrauchs Deutschlands ansteigen koennte, so duerfte Biomasse als speziell zur Energiegewinnung angebaute nachwachsende Rohstoffe mit bestensfalls 0,5 Prozentpunkten daran beteiligt sein. Es beduerfen darueber hinaus auch Nachteile, wie geringe Bereitstellungseffizienz, beschraenkte Verfuegbarkeit und witterungsabhaengige Zuverlaessigkeit, der Beachtung. Die Biomasse kann jedoch mit Erfolg in feste, fluessige und gasfoermige Energietraeger konvertiert werden, sowohl in preiswerte mit geringer Energiedichte (Festbrennstoffe) fuer bevorzugt stationaeren Heizungs-Einsatz als auch

  11. Energy policy under power. Alternatives of power generation in the acceptance test; Energiepolitik unter Strom. Alternativen der Stromerzeugung im Akzeptanztest

    Energy Technology Data Exchange (ETDEWEB)

    Scheer, Dirk [Univ. Stuttgart (Germany). Zentrum fuer interdisziplinaere Risiko- und Innovationsforschung (ZIRIUS); Forschungsinstitut Dialogik, Stuttgart (Germany); Konrad, Wilfried [Forschungsinstitut Dialogik, Stuttgart (Germany); Renn, Ortwin [Univ. Stuttgart (Germany). Lehrstuhl fuer Umwelt- und Techniksoziologie; Forschungsinstitut Dialogik, Stuttgart (Germany); Univ. Stuttgart (Germany). Zentrum fuer interdisziplinaere Risiko- und Innovationsforschung (ZIRIUS); Scheel, Oliver [Univ. Stuttgart (Germany). Lehrstuhl fuer Umwelt- und Techniksoziologie; Univ. Stuttgart (Germany). Zentrum fuer interdisziplinaere Risiko- und Innovationsforschung (ZIRIUS)

    2014-07-01

    As illustrated, both the quantitative and qualitative analysis of the evaluations of the examined seven electricity mixes the image of a rejection of nuclear and coal power with or without carbon capture (CCS) with simultaneous support for a renewable energy focus in the center of the transformation of the German systems on the electricity. Energy-political strategies that the electricity produced from renewable sources less space than concede the nuclear power and/or the coal found only in very rare and exceptional cases decidedly on consent. Conversely: if the way in which renewable energy production convincingly by high levels of the electricity mix of ecological power plants are expressed, reduced amounts of nuclear and coal power are accepted as a transitional phenomenon. The finding that actually can get unpopular technologies from the focus of criticism by an appropriate context design, also applies to the CCS technology. This makes it possible to identify some evidence that in the context of nuclear energy-free RE-mixes modern coal-fired power plants with CCS are not be refused per se. However, it should also be noted that CCS will be rejected as a supposedly extra evil often still more vehement than the ''familiar'' nuclear power. [German] Wie dargestellt wird weist sowohl die quantitative als auch die qualitative Analyse der Bewertungen der untersuchten sieben Strommixe das Bild einer Ablehnung von Atom- und Kohlekraft mit oder ohne Carbon Capture (CCS) bei gleichzeitiger Unterstuetzung fuer eine die Erneuerbaren Energien in den Mittelpunkt stellenden Transformation des deutschen Systems der Stromerzeugung auf. Energiepolitische Strategien, die der Elektrizitaetsgewinnung aus regenerativen Quellen weniger Raum einraeumen als der Atomkraft und/oder der Kohleverstromung treffen nur in sehr seltenen Ausnahmefaellen dezidiert auf Zustimmung. Umgekehrt gilt: Wird der Weg in die regenerative Energieproduktion ueberzeugend durch hohe Anteile

  12. Energy conservation, an economically beneficial air pollution abatement measure. Final report; Energiesparen - Klimaschutz, der sich rechnet. Endbericht

    Energy Technology Data Exchange (ETDEWEB)

    Ostertag, K.; Jochem, E.; Schleich, J.; Walz, R.; Krenicky, G. [Fraunhofer-Institut fuer Systemtechnik und Innovationsforschung (ISI), Karlsruhe (Germany); Kohlhaas, M.; Diekmann, J.; Ziesing, H.J. [Deutsches Inst. fuer Wirtschaftsforschung, Berlin (Germany); Strebel, H. [Karl-Franzens-Univ., Graz (Australia). Inst. fuer Innovationsmanagement

    1998-11-01

    The book intends to put the discussion of economic effects of air pollution abatement and energy efficiency increasing measures on a more rational basis. It addresses all parties taking part in the political discussion. ARguments are presented in a clear and transparent form that will also help the layman. The reader is enabled to interpret data and analyze them critically. A very important basis is the recognition of the various decision making patterns in which the cost and benefits of energy efficiency increasing patterns are key arguments. [German] Ziel der vorliegenden Argumentationshilfe ist es, die Diskussion um die wirtschaftlichen Auswirkungen von Klimaschutzmassnahmen, und insbesondere von energieeffizienzsteigernden Massnahmen, zu versachlichen und transparent zu machen. Sie richtet sich insbesondere an Politiker, aber auch an Vertreter von Wirtschaftsverbaenden und anderen Nicht-Regierungsorganisationen, die an dieser politischen Diskussion teilnehmen. Insofern wurde besonderes Gewicht auf eine einfache, klare und anschauliche Argumentation gelegt, die auch fuer betriebs- oder volkswirtschaftliche Laien verstaendlich ist. Die Argumentationshilfe versetzt den Leser in die Lage, die Zahlenangaben zur wirtschaftlichen Bewertung von Massnahmen zur Energieeinsparung zu interpretieren und ihre Herleitung kritisch zu bewerten. Eine erste wichtige Grundlage dafuer ist das Erkennen der verschiedenen Entscheidungszusammenhaenge, in denen mit Kosten und Nutzen von energieeffizienzsteigernden Massnahmen argumentiert wird. Nach einer kurzen Beschreibung und Abgrenzung dieser verschiedenen Argumentationsebenen im Ueberblick (Abschnitt 2) werden anschliessend fuer jede Ebene (Abschnitt 3 bis 5) die zentralen Einflussparameter aufgezeigt, die bestimmen, ob eine eher positive oder eher negative wirtschaftliche Bewertung von Massnahmen zur Steigerung der Energieeffizienz ausgewiesen wird und in welcher Groessenordnung sich die Werte bewegen. Die Annahmen, die in die

  13. Factors explaining the success and failure of policies for a further diffusion of renewable energies in EU member states; Erklaerungsfaktoren fuer Erfolg und Misserfolg bei der Nutzung erneuerbarer Energien in den Mitgliedsstaaten der Europaeischen Union

    Energy Technology Data Exchange (ETDEWEB)

    Reiche, D.; Korner, S. [Forschungsstelle fuer Umweltpolitik, Freie Univ. Berlin, Berlin (Germany)

    2002-07-01

    Enhanced use of renewable energy sources is an important energy policy objective of the European Union. The conditions of promotion of the diffusion of renewable energy are however different from country to country, due to the framework conditions adopted by the various member states. The reasons for the asymmetry in the respective conditions of promotion or development of r.e.s. will be explained in the article. (orig./CB) [German] Der Ausbau enerneuerbarer Energien ist ein wichtiges Ziel in der euopaeischen Energiepolitik. In den einzelnen Mitgliedsstaaten bestehen fuer den Ausbau unterschiedliche Rahmenbedingungen, die ihn entweder beguenstigen oder behindern. In diesem Artikel werden diese Unterschiede in der Nutzung erneuerbarer Energien in den Mitgliedsstaaten der EU erklaert. (orig.)

  14. The EU electricity production structure requires a differentiated energy policy; Die Stromerzeugungsstruktur der EU erfordert eine differenzierte Energiepolitik

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2016-04-15

    For the electricity production of the EU there are differentiated structures which are based on different natural conditions, political decisions and investments of past decades. It has long been struggled committed to the ''one and correct'' energy policy. But precisely because of the differences in the individual countries, a unified energy and climate policy for the EU is not the right way. Diversity is a strength, which quite the EU Commission considered. Increased understanding of the specifics in other countries should just apply the German politics and the public that all too often judges from their own perspective. [German] Bei der Stromerzeugung in der EU bestehen differenzierte Strukturen, die auf unterschiedlichen natuerlichen Gegebenheiten, politischen Entscheidungen und Investitionen vergangener Jahrzehnte beruhen. Seit langem wird engagiert um die ''eine und richtige'' Energiepolitik gerungen. Doch gerade wegen der Unterschiede in den einzelnen Laendern kann eine vereinheitlichte Energie- und Klimapolitik fuer die EU nicht der richtige Weg sein. Vielfalt ist eine Staerke, was die EU-Kommission durchaus beruecksichtigt. Mehr Verstaendnis fuer die Spezifika in anderen Laendern sollte daher gerade die deutsche Politik und Oeffentlichkeit aufbringen, die allzu oft aus eigener Perspektive heraus urteilt.

  15. 80 years of IEC: Future requirements on teaching and research in the field of energy. Papers; 80 Jahre IEC: Zukuenftige Anforderungen an Lehre und Forschung auf dem Gebiet der Energie. Vortraege

    Energy Technology Data Exchange (ETDEWEB)

    Born, M. [comp.

    2000-07-01

    The conference was part of the festivities of the 80{sup th} Anniversary of the Brown Coal Research Institute, that were celebrated at the Institute of Energy Processing and Chemical Engineering (IEC), Freiberg University of Mining and Technology. The Institute of Energy Processing and Chemical Engineering preserves and continues the traditional cooperation with the Brown Coal Industry in the field of the energy conversion processes. The conference proceedings give the reader an impression of the presently meaning of fossil energy sources and explain the competence of the IEC in educating and researching on fuel techniques in future. (orig.) [German] Die Tagung wurde anlaesslich des 80. Jahrestages der Gruendung des Braunkohlenforschungsinstitutes an der TU Bergakademie Freiberg durchgefuehrt. Das Institut fuer Energieverfahrenstechnik und Chemieingenieurwesen fuehrt die traditionsreiche Kooperation mit der Braunkohleindustrie auf dem Gebiet der Energiewandlungsprozesse fort. Die Beitraege charakterisieren die derzeitige Bedeutung der fossilen Energietraeger und erlaeutern die Kompetenz des IEC fuer eine zukunftsorientierte Lehre und Forschung in der Brennstofftechnik. (orig.)

  16. Farmers as providers of raw materials and energy. Proceedings; Der Landwirt als Energie- und Rohstoffwirt. Konferenzbeitraege

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-07-01

    Within the 10th EUROSOLAR conference at 14th to 15th April, 2008, at Leipzig (Federal Republic of Germany), the following lectures were held: (a) Bioenergy in the Federal Republic of Germany: Potentials, state of the art and perspectives (M. Kaltschmitt, V. Lenz, D. Thraen); (b) Chances and risks of the energy production from biomass in rural area (G. Thalheim); (c) To the compatibility of utilizing bio energy and environmental preservation (K. Mueschen); (d) Biorefinery systems - industrial material use of regenerative raw materials (B. Kamm); (e) Agriculturists and forestry experts as producers of raw material - current risks and new chances (H. Fischer); (f) Potentials of the improvement of productivity by means of an expansion of options of useful plants (K. Goedeke); (g) Farmers as providers of energy and raw materials (H. Loick); (h) Problems and challenges of the utilization of biomass (P. Volkmer); (i) Energetic recycling management (G. Mehler); (j) Pure fuels instead of fuel mixtures - The farmer as providers of energy and raw materials (P. Schrum); (k) Feed and distribution of bio-natural gas from the view of a regional provider (J. Horn); (l) Biogasification and feed into natural gas networks - by the example of BGA Darmstadt-Wixhausen (M. Schlegel); (m) The right framework for the feed of bio methane into natural gas nets (S. Reichelt); (n) Virtual power plants - Efficient option of the local energy production (G. Weissmueller); (o) The role of bio energy in the power mix renewable energies (R. Bischof); (p) The autonomous power supply - from the bio energy village to the autonomous solar energy village (K. Scheffer); (q) Bio energy villages at the Lake Constance - Model projects for the rural area (B. Mueller); (r) Bio energy region Mureck / Steiermark (K. Totter); (s) The bio energy in the current German legislation process (H.-J. Fell).

  17. SECOND1. Security concept for DER (Distributed Energy Resources). Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    Secure communication is becoming increasingly more relevant in a power system where there is a high impact of distributed energy resources (DER). The purpose of this project has been to analyse and develop a proof of concept implementation for a security concept that can be used in a power system with a high degree of decentralized production and with many actors (BRP, DSO, TSO, utilities, retailers) in an unbundled market. One way to maintain flexibility in the communication system for the power grid is to assign access roles to specific operations and not just to a network or server. Security then becomes a matter of verification, namely that an applicant holds a role with privileges to perform the action applied for. The SECOND1 project has investigated various forms of role based access control (RBAC) as well as the underlying security mechanism identification and verification of the actor identity. The project analysed the needs for communication between energy operators and match these needs with a design for secure role based access control. (LN)

  18. Determination of the energy efficiency in animal husbandry by the example of dairy cattle husbandry; Ermittlung der Energieeffizienz in der Tierhaltung am Beispiel der Milchviehhaltung

    Energy Technology Data Exchange (ETDEWEB)

    Kraatz, Simone

    2009-03-11

    The scarcity of resources, the progressive growth of population and the climate change require sustainability in all levels of the agricultural production. The purpose of this research is to contribute to the development of a method for a generally accepted way of balancing energy in livestock husbandry at the example of dairy farming. Afterwards sustainability indicators were determined for the assessment of the sustainable use of energy in dairy farming. For a defined standard procedure which includes an animal performance of 8,000 kg milk cow{sup -1} year{sup -1}, an energy intensity of 3.54 MJ per kg milk is calculated. The investigations show that the CED in dairy farming is strongly affected by the composition of the diet. Increasing pasture in the diet decreases the CED while concentrate in the diet has a reverse effect. Data analyses concerning the energy intensity at two farms confirm the results of the calculations. Dairy farming is a multi-output process. For that reason the allocation of the cumulative energy demand on the different products is done within the scope of a life cycle inventory analysis. The preferable solution of the allocation divides the cumulative energy demand on the four co-products as follows: 59 % for the milk production, 18 % for producing beef from the dairy cow, 2 % for the calf and 21 % for the excrement. An uncertainty analysis is done to verify the influence of single uncertainties on the results of the calculations. As result an uncertainty of {+-} 6 % of the CED of the standard procedure was calculated. This uncertainty of the calculation has a lower influence on the CED than management related decisions on the cultural practices e. g. diet compositions and service life of the cows. Energy intensity in livestock husbandry has been determined as an useful indicator and therefore a reasonable part of an indicator system for the examination of the sustainability of agricultural production procedures. (orig.)

  19. Long-term perspectives of European energy policy - the Energy Roadmap 2050 of the European Union; Langfristperspektiven der europaeischen Energiepolitik. Die Energy Roadmap 2050 der Europaeischen Union

    Energy Technology Data Exchange (ETDEWEB)

    Matthes, Felix C. [Oeko Institut e.V., Berlin (Germany)

    2012-01-15

    Aside from diverse event-related or short or medium-term oriented activities, for the European Union the year 2011 was marked by fundamental work on the long-term perspectives of European energy and climate policy. In the course of the year the European Commission published three so-called roadmaps, all oriented to the time horizon of 2050 and dedicated, amongst other goals, to identifying possible paths of development for the energy markets. This is the first time that a consistent, even if in some points debatable, analysis framework for long-term energy and climate policy in the context of the EU has been presented, and it certainly creates a new basis in qualitative terms.

  20. Systematization of potentials and options. Final report to the enquiry commission ''Sustainable energy supply in times of globalisation and deregulation'' of the German Bundestag; Systematisierung der Potenziale und Optionen. Endbericht an die Enquete-Kommission 'Nachhaltige Energieversorgung unter den Bedingunen der Globalisierung und der Liberalisierung' des Deutschen Bundestages

    Energy Technology Data Exchange (ETDEWEB)

    Cremer, C.; Boede, U.; Bradke, H.; Walz, R.; Behnke, L.; Kleemann, M.; Birnbaum, U.; Heckler, R.; Kolb, G.; Markewitz, P.; Leubner, K.

    2001-12-01

    The goal of the present synopsis was merely to describe the technical and economic potentials starting from 1998 as the baseline year, i.e. on the basis of technical solutions that are immediately available today. In concluding the introduction it should be stressed that the scenarios presented by the inquiry commission must be considered with due regard to the dynamic nature of energy utilisation potentials as described in the paper and that as a rule these potentials only cover a realisation period of one product or reinvestment cycle, i.e. in most cases 10 to 30 years (buildings are an exception because of their very long reinvestment and renovation cycles). [German] Das Ziel der vorgelegten Synopse beschraenkte sich auf die Beschreibung der technischen und wirtschaftlichen Potenziale mit Basisjahr 1998, d. h. anhand der heute unmittelbar verfuegbaren technischen Loesungen. Es sei deshalb abschliessend zu dieser Einfuehrung betont, dass die beschriebene Dynamik der Potenziale der rationellen Energienutzung bei den Szenarien der Enquete-Kommission mitbedacht werden muss und dass die hier beschriebenen Potenziale in der Regel nur einen Realisierungszeitraum von einem Produkt- bzw. Re-Investitionszyklus abdecken, d. h. zwischen 10 und 30 Jahren in der Regel (Ausnahmen: Gebaeude wegen der sehr langen Re-Investitions- und Renovierungszyklen). (orig.)

  1. Demographic determinants of energy demand of households in Germany; Demografische Determinanten der Energienachfrage der Haushalte in Deutschland

    Energy Technology Data Exchange (ETDEWEB)

    Engel, Kerstin

    2010-05-28

    This thesis investigates in demographic determinants of energy demand of households in Germany, with focus on space heating and individual motor car traffic. Result of this thesis is a simulation model based on the approach of system dynamics, which is used to simulate two scenarios. The first scenario, called the reference scenario, is based on demographic data of the next decades, which is assumed to be realistic. The second alternative scenario runs without the probable demographic changes. By comparing the scenarios the role of demography in the range of energy demand is quantified. (orig.)

