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Sample records for molecular electronic rectification

  1. Mechanisms of molecular electronic rectification through electronic levels with strong vibrational coupling

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2002-01-01

    We present a new view and an analytical formalism of electron flow through a donor-acceptor molecule inserted between a pair of metal electrodes. The donor and acceptor levels are strongly coupled to an environmental nuclear continuum. The formalism applies to molecular donor-acceptor systems both in vacuum or air, and in aqueous solution under electrochemical potential control. Multifarious patterns of rectified electron flow from the negatively to the positively biased electrode arise. The electronic interaction between the donor and acceptor fragments, mutually and with the electrodes, can be weak, corresponding to the fully diabatic limit. The rectification process then reduces to a sequence of vibrationally relaxed single-electron transfer steps. In the limits where the interactions are strong, denoted as the partially and fully adiabatic limits, the character of the rectification process is different, and electron flow proceeds coherently, without vibrational relaxation. In still another class of mechanisms the electronic level broadening of either donor or acceptor from the adjacent electrode is so strong that it is comparable to the vibrational broadening. The process then reduces to a three-level transition similar to STM of large redox molecules. Recent data for rectification in hexadecyl-quinolinium tricyanodimethanide monolayers by Metzger and co-workers [J. Am. Chem. Soc. 119, 10455 (1997); Acc. Chem. Res. 32, 950 (1999)], are discussed in terms of the reported views and formalism.

  2. Mechanisms of molecular electronic rectification through electronic levels with strong vibrational coupling

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2002-01-01

    reduces to a three-level transition similar to STM of large redox molecules. Recent data for rectification in hexadecyl-quinolinium tricyanodimethanide monolayers by Metzger and co-workers [J. Am. Chem. Soc. 119, 10455 (1997); Acc. Chem. Res. 32, 950 (1999)], are discussed in terms of the reported views......We present a new view and an analytical formalism of electron flow through a donor-acceptor molecule inserted between a pair of metal electrodes. The donor and acceptor levels are strongly coupled to an environmental nuclear continuum. The formalism applies to molecular donor-acceptor systems both...

  3. Rectification in donor-acceptor molecular junctions

    International Nuclear Information System (INIS)

    We perform density functional theory (DFT) calculations on molecular junctions consisting of a single molecule between two Au(111) electrodes. The molecules consist of an alkane or aryl bridge connecting acceptor, donor or thiol endgroups in various combinations. The molecular geometries are optimized and wavefunctions and eigenstates of the junction calculated using the DFT method, and then the electron transport properties for the junction are calculated within the non-equilibrium Green's function (NEGF) formalism. The current-voltage or i(V) characteristics for the various molecules are then compared. Rectification is observed for these molecules, particularly for the donor-bridge-acceptor case where the bridge is an alkane, with rectification being in the same direction as the original findings of Aviram and Ratner (1974 Chem. Phys. Lett. 29 277-83), at least for relatively large negative and positive applied bias. However, at smaller bias rectification is in the opposite direction and is attributed to the lowest unoccupied orbital associated with the acceptor group

  4. Rectification in one--dimensional electronic systems

    OpenAIRE

    Braunecker, Bernd; Feldman, D. E.; Marston, J. B.

    2005-01-01

    Asymmetric current--voltage ($I(V)$) curves, known as the diode or rectification effect, in one--dimensional electronic conductors can have their origin from scattering off a single asymmetric impurity in the system. We investigate this effect in the framework of the Tomonaga--Luttinger model for electrons with spin. We show that electron interactions strongly enhance the diode effect and lead to a pronounced current rectification even if the impurity potential is weak. For strongly interacti...

  5. Terahertz rectification by periodic two-dimensional electron plasma

    Energy Technology Data Exchange (ETDEWEB)

    Popov, V. V. [Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Saratov 410019 (Russian Federation); Saratov State University, Saratov 410012 (Russian Federation)

    2013-06-24

    The physics of terahertz rectification by periodic two-dimensional electron plasma is discussed. Two different effects yielding terahertz rectification are studied: the plasmonic drag and plasmonic ratchet. Ultrahigh responsivity of terahertz rectification by periodic two-dimensional electron plasma in semiconductor heterostructures and graphene is predicted.

  6. Terahertz rectification by periodic two-dimensional electron plasma

    International Nuclear Information System (INIS)

    The physics of terahertz rectification by periodic two-dimensional electron plasma is discussed. Two different effects yielding terahertz rectification are studied: the plasmonic drag and plasmonic ratchet. Ultrahigh responsivity of terahertz rectification by periodic two-dimensional electron plasma in semiconductor heterostructures and graphene is predicted.

  7. The effects of contact configurations on the rectification of dipyrimidinyl—diphenyl diblock molecular junctions

    International Nuclear Information System (INIS)

    The transport properties of a conjugated dipyrimidinyl—diphenyl diblock oligomer sandwiched between two gold electrodes, as recently reported by [Díez-Pérez et al. Nature Chem. 1 635 (2009)], are theoretically investigated using the fully self-consistent nonequilibrium Green's function method combined with density functional theory. Two kinds of symmetrical anchoring geometries are considered. Calculated current—voltage curves show that the contact structure has a strong effect on the rectification behaviour of the molecular diode. For the equilateral triangle configuration, pronounced rectification behaviour comparable to the experimental measurement is revealed, and the theoretical analysis indicates that the observed rectification characteristic results from the asymmetric shift of the perturbed molecular energy levels under bias voltage. While for the tetrahedron configuration, both rectification and negative differential conductivity behaviours are observed. The calculated results further prove the close dependence of the transporting characteristics of molecular junctions on contact configuration. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  8. Thermal rectification in carbon nanotube intramolecular junctions: Molecular dynamics calculations

    OpenAIRE

    WU, Gang; Li, Baowen

    2007-01-01

    We study heat conduction in (n, 0)/(2n, 0) intramolecular junctions by using molecular dynamics method. It is found that the heat conduction is asymmetric, namely, heat transports preferably in one direction. This phenomenon is also called thermal rectification. The rectification is weakly dependent on the detailed structure of connection part, but is strongly dependent on the temperature gradient. We also study the effect of the tube radius and intramolecular junction length on the rectifica...