  2. Van Der Waals heterogeneous layer-layer carbon nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on graphene and graphane sheets.

    Science.gov (United States)

    Yuan, Kun; Zhao, Rui-Sheng; Zheng, Jia-Jia; Zheng, Hong; Nagase, Shigeru; Zhao, Sheng-Dun; Liu, Yan-Zhi; Zhao, Xiang

    2017-04-15

    Noncovalent interactions involving aromatic rings, such as π···π stacking, CH···π are very essential for supramolecular carbon nanostructures. Graphite is a typical homogenous carbon matter based on π···π stacking of graphene sheets. Even in systems not involving aromatic groups, the stability of diamondoid dimer and layer-layer graphane dimer originates from C - H···H - C noncovalent interaction. In this article, the structures and properties of novel heterogeneous layer-layer carbon-nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on [n]-graphane and [n]-graphene and their derivatives are theoretically investigated for n = 16-54 using dispersion corrected density functional theory B3LYP-D3 method. Energy decomposition analysis shows that dispersion interaction is the most important for the stabilization of both double- and multi-layer-layer [n]-graphane@graphene. Binding energy between graphane and graphene sheets shows that there is a distinct additive nature of CH···π interaction. For comparison and simplicity, the concept of H-H bond energy equivalent number of carbon atoms (noted as NHEQ), is used to describe the strength of these noncovalent interactions. The NHEQ of the graphene dimers, graphane dimers, and double-layered graphane@graphene are 103, 143, and 110, indicating that the strength of C-H···π interaction is close to that of π···π and much stronger than that of C-H···H-C in large size systems. Additionally, frontier molecular orbital, electron density difference and visualized noncovalent interaction regions are discussed for deeply understanding the nature of the C-H···π stacking interaction in construction of heterogeneous layer-layer graphane@graphene structures. We hope that the present study would be helpful for creations of new functional supramolecular materials based on graphane and graphene carbon nano-structures. © 2017 Wiley Periodicals, Inc. © 2017 Wiley

  3. Energy related environmental impact of buildings; Oekoinventar der Entsorgungsprozesse von Baumaterialien; Grundlagen zur Integration der Entsorgung in Oekobilanzen von Gebaeuden

    Energy Technology Data Exchange (ETDEWEB)

    Doka, G.

    2000-07-01

    Ecological assessments of buildings, constructions, and building materials are often focussed on the production and use phase. Disposal is mostly disregarded. This study within the IEA Annex 31 'Energy related environmental impact of buildings' shows that excluding disposal is not generally justified. A life cycle assessment of the disposal of various common building materials in Switzerland was conducted. It heeds energy consumption as well as directly or indirectly emitted pollutants. Valuation methods were Eco-indicator95+ and UBP (ecological scarcity). The study specifies disposal inventories for about 50 building materials. They are fit to complement inventory data for the production of materials. Unlike production, the disposal can only be assessed in the light of a specific building or construction. The potential for recycling is influenced by type of construction, application, and site-specific logistics. Durability of a material determines what proportion will be disposed of in renovation activities. Wherever possible and likely, disposal options with or without re-utilization are considered in the assessment. Building wastes are divided in construction wastes, renovation wastes, and demolition wastes, that can have quite different impact even for identical materials. The system boundary in the assessment includes expenditures on the building site like demolition energies, transports, expenditures in a sorting plant and the final disposal in an incinerator or landfill. According to the Swiss Agency for the Environment, Forests and Landscape, 46% of all burnable building wastes in Switzerland are disposed of illegally. Hence, in one scenario the disposal in an open fire was assessed for burnable wastes. The assessments of the disposal processes are material-specific, i.e. the post use-phase composition of the materials is heeded. The data applies to the situation in Switzerland. The results of the study are compared to the impacts of the

  4. The correlation of energy with entropy and exergy; Die Vernetzung der Energie mit Entropie und Exergie

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Gernot (Dr. Gernot Weber, Energie-Gebaeudetechnik, Kleinostheim)

    2011-07-01

    Thermodynamics generally is regarded as one of the most difficult fields of knowledge. This may be particularly due to the difficulties and due to the often very complicated described correlations between the terms energy, entropy and exergy in the technical literature. The contribution under consideration tries to explain these correlations to the (scientifically trained) technically interested readers understandable.

  5. Further expanding the utilization of wind energy with regard to protecting the climate. Pt. 1; Weiterer Ausbau der Windenergienutzung im Hinblick auf den Klimaschutz. T. 1

    Energy Technology Data Exchange (ETDEWEB)

    Rehfeldt, K. [Deutsches Windenergie-Institut GmbH (DEWI), Wilhelmshaven (Germany); Gerdes, G.J. [Deutsche WindGuard GmbH, Varel (Germany); Schreiber, M. [Schreiber Umweltplanung, Bramsche (Germany)

    2001-04-01

    The main goals of the research project '' Further expanding the utilization of wind energy with regard to protecting the climate'' are to analyse the development of wind energy up today, assessing the present situation and assessing the future development of the offshore utilization of wind energy in Germany. An important subject of the analyses and assessments are conflicts with nature protection, especially the avifauna and a possible pollution caused to the people. In order to be able to provide areas for utilizing wind energy also in the future in Germany, the offshore utilization of wind energy is given more and more attention. Therefore, the results of an analysis of the continental area from the viewpoint of protecting nature and environment have to be taken into consideration when expanding the offshore area in the future. It is the task of the research project to work out proposals taking in to consideration the ecological concerns against wind energy and showing how to overcome hindrances on the way to utilizing wind energy without harming the environment, nature and landscape. In order to facilitate the assessment of the future development of offshore wind energy utilization and also to establish the requirements of planning and licensing procedures, the information on the present offshore wind energy plans was collected and presented to a public consisting of experts on a second workshop. [German] Wesentliches Ziel des Forschungsvorhabens ''Weiterer Ausbau der Windenergienutzung im Hinblick auf den Klimaschutz'' ist die Analyse der bisherigen Entwicklung der Windenergie, die Bestandsaufnahme der derzeitigen Situation und eine Beurteilung einer zukuenftigen Entwicklung der Offshore-Windenergienutzung in Deutschland. Wichtiger Gegenstand von Analyse und Bestandsaufnahme sind Konflikte mit dem Naturschutz, insbesondere Avifauna, und eine moegliche Belastung der Bevoelkerung. Um in Deutschland auch in Zukunft Flaechen

  6. Further development of wind energy use under the aspect of climate protection; Weiterer Ausbau der Windenergienutzung im Hinblick auf den Klimaschutz

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, T. [Deutsches Windenergie-Institut gGmbH (DEWI), Wilhelmshaven (Germany)

    2001-08-01

    The main objectives of this study, which DEWI is carrying out on behalf of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, are stock-taking and analysis of the development of wind energy up to now and an assessment of the prospects of a future use of offshore wind energy in Germany. The potential that a further development of wind energy may hold for protecting the climate is considered as well as the potential conflicts with nature conservation, in particular avifauna, but also the issue of acceptance by the public. These questions are dealt with in workshops and by carrying out specific questionnaire campaigns. On this basis, recommendations for action to be taken with regard to the future development of wind energy especially in the field of nature and environmental protection will be identified. (orig.) [German] Wesentliches Ziel dieser Studie, die das DEWI im Auftrag des Bundesministeriums fuer Umwelt, Naturschutz und Reaktorsicherheit (BMU) erarbeitet, ist eine Bestandsaufnahme und Analyse der bisherigen Entwicklung der Windenergie sowie eine Beurteilung einer zukuenftigen Offshore-Windenergienutzung in Deutschland. Die Moeglichkeiten, die der Ausbau der Windenergie fuer den Klimaschutz darstellt, werden ebenso betrachtet wie ein vorhandenenes Konfliktpotential mit dem Naturschutz, insbesondere Avifauna, aber auch Akzeptanzfragen seitens der Bevoelkerung. Methodisch werden diese Fragen durch die Veranstaltung und Auswertung von Workshops sowie der Durchfuehrung gezielter Fragebogenaktionen erarbeitet. Auf dieser Basis wurden Handlungshinweise insbesondere auch im Bereich des Natur- und Umweltschutzes fuer einen zukuenftigen Ausbau der Windenergienutzung abgeleitet. (orig.)

  7. EDISON - Analysis of economic efficiency and environment compatibility of decentralized energy supply systems. Part. project 8: Commercialization; EDISON - Analse der Wirtschaftlichkeit und Umweltvertraeglichkeit dezentraler Energieversorgungssystemte. Teilprojekt 8: Vermarktung

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The objective of this part of the project is to identify possible resource saving potentials and emission reducing effects by successively increasing the share of decentralized energy supply systems, on the basis of a regional supply concept. With this background, 21 different energy supply systems were construed and analysed regarding their ecological and economical effects. The scenario technique is employed to cover a broad range of future developments. The technical method first presents the resources of fossil energies in global and national terms, as well as the structure of the energy consumption in the Federal Republic of Germany. After a short description of the relevant legal framework and regulations and the consequences of the liberalization of energy markets, the various fossil and renewable energy sources and their emissions are described in detail within the framework of the national central and decentralized energy supply structures. The outcome shows that there is a broad margin of possible measures of saving resources. In the third chapter, the effects of decentralized energy supply on networks operations are described. The present situation was determined using the data of the region supplied by the Karlsruhe Utilities (Stadtwerke Karlsruhe GmbH). The present situation is regarded as the reference scenario. Thus it serves as a comparative standard value in the evaluation of the supply scenarios. Starting from the energy supply structure of the Federal Republic of Germany, the consumption of resources and the emission load of the centralized and decentralized effect components of the Karlsruhe Utilities resulting from this are shown. (orig.) [German] Ziel der Untersuchungen dieses Arbeitspaketes ist es, auf der Basis eines regionalen Versorgungskonzeptes, moegliche Ressourceneinsparpotenziale und Emissionsminderungseffekte durch die sukzessive Erhoehung des Anteils dezentraler Energieerzeugungsanlagen aufzuzeigen. Vor diesem Hintergrund werden

  8. The planning of transmission grids. Conditions of the energy policy turnaround; Die Planung der Uebertragungsnetze. Bedingung der Energiewende.

    Energy Technology Data Exchange (ETDEWEB)

    Witt, Siegfried de; Durinke, Peter; Kause, Harriet [DE WITT Rechtsanwaltsgesellschaft mbH, Berlin (Germany)

    2012-07-01

    The book reports on planning processes for the power transmission grid. The design and implementation of a high-voltage line of the transmission system consists of four stages (Part I): (a) National planning of requirements; (b) Planning procedures or federal sector planning; (c) Planning approval procedure; (d) Expropriation proceedings. Part II of this book describes the planning according to the Energy Economy Law (EnWG) and Electricity Grid Expansion Act (EnLAG). The Part III of the book under consideration describes the procedures to be taken out by the NABEG (Act for the Acceleration of Network Expansion) from the scope of paragraph 15 ROG (Regional Planning Act) and paragraph 43 EnWG.

  9. Mineralogical investigations of the role of the clay fraction in geothermal energy use; Mineralogische Untersuchungen zur Rolle der Tonfraktion bei der Gewinnung geothermischer Energie

    Energy Technology Data Exchange (ETDEWEB)

    Althaus, E.; Frosch, G. [Karlsruhe Univ. (T.H.) (Germany). Mineralogisches Inst.

    1997-12-01

    Authigenic clay minerals strongly influence the quality of geothermal reservoir systems. Their precipitation may drastically change the properties of reservoir sandstones. They interact more strongly with non-equilibrium fluids than most other mineral phases. The most abundant clay minerals in geothermal wells of Northeastern Germany are kaolinite, illite and mixed-layer minerals. Experiments are being carried out to study the dissolution rates of these minerals in NaCl brines at different pH-values. (orig.) [Deutsch] Im Rahmen des BMBF-Projektes `Evaluierung geowissenschaftlicher und wirtschaftlicher Bedingungen fuer die Nutzung hydrogeothermaler Ressourcen` werden am Mineralogischen Institut der Universitaet Karlsruhe (T.H.) Experimente zur Stabilitaet von Tonmineralen in geothermischen Systemen durchgefuehrt. Die Untersuchungen beziehen sich auf Gesteine und Solen, wie sie durch die nordostdeutschen Geothermiebohrungen Neustadt-Glewe, Rheinsberg und Neubrandenburg aufgeschlossen sind. Die Untersuchten Gesteinsproben enstammen der oberen Trias und dem Jura. Die vergleichbaren stratigraphischen Einheiten sind in den Bohrungen in unterschiedlicher Teufe und Maechtigkeit anzutreffen: So finden sich die Contorta-Schichten (Raetkeuper) bei Neustadt-Glewe in ca. 2200 m, bei Rheinsberg in ca. 1680 m und bei Neubrandenburg in ca. 1250 m Tiefe. (orig.)

  10. GLobal energy perspectives up to and beyond 2050. Short version of the IIASA-WEC study; Globale Energieperspektiven 2050. Kurzfassung der IIASA-WEC-Studie

    Energy Technology Data Exchange (ETDEWEB)

    Gruebler, A. [Internationales Inst. fuer Angewandte Systemanalyse (IIASA), London (United Kingdom); Nakicenovic, N. [Internationales Inst. fuer Angewandte Systemanalyse (IIASA), London (United Kingdom)

    1996-05-01

    At the Sixteenth World Energy Conference in Tokyo in October 1995 the International Institute for Applied System Analysis (IIASA) presented the more than 5,000 conference members with a study on different scenarios for `Global Energy Perspectives Up To and Beyond 2050. The present article is a short version of this study on long-term energy perspectives which IIASA performed in cooperation with the World Energy Council. This summary omits many of the details of the original study so as to be able to focus on five of its essential elements: Population development, economic growth, energy intensity, technical developments, and resource availability. It also includes statements on primary and final energy as well as on the financial and ecological ramifications of the scenarios. (orig.) [Deutsch] Anlaesslich der 16. Weltenergiekonferenz in Tokio legte das Internationale Institut fuer Angewandte Systemanalyse (IIASA) im Oktober 1995 den ueber 5 000 Kongressteilnehmern eine Studie vor, in der in verschiedenen Szenarien `Globale Energieperspektiven bis 2050 und darueber hinaus` entworfen wurden. Der folgende Beitrag liefert eine Kurzfassung der Studie ueber langfristige Energieperspektiven, die in Zusammenarbeit mit dem Weltenergierat (WEC) durchgefuehrt wurde. Diese Zusammenfassung kann nicht alle Details der gesamten Studie wiedergeben, doch sollen hier fuenf ihrer wesentlichen Elemente angefuehrt werden: Bevoelkerungsaussichten, Wirtschaftswachstum, Energieintensitaet, technische Entwicklung und Ressourcenverfuegbarkeit. Primaer- und Endenergie, sowie finanzielle und oekologische Auswirkungen der Szenarien werden ebenfalls vorgestellt. (orig.)

  11. Attenuation corrections through energy spectra analysis of whole body and partial body measurements applying gamma spectroscopy; Schwaechungskorrektur bei gammaspektroskopischen Ganz- und Teilkoerpermessungen durch Analyse der Energiespektren

    Energy Technology Data Exchange (ETDEWEB)

    Schelper, L.F.; Lassmann, M.; Haenscheid, H.; Reiners, C. [Wuerzburg Univ. (Germany). Klinik und Poliklinik fuer Nuklearmedizin

    1997-12-01

    The study was carried out within the framework of activities for testing means of direct determination of radioactivity levels in the human body due to incorporated, inhomogenously distributed radionuclides. A major task was to derive the average depth of activity distributions, particularly from photon radiation at energies below 500 keV, for the purpose of making suitable attenuation corrections. The paper presents two applicable methods which yield information on the mean depths of activity distributions, obtained through additional analyses of the energy spectra. The analyses are based on measuring the dependence of intensity of the Compton radiation on the length of pathways of the photons penetrating the soft tissue, or on measuring the energy-dependent absorption effects with photons. (orig./CB) [Deutsch] Im Rahmen der direkten Aktivitaetsbestimmung bei inhomogener Radionukliddeposition im menschlichen Koerper mittels Ganz- oder Teilkoerpermessanlagen im klinischen Bereich oder im Strahlenschutz sollte besonders bei Photonenstrahlung mit Energien von weniger als 500 keV eine Ermittlung der mittleren Tiefe der Aktivitaetsverteilung zur Schwaechungskorrektur erfolgen. Im klinischen Umfeld ist es haeufig moeglich, zur Tiefenkorrektur die mittlere Organtiefe und damit die schwaechende Gewebsschicht mittels Ultraschall zu bestimmen. Ergaenzend hierzu werden im Folgenden zwei Methoden vorgestellt, welche Aussagen ueber die mittlere Tiefe von Aktivitaetsverteilungen durch Gewinnung von Zusatzinformationen aus dem Energiespektrum im Rahmen von gamma-spektroskopischen Personenmessungen ermoeglichen. Dazu werden einerseits die Abhaengigkeit der Intensitaet der Comptonstrahlung von der Laenge der Wegstrecke von Photonen durch Weichgewebe und andererseits energieabhaengige Absorptionseffekte bei Photonen als Grundlage herangezogen. (orig.)

  12. The dependence of scattering length on van der Waals interaction ...

    Indian Academy of Sciences (India)

    2016-06-16

    Jun 16, 2016 ... Abstract. The static exchange model (SEM) and the modified static exchange model (MSEM) recently introduced by Ray in Pramana – J. Phys. 83, 907 (2014) are used to study the elastic collision between two hydrogen-like atoms when both are in ground states by considering the system as a four-body ...

  13. Dynamics of open-shell van der Waals complexes

    NARCIS (Netherlands)

    Zeimen, W.

    2004-01-01

    This thesis deals with open-shell atom-diatom complexes which are of interest because they can be considered as model systems for complexes of larger open-shell molecules. Intermolecular potential surfaces were computed by means of ab initio electronic structure calculations or taken from the

  14. The dependence of scattering length on van der Waals interaction ...

    Indian Academy of Sciences (India)

    MSEM) recently introduced by Ray in {\\it Pramana – J. Phys.} 83, 907 (2014) are used to study the elastic collision between two hydrogen-like atoms when both are in ground states by considering the system as a four-body Coulomb system in the ...