  9. Current rectification by simple molecular quantum dots: an ab-initio study

    CERN Document Server

    Larade, B

    2003-01-01

    We calculate a current rectification by molecules containing a conjugated molecular group sandwiched between two saturated (insulating) molecular groups of different length (molecular quantum dot) using an ab-initio non-equilibrium Green's function method. In particular, we study S-(CH2)m-C10H6-(CH2)n-S dithiol with Naphthalene as a conjugated central group. The rectification current ratio ~35 has been observed at m = 2 and n = 10, due to resonant tunneling through the molecular orbital (MO) closest to the electrode Fermi level (lowest unoccupied MO in the present case). The rectification is limited by interference of other conducting orbitals, but can be improved by e.g. adding an electron withdrawing group to the naphthalene.

  10. Molecular rectification of thiol-linked Au|PTCDI-[CH2]n|Au junctions

    Science.gov (United States)

    Zheng, Ganhong; Dai, Zhenxiang; Zhang, Yanyan; Dong, Yuqin; Ma, Yongqing; Li, Guang

    2012-08-01

    The electronic transport properties of the PTCDI-[CH2]n(0?n?6) molecular junctions with different molecular lengths are theoretically investigated via the first-principles density functional theory (DFT) and non-equilibrium Green's function (NEGF) method. Our results show that the transport properties depend on molecular lengths. The equilibrium conductance of the probed systems decreases exponentially with the increasing number n of the CH2 unit. With n?1, the rectifying effect has been found. In the n=6 case, a significant rectification ratio of 72.6 is achieved at the bias of ±2.1 V in our probed voltage range. The rectification effect arises from asymmetric molecular structures. Our results suggest these molecules have great potential application in the molecular-scale device.

  11. Electronic heat current rectification in hybrid superconducting devices

    Science.gov (United States)

    Fornieri, Antonio; Martínez-Pérez, María José; Giazotto, Francesco

    2015-05-01

    In this work, we review and expand recent theoretical proposals for the realization of electronic thermal diodes based on tunnel-junctions of normal metal and superconducting thin films. Starting from the basic rectifying properties of a single hybrid tunnel junction, we will show how the rectification efficiency can be largely increased by combining multiple junctions in an asymmetric chain of tunnel-coupled islands. We propose three different designs, analyzing their performance and their potential advantages. Besides being relevant from a fundamental physics point of view, this kind of devices might find important technological application as fundamental building blocks in solid-state thermal nanocircuits and in general-purpose cryogenic electronic applications requiring energy management.

  12. Thermal rectification of a single-wall carbon nanotube: a molecular dynamics study

    OpenAIRE

    Foulaadvand, M. Ebrahim; Saeedi, Azadeh; Yousefi, Farrokh; Khadesadr, Saeed

    2014-01-01

    We have investigated the thermal rectification phenomenon in a single-wall mass graded carbon nanotube by molecular dynamics simulation. Second generation Brenner potential has been used to model the inter atomic carbon interaction. Fixed boundary condition has been taken into account. We compare our findings to a previous study by Alaghemandi et al which has been done with a different potential and boundary condition. The dependence of the rectification factor $R$ on temperature, nanotube di...

  13. Current rectification by simple molecular quantum dots: an ab-initio study

    OpenAIRE

    Larade, B.; Bratkovsky, A. M.

    2003-01-01

    We calculate a current rectification by molecules containing a conjugated molecular group sandwiched between two saturated (insulating) molecular groups of different length (molecular quantum dot) using an ab-initio non-equilibrium Green's function method. In particular, we study S-(CH2)m-C10H6-(CH2)n-S dithiol with Naphthalene as a conjugated central group. The rectification current ratio ~35 has been observed at m = 2 and n = 10, due to resonant tunneling through the molecular orbital (MO) ...

  14. Theory of electrical rectification in a molecular monolayer

    CERN Document Server

    Krzeminski, Christophe; Allan, Guy; Vuillaume, Dominique; Metzger, R M; 10.1103/PhysRevB.64.085405

    2011-01-01

    The current-voltage characteristics in Langmuir-Blodgett monolayers of \\gamma-hexadecylquinolinium tricyanoquinodimethanide (C16H33Q-3CNQ) sandwiched between Al or Au electrodes is calculated, combining ab initio and self-consistent tight binding techniques. The rectification current depends on the position of the LUMO and HOMO relative to the Fermi levels of the electrodes as in the Aviram-Ratner mechanism, but also on the profile of the electrostatic potential which is extremely sensitive to where the electroactive part of the molecule lies in the monolayer. This second effect can produce rectification in the direction opposite to the Aviram-Ratner prediction.

  15. Transverse rectification in density-modulated two-dimensional electron gases

    OpenAIRE

    Ganczarczyk, A.; Rojek, S.; Quindeau, A.; Geller, M.; Hucht, A.; Notthoff, C.; Reuter, D; Wieck, A. D.; König, J.; Lorke, A.

    2008-01-01

    We demonstrate tunable transverse rectification in a density-modulated two-dimensional electron gas (2DEG). The density modulation is induced by two surface gates, running in parallel along a narrow stripe of 2DEG. A transverse voltage in the direction of the density modulation is observed, i.e. perpendicular to the applied source-drain voltage. The polarity of the transverse voltage is independent of the polarity of the source-drain voltage, demonstrating rectification in t...

  16. The preparation of metal oxygen molecular cluster embedded organic-inorganic nanocomposite and its rectification behaviour

    International Nuclear Information System (INIS)

    A metal oxygen molecular cluster compound has been utilized for the preparation of organic-inorganic nanocomposite film by a sol-gel method. The entrapment of these cluster compounds in a composite film has been characterized by various physico-chemical techniques. The entrapped metal oxygen cluster stabilizes its energy levels, which is evidenced from the change in redox potential and band gap. The rectification phenomenon of composite films is attributed to the embedded cluster compounds. The rectification behaviour of the composite film, which is due to the charge transfer from molecular cluster and the electrode, has been studied

  17. Rectification in single molecular dimers with strong polaron effect

    OpenAIRE

    Kaat, Gregers A.; Flensberg, Karsten

    2004-01-01

    We study theoretically the transport properties of a molecular two level system with large electron-vibron coupling in the Coulomb blockade regime. We show that when the electron-vibron coupling induces polaron states, the current-voltage characteristic becomes strongly asymmetric because, in one current direction, one of the polaron state blocks the current through the other. This situation occurs when the coupling between the polaron states is smaller than the coupling to the leads. We disc...

  18. Molecular rectification with identical metal electrodes at low temperatures

    International Nuclear Information System (INIS)

    A gold deposition technique for the fabrication of Au/LB/Au structures has been developed. The kinetic energy of evaporated gold atoms is reduced by scattering the gold atoms from argon gas. Moreover, the samples are cooled down below 173K (-100 deg C) to avoid the diffusion of gold atoms into the LB films and to fabricate electrically continuous thin gold electrodes (This technique has since been used in fabrication of Au/LB/Au structures even with monolayer LB films (Metzger, et al. (2001)). To measure the current-voltage characteristics of the Au/LB/Au structures at liquid helium temperatures, new junction geometries have been explored. To avoid the direct contact of the Gallium-Indium eutectic onto the LB films, which is the cause of the breakdown of the junction at lower temperatures, a cross electrode junction geometry is used. The problem of poor Langmuir-Blodgett film deposition at the penumbra region of the base electrode is avoided by covering the penumbra region with an insulating ?-tricosenoic acid LB film. Using modified Au/LB/Au structures, the current-voltage characteristics have been successfully measured down to 8K. From the temperature dependence of the current-voltage characteristics, the possible conduction mechanisms of the Au/C16H33Q-3CNQ LB film/Au structures have been discussed. At lower voltages at which non-linear symmetric current-voltage characteristics occur, the possible conduction mechanisms are found to be ohmic conduction at V <0.05V and space-charge-limited conduction above this voltage. At higher voltages, rectification occurs and the conduction mechanism for the rectification is found to be a mixture of Poole-Frenkel hopping conduction and tunnelling. From the data analysis, the signatures of the possible cause of the rectification have been discussed. (author)

  19. Nonlinear electromagnetic rectification of BCS-paired electrons at a superconductor surface

    International Nuclear Information System (INIS)

    A theory describing nonlinear electromagnetic rectification of BCS-paired electrons at a superconductor-vacuum interface by means of a monochromatic, plane electromagnetic wave incident at an oblique angle is presented. On the basis of a recently constructed nonlinear-response tensor, the forced nonlinear dc-current density is analyzed. A fundamental integro-differential equation incorporating the Meissner screening of the nonlinear response is established, and the prevailing dc-current density and the associated magnetostatic field are determined assuming the BCS-paired electrons to be specularly reflected from the surface. A self-consistency requirement for the forced nonlinear current density which has to be obeyed for any specular-reflection model is derived, and polarization selection rules for the incident electromagnetic field are established. For temperatures above the transition temperature, the present theory describes nonlinear electromagnetic rectification in a collisionless unpaired jellium. In the final part of the present work, the possibilities of achieving nonlinear electromagnetic rectification using incident waves of frequencies around the plasma edge, i.e., far above the superconducting gap frequency, are investigated. It is predicted that polariton-plasmon and plasmon-plasmon interactions can give rise to optical rectification

  20. Understanding the anchoring group effect of molecular diodes on rectification.

    Science.gov (United States)

    Lee, Youngu; Carsten, Brian; Yu, Luping

    2009-02-01

    This paper describes the anchoring group effect of molecular diodes on rectifying behavior. Two molecular diodes with different anchoring groups, which are based on diblock co-oligomeric structures, have been synthesized and characterized. Scanning tunneling spectroscopy (STS) measurements revealed the correlation of rectifying effects in these molecular diodes with anchoring groups such as thiol and isocyanide. The combination of theoretical calculation and experimental results on these molecular diodes demonstrated that the rectifying effect could be affected by the nature of anchoring groups due to the bond dipoles at the interface and internal polarization inside the molecules. PMID:19086890