  15. Hybrid Van Der Waals Materials In Next-Generation Electronics

    Data.gov (United States)

    National Aeronautics and Space Administration — In nature, there exists a class of materials which are inherently two-dimensional (2D). Although they form solid 3D structures, the individual atoms have strong...

  16. Nucleotide insertion initiated by van der Waals interaction during ...

    Indian Academy of Sciences (India)

    Up to this point, it is true that we have no constrained parameters to handle because we deliberately ignored them, not because ignorance is bliss, but to keep all the analyses exact and unambiguous within the chemi- cal process, sandwiched between the pre- and post- chemistry avenues. The complex processes and their.

  17. The dielectric genome of van der Waals heterostructures

    DEFF Research Database (Denmark)

    Andersen, Kirsten; Latini, Simone; Thygesen, Kristian Sommer

    2015-01-01

    with ab-initio accuracy using a multi-scale approach where the dielectric functions of the individual layers (the dielectric building blocks) are coupled simply via their long-range Coulomb interaction. We use the method to illustrate the 2D- 3D dielectric transition in multi-layer MoS2 crystals...

  18. Van der Waal Interactions in Ultrafine Nanocellulose Aerogels

    Science.gov (United States)

    Fritch, Byron; Bradley, Derek; Kidd, Tim

    Nanocellulose aerogels have shown an ability to be used in many different applications ranging from oil sponges to conductive materials to possibly a low calorie food substitute. Not much is known about the structural and physical property changes that occur when the composition of the aerogel changes. We studied what properties change when the aerogel amounts change, as well as how sticky the aerogels are and how strong they are. The higher concentrations appeared to have more plate-like structures while the lower concentrations had a more fibrous material. These fibers in the low concentrations had a smaller diameter than a human hair. Only the low concentration aerogels were able to stick to a glass surface in the adhesion test, but were able to support a mass much larger than their own. These low concentrations also would stick to your finger when lightly touched. Preliminary tests show that a concentration that is not too low, but not too high, is best for tensile strength. All concentrations were able to hold many times their own mass. Cellulose should be studied more because it is a renewable material and is easily accessed. Nanocellulose is also not environmentally dangerous allowing it to be used in applications involving humans and the environment like noted above. National Science Foundation Grant DMR-1410496.

  19. Hauts-de-France. A pioneer in the French energy transition; Hauts-de-France. Vorreiter in der franzoesischen Energiewende

    Energy Technology Data Exchange (ETDEWEB)

    Falk, Thomas

    2016-08-15

    France had established in advance of last year's climate summit in Paris on ambitious energy policy goals. Especially the 2016 newly formed Region Hauts-de-France stands out as a pioneer here. There one drives innovation and investments with the objective of fulfilling by 2050 their own needs completely by renewable sources. The orientation to supplies Jeremy Rifkin idea of the third industrial revolution. If successful, the region would be on climate protection well ahead of the national targets, the 2050 ''only'' provide a CO{sub 2} emission reduction of 75%. In addition to the Research and development (R and D) to many future ideas in Hauts-de-France but also some major projects for Security of European energy supplies are realized that show the local agility. [German] Frankreich hatte sich im Vorfeld des letztjaehrigen Pariser-Klimagipfels auf ambitionierte Energiewendeziele festgelegt. Insbesondere die 2016 neu gebildete Region Hauts-de-France sticht dabei als Vorreiter heraus. Dort treibt man Innovationen und Investitionen mit dem Ziel an, bis 2050 den Eigenbedarf vollstaendig mittels erneuerbarer Quellen zu decken. Die Orientierung dazu liefert Jeremy Rifkins Idee der dritten industriellen Revolution. Im Erfolgsfall laege die Region beim Klimaschutz deutlich vor den nationalen Zielen, die bis 2050 ''nur'' eine CO{sub 2}-Emissionsreduktion von 75 % vorsehen. Neben der Forschung und Entwicklung (F and E) zu vielen Zukunftsideen werden in Hauts-de-France aber auch einige Grossprojekte zur Absicherung der europaeischen Energieversorgung realisiert, die Ausweis der dortigen Agilitaet sind.

  20. Switchable insulation for using solar energy in buildings. Final report; Schaltbare Waermedaemmung (SWD) zur Nutzung der Sonnenenergie in Gebaeuden. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Stark, C.; Horn, R.; Hetfleisch, J.; Fricke, J.

    2003-02-25

    Solar energy can be used in buildings via use of transparent insulations. But thereby problems occur, like overheating of building walls in summer and heat losses in the cold season. To solve these problems ZAE Bayern has designed and optimized the switchable insulation SWD, the thermal conductivity of which can be changed from highly insulating to conducting. A computer routine was developed to calculate and to optimize the heat gains. The SWD is switched by desorbing/adsorbing as small amount of hydrogen gas. Desorption is facilitated with an electric heating element. The thermal conductivity of the filling can be varied by about a factor of 40. Several SWD-modules were produced and installed in an outside measuring facility. The heat gains and the durability were investigated for three years. The results of the simulation could be verified and ageing did not occur. For an optimal system the heat gains are in the range of 150 kWh/(m{sup 2}a). The mounting of these panels at south facades is simple, especially for post bolt systems. Contrary to transparent systems the loss of heat in winter is very small and the overheating of the walls behind the SWD in summer can be avoided. (orig.) [German] Zur Nutzung der Sonnenenergie in Gebaeuden werden bisher transparente Waermedaemmsysteme eingebaut, die jedoch oft mit Problemen wie Wandueberhitzung im Sommer und Waermeverlusten in der kalten Jahreszeit behaftet sind. Zur Loesung dieser Probleme wurde am ZAE Bayern eine schaltbare Waermedaemmung entwickelt und optimiert, deren Daemmeigenschaft je nach Sonneneinstrahlung und Waermebedarf variiert werden kann. Es wurde ein Programm entwickelt, mit dem die Waermegewinne berechnet und optimiert werden koennen. Die Schaltbarkeit wird durch einen Getter ermoeglicht, der eine ungefaehrliche Menge Wasserstoffgas reversibel aufnehmen und abgeben kann. Die Wasserstoff-Austreibung erfolgt mittels elektrischer Heizung und veraendert die Waermeleitfaehigkeit der Fuellung um einen

  1. Energy policy programmes of the Federal Government 1973 to 2017; Energiepolitische Programme der Bundesregierung 1973 bis 2017

    Energy Technology Data Exchange (ETDEWEB)

    Schiffer, Hans-Wilhelm [World Energy Council, London (United Kingdom). World Energy Resources

    2017-11-15

    An analysis of the energy policy programs presented since 1973 shows that all government coalitions have been known in the past 45 years in principle for the objectives of security of supply, efficiency and affordability as well as environmental protection and conservation of resources - together with the statement that these goals should be pursued on an equal footing. In fact, there has never been this ''consonance'' of goals. Rather, concrete events or political currents have led to a changing prioritization of individual goals. At the same time, the intensity of government intervention in the management of supply and demand has changed. [German] Eine Analyse der seit 1973 vorgelegten energiepolitischen Programme zeigt: Alle Regierungskoalitionen haben sich in den vergangenen 45 Jahren im Grundsatz zu den Zielen Versorgungssicherheit, Wirtschaftlichkeit und Bezahlbarkeit sowie Umweltschutz und Ressourcenschonung bekannt - verknuepft mit der Aussage, dass diese Ziele gleichrangig zu verfolgen seien. Tatsaechlich hat es diesen ''Gleichklang'' der Ziele nie gegeben. Konkrete Ereignisse oder politische Stroemungen haben vielmehr zu einer wechselnden Priorisierung einzelner Ziele gefuehrt. Parallel dazu hat sich die Eingriffsintensitaet des Staates in die Steuerung von Angebot und Nachfrage veraendert.

  2. A mixed integer linear programming approach for optimal DER portfolio, sizing, and placement in multi-energy microgrids

    International Nuclear Information System (INIS)

    Mashayekh, Salman; Stadler, Michael; Cardoso, Gonçalo; Heleno, Miguel

    2017-01-01

    Highlights: • This paper presents a MILP model for optimal design of multi-energy microgrids. • Our microgrid design includes optimal technology portfolio, placement, and operation. • Our model includes microgrid electrical power flow and heat transfer equations. • The case study shows advantages of our model over aggregate single-node approaches. • The case study shows the accuracy of the integrated linearized power flow model. - Abstract: Optimal microgrid design is a challenging problem, especially for multi-energy microgrids with electricity, heating, and cooling loads as well as sources, and multiple energy carriers. To address this problem, this paper presents an optimization model formulated as a mixed-integer linear program, which determines the optimal technology portfolio, the optimal technology placement, and the associated optimal dispatch, in a microgrid with multiple energy types. The developed model uses a multi-node modeling approach (as opposed to an aggregate single-node approach) that includes electrical power flow and heat flow equations, and hence, offers the ability to perform optimal siting considering physical and operational constraints of electrical and heating/cooling networks. The new model is founded on the existing optimization model DER-CAM, a state-of-the-art decision support tool for microgrid planning and design. The results of a case study that compares single-node vs. multi-node optimal design for an example microgrid show the importance of multi-node modeling. It has been shown that single-node approaches are not only incapable of optimal DER placement, but may also result in sub-optimal DER portfolio, as well as underestimation of investment costs.

  3. Powering the future. How we will (eventually) solve the energy crisis and fuel the civilization of tomorrow; Der Letzte macht das Licht aus. Die Zukunft der Energie

    Energy Technology Data Exchange (ETDEWEB)

    Laughlin, Robert B. [Stanford Univ., CA (United States)

    2012-07-01

    When it gets dark, we turn on the light. When it gets cold, we heat. When we need energy for the global industry and technology, we make use of the energy. Every time. But soon the earth fuels such as coal, gas, oil and uranium are irrevocably depleted. And then? The Nobel laureate Robert B. Laughlin reports on the future of our energy supply.

  4. Energy conservation, an economically efficient way of air pollution abatement. Economic arguments in air pollution policy; Energiesparen - Klimaschutz, der sich rechnet. Oekonomische Argumente in der Klimapolitik

    Energy Technology Data Exchange (ETDEWEB)

    Ostertag, K.; Jochem, E.; Schleich, J.; Walz, R. [Fraunhofer-Institut fuer Systemtechnik und Innovationsforschung (ISI), Karlsruhe (Germany); Kohlhaas, M.; Diekmann, J.; Ziesing, H.J. [Deutsches Inst. fuer Wirtschaftsforschung, Berlin (Germany)

    2000-07-01

    Experts tend to disagree about the economic effects of air pollution abatement measures. This book, which addresses also non-experts, explains the analytical background on the basis of available data. The authors conclude that there is a wide range of political options for achieving the goal of air pollution abatement. They differentiate between the various levels of discussion and show how misinterpretations of scientific results come about, thus making an important contribution to a discussion that is based on facts rather than emotions. [German] Die Einschaetzungen zur wirtschaftlichen Bewertung von Klimaschutzmassnahmen, insbesondere zur Steigerung der Energieeffizienz, sind sehr widerspruechlich. Dieses Buch erlaeutert anhand von Zahlenmaterial die analytischen Hintergruende und ist auch fuer Nicht-Oekonomen verstaendlich geschrieben. Die Autoren kommen zu dem Schluss, dass in vielen Bereichen rentable Energiesparpotentiale nicht erkannt und umgesetzt werden. Sie zeigen, dass die Politik bei der Verfolgung von Klimaschutzzielen und der Vorbeugung gegen Klimaschaeden ueber erheblichen Gestaltungsspielraum verfuegt. Mit der Entflechtung verschiedener Diskussionsebenen und dem Aufzeigen der Quellen fuer Fehlinterpretationen von Studienergebnissen leistet das Buch einen wichtigen Beitrag zur Versachlichung der Klimaschutzdiskussion. (orig.)

  5. Der Fachbereich Fertigungstechnik der Zukunft

    DEFF Research Database (Denmark)

    Alting, Leo

    1998-01-01

    Forscher sowie für eine industrielle Zusammenarbeit/Beratung eine attraktive Umgebung zu bieten.Im vorliegenden Papier wird ein internes Entwicklungsprojekt, genannt "Der Fachberich der Zukunft", beschrieben. Ausgehend von den Bedürfnissen und Erwartungen der Kunden (Studierende, Einrichtungen der...

  6. Quantitative analysis of the scattering contributions in high-energy X-ray computed tomography; Quantitative Untersuchung der Streubeitraege in Hochenergie-Roentgencomputertomographie

    Energy Technology Data Exchange (ETDEWEB)

    Stritt, Carina; Schuetz, Philipp; Plamondon, Mathieu; Flisch, Alexander; Hofmann, Juergen; Sennhauser, Urs [Eidgenoessische Materialpruefungs- und Forschungsanstalt (EMPA), Duebendorf (Switzerland)

    2015-07-01

    Computed tomography (CT) is a proven method in the fields of failure analysis and quality control. The energy of X-rays used in this case determines the penetration depth of the radiation, limited by the size and material of the object to be examined. For large, dense and heavy objects photon energies of more than one mega electron volts (MeV) are needed in order to achieve usable transmission values. An important factor for the quality of high-energy X-ray tomography is the proportion of scattered radiation on the CT images. X-rays can be used both in the object to be examined, as well as the measuring instrument and sprinkle operating environment and leads to a distorted picture transmission. Besides scattering effects comes for MeV photons in addition the physical process of pairing into play. The impact of the individual scattering processes on the transmission image should be examined here. But the influence of the different scattering contributions is examined using Monte Carlo simulations. In contrast to previous studies, not only a set of simple geometric objects made of different materials is examined, but also simplified models of the components of a CT scanner is used to estimate the contribution of scattering of various system components. [German] Computertomographie (CT) ist eine bewaehrte Methode in den Bereichen Fehleranalyse und Qualitaetskontrolle. Die Energie der hierbei benutzten Roentgenstrahlung bestimmt die Eindringtiefe der Strahlung und schraenkt damit die Groesse und das Material des zu untersuchenden Objektes ein. Fuer grosse, dichte und schwere Objekte sind Photonenenergien von mehr als einem Megaelektronenvolt (MeV) noetig, um nutzbare Transmissionswerte zu erreichen. Ein wichtiger Faktor fuer die Qualitaet hochenergetischer Roentgentomographien ist der Anteil der Streustrahlung auf den CT-Bildern. Roentgenstrahlung kann sowohl im zu untersuchenden Objekt, als auch vom Messinstrument und -umfeld streuen und fuehrt zu einem verfaelschten

  7. Energy Research 2006 - Overview; Recherche energetique/Energie-Forschung 2006. Rapports de synthese des chefs de programme/Ueberblicksberichte der Programmleiter. Konzept der Energieforschung des Bundes

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-05-15

    This comprehensive annual report for the Swiss Federal Office of Energy (SFOE) contains the overview-reports for the year 2006 that were made by the heads of the following Swiss energy research programmes: Efficient energy use, renewable energy, nuclear energy and fundamentals of energy economics. Under the topic of efficient energy use, new planning tools and a building component catalogue are mentioned along with new developments in building technology. In the traffic area, energy-optimisation of components and drive systems are mentioned as are electric bikes and a taxi system running on tracks. High-temperature superconductors, permanent magnet motors along with alternative power generation and storage systems are reviewed. New electricity grid systems and energy hubs are reported on. In the heat pump area, hot-water preparation, quality assurance and magnetic heat pumps are listed. Combustion topics reviewed include large diesel engines and catalytic oxidation in gas turbines. The new 'Power Station 2020' program is introduced with combined heat and power stations and efficient gas turbines. Fuel cells and hydrogen production and storage are looked at, as are process integration topics in the industrial area. Renewable energy topics described include design software and testing systems for solar heating systems, thin-film photovoltaics, industrial use of solar energy and solar production of hydrogen. Biomass and wood-fuel topics are covered, including the gasification of biomass. Cost reduction in small-scale hydro schemes is reported on as are hydropower schemes using drinking water and waste water. Geothermal energy and deep-heat mining are reported on, as is the use of geothermal probes for heating and cooling. Research and field testing done in the wind-energy area and the social acceptance of such installations are presented. In the nuclear energy area, safety and waste disposal issues are covered, as are a future reactor generation, safety

  8. Farmers as energy producers? Conditions for an ecological modernisation of the agriculture using generation of biogas as an example; Landwirte als Energiewirte? Bedingungen einer oekologischen Modernisierung der Landwirtschaft am Beispiel der Biogaserzeugung

    Energy Technology Data Exchange (ETDEWEB)

    Trojecka, Anetta Ewa

    2007-07-01

    The author of the contribution under consideration examines the socio-economic and cultural conditions for the biogas technology in the agriculture. Special attention is paid to the effects on resources and climate protection. Biological gas facilities are outlined as an integrative technology. They can be inserted into the regional and local cycles - with positive effects for nature and environment. But in the meantime, these ecological characteristics of the biogas technology are lost due to their adjustment on maximum output. The starting point of this consideration is the theory of an ecological modernization of the society which specifically will be transferred to the agriculture. The connection of modernity and ecology is a central question of the future of rural economy and the rural areas. The extension of the rationalization on ethical and normative questions of environmental and nature protection is a challenge for modern farmers. The contradictory requirements to the farmers - economic efficiency on the one hand, ecological requirements on the other hand - had contributed to the crisis of the consciousness condition of the agrarian human being. A typology of the ecological-modern farmer serves the later analysis of groups of energy managers, who were identified in the empirism. In the sense of an ecological reform of agriculture the group of transferring persons particularly emphasizes itself. Operators of biogas plants belong to it which would bring in the ecological innovations due to long-term economic advantages and strengthened their new social role as resources managers. The question arises how these farmers should be promoted in their contribution to the development of decentralized energy production. [German] Untersucht werden die soziooekonomischen und kulturellen Voraussetzungen fuer die Biogastechnik in der Landwirtschaft. Besondere Aufmerksamkeit gilt den Auswirkungen auf den Ressourcen- und Klimaschutz. Biogasanlagen sind als integrative

  9. Development of renewable energy sources in Germany 2014. Charts and figures based on statistical data from the working group on renewable energy-statistics (AGEE-Stat); Entwicklung der erneuerbaren Energien in Deutschland im Jahr 2014. Grafiken und Diagramme unter Verwendung aktueller Daten der Arbeitsgruppe Erneuerbare Energien-Statistik (AGEE-Stat)

    Energy Technology Data Exchange (ETDEWEB)

    Nieder, Thomas; Bickel, Peter; Musiol, Frank (comps.) [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Stuttgart (Germany)

    2015-12-15

    The more than 30 diagrams and graphs describe the development of the importance of renewable energy in Germany by the year 2014. Also, discusses the development of avoided greenhouse emissions through renewable energies, as well as the investments and their economic impulses for Germany. Some technical terms are conclusively explained in a glossary. [German] Die mehr als 30 Diagramme und Graphiken beschreiben die Entwicklung der Bedeutung der erneuerbaren Energien fuer Deutschland bis zum Jahr 2014. Auch wird auf die Entwicklung der vermiedenen Treibhaus-Emissionen durch erneuerbare Energien, sowie die Investitionen und deren wirtschaftlichen Impulse fuer Deutschland eingegangen. Einige Fachbegriffe werden abschliessend in einem Glossar erlaeutert.

  10. Energy report for Bavaria, 1998/99. Data on the development of the Bavarian energy industry, with an energy balance; Energiebericht Bayern 1998/99. Daten zur Entwicklung der bayerischen Energiewirtschaft mit Energiebilanz

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-07-01

    The energy report presents an annotated statistical review of energy supply in Bavaria and addresses the energy policy and resulting activities of the Bavarian Land government. The energy balance and tabulated data for the various branches of the energy industry predominantly cover the year 1997, but whenever available, data for the years 1998 and 1999 have been included. As in previous energy reports, an annex to the report contains statements of the Bavarian Land government in reply to written questions of members of the Land Parliament, and energy policy decisions of the Land Parliament taken within the reporting period. (orig./CB) [German] Der vorliegende Bericht zeigt die Entwicklung der Energieversorung in Bayern und gibt einen Ueberblick ueber die energiepolitischen Aktivitaeten der Staatsregierung. Die Energiebilanz und die Datentabellen zu den einzelnen Energiezweigen beziehen sich im allgemeinen auf das Jahr 1997. Soweit bei einigen Energietraegern bereits Zahlen fuer 1998 und 1999 vorliegen, wurden sie in den Bericht mit aufgenommen. Im Anhang des Energieberichts sind wieder Stellungnahmen der Bayerischen Staatsregierung zu Schriftlichen Anfragen von Abgeordneten sowie Beschluessen des Bayerischen Landtags zur Energiepolitik aus dem Berichtszeitraum wiedergegeben. (orig.)

  11. Energy report for Bavaria, 1996/97. Data on the development of the Bavarian energy industry, with an energy balance; Energiebericht Bayern 1996/97. Daten zur Entwicklung der bayerischen Energiewirtschaft mit Energiebilanz

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    The report presents the energy balance for Bavaria and provides information on: Bavarian energy industry; structure and development of primary and end-use energy consumption; situation and development of energy sources (electricity, gas, mineral oil, coal, district heating). (orig.) [Deutsch] Der Bericht enthaelt die Energiebilanz Bayern fuer das Berichtsjahr und bietet Informationen zur Energiewirtschaft in Bayern, zur Struktur und Entwicklung des Primaer- und Endenergieverbrauchs und zur Situation und Entwicklung bei den einzelnen Energietraegern (Elektrizitaet, Gas, Mineraloel, Kohle, Fernwaerme). (orig.)

  12. Energy pole system in the new building of the PAGO AG, Grabs (CH); Energiepfahlsystem im Neubau der PAGO AG, Grabs (CH)

    Energy Technology Data Exchange (ETDEWEB)

    Scheuss, U. [NDS-HTL, Ingenieurbuero Lippuner und Partner AG, Grabs (Switzerland)

    1997-12-01

    With 570 concrete poles and 80 km of tubes, 100,000 m{sup 3} of ground serve as a cold and heat storage resservoir for a building. The building houses a printing shop, which needs cooling in summer and heating in winter. The energy pole system can be used as a dual system for heating and cooling in both seasons. The project is a pilot project of the BWE (Swiss General Office for Utilities and Power Supply), who also started an extensive accompanying measurig campaign. The results during the first year of operation were very positive, and the performance of the energy pole system was up to expectations. (orig.) [Deutsch] Mittelpunkt der PAGO-Energietechnik ist das Energiepfahlsystem. Mittels 570 Betonpfaehlen und 80 km Rohrschlangen wird das Erdreich unter dem Gebaeude als ueber 100.000 m{sup 3} grosser Waerme- und Kaeltespeicher genutzt. Ueber dieses Energiepfahlsystem wird dieser Druckereibetrieb mit hohen Anforderungen an das Raumklima und viel Maschinenabwaerme sehr umweltschonend im Winter behizt und im Sommer gekuehlt. Das Besondere an diesem System ist diese ganzjaehrige Doppelnutzung zu Heiz- und Kuehlzwecken. Aus diesem Grunde wurde dieses Projekt vom Bundesamt fuer Energiewirtschaft (BEW) als Pilot- und Demonstrationsprojekt anerkannt. Zur Ueberpruefung von dessen Ausbeute und der Wirksamkeit der gesamten Energietechnik wurde vom BEW ein umfangreiches Messprojekt gestartet. Der Innovationswert der PAGO -Energietechnik liegt allerdings nicht allein im Einsatz der alternativen Komponenten. Mindestens so wichtig ist die Konzeption und die Feinabstimmung der gesamten Energietechnik. Der Betrieb lief im ersten Betriebsjahr sehr positiv und von Anfang an ohne groessere Probleme. Das Energiepfahlsystem konnte im wesentlichen die Erwartungen erfuellen. (orig.)

  13. Electronic Properties of h-BCN-Blue Phosphorene van der Waals Heterostructures.

    Science.gov (United States)

    Kaewmaraya, Thanayut; Srepusharawoot, Pornjuk; Hussian, Tanveer; Amornkitbamrung, Vittaya

    2018-03-05

    Van der Waals heterostructures, a new class of materials made of a vertically selective assembly of various 2D monolayers held together by van der Waals forces, have attracted a great deal of attention due to their promise to deliver novel electronic and optoelectronic properties that are not achievable by using individual 2D crystals. Using density functional theory (DFT), it is revealed that van der Waals heterostructures composed of monolayers of hexagonal boron nitride (h-BN) and the latest P allotrope blue phosphorus (blue phosphorene, BlueP) forms a straddling type I band offset for which the band edges exclusively belong to BlueP. This feature enables h-BN to act as a protective coating material to resolve the air instability of BlueP. Furthermore, substitutional doping of C into h-BN (h-BCN) at a suitable concentration induces h-BCN-BlueP into staggered type II band offset. The type II band alignment triggered by the intensified built-in electric field across the sheets implies improved carrier mobility and the suppressed recombination of photogenerated hole pairs. These major benefits can pave the way for the potential functionality of h-BCN-BlueP to be exploited for efficient photovoltaic devices. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Diagnostic accuracy of dual energy CT angiography in patients with diabetes mellitus; Diagnostische Genauigkeit der Dual-energy-CT-Angiographie bei Patienten mit Diabetes mellitus

    Energy Technology Data Exchange (ETDEWEB)

    Schabel, C.; Bongers, M.N.; Syha, R. [Klinikum der Eberhard-Karls-Universitaet, Abteilung fuer Diagnostische und Interventionelle Radiologie, Tuebingen (Germany); Klinikum der Eberhard-Karls-Universitaet, Sektion fuer Experimentelle Radiologie der Abteilung fuer Diagnostische und Interventionelle Radiologie, Tuebingen (Germany); Ketelsen, D.; Homann, G.; Notohamiprodjo, M.; Nikolaou, K.; Bamberg, F. [Klinikum der Eberhard-Karls-Universitaet, Abteilung fuer Diagnostische und Interventionelle Radiologie, Tuebingen (Germany); Thomas, C. [Universitaetsklinikum Duesseldorf, Abteilung fuer Diagnostische und Interventionelle Radiologie, Duesseldorf (Germany)

    2015-04-01

    Herausforderung dar. Ziel dieser Arbeit war die Ermittlung der diagnostischen Genauigkeit der Dual-energy-CT-Angiographie (DE-CTA) im Vergleich zum Goldstandard, der invasiven digitalen Subtraktionsangiographie (DSA) bei der Stenoseerkennung, da die DE-CTA potenziell eine Differenzierung von Verkalkungen und jodhaltigem Kontrastmittel ermoeglicht. Dreissig Patienten mit dem Verdacht auf das Vorliegen oder bekannter PAVK und zusaetzlich bestehendem Diabetes mellitus wurden retrospektiv in die Studie eingeschlossen. Bei allen Teilnehmern wurde eine DE-CTA (Somatom Definition Flash, Siemens Healthcare, Germany), gefolgt von einer invasiven Angiographie durchgefuehrt. Das Vorhandensein von Stenosen in gekruemmten multiplanaren Reformationen (MPR) und Projektionen maximaler Intensitaet (MIP) wurde verblindet evaluiert. Die diagnostische Genauigkeit wurde mit der Angiographie als Goldstandard errechnet. Bei den 30 in die Analyse eingeschlossenen diabetischen Patienten (83 % maennlich, 70,0 ± 10,5 Jahre alt, 83 % Diabetes mellitus Typ 2) war die Praevalenz behandlungsbeduerftiger Stenosen in 331 evaluierten Gefaesssegmenten hoch (30 %). Die DE-CTA detektierte kritische Stenosen mit einer hohen Sensitivitaet und guten Spezifitaet anhand gekruemmter MPR (100 und 93,1 %) und MIP (99 und 91,8 %). In einer Subanalyse war die diagnostische Genauigkeit am hoechsten fuer Stenosen im Bereich der Beckenstrombahn (gekruemmte MPR 97,1 % vs. MIP 100 %) und im Oberschenkelbereich (99,2 vs. 96,6 %) verglichen mit dem Unterschenkelkompartiment (90,9 vs. 88 %). Die DE-CTA weist eine hohe diagnostische Genauigkeit bei der Stenosenerkennung und -charakterisierung im Rahmen der PAVK bei Patienten mit Diabetes mellitus auf, hat jedoch eine eingeschraenkte Genauigkeit im Bereich des Unterschenkelkompartiments. (orig.)

  15. Is the 10-point agenda of the Federal Government useful for a successful energy transition?; Dient die 10-Punkte-Agenda der Bundesregierung einer erfolgreichen Energiewende?

    Energy Technology Data Exchange (ETDEWEB)

    Dinther, Clemens van [Reutlingen Hochschule (Germany). ESB Business School; Fey, Bernhard [Rheinenergie AG, Koeln (Germany); Renelt, Sven [Paatz Scholz van der Laan Unternehmensberatung GmbH, Duesseldorf (Germany); Strueker, Jens [Hochschule Fresenius, Frankfurt (Germany). Inst. fuer Energiewirtschaft; Flath, Christoph [Wuerzburg Univ. (Germany); Terzidis, Orestis [KIT - Karlsruher Institut fuer Technologie (Germany). Inst. fuer Entrepreneurship, Technologiemanagement und Innovation; Bretschneider, Peter [Technische Univ. Ilmenau (Germany). Fachgebiet Energieeinsatzoptimierung

    2017-03-15

    With the energy transition, the Federal Government has begun the conversion of the energy supply. Because of the success of the energy transition is essential for the future and competitiveness of Germany as a business location The Federal Association of German Industry (BDI) has already published 2013 Stimulus for a smart energy market, in which are derived five principles which provide a framework for discourse on the measures to be taken. Renewable energies will be the dominant source of electricity in the coming years. This results in new challenges. The Federal Ministry of Economics and Technology (BMWi) has recently adopted a 10-point agenda to address these issues (ZPA) for the central energy projects. To be discussed is to what extent they are in harmony with the five principles of the BDI and at which points adjustments are necessary, so that the conversion of the energy system can succeed. [German] Mit der Energiewende hat die Bundesregierung den Umbau der Energieversorgung begonnen. Da das Gelingen der Energiewende fuer die Zukunfts- und Wettbewerbsfaehigkeit des Wirtschaftsstandorts Deutschlands essenziell ist, wurden seitens des Bundesverbandes der deutschen Industrie (BDI) bereits 2013 Impulse fuer eine smarte Energiewende veroeffentlicht, in denen fuenf Prinzipien abgeleitet werden, die einen Rahmen fuer den Diskurs ueber die zu ergreifenden Massnahmen setzen. erneuerbare Energien werden in den kommenden Jahren die dominierende Stromquelle darstellen. Daraus entstehen neue Herausforderungen. Zu deren Bewaeltigung hat das Bundeswirtschaftsministerium (BMWi) kuerzlich eine 10-Punkte-Agenda (ZPA) fuer die zentralen Vorhaben der Energiewende vorgelegt. Zu diskutieren ist, inwieweit sie im Einklang mit den fuenf Prinzipien des BDI steht und an welchen Stellen Anpassungen notwendig werden, damit der Umbau des Energiesystems erfolgreich gelingen kann.

  16. Surface free energy analysis of adsorbents used for radioiodine adsorption

    Energy Technology Data Exchange (ETDEWEB)

    González-García, C.M. [Departamento de Física Aplicada, Universidad de Extremadura, Avda. Elvas s/n, 06006 Badajoz (Spain); Román, S., E-mail: sroman@unex.es [Departamento de Física Aplicada, Universidad de Extremadura, Avda. Elvas s/n, 06006 Badajoz (Spain); González, J.F.; Sabio, E. [Departamento de Física Aplicada, Universidad de Extremadura, Avda. Elvas s/n, 06006 Badajoz (Spain); Ledesma, B. [Departamento de Ingeniería Mecánica, Energética y de los Materiales, Universidad de Extremadura, Avda. Elvas s/n, 06006 Badajoz (Spain)

    2013-10-01

    In this work, the surface free energy of biomass-based activated carbons, both fresh and impregnated with triethylenediamine, has been evaluated. The contribution of Lifshitz van der Waals components was determined by the model proposed by van Oss et al. The results obtained allowed predicting the most probable configurations of the impregnant onto the carbon surface and its influence on the subsequent adsorption of radioactive methyl iodide.

  17. The energy consumption of private households 1990 - 2035 - Results of scenarios I - IV; Der Energieverbrauch der Privaten Haushalte, 1990 - 2035. Ergebnisse der Szenarien I bis IV und der zugehoerigen Sensitivitaeten BIP hoch, Preise hoch und Klima waermer

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, P.

    2007-07-01

    This comprehensive report for the Swiss Federal Office of Energy (SFOE) presents four scenarios concerning the development of energy consumption in Swiss private households for the period 1990 - 2035. The four scenarios - status quo, increased co-operation between the state and the economy with various levies, global reduction of energy consumption and, finally, scenario IV 'on the way to a 2000-Watt Society' - are briefly described. In particular, the scenarios are examined for various sensitivities: high gross domestic product GDP, high prices and warmer climate. The results of the sensitivity analyses are compared and discussed and the necessary instruments are examined. This comprehensive report contains a large number of data-tables and graphical representations

  18. Energy policy and environmental policy of the Czech Republic. Vol. 1: Eastern enlargement of the EU; Energie- und Umweltpolitik der Tschechischen Republik. Bd. 1: Osterweiterung der Europaeischen Union

    Energy Technology Data Exchange (ETDEWEB)

    Brauch, H.G. [Arbeitsgruppe Friedensforschung und Europaeische Sicherheitspolitik (AFES), Mosbach (Germany)

    2002-01-01

    This report has been prepared as part of a bilateral German-Czech project on ''Energy and Environment in the Czech Republic'' that has been financed by the German Federal Ministry of Environment, Nature protection and Nuclear Safety. The project is focused on strengthening the cooperation between Germany and the Czech Republic in the field of energy and environment as well as on assisting the Czech Republic in its EU accession process. The project was launched by the German Federal Environmental Agency (UBA) and is managed by Gertec GmbH, an engineering company in Essen. Additional subcontractors and cooperating organisations included both German and Czech partners: ITUT, e.V., Leipzig, AFES-PRESS, Mosbach, the Czech Energy Agency - CEA Prague, SEVEn, the Energy Efficiency Center, o.p.s., Prague, the German-Czech Chamber of Commerce in Prague, the Euroregion Nisa, Liberec, and KSUE, o.p.s., Litvinov. The goal of this report is to provide brief but focused information for the German and Czech business community, for investors and decision makers both on the current situation and the development in 1990s in the area of energy and environment in the Czech Republic. This report consists of an Executive Summary, a detailed survey in part I with a detailed description of the energy sector and environment and in part II three regional studies focusing on North Bohemia, North Moravia, and Prague. These are supplemented by six appendices. As part of this project two additional studies were prepared by AFES-PRESS that focus - from a social science perspective - on the accession process of the Czech Republic: Enlargement of the European Union - Energy and Environment Policy of the Czech Republic (Volume 1), Liberalisation of the Energy Market for Electricity and Gas in the European Union: a Survey and Implications for the Czech Republic (Volume 3) More information on the whole project, the conducted studies and project partners can be found on internet www

  19. The zero-point field. On the search for the cosmic basic energy; Das Nullpunkt-Feld. Auf der Suche nach der kosmischen Ur-Energie

    Energy Technology Data Exchange (ETDEWEB)

    McTaggart, L.

    2007-02-15

    Does an inexhaustable energy source exist from which all life is fed? A form of energy, which penetrates all dead and living expression forms of life? Does a logical, scientific explanation exist for parapsychological phenomena like clairvoyance, telepathy, ghost healing, synchronicity, and a model for the mode of action of homeopathy? Do serious researchers and scientific studies to be token in ernest exist, which not only deal with this questions but also have found answers? During eight years the British scientific journalist Lynne McTaggart has researched. ''Teh zero-point field'' is the result of numerous speeches with renowned physicists, biophysicists, neuroscientists, biologist, and consciousness researchers on the whole world, which have independently discovered phenomena, which are combined like puzzle pieces to a fascinating total picture.