  1. Obvious variation of rectification behaviors induced by isomeric anchoring groups for dipyrimidinyl–diphenyl molecular junctions

    International Nuclear Information System (INIS)

    The rectifying properties modulated by isomeric anchoring groups of dipyrimidinyl–diphenyl co-oligomer diodes sandwiched between two gold electrodes are investigated using density functional theory combined with the nonequilibrium Green's function method. Our results show that the rectifying behaviors of the co-oligomer diode are significantly modulated by isomeric substitution of anchoring groups. When the isomeride nitrile end group is replaced by the isocyanide one, for symmetric arrangement of electrodes, the rectifying direction shows obvious inversion for the isocyanide–diblock–thiol junction, and the rectification ratio is obviously enhanced for the thiol–diblock–isocyanide junction. The influence on rectification induced by asymmetric electrodes is also discussed. The analysis of the transmission spectra and the molecular projected self-consistent Hamiltonian under various external bias voltages gives inside mechanisms of the observed results.

  2. Electronic structure and nonlinear optical rectification in a quantum dot: effects of impurities and external electric field

    International Nuclear Information System (INIS)

    The electronic structure of a spherical quantum dot with parabolic confinement that contains a hydrogenic impurity and is subjected to a DC electric field is studied. In our calculations we vary the position of the impurity and the electric field strength. The calculated electronic structure is further used for determining the nonlinear optical rectification coefficient of the quantum dot structure. We show that both the position of the impurity and the strength of the electric field influence the nonlinear optical rectification process

  3. Molecular Electronics

    DEFF Research Database (Denmark)

    Jennum, Karsten Stein

    This thesis includes the synthesis and characterisation of organic compounds designed for molecular electronics. The synthesised organic molecules are mainly based on two motifs, the obigo(phenyleneethynylenes) (OPE)s and tetrathiafulvalene (TTF) as shown below. These two scaffolds (OPE and TTF...... electron transistors (Part 2). The synthetic protocols rely on stepwise Sonogashira coupling reactions. Conductivity studies on various OPE-based molecular wires reveal that mere OPE compounds have a higher electrical resistance compared to the cruciform based wires (up to 9 times higher). The most...... spectacular result, however, was obtained by a study of a single molecular transistor. The investigated OPE5-TTF compound was captured in a three-terminal experiment, whereby manipulation of the molecule’s electronic spin was possible in different charge states. Thus, we demonstrated how the cruciform...

  4. Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode

    CERN Document Server

    Li, Yunyun; Marchesoni, Fabio; Li, Baowen

    2014-01-01

    Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schr\\"odinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring.

  5. Rectification of electronic heat current by a hybrid thermal diode

    OpenAIRE

    Martínez-Pérez, M. J.; Fornieri, A.; Giazotto, F.

    2014-01-01

    We report the realization of an ultra-efficient low-temperature hybrid heat current rectifier, thermal counterpart of the well-known electric diode. Our design is based on a tunnel junction between two different elements: a normal metal and a superconducting island. Electronic heat current asymmetry in the structure arises from large mismatch between the thermal properties of these two. We demonstrate experimentally temperature differences exceeding $60$ mK between the forwa...

  6. Molecular dynamics study on the thermal conductivity and thermal rectification in graphene with geometric variations of doped boron

    International Nuclear Information System (INIS)

    Thermal conductivity and thermal rectification of graphene with geometric variations have been investigated by using classical non-equilibrium molecular dynamics simulation, and analyzed theoretically the cause of the changes of thermal conductivity and thermal rectification. Two different structural models, triangular single-boron-doped graphene (SBDG) and parallel various-boron-doped graphene (VBDG), were considered. The results indicated that the thermal conductivities of two different models are about 54–63% lower than pristine graphene. And it was also found that the structure of parallel various-boron-doped graphene is inhibited more strongly on the heat transfer than that of triangular single-boron-doped graphene. The reduction in the thermal conductivities of two different models gradually decreases as the temperature rises. The thermal conductivities of triangular boron-doped graphene have a large difference in both directions, and the thermal rectification of this structure shows the downward trend with increasing temperature. However, the thermal conductivities of parallel various-boron-doped graphene are similar in both directions, and the thermal rectification effect is not obvious in this structure. The phenomenon of thermal rectification exits in SBDG. It implies that the SBDG might be a potential promising structure for thermal rectifier by controlling the boron-doped model

  7. Terahertz radiation by optical rectification in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenylmalondialdehyde

    CERN Document Server

    Guan, W; Sotome, M; Kinoshita, Y; Takeda, R; Inoue, A; Horiuchi, S; Okamoto, H

    2014-01-01

    Terahertz radiation by optical rectification has been observed at room temperature in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenyl malondialdehyde (PhMDA). The radiated electromagnetic wave consisted of a single-cycle terahertz pulse with a temporal width of $\\sim$ 0.5 ps. The terahertz radiation amplitude divided by the sample thickness in PhMDA was nearly equivalent to that in a typical terahertz wave emitter ZnTe. This is attributable to a long coherence length in the range of 130 $\\sim$ 800 $\\mu$m for the terahertz radiation from PhMDA. We also discussed the possibility of PhMDA as a terahertz wave emitter in terms of the phase-matching condition.