  20. Wind energy. From the garage workshop to a global market. 25 years scientific accompaniment; Windenergie - von der Garagen-Werkstatt zum Weltmarkt. 25 Jahre wissenschaftliche Begleitung

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Berthold; Stuebig, Cornelia [Fraunhofer Institut fuer Windenergie und Energiesystemtechnik (IWES), Kassel (Germany); Ponick, Bernd [Fraunhofer Institut fuer Windenergie und Energiesystemtechnik (IWES), Kassel (Germany); Hannover Univ. (Germany); Keller, Sarina [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Koeln (Germany); Felder, Martin; Jachmann, Henning [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Stuttgart (Germany)

    2015-04-15

    The plant technology for the use of wind energy on land is so sophisticated that the WEA can be operated as ''normal'' power plants to the grid. Of course, there are still potential for development, for example, in terms of improved reliability, or concerning the fledgling offshore use, always with an emphasis on the simultaneous reduction in costs. Although from the former garages workshops is little remaining, the production techniques are another major issue in terms of quality and costs. The cost of electricity from wind energy is taking account of external costs are already competitive with conventional power generation. To limit the costs of the energy transition one to expect from the wind energy as of the other technologies cost reduction. Various studies show that the wind energy supply in the balance is sufficient several times to provide the expected contribution to supply. [German] Die Anlagentechnologie fuer die Windenergienutzung an Land ist so ausgereift, dass die WEA als ''normale'' Kraftwerke am Netz betrieben werden koennen. Selbstverstaendlich bestehen weiterhin Entwicklungspotenziale, z. B. hinsichtlich verbesserter Zuverlaessigkeit oder bezueglich der noch jungen Offshore Nutzung, immer mit einem Augenmerk auf die gleichzeitige Kostenreduktion. Auch wenn von den ehemaligen Garagen Werkstaetten wenig uebrig geblieben ist, sind die Produktionstechniken ein weiteres wesentliches Thema bezueglich Qualitaet und Kosten. Die Kosteneffizienz der Stromerzeugung aus Windenergie ist unter Beruecksichtigung externer Kosten heute schon konkurrenzfaehig zur konventionellen Stromerzeugung. Zur Begrenzung der Kosten der Energiewende wird aber von der Windenergie wie von den anderen Technologien weiterhin eine Kostenreduktion erwartet. Diverse Studien zeigen, dass das Windenergieangebot in der Bilanz mehrfach ausreicht, um den erwarteten Beitrag zur Versorgung leisten zu koennen.

  1. Promotion of renewable energies in the European Union. Critical analysis in view of regulatory policy; Die Foerderung erneuerbarer Energien in der Europaeischen Union. Eine kritische Analyse aus Sicht der Ordnungspolitik

    Energy Technology Data Exchange (ETDEWEB)

    Haeder, M. [Fachhochschule Bochum (Germany). Fachbereich Wirtschaft

    2004-06-15

    The intention of the article is to examine from regulatory perspective whether the specific incentives for renewable energies are sensible and justified at all. In a second step some recommendations are given for efficient adjustment of incentive regulations. [German] Ziel des Artikels ist es, zunaechst zu untersuchen, ob eine spezifische Foerderung erneuerbarer Energien ordnungspolitisch ueberhaupt sinnvoll und gerechtfertigt ist. In einem zweiten Schritt werden sodann einige Handlungsempfehlungen fuer eine effiziente Ausrichtung der Foerderregelungen gegeben. (orig.)

  2. Legal basis of the energy market in the Czech Republic; Grundlagen des Energierechts in der Tschechischen Republik

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmik, T.; Macova, J. [Rechtsanwaltsbuero Fiala, Profous, Mainer a spol, Prag (Czech Republic)

    2002-07-01

    Legal foundations of liberalism of the electric power and gas market were laid in the Czech Republic with regards to the requirements of the European Union in 2000. The story deals with important definitions, framework conditions and specificities of an entrepreneurial activity on the Czech market with electric power and gas. [German] In der Tschechischen Republik wurden die rechtlichen Grundlagen fuer die Liberalisierung der Strom- und Gasmaerkte unter Beruecksichtigung der Anforderungen der Europaeischen Union im Jahr 2000 gelegt. Der Beitrag behandelt wichtige Definitionen, Rahmenbedingungen und Besonderheiten fuer unternehmerische Taetigkeiten im tschechischen Energiemarkt.

  3. Operational energy management in the industrial production. Brief study; Betriebliches Energiemanagement in der industriellen Produktion. Kurzstudie

    Energy Technology Data Exchange (ETDEWEB)

    Hirzel, Simon; Sontag, Benjamin; Rohde, Clemens

    2011-09-15

    Increasing energy prices and raw material prices, an increased public interest in energy issues and new customer requirements result in a responsible utilization of energy as a resource. The energy management provides the opportunity to evaluate and assess energy flows. Measures for a better utilization of resources can be derived and implemented by means of an energy management system. Under this aspect, the authors of the contribution under consideration report on current issues and developments in the field of corporate energy management in industry as well as the future developments of energy management.

  4. The energy spectrum of electromagnetic normal modes in dissipative media: modes between two metal half spaces

    International Nuclear Information System (INIS)

    Sernelius, Bo E

    2008-01-01

    The energy spectrum of electromagnetic normal modes plays a central role in the theory of the van der Waals and Casimir interaction. Here we study the modes in connection with the van der Waals interaction between two metal half spaces. Neglecting dissipation leads to distinct normal modes with real-valued frequencies. Including dissipation seems to have the effect that these distinct modes move away from the real axis into the complex frequency plane. The summation of the zero-point energies of these modes render a complex-valued result. Using the contour integration, resulting from the use of the generalized argument principle, gives a real-valued and different result. We resolve this contradiction and show that the spectrum of true normal modes forms a continuum with real frequencies

  5. Two atoms scattering at low and cold energies

    Indian Academy of Sciences (India)

    1National Institute of Technical Teachers' Training and Research Kolkata, Salt Lake City,. Kolkata 700 106, India. 2New Alipore College, New Alipore, Kolkata 700 ... determine the strength of effective interatomic potential, as van der Waals interaction is defined as. Vvan(R) = −. CW. R6 ,. (1) where CW is the van der Waals ...

  6. Swiss Federal Energy Research Concept 2008 - 2011; Konzept der Energieforschung des Bundes 2008 bis 2011

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-04-15

    This report for the Swiss Federal Office of Energy (SFOE) presents the plan for the activities of the Swiss Federal Commission on Energy Research CORE during the period 2008 - 2011. The motivation behind the state promotion of energy research is discussed. The visions, aims and strategies of the energy research programme are discussed. The main areas of research to be addressed during the period are presented. These include the efficient use of energy in buildings and traffic - batteries and supercaps, electrical technologies, combustion systems, fuel cells and power generation are discussed. Research to be done in the area of renewable sources of energy are listed. Here, solar-thermal, photovoltaics, hydrogen, biomass, geothermal energy, wind energy and ambient heat are among the areas to be examined. Research on nuclear energy and safety aspects are mentioned. Finally, work on the basics of energy economy are looked at and the allocation of funding during the period 2008 - 2011 is looked at.

  7. Hydration free energies of cyanide and hydroxide ions from molecular dynamics simulations with accurate force fields

    Science.gov (United States)

    Lee, M.W.; Meuwly, M.

    2013-01-01

    The evaluation of hydration free energies is a sensitive test to assess force fields used in atomistic simulations. We showed recently that the vibrational relaxation times, 1D- and 2D-infrared spectroscopies for CN(-) in water can be quantitatively described from molecular dynamics (MD) simulations with multipolar force fields and slightly enlarged van der Waals radii for the C- and N-atoms. To validate such an approach, the present work investigates the solvation free energy of cyanide in water using MD simulations with accurate multipolar electrostatics. It is found that larger van der Waals radii are indeed necessary to obtain results close to the experimental values when a multipolar force field is used. For CN(-), the van der Waals ranges refined in our previous work yield hydration free energy between -72.0 and -77.2 kcal mol(-1), which is in excellent agreement with the experimental data. In addition to the cyanide ion, we also study the hydroxide ion to show that the method used here is readily applicable to similar systems. Hydration free energies are found to sensitively depend on the intermolecular interactions, while bonded interactions are less important, as expected. We also investigate in the present work the possibility of applying the multipolar force field in scoring trajectories generated using computationally inexpensive methods, which should be useful in broader parametrization studies with reduced computational resources, as scoring is much faster than the generation of the trajectories.

  8. Cooperative project for energy-oriented modernisation of industrial buildings - coordination results; Projektverbund zur energiegerechten Sanierung industriell errichteter Gebaeude - Ergebnisse der Koordination

    Energy Technology Data Exchange (ETDEWEB)

    Kerschberger, A. [Assmann Beraten und Planen GmbH, Stuttgart (Germany)

    1997-12-31

    The cooperative project concept of the federal ministry of science and technology is discussed. Coordination activities as well as pilot projects and comparative projects are described. Results obtained so far are reported in detail; heat energy conservation potentials as substantiated by means of measurements are shown in tabulated form. Further indicated in tabulated form are the redevelopment costs per residential unit, the payback period of the entire project, and a comparison of reduced heating costs with increased basic rent for apportioning the costs of modernization. (MSK) [Deutsch] Die Konzeption des Projektverbundes des BMBF wird naeher erlaeutert. Die Aktivitaeten der Koordination und die Versuchs-und Vergleichsbauvorhaben werden beschrieben. Die bisherigen Ergebnisse werden detailliert geschildert und die messder Gesamtmassder Vergleich von Heizkostenverminderung und Kaltmietenerhoehungen durch Modernisierungsumlagen.

  9. Energy summit Hessen. Implementation concept of the state government Hessen; Hessischer Energiegipfel. Umsetzungskonzept der Hessischen Landesregierung

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-02-15

    By means of the concept under consideration, the state government of Hessen (Federal Republic of Germany) has pursued the possible and realistic course for the implementation of the targets of the energy summit. The main aspects of this contribution are the implementation of the energy policy of Hessen into the European and national framework; Status quo of the energy consumption in Hessen; Areas of action and measures of the state government of Hessen; Actors of the energy policy turnaround; Monitoring.

  10. Law of the energy economy. A practical manual. 4. new rev. ed.; Recht der Energiewirtschaft. Praxishandbuch

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Jens-Peter [Freiburg Univ. (Germany); Theobald, Christian (ed.)

    2013-07-01

    This manual presents the laws governing the electricity and gas markets, a field that has evolved at ever greater speed since the onset of liberalisation. Its content is of practical relevance and well-founded, yet nonetheless readily comprehensible to the layman. Following introductory sections on the technical and economic as well as national and European foundations of energy law are a wealth of contributions offering detailed analyses of the regulation of market structures; planning and licensing of energy infrastructure and energy installations; granting of municipal concessions to energy supply companies; trade in energy and emission permits as well as grid operation and grid utilisation; energy regulatory authorities and procedures; promotion of renewable energy, cogeneration and energy saving. The manual consistently takes account of the relevant regulations of cartel, municipal, environmental, tax, contractual and financial market law. Links to energy law proper are duly covered wherever practically relevant. The following legislation in particular has been incorporated in this new edition: 2011 amendment to the Energy Economy Law (unbundling, transmission system operator, grid development plans, modernisation in metrology, new consumer rights); 2012 amendment to the Nuclear Energy Law; Grid Expansion Acceleration and Transmission System Law of 2011 (NABEG); Renewable Energy Law of 2012; and Cogeneration Law of 2012.

  11. Climate-relevant reporting. Carbon disclosure within the framework of environmental and sustainability reporting in the energy and cement industries; Klimaberichterstattung. Offenlegung der Klimaleistung im Rahmen der Umwelt- und Nachhaltigkeitsberichterstattung in der Energie- und Zementbranche

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Gabriel; Guenther, Edeltraud; Nowack, Martin; Arndt, Stephanie [Technische Univ. Dresden (Germany). Professur fuer Betriebswirtschaftslehre, insb. Betriebliche Umweltoekonomie

    2009-07-01

    This paper analyses the status quo of carbon disclosure in the carbon-intensive energy and cement industries. It makes use of content analysis to evaluate 204 environmental reports from the years 2002 to 2007, scrutinising the compliance of carbon disclosure with the guidelines of the Global Reporting Initiative. The issues investigated include: How has carbon disclosure evolved over time? What information on carbon management can be gained from the carbon disclosure of energy and cement companies? Based on stakeholder theory [1], the impact of higher external pressure on the energy sector regarding carbon disclosure will be assessed. It is proposed to add to existing literature on carbon disclosure by applying stakeholder theory and through a sectoral approach. (orig.)

  12. Swiss Energy research 2007 - Overview from the Heads of the Programs; Energie-Forschung 2007. Ueberblicksberichte der Programmleiter

    Energy Technology Data Exchange (ETDEWEB)

    Calisesi, Y.

    2008-04-15

    This comprehensive document issued by the Swiss Federal Office of Energy (SFOE) presents the overview reports elaborated by the heads of the various Swiss energy research programmes. Topics covered include the efficient use of energy, with reports covering energy in buildings, traffic and accumulators, electrical technologies, applications and grids, ambient heat, combined heat and power, cooling, combustion, the 'power station 2000', fuel cells and hydrogen and process engineering. Renewable energy topics reported on include solar heat, photovoltaics, industrial solar energy, biomass and wood energy, hydropower, geothermal heat and wind energy. Nuclear energy topics include safety, regulatory safety research and nuclear fusion. Finally, energy economics basics are reviewed. The report is completed with annexes on the Swiss Energy Research Commission, energy research organisations and a list of important addresses.

  13. Competitiveness of renewable energies in the electricity supply system; Wettbewerbsfaehigkeit erneuerbarer Energien in der Stromversorgung

    Energy Technology Data Exchange (ETDEWEB)

    Karl, Hans-Dieter [ifo Institut, Muenchen (Germany)

    2013-05-15

    The introduction of competitive structures to Germany's grid-bound energy supply resulted in tangible gains in efficiency. Then came the energy turnaround with massive subsidisation of renewable energies, hampering competition, especially in the area of electricity production, and creating renewed instances of inefficiency. However, even under the altered conditions now prevailing after the energy turnaround decision, with increasing shares of renewable energy, every effort should be made to organise the sector in a way conducive to competition so that economically efficient electricity production processes can emerge.

  14. Energy supply for the town of the future; Energieversorgung fuer die Stadt der Zukunft

    Energy Technology Data Exchange (ETDEWEB)

    Leithner, R. [ed.

    1998-06-01

    Thanks to the development of new energy systems which combine environmentally benign, heavily insulated buildings with renewable energy sources it is possible today to use energy in a responsible manner. This article presents concepts of urban planning and architecture which make use of integral energy systems, techniques for using renewable energy resources such as solar installations, energy supply through biomass and biogas, and the integration of renewable energy resources such as wind power in municipal supply systems and hydrogen as a clean energy source. Ten papers have been abstracted individually for the Energy Database. [Deutsch] Die Entwicklung neuer Energiesysteme, in denen oekologische, hochwaermegedaemmte Baukonstruktionen mit regenerativen Energiequellen kombiniert werden laesst einen verantwortungsvollen Umgang mit Energie zu. Im Folgenden werden dazu Stadtplanung und Architektur im Kontext integraler Energiekonzepte, Techniken zur Nutzung von regenerativen Energietraegern, wie Solaranlagen, Energiebereitstellung durch Biomasse und Biogas, sowie die Integration von regenerativen Energietraegern, z.B. Windenergienutzung im staedtischen Verbund und Wasserstoff als sauberer Energietraeger vorgestellt. Fuer die Datenbank Energy wurden zehn Beitraege einzeln aufgenommen.

  15. Law of the energy economy. A practical manual. 2. ed.; Recht der Energiewirtschaft. Praxishandbuch

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, J.P. [Osnabrueck Univ. (Germany); Theobald, C. (eds.)

    2008-07-01

    The handbook under consideration describes the substantive law of the electricity market and gas market in a form understandable for laymen. After an introductory presentation of the technical-economical, national and European fundamentals of the energy law, contributions follow to the topics: (a) Adjustment of market structures and market participants; (b) Planning and permission of energy installations; (c) Questions of licensing and expropriation; (d) Rules for energy trade and emissions trading, grid operation and grid utilization; (e) Energy authorities and adjustment procedures; (f) Promotion of renewable energies, combined heat and power generation and energy conservation as well as current expensive law. The manual considers comprehensively the legal and energy-industry developments since the fundamental revised version of the power industry law.

  16. Energy research 2004 - Overview; Recherche energetique / Energie-Forschung 2004. Rapport de synthese des chefs de programme / Ueberblicksberichte der Programmleiter

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-05-15

    This publication issued by the Swiss Federal Office of Energy (SFOE) presents an overview of advances made in energy research in Switzerland in 2004. In the report, the heads of various programmes present projects and summarise the results of research in four main areas: Efficient use of energy, renewable energies, nuclear energy and energy policy fundamentals. Energy-efficiency is illustrated by examples from the areas of building, traffic, electricity, ambient heat and combined heat and power, combustion, fuel cells and in the process engineering areas. In the renewable energy area, projects concerning solar heating and cooling, energy storage, photovoltaics, solar chemistry and hydrogen, biomass, small-scale hydro, geothermal energy and wind energy are presented. Work being done on nuclear safety and disposal regulations as well as controlled thermonuclear fusion are discussed.

  17. Biogenic materials in Switzerland - mass and energy flows; Biogene Gueter in der Schweiz: Massen- und Energiefluesse

    Energy Technology Data Exchange (ETDEWEB)

    Scheurer, K.; Baier, U.