  8. Dependence of electronic rectification in carbon nanocone devices upon electrode materials

    International Nuclear Information System (INIS)

    Very recently, we found that single-walled carbon nanocones (SWCNCs) of tens of atoms can serve as rectifiers if Au electrodes are applied (Ming et al 2012 Appl. Phys. Lett. 100 063119). In this paper, the dependence of rectification effects on different electrode materials (Au, Cu, Ag, Li, Be, Pd and Pt) is systematically investigated by density functional theory and non-equilibrium Green's function, showing that materials with lower energy bonded with the SWCNC possess better rectification effects. The rectification mechanism is revealed, including the fact that the contact distance between the tip of the SWCNC and the electrode is also an important factor for rectification effects.

  9. Rectification Properties of Carbon Nanotube ''Y-Junctions''

    International Nuclear Information System (INIS)

    Quantum conductivity of single-wall carbon nanotube Y-junctions is calculated. The current versus voltage characteristics of these junctions show asymmetry and rectification, in agreement with recent experimental results. Furthermore, rectification is found to be independent of the angle between the branches of these junctions, indicating this to be an intrinsic property of symmetric Y-junctions. The implications for the Y-junction to function as a nanoscale molecular electronic switch are investigated

  10. Thermal rectification of electrons in hybrid normal metal-superconductor nanojunctions

    International Nuclear Information System (INIS)

    We theoretically investigate heat transport in hybrid normal metal-superconductor (NS) nanojunctions focusing on the effect of thermal rectification. We show that the heat diode effect in the junction strongly depends on the transmissivity and the nature of the NS contact. Thermal rectification efficiency can reach up to ?123% for a fully transmissive ballistic junction and up to 84% in diffusive NS contacts. Both values exceed the rectification efficiency of a NIS tunnel junction (I stands for an insulator) by a factor close to ?5 and ?3, respectively. Furthermore, we show that for NS point-contacts with low transmissivity, inversion of the heat diode effect can take place. Our results could prove useful for tailoring heat management at the nanoscale, and for mastering thermal flux propagation in low-temperature caloritronic nanocircuitry

  11. Thermal rectification of electrons in hybrid normal metal-superconductor nanojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Giazotto, F., E-mail: giazotto@sns.it [NEST, Instituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa (Italy); Bergeret, F. S., E-mail: sebastian-bergeret@ehu.es [Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, Manuel de Lardizabal 4, E-20018 San Sebastián (Spain); Donostia International Physics Center (DIPC), Manuel de Lardizabal 5, E-20018 San Sebastián (Spain)

    2013-12-09

    We theoretically investigate heat transport in hybrid normal metal-superconductor (NS) nanojunctions focusing on the effect of thermal rectification. We show that the heat diode effect in the junction strongly depends on the transmissivity and the nature of the NS contact. Thermal rectification efficiency can reach up to ?123% for a fully transmissive ballistic junction and up to 84% in diffusive NS contacts. Both values exceed the rectification efficiency of a NIS tunnel junction (I stands for an insulator) by a factor close to ?5 and ?3, respectively. Furthermore, we show that for NS point-contacts with low transmissivity, inversion of the heat diode effect can take place. Our results could prove useful for tailoring heat management at the nanoscale, and for mastering thermal flux propagation in low-temperature caloritronic nanocircuitry.

  12. Theory of Rectification in Tour Wires: The Role of Electrode Coupling

    OpenAIRE

    Taylor, Jeremy Philip; Brandbyge, Mads; Stokbro, Kurt

    2002-01-01

    We report first-principles studies of electronic transport and rectification in molecular wires attached to gold electrodes. Our ab initio calculation gives an accurate description of the voltage drop as well as the broadening and alignment of the molecular levels in the metal-molecule-metal complex. We find that the operation range and rectification in such strongly chemisorbed molecules is limited by the width of the transmission resonances and their proximity to the Fermi level.

  13. Theory of Rectification in Tour Wires: The Role of Electrode Coupling

    DEFF Research Database (Denmark)

    Taylor, Jeremy Philip; Brandbyge, Mads; Stokbro, Kurt

    2002-01-01

    We report first-principles studies of electronic transport and rectification in molecular wires attached to gold electrodes. Our ab initio calculation gives an accurate description of the voltage drop as well as the broadening and alignment of the molecular levels in the metal-molecule-metal comp......-molecule-metal complex. We find that the operation range and rectification in such strongly chemisorbed molecules is limited by the width of the transmission resonances and their proximity to the Fermi level....

  14. Thermal rectification in mass-graded nanotubes: a model approach in the framework of reverse non-equilibrium molecular dynamics simulations

    International Nuclear Information System (INIS)

    The thermal rectification in nanotubes with a mass gradient is studied by reverse non-equilibrium molecular dynamics simulations. We predict a preferred heat flow from light to heavy atoms which differs from the preferential direction in one-dimensional monoatomic systems. This behavior of nanotubes is explained by anharmonicities caused by transverse motions which are stronger at the low-mass end. The present simulations show an enhanced rectification with increasing tube length, diameter and mass gradient. Implications of the present findings for applied topics are mentioned concisely.