    2001-07-01

    This study supplements a series of studies carried out under the 'Energy 2000' programme and its follow-up 'SwissEnergy' on the energy potential of biomass in Switzerland. This study compiles data from existing studies and statistics and presents them as detailed mass and energy flow diagrams. The findings of the study confirm that the most important biomass fluxes are generated by animal feed stuffs and manure and that these represent an important potential for use as a source of energy. The authors state that in the foodstuffs and wood/paper industries a high level of sustainability in resource usage has been attained and that the largest losses in mass and energy flows can be found in livestock breeding and human biomass consumption.

  18. Control of Greenhouse Gas Emissions by Optimal DER Technology Investment and Energy Management in Zero-Net-Energy Buildings

    OpenAIRE

    Stadler, Michael

    2010-01-01

    The U.S. Department of Energy has launched the commercial building initiative (CBI) in pursuit of its research goal of achieving zero-net-energy commercial buildings (ZNEB), i.e. ones that produce as much energy as they use. Its objective is to make these buildings marketable by 2025 such that they minimize their energy use through cutting-edge, energy-efficiency technologies and meet their remaining energy needs through on-site renewable energy generation. This paper examines how such buil...

  19. Load management - utilization of thermal capacity of buildings as non-electric energy storage in electric supply grids; Lastmanagement - Nutzung der Thermischen Kapazitaet von Gebaeuden als nichtelektrischer Energiespeicher in elektrischen Versorgungsnetzen

    Energy Technology Data Exchange (ETDEWEB)

    Bukvic-Schaefer, Aleksandra Sasa

    2008-07-01

    The increasingly decentralised structure of the public power supply and its increasing use of renewable energy resources with fluctuating yields will necessitate changes in the operation of electricity grids, which until now has been driven by demand. One way of responding to the altered framework conditions is to use load management to make the load side more flexible. Consumers which permit the storage of useful energy are particularly suitable for load management. The present dissertation only considers loads which are directly coupled to the thermal mass of a building, i.e. heating or air conditioning systems. It focuses on the advantages for the load side, i.e. for the user of the installations that are coupled to the building acting as thermal storage. Two extreme cases of variable pricing are considered as possible incentives to use load management: the spot market price as a theoretical guide value and the adapted household rate, this being the least favourable case of a variable price. The author develops new system management strategies for different topologies based on an analysis of the existing building and equipment structures and for each strategy determines the potential costs savings on the basis of real-time rates. [German] Durch die verstaerkte Dezentralisierung der Stromerzeugung sowie eine verstaerkte Integration von fluktuierenden regenerativen Energiequellen in das Versorgungssystem wird eine Aenderung der bisherigen, nachfrageabhaengigen Betriebsfuehrung der Stromnetze notwendig. Eine Moeglichkeit auf die veraenderten Bedingungen zu reagieren, bietet die Flexibilisierung der Lastseite - das Lastmanagement. Dabei sind die Verbraucher, bei denen eine Moeglichkeit der Speicherung der Nutzenergie moeglich ist, besonders fuer das Lastmanagement geeignet. Im Rahmen der Dissertation werden nur die Lasten, die eine direkte Kopplung mit der thermischen Masse des Gebaeudes aufweisen, wie z.B. Heizungs- oder Klimaanlagen, betrachtet. Dabei wurde das

  20. Optimization of energy input for massive forming manufacturing processes. Optimaler Energieeinsatz bei der Fertigung durch Massivumformung

    Energy Technology Data Exchange (ETDEWEB)

    Herlan, T. (Stuttgart Univ. (Germany, F.R.). Inst. fuer Umformtechnik)

    1989-01-01

    The specific end or primary energy consumption of single manufacturing stages is determined with the help of process chain analysis. The overall system considered is divided into process chain segments which themselves are represented in units of process stages. For the investigation of the energy used in single-piece manufacture by massive forming, there is a projected process stage which shows the energy consumption of the initial semi-finished product. The second process stage determines the energy used for manufacturing by means of massive forming. The materials examined are steel and aluminium materials from which workpieces are produced almost waste-free by means of cold, warm or hot extrusion. The required energy consumption as well as the manufacturing and energy costs for any manufacturing by means of massive forming are determined with the help of a computer program. From surveys of several manufacturing sequences it can be shown that 10-20% of the energy consumption can be saved under existing operational conditions, without investments having to be made. On a long-term basis, up to 40% of the energy consumption may be saved by adjusting the manufacturing equipment. (orig./MM).

  1. Twenty years of renewable energy law; 20 Jahre Recht der Erneuerbaren Energien

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Thorsten (ed.)

    2012-07-01

    The present volume was compiled as part of a project funded by the German Federal Ministry for Environment, Nature Conservation and Reactor Safety, one event under which was the seventh Wuerzburg conference on environmental energy law with the title ''Twenty Years of Renewable Energy Law'' which took place on 13/14 October 2010. It comprises 36 contributions which, from different scientific perspectives, take stock of the significance of renewable energies for climate protection and the energy supply, examine the developments of the past 20 years and draw conclusions for the future use of renewable energy. The authors are scientists from the areas of climate research, economics, political science, engineering, environmental psychology and jurisprudence who have dedicated their work to issues that directly or indirectly relate to the expansion of renewable energies. Together they have created an overall picture of renewable energies with its many different aspects and related topics, a picture that necessarily cannot be complete but which nevertheless provides many rich insights. The great majority of articles were written around the turn of the year to 2011, just after the granting of lifetime extension for German nuclear power plants. They thus only take sparse account of the diverse and for some part far-reaching changes in German energy policy that came about after the reactor disaster in Fukushima.

  2. Efficient use of energy: investment practice in industry; Effiziente Energienutzung: Investitionspraxis in der Industrie

    Energy Technology Data Exchange (ETDEWEB)

    Kuster, J. [BHP - Brugger, Hanser und Partner AG, Zuerich (Switzerland); Zweiacker, J.-F. [Rapp AG Ingenieure und Planer, Biel (Switzerland); Rosch, M. [Consulting Verfahrenstechnik, Allschwil (Switzerland)

    2000-07-01

    This report for the Swiss Federal Office of Energy (SFOE) presents the results of a study made on drying processes used in industry and possible ways of promoting investment in measures to increase the efficient use of energy. The energy consumption of dehydration and drying processes used in industry is examined and the savings potential for these processes estimated. Examples of the processes investigated are given and figures for the energy consumption for dehydration and drying processes in several different industrial sectors are quoted. The report then examines, on the one hand, the factors that hem innovations in this area and, on the other, those that promote them. Further, the report looks into which reasons are responsible for the realisation or non-realisation of technically and economically viable solutions for improving the energy-efficiency of the dehydration and drying processes.

  3. Energy consumption of mobile communication systems; Energieverbrauch der mobilen Kommunikation - Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Corliano, A.; Hufschmid, M.

    2008-02-15

    This final report for the Swiss Federal Office of Energy (SFOE) reports on a research project that was concerned with the energy consumption of the infrastructure necessary to provide mobile communication services. The measurement and analysis of the energy consumption of the infrastructure was an essential part of this research project. Furthermore, future scenarios and their impact on energy consumption are discussed. The results of the research work are presented and the correlation between power requirements and the data traffic encountered at GSM and UMTS base stations is analysed. Furthermore, measurements that were conducted to determine the power consumption of different network elements are discussed. Finally, alternatives for further action and recommendations for improvements in the energy consumption of such installations are formulated.

  4. German Bundestag: New enquiry commission. ''Sustainable energy supply in times of globalisation and deregulation''; Deutscher Bundestag: neue Enquete-Kommission. Ziel: ''Nachhaltige Energieversorgung unter den Bedingungen der Globalisierung und der Liberalisierung''

    Energy Technology Data Exchange (ETDEWEB)

    Schafhausen, F. [Bundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Berlin (Germany)

    2000-08-01

    The new enquiry commission was authorized by the German Bundestag on 24 March 2000. It consists of 13 parliament members and 13 scientists and will investigate the issue of sustainable energy supply. The German Bundestag thus takes account of the current discussion on the characteristics and details of sustainable energy supply. [German] Am 24. Maerz 2000 setzte der Deutsche Bundestag eine neue Euquete-Kommission ein. Diese besteht aus 13 Mitgliedern des Parlaments und 13 Wissenschaftlern und soll sich dem Thema 'Nachhaltige Energieversorgung' widmen. Damit zog der Deutsche Bundestag die Konsequenz aus der mittlerweile stattfindenden Diskussion ueber die Kennzeichen und Ausgestaltung einer 'nachhaltigen Energieversorgung'. (orig.)

  5. Enhanced energy efficiency in waste water treatment plants; Steigerung der Energieeffizienz auf kommunalen Klaeranlagen

    Energy Technology Data Exchange (ETDEWEB)

    Haberkern, Bernd; Maier, Werner; Schneider, Ursula [iat - Ingenieurberatung fuer Abwassertechnik, Darmstadt und Stuttgart, Darmstadt (Germany)

    2008-03-15

    In order to implement the requests of EU-IPCC-directive in a new decree for waste water treatment in Germany, best available techniques have to be defined to optimize energy efficiency in waste water treatment plants (WWTP). Therefore energy efficiency was investigated for common treatment processes and new technologies like membrane filtration, co-digestion or phosphorus recycling. In addition, the occurrence of different technologies for waste water and sludge treatment was evaluated for different size ranges of treatment plants (in population equivalents, PE) nationwide in Germany. The definition of actual and aimed values for specific energy consumption (in kWh/(PE.a)) allowed to calculate the potential energy savings in WWTP and the additional consumption due to new processes on a national level. Under consideration of the reciprocations between optimized energy consumption in WWTP and operation practice, toe-holds to increase energy efficiency according to their relevancy for the national balance could be listed. Case studies prove the feasibility of the investigated techniques and allow proposals for minimum requirements in legal regulation concerning energy efficiency in WWTP. (orig.)

  6. Energy efficiency improvements in sewage sludge processing plants; Energetische Optimierung der Klaerschlammaufbereitung

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, H.; Burger, S.

    2006-07-01

    From October 1st, 2006, sewage sludge may no longer be used as a fertilizer by farmers in Switzerland. Mechanical dewatering and drying of the sludge are the pre-stages of incineration. Based on a monitoring campaign and the results thereof, recommendations aiming at improving the energy efficiency have been worked out for use by waste water treatment plant operators and engineers for the design of drying plants. From the energetic point of view, solar drying of sludge is the best process. However, due to the large area required and the limited drying capacity, solar drying cannot be implemented everywhere. Therefore, three further drying processes have been monitored for eleven months: the fluidized bed drying process at the waste water treatment plant (WWTP) of the Region Berne, the low temperature/air recirculation dryer at WWTP Schwyz and the middle-temperature belt dryer at WWTP Wohlen. The electric energy consumption of the three investigated sludge drying processes was between 22 and 94 kWh per ton of evaporated water. The low temperature dryer showed the lowest energy consumption. The thermal energy consumption (expressed in useful energy) was between 648 and 1'033 kWh per ton of evaporated water, with the middle temperature dryer having the lowest consumption. On the other hand, the most advantageous process is the low temperature dryer if the comparison is based on the final energy consumption. This process has the advantage of making possible the integration of low-temperature waste heat. For whole Switzerland, the energy savings potential is estimated to be 133 GWh/year for fuel and 32 GWh/year for electricity, provided the drying process with the lowest energy consumption is implemented. It is recommended to conduct another measuring campaign at the first just commissioned sludge drying plant comprising a heat pump using waste water as a heat source, to check the effective energy savings. (author)

  7. Energy saving in houses. Seminar of Zentrale Informationsstelle Umweltberatung Bayern, Vol. 19; Energiesparen rund ums Haus. Seminarband der Zentralen Informationsstelle Umweltberatung Bayern. Bd. 19

    Energy Technology Data Exchange (ETDEWEB)

    Stroh, K.; Behling, G; Koller, U.; Lattner, A. (eds.)

    2002-02-01

    Contents: Information on energy conservation and state funds, Energy management at communal level, eco-balance of power generation; The new Energy Conservation Ordinance; Energy conservation in domestic buildings; Low-consumption power supply systems; Potential savings resulting from consumption patterns; Eco-balances and preventive cost. [German] Referenten aus wissenschaftlichen und behoerdlichen Institutionen informierten ueber aktuelle Erkenntnisse zum Energiesparen in oeffentlichen und privaten Gebaeuden. Dabei wurden folgende Themen behandelt: - Informationen ueber Energiesparen und Foerderprogramme - Energiemanagement fuer Kommunen, Oekobilanz der Stromerzeugung - Die neue Energieeinsparverordnung - Energiesparen in Wohngebaeuden - Sparsame Energieversorgungssysteme - Verhaltensbedingte Einsparpotenziale - Oekobilanzen und Vermeidungskosten. (orig.)

  8. Energy-efficiency in inductive heating of forging ingots; Energieeffizienz bei der induktiven Erwaermung von Schmiedebloecken

    Energy Technology Data Exchange (ETDEWEB)

    Padberg, Michael; Doetsch, Erwin [ABP Induction Systems, Dortmund (Germany)

    2012-03-15

    The continuously increasing importance of the CO{sub 2} balance and of conservation of resources is resulting in ever greater demands for high energy-efficiency in the process used for heating of forging ingots. Plant and process engineering play roles of parallel significance in the fulfillment of these requirements, and this article focuses on both in equal degree. The shares of the individual components in the overall energy consumption of an induction heating installation are therefore firstly determined, and their respective potentials for optimization then discussed. The quality of the heating process itself, and its optimum design for reduction of energy consumption, are then examined. (orig.)

  9. Adapting the energy economy to the climate; Klimaanpassung in der Energiewirtschaft

    Energy Technology Data Exchange (ETDEWEB)

    Leyens, Dirk [EnBW Regional AG, Biberach (Germany); Engelhard, Peter [RWE AG, Essen (Germany). Energiepolitik; Reck, Hartmut [EnBW Regional AG, Biberach (Germany). RZ Oberschwaben

    2012-09-15

    The great societal and economic significance of a reliably functioning energy infrastructure makes it necessary to give careful thought to the expected influences of the climate change on the energy supply. It will in particular be important to do justice to the technical, business management and political necessities and to take adaptive measures in the various fields in which energy suppliers do business. This article relates the present state of knowledge on influences emanating from the climate change, expanding the scope of its deliberations to include experiences from regional projects. It also points out the dimensions of a climate change resilient electricity supply from the viewpoints of market economy and Europe.

  10. Historisierung der Energiefrage

    DEFF Research Database (Denmark)

    Czeskleba-Dupont, Rolf

    2014-01-01

    Anmeldelse af prof.em.Bent Sørensens bog, der præsenterer energiregnskaber fra Neanderthalerne til vor tid inden for det geografiske område, som Danmark dækker/har dækket. Bidrag til et kommende fag energi-historie.......Anmeldelse af prof.em.Bent Sørensens bog, der præsenterer energiregnskaber fra Neanderthalerne til vor tid inden for det geografiske område, som Danmark dækker/har dækket. Bidrag til et kommende fag energi-historie....

  11. Energy-optimised mini-refrigerators; Energieoptimierter Minikuehlschrank. Massnahmen zur Optimierung der Energieeffizienz von Minikuehlschraenken

    Energy Technology Data Exchange (ETDEWEB)

    Burri, A.

    2007-10-15

    This illustrated final report for the Swiss Federal Office of Energy (SFOE) takes a look at measures to be taken to optimise the energy-efficiency of small refrigerators. Such devices are typically to be found in hotel rooms and on boats as well as in caravans and motor homes. The majority of these mini-refrigerators use the absorption principle for cooling. Although less efficient than their compressor-driven counterparts, absorption refrigerators satisfy market requirements and customer wishes with regard to noiseless and maintenance-free operation. The report discusses how optimisation of the absorption principle could lead to energy savings in the long term. The operating principles and energy balances of such refrigerators are discussed and a market overview is presented. Energy consumption of the refrigerators, possible savings and energy costs are discussed. The advantages and disadvantages of various cooling systems are examined as are further possibilities for making savings such as the optimisation of sizing, installation methods, airflow factors and operating temperatures.

  12. A new energy policy for the European Union?; Eine neue Energiepolitik fuer die Europaeische Union? Das Weissbuch der EU-Kommission zur Energiepolitik

    Energy Technology Data Exchange (ETDEWEB)

    Loo, K. van de [Abt. Wirtschaftspolitik und Europa-Angelegenheiten, Gesamtverband des Deutschen Steinkohlenbergbaus, Essen (Germany)

    1996-04-11

    At the turn of the year 1995/96 the European Commission has presented a `White Paper` on EU enenrgy policy. The White Paper formulates general guidelines for the future energy policy in the EU, the annex includes an `indicative work programme` of the Commission. The energy-economic trend forecasts cover the period until 2020. Fundamentally new political orientations are not discernible. The White Paper counts on the completion of the internal energy market and an `overall balance of fuels`. The objectives of competitiveness and environmental protection are to be balanced out, the EU`s import dependence increasing up to 75% is to be a `point of concern`. The concrete statements on security of supply are, however, unsatisfactory. Several issues of particular significance for the coal producers are to be dealt with only in subsequent individual reports. In terms of immediate energy policy actions, the Commission intends to set up a programme to monitor energy trends, establish an Energy Consultative Committee and organize a regular cooperation between Member States on agreed energy objectives. The Commission also complains about the lacking coherence and gaps in the basic Treaty provisions for the EU energy policy but leaves open in which form it intends to change the energy responsibilities. This will have to be discussed in the intergovernmental conference on the revision of the Maastricht Union Treaty. (orig.) [Deutsch] Die Europaeische Kommission hat ein `Weissbuch` zur kuenftigen EU-Energiepolitik vorgelegt. Es formuliert allgemeine Leitlinien bis 2020. Neue energiepolitische Weichenstellungen sind nicht zu erkennen. Das Weissbuch setzt auf Vollendung des Energiebinnenmarkts und ein `globales Gleichgewicht der Energietraeger`. Die Ziele Wettbewerbsfaehigkeit und Umweltschutz sollen miteinander abgewogen werden, die auf bis zu 75% ansteigende Importabhaengigkeit der EU muesse ein `Brennpunkt der Sorge` sein. Die konkreten Aussagen zum Thema Versorgungssicherheit

  13. Control of Greenhouse Gas Emissions by Optimal DER Technology Investment and Energy Management in Zero-Net-Energy Buildings

    International Nuclear Information System (INIS)

    Stadler, Michael; Siddiqui, Afzal; Marnay, Chris; Aki, Hirohisa; Lai, Judy

    2009-01-01

    The U.S. Department of Energy has launched the commercial building initiative (CBI) in pursuit of its research goal of achieving zero-net-energy commercial buildings (ZNEB), i.e. ones that produce as much energy as they use. Its objective is to make these buildings marketable by 2025 such that they minimize their energy use through cutting-edge, energy-efficiency technologies and meet their remaining energy needs through on-site renewable energy generation. This paper examines how such buildings may be implemented within the context of a cost- or CO2-minimizing microgrid that is able to adopt and operate various technologies: photovoltaic modules (PV) and other on-site generation, heat exchangers, solar thermal collectors, absorption chillers, and passive/demand-response technologies. A mixed-integer linear program (MILP) that has a multi-criteria objective function is used. The objective is minimization of a weighted average of the building's annual energy costs and CO2 emissions. The MILP's constraints ensure energy balance and capacity limits. In addition, constraining the building's energy consumed to equal its energy exports enables us to explore how energy sales and demand-response measures may enable compliance with the ZNEB objective. Using a commercial test site in northernCalifornia with existing tariff rates and technology data, we find that a ZNEB requires ample PV capacity installed to ensure electricity sales during the day. This is complemented by investment in energy-efficient combined heat and power (CHP) equipment, while occasional demand response shaves energy consumption. A large amount of storage is also adopted, which may be impractical. Nevertheless, it shows the nature of the solutions and costs necessary to achieve a ZNEB. Additionally, the ZNEB approach does not necessary lead to zero-carbon (ZC) buildings as is frequently argued. We also show a multi-objective frontier for the CA example, whichallows us to estimate the needed technologies

  14. Use of geothermal energy in the region of Basel at the south-eastern end of the Rheingraben; Die Nutzung der Erdwaerme in der Region Basel am Suedostende des Rheingrabens

    Energy Technology Data Exchange (ETDEWEB)

    Hauber, L.

    1997-12-01

    The idea of using geothermal energy in the Basel region came up during the years 1973-1980, due to the shortages in oil and gas supply. Independency of foreign suppliers, diversification and renewable energies have been demanded. Geothermal energy was one of the possibilities discussed in those years. Today, geothermal energy is also and mainly seen as a environmental clean energy without output of CO{sub 2} and other gases. For these reasons, and because it is well known that the Rheingraben has a good geothermal gradient, the two Cantons of Basel-Stadt and Basel-Land made efforts to develop the use of this energy. The Canton Basel-Stadt together with the Community of Riehen decided to test these possibilities with two wells (1988-1990). The well Riehen 1 (depth 1`547 m) showed in the Upper Muschelkalk a pumping rate of 20,5 l/s with a temperature of 66,4 C and Riehen 2 (depth 1`247 m) made 22 l/s with 52,2 C. The salinity of the water was 17 g/l (Riehen 1) and 14 g/l (Riehen 2), mainly NaCl and CaSO{sub 4}, together with CO{sub 2}. Due to the high salinity, well Riehen 2 is used as a production well, Riehen 2 as a rejection well. Riehen decided to construct a distant heating system and therefore it was possible to add the geothermal energy into this system, avoiding the consumption of 1750 t oil per year (=50%). The power of the whole heating system is 15`200 kW. Production started in April 1994. (orig.) [Deutsch] In den vergangenen Jahren sind in der Region Basel 3 Geothermiebohrungen zur Nutzung der Erdwaerme abgetieft worden: Riehen 1: 1`547 m tief T=66,4 C Salinitaet=17`031,9 mg/l Gradient=4,05 C/100 m Riehen 2: 1`247 m tief T=52,2 C Salinitaet 14`162,7 mg/l Gradient=3,65 C/100 m Reinach 1: 1`793 m tief T=78,0 C Salinitaet=43`896 mg/l Gradient=3,75 C/100 m Riehen 1 und 2 erwiesen sich von der Ergiebigkeit (>20 l/s) her als interesant, waehrend Reinach 1 als Misserfolg bezeichnet werden muss, da keine nutzbare Menge gefoerdert werden konnte und auch die

  15. Ion assisted deposition with low-energy ions for applications in modern optics; Ionengestuetzte Beschichtungen mit niederenergetischen Ionen fuer Anwendungen in der modernen Optik

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, M.

    1999-07-01

    Main objective of this work is the development of ion assisted deposition processes without additional substrate heating for applications in precision and laser optics. New low-energy ion sources with ion energies below 100 eV were employed for the research work. Starting point of the process development are basic investigations on the ion assisted evaporation of fluoride and oxide thin film materials. The optimisation of the coating processes is primary done with the help of optical characterisation methods (spectral photometry, laser calorimetry, measurement of the total scattering). For the fluoride materials it has been possible to minimise the preferential sputtering effects, which are combined with absorptive losses caused by stoichiometric degradation, using low-energy xenon ions. The properties of ion assisted oxide films can be scaled with the deposited ion energy per condensing thin film molecule. The refraction index and the packing density increase with this energy, simultaneously the absorption of the thin film is reduced and the absorption edge comes close to the corresponding bulk value. Compared to conventionally deposited films the packing density is increased and the absorption, the water content and the scattering is reduced. The extinction coefficients at a wavelength of 532 nm lie below 5.10{sup -5}. The results of the investigations on single films are employed for the production of wideband antireflective coatings. Coatings on PMMA can be realised by a process adaptation with UV-absorbing films. A further focal point are antireflective coatings on alkali halides optics for high-power CO{sub 2}-lasers. Ion assisted deposition of NaF-films at extremely low ion energies (E{sub ion}{approx}5 eV) qualifies antireflective coatings with minimal absorption ({alpha}{approx}1.5 cm{sup -1}), high short-pulse damage threshold (50%-LIDT{approx}60J/cm{sup 2}) and improved degradational stability. [German] Hauptzielsetzung dieser Arbeit ist die Entwicklung

  16. Developments in energy policy. Impact on hydro power; Entwicklungen in der Energiepolitik. Auswirkungen auf die Wasserkraft

    Energy Technology Data Exchange (ETDEWEB)

    Buenting, Hans [RWE Innogy GmbH, Essen (Germany)

    2012-07-01

    In the summer 2011 the German Government launched the so-called ''Energiewende'', which determines for the first time a long-term road map for the conversion of the German energy landscape until2050. The shape of the German electricity market will change drastically due to an increasing focus on energy efficiency, ongoing support for renewable generation capacity and increasing electricity imports. Hydro power generation plays a minor role in these scenarios and is restricted mainly to additional capacity of pump storage power plants in Germany and adjacent countries. The role of these pump storages is to provide balancing energy to manage the increasing volatile generation from wind and solar power. (orig.)

  17. Efficiency improvement of flue gas cleaning plants. Use of adipic acid in lignite-fired power plant Frimmersdorf of RWE Energie AG; Wirkungsgradverbesserung von Rauchgasreinigungsanlagen. Einsatz von Adipinsaeure im Braunkohlenkraftwerk Frimmersdorf der RWE Energie AG

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, W.; Krug, M.; Schuetz, M. [RWE Power AG, Regenerative Stromerzeugung, Essen (Germany)

    2001-07-01

    The further improvement of desulphurization plants is an important task not only with a view to procedure technology but also economically. The aim of the optimization is mainly the adaptation of FGD plants to changing lignite qualities, the safe adherence to the required gypsum qualities and the reduction of the energy requirement (operating costs). Findings were compiled from many studies that, among others, concern the effects of adipic acid addition on the adsorbent, the retention behaviour and the gypsum produced. On the basis of this experience, the use of adipic acid was also tested in the FGD facilities of the Frimmersdorf power plant. (orig.) [German] In den Rauchgasentschwefelungsanlagen des Braunkohlenkraftwerks Frimmersdorf, die nach dem Kalkstein-Nasswaschverfahren arbeiten, wurden in den Jahren 1998/99 zur Erhoehung des SO{sub 2}-Abscheidegrades der Einsatz von 300 ppm Adipinsaeure in der Waschsuspension erprobt. Hierdurch soll die normalerweise zur Erhoehung der Abscheideleistung benoetigte Energie fuer die Zuschaltung weiterer Absorberkreislaufpumpen teilweise eingespart werden. Die Auswertung der Ergebnisse des Versuchsbetriebes hat gezeigt, dass in Abhaengigkeit vom SO{sub 2}-Rohgasgehalt eine Verbesserung der SO{sub 2}-Abscheidung um bis zu 6%-Punkte erreicht werden kann. (orig.)

  18. Directory of German wind energy 1998; 3. rev. ed.; Adressbuch der Windenergie 1998

    Energy Technology Data Exchange (ETDEWEB)

    Strunk-Stueckemann, C. [ed.

    1998-06-01

    The 3rd edition of the DEWI German Directory of Wind Energy comprises information on the following topics: (a) Manufacturers and suppliers of wind energy converters and components; measuring equipment; (b) Public and commercial research organisations; (c) Engineering offices and consultants; (d) Banks and insurance companies; (e) Investment and operators companies; (f) Electric supply utilities; (g) Services; (h) Public relations and education; (i) Subject index in German and English. (AKF) [Deutsch] Die dritte Auflage des DEWI-Adressbuches 1998 beinhaltet Angaben zu den folgenden Themen: (a) Hersteller/Lieferer von: Windkraftanlagen und Komponenten; Messtechnik; (b) Oeffentliche und gewerbliche Forschung; (c) Enginieurbueros/Beratung; (d) Banken und Versicherungen; (e) Beteiligungs- und Betreibergesellschaften; (f) Energieversorgungsunternehmen; (g) Dienstleistungen; (h) Oeffentlichkeitsarbeit und Aus- und Weiterbildung; (i) Register (deutsch-englich). (AKF)

  19. Energy-efficient electrical drives in the education of professionals; Energieeffiziente elektrische Antriebe in der Ausbildung

    Energy Technology Data Exchange (ETDEWEB)

    Bachmann, R.

    2007-03-15

    This final report for the Swiss Federal Office of Energy (SFOE) discusses how the electricity consumption of drive systems can be reduced. Such electrical drive systems are responsible for approximately 45% of Switzerland's electricity consumption. The paper discusses how this amount could be reduced by 10-20% by employing more energy-efficient drive systems. The authors are of the opinion that, in future, this fact should be taken into account by professors and teachers in their courses at all levels of education for technicians and electrical engineers. The results of a survey made on the present situation are discussed. Teaching modules that are to help facilitate the integration of this subject in the educational curricula at various levels are looked at. The report is completed with a comprehensive appendix on teaching modules, documentation and check-lists from the University of Applied Sciences of North-western Switzerland.

  20. Free energy evaluation in polymer translocation via Jarzynski equality

    Energy Technology Data Exchange (ETDEWEB)

    Mondaini, Felipe, E-mail: fmondaini@if.ufrj.br [Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Petrópolis, 25.620-003, RJ (Brazil); Moriconi, L., E-mail: moriconi@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, C.P. 68528, 21945-970, Rio de Janeiro, RJ (Brazil)

    2014-05-01

    We perform, with the help of cloud computing resources, extensive Langevin simulations, which provide free energy estimates for unbiased three-dimensional polymer translocation. We employ the Jarzynski equality in its rigorous setting, to compute the variation of the free energy in single monomer translocation events. In our three-dimensional Langevin simulations, the excluded-volume and van der Waals interactions between beads (monomers and membrane atoms) are modeled through a repulsive Lennard-Jones (LJ) potential and consecutive monomers are subject to the Finite-Extension Nonlinear Elastic (FENE) potential. Analysing data for polymers with different lengths, the free energy profile is noted to have interesting finite-size scaling properties.

  1. Gestalttheorie in der Psychotherapie

    OpenAIRE

    Kästl, Rainer; Stemberger, Gerhard

    2005-01-01

    Der vorliegende Beitrag gliedert sich in zwei Abschnitte. Der erste stellt eine Spurensuche zur Geschichte der Anwendung der Gestalttheorie auf das psychotherapeutische Arbeitsfeld ohne Anspruch auf Vollständigkeit dar. Im zweiten Abschnitt werden einige metatheoretische Grundkonzepte der Gestalttheoretischen Psychotherapie vorgestellt, einem von H.-J. P. Walter begründeten, auf der Gestalttheorie der Berliner Schule aufbauenden psychotherapeutischen Ansatz, der während der letzten 30 Jahre i...

  2. Renewable energies in the EU's current energy policy; Erneuerbare Energien in der aktuellen EU-Energiepolitik

    Energy Technology Data Exchange (ETDEWEB)

    Boerner, Achim-Ruediger

    2011-10-15

    The EU's energy policy is under constant observation. This also holds for its policy on renewables, where it is under an obligation to create a legal framework for a well-coordinated expansion and restructuring of the energy supply system in a manner that ensures more sustainability and environmental protection while at the same time safeguarding security of supply and economic efficiency and also fending off threats to the liberalisation of the energy market. But how successful is the present regime in actual fact? This is put to a systematic, critical analysis in the following.

  3. Activities in the energy sectors of central and eastern European countries in preparation for their accession to the European Union; Stand der energiewirtschaftlichen EU-Beitrittsvorbereitungen in Mittel-Osteuropa

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, H.; Kraemer, J. [TETRA ENERGIETECHNOLOGIE TRANSFER GmbH, Berlin (Germany); Riesner, W. [Hochschule fuer Technik, Wirtschaft und Sozialwesen Zittau/Goerlitz (Germany)

    2002-08-01

    The energy sector and the liberalised energy markets play a key role in negotiations for accession between the authorities of the European Union and the candidate counties. The article reviews the current status of activities and achievements of Hungary, the Czech Republic and Slovakia. (orig./CB) [German] Die Energiewirtschaft nimmt beim EU-Beitritt eine Schluesselrolle ein. Stand der Vorbereitungen der Kandidatenlaender Ungarn, Slowakische Republik und Tschechische Republik im Energiesektor (orig./CB)

  4. Wood production for energy purposes in the agriculture. 4. rev. ed.; Energieholzproduktion in der Landwirtschaft

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Martin [Kompetenzzentrum HessenRohstoffe (HeRo) e.V., Witzenhausen (Germany)

    2010-07-01

    The cultivation of fast growing tree species such as poplars or willows in short harvesting periods is an extensive form of land use which increasingly is interesting with respect to the climate protection and development of the prices for fossil energy sources. Cultivation concepts have to be oriented towards the existing agrarian structure and the possible lines of utilization. This requires an answer of the following questions: (a) What has to be considered with the cultivation?; (b) Which tree species are recommended?; (c) Which procedures of harvesting do exist?; (d) How does economy present itself? The contribution under consideration tries to give answers to these questions. The contribution summarizes the actual state of knowledge from research and first practical cultivations. The contribution under consideration also dedicates itself to the practical farmer.

  5. Frost protection for wind energy installations; Frostschutz fuer Windenergieanlagen. Eisfreie Oberflaechen der Natur abgeschaut

    Energy Technology Data Exchange (ETDEWEB)

    Siegmann, K.; Meola, G.; Hirayama, M.

    2009-07-01

    This article discusses how naidered intural materials can be used to prevent wind energy installations in exposed alpine locations from icing up. The problems encountered with wind turbines in Scandinavia and in the Swiss Alps due to icing-up are discussed. The mechanisms involved in the formation of hoar frost and clear ice on the rotors of the wind turbines are discussed. Techniques and materials for fighting the icing-up of the rotors are examined. Various special 'ice-phobic' coatings for the rotor blades are listed and discussed. These must adhere to the rotor blades but be repellent to ice. Teflon is quoted as being the most tested material. So-called 'anti-freeze' proteins that can be found in fish and insects are also being examined as a possible coating for the rotors.

  6. DER 83: outstanding events

    International Nuclear Information System (INIS)

    1984-01-01

    The DER's activity is presented through 82 ''outstanding events''. Each one is a stage in the effort of research and development of the DER. These events concern the following fields: new applications of electric power for customers; environment protection and new energy sources; improvements of electric power production units; electrical materials; electric network planning and control; computer codes. In the production field, one deals more particularly with nuclear reactor safety studies: analysis of the behaviour of different components; reactor safety experiments; reliability of different systems (safety, communications...) [fr

  7. Artificial intelligence for enhancing energy efficiency. Fundamentals, instruments, practice; Kuenstliche Intelligenz zur Steigerung der Energie-Effizienz. Grundlagen, Instrumente, Praxis

    Energy Technology Data Exchange (ETDEWEB)

    Brammer, R.

    2006-07-01

    In a time of rising energy prices and a growing field for information technology, its worth to take a glance of how to combine the two fields of energy efficiency and artificial intelligence. Aim of this combination is to support human beings in their energy consuming habits and to adjust the usage to the individual requirement. An artificial intelligence today is able to mine data, plan actions and make decisions on a rational basis. Thus an intelligent agent can help to lower energy wastage by controlling and regulating a heating system. For this application only few sensors and a control for the heating power are sufficient to support the artificial intelligence with enough information about its environment and enough actuators to manipulate it. On the basis of the collected information the software is able to deduce knowledge, which in turn is stored in a database for later access. This knowledge is used to take in states, which consume less heating power by still keeping the temperature on the same level. Because the acceptance by the user, next to saving energy, is the prime target of the artificial intelligence, its success is measured on how little intervention by humans occur. With the help of probability and benefit based algorithms, several training runs before the applied operation and given performance standard the software is able to reduce calculating times to practicables times. Considering the application possibilities given in this thesis, it is feasible to devolve the use of artificial intelligence and its ability to save energy for many different process controls. (orig.)