  15. A theoretical view of unimolecular rectification

    International Nuclear Information System (INIS)

    The concept of single molecule rectifiers proposed in a theoretical work by Aviram and Ratner in 1974 was the starting point of the now vibrant field of molecular electronics. In the meantime, a built-in asymmetry in the conductance of molecular junctions has been reported at the experimental level. In this contribution, we present a theoretical comparison of three different types of unimolecular rectifiers: (i) systems where the donor and acceptor parts of the molecules are taken from charge-transfer salt components; (ii) zwitterionic systems and (iii) tour wires with nitro substituents. We conduct an analysis of the rectification mechanism in these three different types of asymmetric molecules on the basis of parameterized quantum chemical models as well as with a full non-equilibrium Green's function-density functional theory (NEGF-DFT) treatment of the current-voltage characteristics of the respective metal-molecule-metal junctions. We put a particular emphasis on the prediction of rectification ratios (RRs), which are crucial for the assessment of the technological usefulness of single molecule junctions as diodes. We also compare our results with values reported in the literature for other types of molecular rectification, where the essential asymmetry is not induced by the structure of the molecule alone but either by a difference in the electronic coupling of the molecule to the two electrodes or by attaching alkyl chains of different lengths to the central molecular moiety

  16. Electronic properties of organic monolayers and molecular devices

    Indian Academy of Sciences (India)

    D Vuillaume; S Lenfant; D Guerin; C Delerue; C Petit; G Salace

    2006-07-01

    We review some of our recent experimental results on charge transport in organic nanostructures such as self-assembled monolayer and monolayers of organic semiconductors. We describe a molecular rectifying junction made from a sequential self-assembly on silicon. These devices exhibit a marked current–voltage rectification behavior due to resonant transport between the Si conduction band and the molecule highest occupied molecular orbital of the molecule. We discuss the role of metal Fermi level pinning in the current–voltage behavior of these molecular junctions. We also discuss some recent insights on the inelastic electron tunneling behavior of Si/alkyl chain/metal junctions.

  17. Effect of proportion on rectification in organic co-oligomer spin rectifiers

    International Nuclear Information System (INIS)

    The rectification behaviours in organic magnetic/nonmagnetic co-oligomer spin rectifiers are investigated theoretically. It is found that both the charge current and the spin current through the device are rectified at the same time. By adjusting the proportion between the magnetic and nonmagnetic components, the threshold voltage and the rectification ratio of the rectifier are modulated. A large rectification ratio is obtained when the two components are equal in length. The intrinsic mechanism is analysed in terms of the asymmetric localization of molecular orbitals under biases. The effect of molecular length on the rectification is also discussed. These results will be helpful in the future design of organic spin diodes. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  18. Rectification in three-terminal graphene junctions

    OpenAIRE

    Jacobsen, A.; Shorubalko, I.; Maag, L.; Sennhauser, U.; Ensslin, K.

    2010-01-01

    Nonlinear electrical properties of graphene-based three-terminal nanojunctions are presented. Intrinsic rectification of voltage is observed up to room temperature. The sign and the efficiency of the rectification can be tuned by a gate. Changing the charge carrier type from holes to electrons results in a change of the rectification sign. At a bias < 20mV and at a temperature below 4.2K the sign and the efficiency of the rectification are governed by universal conductance fluctuations.

  19. Hemichannel composition and electrical synaptic transmission: molecular diversity and its implications for electrical rectification

    OpenAIRE

    Palacios-Prado, Nicolás; Huetteroth, Wolf; Pereda, Alberto E.

    2014-01-01

    Unapposed hemichannels (HCs) formed by hexamers of gap junction proteins are now known to be involved in various cellular processes under both physiological and pathological conditions. On the other hand, less is known regarding how differences in the molecular composition of HCs impact electrical synaptic transmission between neurons when they form intercellular heterotypic gap junctions (GJs). Here we review data indicating that molecular differences between apposed HCs at electrical synaps...

  20. Measurement and understanding of single-molecule break junction rectification caused by asymmetric contacts

    International Nuclear Information System (INIS)

    The contact effects of single-molecule break junctions on rectification behaviors were experimentally explored by a systematic control of anchoring groups of 1,4-disubstituted benzene molecular junctions. Single-molecule conductance and I-V characteristic measurements reveal a strong correlation between rectifying effects and the asymmetry in contacts. Analysis using energy band models and I-V calculations suggested that the rectification behavior is mainly caused by asymmetric coupling strengths at the two contact interfaces. Fitting of the rectification ratio by a modified Simmons model we developed suggests asymmetry in potential drop across the asymmetric anchoring groups as the mechanism of rectifying I-V behavior. This study provides direct experimental evidence and sheds light on the mechanisms of rectification behavior induced simply by contact asymmetry, which serves as an aid to interpret future single-molecule electronic behavior involved with asymmetric contact conformation

  1. Spin-excited states and rectification in an organic spin rectifier

    International Nuclear Information System (INIS)

    Spin-excited states in an asymmetric magnetic organic co-oligomer diode are investigated theoretically. The results demonstrate that the structural asymmetry of the co-oligomer is modulated by the spin-excited states, which is embodied in the wave functions of the eigenstates as well as the spin density wave. By calculating the transport property, a robust spin-current rectification concomitant with a charge-current rectification is observed in all spin-excited states. However, the current through the diode is suppressed distinctly by the spin-excited states, while the rectification ratios may be reduced or enhanced depending on the bias and the excited spins. The intrinsic mechanism is analyzed from the spin-dependent transmission combined with the change of molecular eigenstates under bias. Finally, the temperature-induced spin excitation is simulated. Significant rectification behavior is obtained even at room temperature. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  2. Measurement and understanding of single-molecule break junction rectification caused by asymmetric contacts

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Kun; Zhou, Jianfeng; Hamill, Joseph M.; Xu, Bingqian, E-mail: bxu@engr.uga.edu [Single Molecule Study Laboratory, College of Engineering and Nanoscale Science and Engineering Center, University of Georgia, Athens, Georgia 30602 (United States)

    2014-08-07

    The contact effects of single-molecule break junctions on rectification behaviors were experimentally explored by a systematic control of anchoring groups of 1,4-disubstituted benzene molecular junctions. Single-molecule conductance and I-V characteristic measurements reveal a strong correlation between rectifying effects and the asymmetry in contacts. Analysis using energy band models and I-V calculations suggested that the rectification behavior is mainly caused by asymmetric coupling strengths at the two contact interfaces. Fitting of the rectification ratio by a modified Simmons model we developed suggests asymmetry in potential drop across the asymmetric anchoring groups as the mechanism of rectifying I-V behavior. This study provides direct experimental evidence and sheds light on the mechanisms of rectification behavior induced simply by contact asymmetry, which serves as an aid to interpret future single-molecule electronic behavior involved with asymmetric contact conformation.

  3. Switching and Rectification in Carbon-Nanotube Junctions

    Science.gov (United States)

    Srivastava, Deepak; Andriotis, Antonis N.; Menon, Madhu; Chernozatonskii, Leonid

    2003-01-01

    Multi-terminal carbon-nanotube junctions are under investigation as candidate components of nanoscale electronic devices and circuits. Three-terminal "Y" junctions of carbon nanotubes (see Figure 1) have proven to be especially interesting because (1) it is now possible to synthesize them in high yield in a controlled manner and (2) results of preliminary experimental and theoretical studies suggest that such junctions could exhibit switching and rectification properties. Following the preliminary studies, current-versus-voltage characteristics of a number of different "Y" junctions of single-wall carbon nanotubes connected to metal wires were computed. Both semiconducting and metallic nanotubes of various chiralities were considered. Most of the junctions considered were symmetric. These computations involved modeling of the quantum electrical conductivity of the carbon nanotubes and junctions, taking account of such complicating factors as the topological defects (pentagons, heptagons, and octagons) present in the hexagonal molecular structures at the junctions, and the effects of the nanotube/wire interfaces. A major component of the computational approach was the use of an efficient Green s function embedding scheme. The results of these computations showed that symmetric junctions could be expected to support both rectification and switching. The results also showed that rectification and switching properties of a junction could be expected to depend strongly on its symmetry and, to a lesser degree, on the chirality of the nanotubes. In particular, it was found that a zigzag nanotube branching at a symmetric "Y" junction could exhibit either perfect rectification or partial rectification (asymmetric current-versus-voltage characteristic, as in the example of Figure 2). It was also found that an asymmetric "Y" junction would not exhibit rectification.

  4. A direct current rectification scheme for microwave space power conversion using traveling wave electron acceleration

    Science.gov (United States)

    Manning, Robert M.

    1993-01-01

    The formation of the Vision-21 conference held three years ago allowed the present author to reflect and speculate on the problem of converting electromagnetic energy to a direct current by essentially reversing the process used in traveling wave tubes that converts energy in the form of a direct current to electromagnetic energy. The idea was to use the electric field of the electromagnetic wave to produce electrons through the field emission process and accelerate these electrons by the same field to produce an electric current across a large potential difference. The acceleration process was that of cyclotron auto-resonance. Since that time, this rather speculative ideas has been developed into a method that shows great promise and for which a patent is pending and a prototype design will be demonstrated in a potential laser power beaming application. From the point of view of the author, a forum such as Vision-21 is becoming an essential component in the rather conservative climate in which our initiatives for space exploration are presently formed. Exchanges such as Vision-21 not only allows us to deviate from the 'by-the-book' approach and rediscover the ability and power in imagination, but provides for the discussion of ideas hitherto considered 'crazy' so that they may be given the change to transcend from the level of eccentricity to applicability.

  5. Towards graphyne molecular electronics

    Science.gov (United States)

    Li, Zhihai; Smeu, Manuel; Rives, Arnaud; Maraval, Valérie; Chauvin, Remi; Ratner, Mark A.; Borguet, Eric

    2015-02-01

    ?-Graphyne, a carbon-expanded version of graphene (‘carbo-graphene’) that was recently evidenced as an alternative zero-gap semiconductor, remains a theoretical material. Nevertheless, using specific synthesis methods, molecular units of ?-graphyne (‘carbo-benzene’ macrocycles) can be inserted between two anilinyl (4-NH2-C6H4)-anchoring groups that allow these fragments to form molecular junctions between gold electrodes. Here, electrical measurements by the scanning tunnelling microscopy (STM) break junction technique and electron transport calculations are carried out on such a carbo-benzene, providing unprecedented single molecule conductance values: 106?nS through a 1.94-nm N-N distance, essentially 10 times the conductance of a shorter nanographenic hexabenzocoronene analogue. Deleting a C4 edge of the rigid C18 carbo-benzene circuit results in a flexible ‘carbo-butadiene’ molecule that has a conductance 40 times lower. Furthermore, carbo-benzene junctions exhibit field-effect transistor behaviour when an electrochemical gate potential is applied, opening the way for device applications. All the results are interpreted on the basis of theoretical calculations.

  6. Thermal Rectification In Asymmetric Graphene Ribbons

    OpenAIRE

    Yang, Nuo; ZHANG, GANG; Li, Baowen

    2009-01-01

    In this paper, heat flux in graphene nano ribbons has been studied by using molecular dynamics simulations. It is found that the heat flux runs preferentially along the direction of decreasing width, which demonstrates significant thermal rectification effect in the asymmetric graphene ribbons. The dependence of rectification ratio on the vertex angle and the length are also discussed. Compared to the carbon nanotube based one-dimensional thermal rectifier, graphene nano ribbons have much hig...