  8. Fuel cells for stationary energy supply; Brennstoffzellen in der stationaeren Energieversorgung

    Energy Technology Data Exchange (ETDEWEB)

    Leprich, Uwe; Thiele, Andreas [Institut fuer ZukunftsEnergieSysteme (IZES), Saarbruecken (Germany)

    2005-06-15

    Starting point for this investigation was the question, whether the incentives, caused by the CHP law from March the 19th 2002, are short- and medium term adequate to introduce fuel cells as small CHP plants broadly on the market or rather develop them at least to a standard of market maturity. This has - based on our analysis - definitely to be answered in the negative: for this, the fixed bonus is too small to influence the costs for investment and running of a fuel cell plant lasting. One of the aims of the CHP law - the reduction of the yearly CO2-emissions in Germany by a broader introduction of the technology on the market - can actually not be reached. Although, fuel cells may obtain a quite important climate-political significance, if their economical availability will be secured and related basic conditions are set today. By the CHP law, the federal government however demonstrated publicly that it is willing to support the development of the fuel cell and its introduction on the market. This signal is not only supporting the industry to align its middle- and long term decisions but it is also helping users and operators of fuel cells by providing a legal security about the guarantee for grid connection and remuneration Based on the perspectives for an establishing of small CHP plants including fuel cells, the range of possible stimulating and supporting measures was investigated in a second step. While doing so, it was differentiated between a flanking of the existing CHP law, its further development and other alternative measures. By this, there are several starting points to realize changes or rather adaptations in the CHP law. According to this investigation and in the interest of an increased spreading of small CHP- and fuel cell plants, these possibilities should be made use of as fast as possible. The investigation was terminated by examinating selected technical, energy-economical as well as energy political chances and requirements for hydrogen

  9. Der Heilige Geist und die Realisierung des Glaubens in der ...

    African Journals Online (AJOL)

    29. Juli 2016 ... Erörtert wird der Gottesgeist in der Trinitätslehre, der Lehre von der Heilszueignung. (Soteriologie) und der von der Ekklesiologie, aber auch in der Schriftlehre sowie der Eschatologie und der Lehre von der Schöpfung. Als eine eigenständige dogmatische Lehre ist die. Pneumatologie nicht ausgearbeitet ...

  10. Cogeneration and the regulatory framework of energy law; Kraft-Waerme-Kopplung und der energiewirtschaftliche Ordnungsrahmen

    Energy Technology Data Exchange (ETDEWEB)

    Cornehl, Angelika Bettina

    2009-06-15

    The present publication shows that the existing regulatory framework poses numerous impediments to cogeneration plants. This holds especially for industrial operators, but also for municipalities. It has prevented cogeneration from developing its full potential both as an element of competition and as a relief for the environment. Unlike industrial cogeneration plants, those serving the public energy supply at least enjoy the privilege of regional monopoly rights. In today's liberalised electricity market, however, this can be a burden for existing municipal plants which were installed under territorial protection and in many cases have incurred high cost levels and become inflexible and lacking in entrepreneurial spirit as a result. On account of its tendency to promote optimal resource input and efficiency, competition promises positive impulses for the use of cogeneration in small-scale heat grids, where high fuel efficiency matters more. A reform of the competition regime in the power economy would eliminate numerous impediments, particularly for industrial cogeneration operators. Good hopes for the future of cogeneration in a liberalised electricity and gas market are also nurtured by cooperative supply concepts and, within the large domain of services, opportunities held out by special contracting offers.

  11. Gesellschaftlicher Wandel und der Umbau der Jugendhilfe

    OpenAIRE

    Plankensteiner, Annette

    2013-01-01

    Gesellschaftlicher Wandel und der Umbau der Jugendhilfe. - In: Flexible Erziehungshilfen : Grundlagen und Praxis des "Augsburger Weges" zur Modernisierung der Jugendhilfe / Annette Plankensteiner ... (Hrsg.). - Weinheim u.a. : Beltz Juventa, 2013. - S. 14-32

  12. Raw materials for the energy supply of the future. Geology, markets, environmental influences; Rohstoffe fuer die Energieversorgung der Zukunft. Geologie, Maerkte, Umwelteinfluesse

    Energy Technology Data Exchange (ETDEWEB)

    Hagelueken, Christian [Umicore, Hanau-Wolfgang (Germany); Thauer, Rudolf K. [Max-Planck-Institut fuer Terrestrische Mikrobiologie, Marburg (Germany); Buchholz, Peter [Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany). Deutsche Rohstoffagentur; Herzig, Peter [GEOMAR Helmholtz-Zentrum fuer Ozeanforschung Kiel (Germany); Gutzmer, Jens [Technische Univ. Bergakademie Freiberg (Germany); Helmholtz-Institut Freiberg fuer Ressourcentechnologie (Germany); Littke, Ralf [Rheinisch-Westfaelische Technische Hochschule (RWTH), Aachen (Germany); Angerer, Gerhard; Wellmer, Friedrich-Wilhelm

    2015-11-15

    More and more metals are needed to expand modern energy technologies, but we can not completely dispense with fossil raw materials and biomass in the near future either. Are the incidence of the conversion of energy sources sufficient? The analysis of the academy project ''Energy Systems of the Future'' (ESYS) comes to the conclusion that geologically enough raw materials are available. The challenge, however, is to make the supply safe, affordable and environmentally and socially compatible. The analysis explains the mechanisms of action on the global commodity markets and identifies supply risks. These include, for example, sudden demand on the international markets as well as the unequal distribution of the world's raw material reserves. This is followed by the analysis approaches, in order to recognize warning signals for potential raw material bottlenecks in time, to develop evasive strategies and to secure the raw material supply for the energy turnarounds. For example, the expansion of recycling can help to reduce the dependence on metal imports. In mining, on the other hand, innovative technologies have to be developed in order to improve the exploration and utilization of the deposits. By establishing binding environmental and social standards, the extraction of raw materials could also become more sustainable. The analysis also highlights the importance of bioenergy and fossil raw materials, such as oil and natural gas, for energy generation. The authors describe the advantages and disadvantages of these energy carriers and the measures that can be used to reduce environmental pollution such as greenhouse gas emissions. [German] Fuer den Ausbau moderner Energietechnologien werden immer mehr Metalle benoetigt, doch auch auf fossile Rohstoffe und Biomasse koennen wir in naher Zukunft nicht vollstaendig verzichten. Reichen die Vorkommen zur Umsetzung der Energiewende aus? Die Analyse des Akademienprojekts &apos

  13. Considering wind energy in regional planning guidelines and communal land-use planning; Die Beruecksichtigung der Windenergie in der Richt- und Nutzungsplanung

    Energy Technology Data Exchange (ETDEWEB)

    Soguel, R. [Atelier North and Robyr, Neuchatel (Switzerland); Henz, H.R. [Metron Raumplanung AG, Brugg (Switzerland)

    2001-07-01

    This report made for the Swiss Federal Office of Energy (SFOE) discusses the situation in Switzerland regarding the planning guidelines required at regional and communal level that are required for the granting of permission to build wind energy installations. Various types of wind turbines and wind farms are described and topics such as planning tools, landscape protection and promotional concepts are discussed. The role of the Swiss Cantons in the promotion of wind energy is examined and the question of how to integrate wind energy plant into cantonal and communal planning guidelines is looked at. This working guide introduces two schemes that demonstrate how the planning process for the construction of wind farms can be co-ordinated with the development of land-use plans. Examples of current cantonal guidelines are presented in the appendix to the report.

  14. powerado-plus. Promotion of education, instruction and training for renewable energy sources; powerado-plus. Foerderung der Bildung, der Aus- und Weiterbildung fuer erneuerbare Energien

    Energy Technology Data Exchange (ETDEWEB)

    Scharp, Michael (ed.)

    2012-05-15

    The research project 'World of Renewables: powerado' explores the effective communication to promote renewable energies in children, adolescents, teachers and multipliers. In several modules, materials and training approaches for different age groups and audiences are developed. Fundamental studies are carried out. Based on these fundamental studies, successful communication strategies of renewable energy are performed. The contribution under consideration reports on the main findings from the period 2009 to 2012.

  15. Models of a zero-sum energy price increase and their economic effects. Pt. 1. Models of energy taxation and compensation; Modelle einer aufkommensneutralen Energiepreiserhoehung und ihre wirtschaftlichen Auswirkungen T. 1. Modelle der Energiebesteuerung und Kompensation

    Energy Technology Data Exchange (ETDEWEB)

    Kohlhaas, M. [Deutsches Inst. fuer Wirtschaftsforschung, Berlin (Germany); Welsch, H. [Energiewirtschaftliches Inst. an der Univ. zu Koeln (Germany)

    1995-03-01

    This two-part article makes various proposals for an energy taxation and describes and discusses already published analyses of the effects of such measures. The first part begins with a review of principal alternatives of energy taxation and its compensation. Working from this basis it assesses the theoretical properties of the concrete models proposed. The second part contains a systematic presentation of analyses of the economic effects of the proposed models and examines where the results of these analyses are in agreement and where they disagree. It then endeavours to point out the weak and strong points of the empirical methods applied and attempts an interpretation of the results with this in mind. (orig.) [Deutsch] In dieser zweiteiligen Artikelserie werden verschiedene Vorschlaege fuer eine Energiebesteuerung und vorliegende Wirkungsanalysen fuer diese Vorschlaege systematisch dargestellt und diskutiert. Der erste Teil beginnt mit einer Betrachtung grundsaetzlicher Alternativen der Energiebesteuerung und der Kompensation. Darauf aufbauend sollen konkrete Vorschlaege bezueglich ihrer theoretischen Eigenschaften beurteilt werden. Im zweiten Teil werden Analysen der wirtschaftlichen Auswirkungen dieser Vorschlaege systematisch dargestellt. Hierbei wird untersucht, inwieweit die Ergebnisse verschiedener Analysen einander bestaetigen oder widersprechend. Danach soll herausgearbeitet werden, welche Staerken und Schwaechen die angewandten empirischen Methoden aufweisen und wie die Ergebnisse vor diesem Hintergrund zu interpretieren sind. (orig.)

  16. The need for a coordinated development of electromobility and renewable energies; Die Notwendigkeit einer koordinierten Entwicklung der Elektromobilitaet und regenerativer Energien

    Energy Technology Data Exchange (ETDEWEB)

    Herzog, Helmut [Humboldt Univ. Berlin (Germany). Lebenswissenschaftliche Fakultaet; Herzog, Raimond [FH Kiel (Germany)

    2017-08-15

    It is a declared goal of the Federal Government and almost all German parties to implement e-mobility by 2050 and to achieve the decarbonisation of the energy industry by the end of the century. Starting from these two premises, the motor vehicle industry and the electricity market will develop very dynamically. However, they must be coordinated by legal frameworks and, as far as possible, driven by market incentives for producers and purchasers of motor vehicles, electricity producers and consumers as well as network and storage system operators. Various approaches can be developed for this. [German] Es ist erklaertes Ziel der Bundesregierung und nahezu aller deutschen Parteien, die E-Mobilitaet bis 2050 durchzusetzen und die Dekarbonisierung der Energiewirtschaft bis Ende des Jahrhunderts zu erreichen. Von diesen beiden Praemissen ausgehend, werden sich die Kraftfahrzeugbranche und der Strommarkt sehr dynamisch entwickeln. Sie muessen aber durch gesetzliche Rahmenbedingungen koordiniert und moeglichst marktkonform durch Anreize fuer Produzenten und Kaeufer von Kraftfahrzeugen, Stromerzeuger und -verbraucher sowie Netz- und Speicherbetreiber gelenkt werden. Dafuer lassen sich verschiedenen Ansaetze entwickeln.

  17. Guidelines for the revision and extension of the Swiss energy consumption statistics regarding the industrial sector; Revision und Erweiterung der Energieverbrauchsstatistik der Industrie. Konzept

    Energy Technology Data Exchange (ETDEWEB)

    Bendel, R.; Scherer, R.

    1999-07-01

    This report for the Swiss Federal Office of Energy presents a proposal on how to revise and extend the Swiss energy consumption statistics regarding the industrial sector. Companies and officials admitted that the current procedure is no longer satisfactory, because of systematic bias related to the applied procedure. As the introduction of a tax on CO{sub 2} emissions is most probable in Switzerland, the energy consumption figures used to calculate the tax shall be incontestable. The suggested procedure described in the report fulfils this requirement. Instructions for the data collection are given together with the forms to be used in the survey, distinguishing the energy sources. Detailed indications on how many companies shall be randomly selected in each of the 18 industrial sectors (both manufacturing and services) and each of the categories 'small', 'middle-size' and 'large companies' have ben established. In this way, data extrapolation for the whole industrial sector will be reliable. Both the official offices and the industry representatives agreed to the suggested procedure. The sectorial structure has been defined in accordance with international practice.

  18. Competitiveness of photovoltaics in the German energy mix. Redefining the grid parity approach; Wettbewerbsfaehigkeit der Photovoltaik im deutschen Energiemix. Neudefinition des Ansatzes der Netzparitaet

    Energy Technology Data Exchange (ETDEWEB)

    Ammon, Martin [EuPD Research, Bonn (Germany); TU Bergakademie Freiberg (Germany). Lehrstuhl fuer Umwelt- und Ressourcenmanagement

    2013-09-15

    Photovoltaics are one of the fastest growing energy sources in the world. Despite high costs and a limited energy yield, attractive support schemes particularly the German renewable energy law have paved the way for the strong market growth of this technology within the last decade. Here the question arises as to when photovoltaics will reach a competitive level in Germany without the support of subsidies. The prominent grid parity approach is simple and considered critical in this discussion. It is critical because of the different references regarding the costs of electricity generated by a newly installed PV system and the electricity price of private households, which consists of electricity generation, distribution, sales as well as taxes and duties on the one hand. On the other hand, there are different time references in the calculation of electricity generation costs and electricity prices of private households. Transferring the approach of Levelized Costs of Electricity (LCOE) to all power generation plants within the energy mix means a redefinition of the grid parity of photovoltaics will be carried out. Here the electricity generation costs of photovoltaics as well as the energy mix will be calculated in the same way. The LCOE calculation refers to the whole life cycle of every power generation plant. That is why a balance between the high investment costs of photovoltaics and the increasing operation costs of fossil fuelled power plants is made. It can be shown that the reaching of competitiveness of photovoltaics in Germany depends on structural changes in electricity generation and it is to be realized within the anticipated time frame until the year 2020.

  19. Measures to enhance rational energy use in electric drives. Final report; Massnahmen zur Foerderung der rationellen Energienutzung bei elektrischen Antrieben. Endbericht

    Energy Technology Data Exchange (ETDEWEB)

    Reichert, J.; Schleich, J.; Herzer, G.; Toensing, E. [Fraunhofer-Institut fuer Systemtechnik und Innovationsforschung (ISI), Karlsruhe (Germany); Rath, U.; Hellmann, R. [Ingenieurbuero fuer Energieberatung, Haustechnik und Oekologische Konzepte GbR (eboek), Tuebingen (Germany)

    1999-05-01

    Electric drives account for nearly 60 % of the total power consumption in Germany (70 % in the industrial sector and about 44 % in the small consumer sector). There is a high potential for savings (Landwehr et al. 1996, ISR et al. 1996, Nadel et al. 1992) but it is little used so far. The study attempts to identify and systematize the limits set by the market to the application of energy conservation measures in electric motors. This is followed by an outline of strategies to overcome these obstacles. Experience from other countries are integrated where efforts were made to put the potential savings into practice. [German] Der Kraftstrombedarf fuer elektrische Antriebe betraegt in Deutschland knapp 60% des gesamten Stromeinsatzes (ca. 70% des Industriestrombedarfs und ca. 44% des Strombedarfs im Sektor Kleinverbrauch). Trotz dieser hohen Anteile ist bisher bei keinem der Marktteilnehmer (Motoren- und Anlagenhersteller, Haendler und Endanwender) grosses Interesse an Stromsparmassnahmen im Bereich Elektromotoren zu erkennen. Zudem zeigen erste grobe Schaetzungen (Landwehr et al. 1996, ISR et al. 1996, Nadel et al. 1992), dass im Bereich Elektromotoren erhebliche wirtschaftliche Einsparpotentiale bestehen. Durch eine Erhoehung des Wirkungsgrades allein lassen sich ca. 3% einsparen. Groessere Potentiale koennen durch Drehzahlregelung - ca. 10% - und vor allem bei Optimierung des gesamten Systems (Stromuebertragung - Motor - Regelung - Kraftuebertragung - Arbeitsmaschine) - ueber 20% - erschlossen werden. Ziel dieser Studie ist es, zunaechst die Marktbeschraenkungen bei der Umsetzung von Massnahmen zur rationellen Energienutzung bei Elektromotoren zu identifizieren und zu systematisieren. Im Anschluss daran werden moegliche Strategien zur Ueberwindung dieser Marktbeschraenkungen aufgezeigt, systematisiert und analysiert. In diesem Zusammenhang werden auch Erfahrungen aus anderen Laendern, in denen von politischer und wirtschaftlicher Seite zum Teil betraechtliche

  20. Research promotion of the FNR on biofuels. Energy from algae; Forschungsfoerderung der FNR zu Biokraftstoffen. Energie aus Algen

    Energy Technology Data Exchange (ETDEWEB)

    Spittel, Maria [Fachagentur Nachwachsende Rohstoffe e.V. (FNR), Guelzow (Germany). Abt. Projektmanagement

    2012-07-01

    There is an increasing interest in biofuels motivated mainly by climate and environment conservation aspects, but also due to aiming at more independence in fuel supply security. Biofuels had a share of 5,6 % (33.7 TWh) in the total fuel consumption in 2011. The total turnover in the biofuel sector added up to about 3,350 Mill. EUR, showing its economic importance. In this context algae technology is becoming more and more prominent. Algae are seen as alternative resource with increasing importance for the production of biofuels. However, the viability of the involved production and conversion processes are strongly connected to further development and increasing efficiency of algae biotechnology. To date, using algae for energy purposes only is economically not viable. The synergetic combination of industrial and energetic uses of algae will become more important in the future. The Agency for Renewable Resources (FNR) funds innovative R and D and demonstration projects in the framework of the funding program ''Renewable Resources'' initiated by the German Ministry of Food Agriculture and Consumer Protection (BMELV). In this context, FNR supports the optimisation of already commercialised biofuels as well as the further development of future options like fuels from algae biomass. (orig.)