  7. Current rectification by mediating electroactive polymers

    International Nuclear Information System (INIS)

    In this work we briefly review the theoretical basis for the electrochemical rectification in mediated redox reactions at redox polymer modified electrodes. Electrochemical rectification may have two distinct origins. It is either caused by a slow kinetics of the reaction between the external redox couple and the mediator or it is originated by a slow electronic transport within the film under an unfavorable thermodynamic condition. We show experimental results for the redox mediation reaction of poly(o-aminophenol) (POAP) on the Fe2+/3+ and on the Fe(CN)63-/4- redox couples in solution that prove the proposed mechanisms of electrochemical rectification

  8. Rectification effects in coherent transport through single molecules

    OpenAIRE

    Pump, Florian; Cuniberti, Gianaurelio

    2006-01-01

    A minimal model for coherent transport through a donor/acceptor molecular junction is presented. The two donor and acceptor sites are described by single levels energetically separated by an intramolecular tunnel barrier. In the limit of strong coupling to the electrodes a current rectification for different bias voltage polarities occurs. Contacts with recent experiments of molecular rectification are also given.

  9. Thermal rectification in thickness-asymmetric graphene nanoribbons

    OpenAIRE

    Zhong, Wei-Rong; Huang, Wei-Hao; Deng, Xi-Rong; Ai, Bao-Quan

    2011-01-01

    Thermal rectification in thickness asymmetric graphene nanoribbons connecting single-layer with multi-layer graphene is investigated by using classical nonequilibrium molecular dynamics. It is reported that the graphene nanoribbons with thickness-asymmetry have a good thermal rectification. The thermal rectification factor depends on temperature as well as the thickness-ratio of the two-segment. Our results provide a direct evidence that the thermal rectifier can be achieved in a nanostructur...

  10. Electron transport through molecular junctions

    Science.gov (United States)

    Zimbovskaya, Natalya A.; Pederson, Mark R.

    2011-12-01

    At present, metal-molecular tunnel junctions are recognized as important active elements in molecular electronics. This gives a strong motivation to explore physical mechanisms controlling electron transport through molecules. In the last two decades, an unceasing progress in both experimental and theoretical studies of molecular conductance has been demonstrated. In the present work we give an overview of theoretical methods used to analyze the transport properties of metal-molecular junctions as well as some relevant experiments and applications. After a brief general description of the electron transport through molecules we introduce a Hamiltonian which can be used to analyze electron-electron, electron-phonon and spin-orbit interactions. Then we turn to description of the commonly used transport theory formalisms including the nonequilibrium Green’s functions based approach and the approach based on the “master” equations. We discuss the most important effects which could be manifested through molecules in electron transport phenomena such as Coulomb, spin and Frank-Condon blockades, Kondo peak in the molecular conductance, negative differential resistance and some others. Bearing in mind that first principles electronic structure calculations are recognized as the indispensable basis of the theory of electron transport through molecules, we briefly discuss the main equations and some relevant applications of the density functional theory which presently is often used to analyze important characteristics of molecules and molecular clusters. Finally, we discuss some kinds of nanoelectronic devices built using molecules and similar systems such as carbon nanotubes, various nanowires and quantum dots.

  11. Molecular motor efficiency is maximized in the presence of both power-stroke and rectification through feedback

    Science.gov (United States)

    Schmitt, R. K.; Parrondo, J. M. R.; Linke, H.; Johansson, J.

    2015-06-01

    We present a model for a feedback-controlled ratchet consisting of a Brownian particle and a moving, finite barrier that is shifted by an external agent depending on the position of the particle. By modifying the value of a single parameter of the feedback protocol, the model can act either as a pure rectifier, a power-stroke (PS) motor, or a combination of both. Interestingly, in certain situations the motor reaches a maximum efficiency for an intermediate value of that parameter, i.e., for a combination of the information ratchet and the PS mechanisms. We relate our results to the biological motors kinesin, myosin II, and myosin V, finding that these motors operate in a regime of length scales and forces where the efficiency is maximized for a combination of rectification and PS mechanisms.

  12. Exploiting hydrogenation for thermal rectification in graphene nanoribbons

    Science.gov (United States)

    Melis, Claudio; Barbarino, Giuliana; Colombo, Luciano

    2015-12-01

    We present a molecular dynamics study providing evidence that it is possible to conceive efficient thermal diodes by a suitable hydrogen decoration of graphene nanoribbons. We estimate thermal rectifications at graphane/graphene interfaces with vertical, triangular, and T-shaped morphologies, and we report a significant thermal rectification up to ˜54 % for the triangular one. The dependence of the thermal rectification on the nanoribbon dimensions, vertex angle, and temperature gradient is also explored. The physical origin of the observed rectification is analyzed in terms of the different temperature dependence of the thermal conductivity in the pristine materials and the overlap of phonon densities in the different morphologies. Finally, we propose an effective continuum model to describe thermal rectification, which is only based on the steady state temperature profile rather than the actual heat flux. The model quantitatively predicts thermal rectification in very good agreement with the standard analysis based on the heat flux estimate.

  13. Molecular electronic junction transport

    DEFF Research Database (Denmark)

    Solomon, Gemma C.; Herrmann, Carmen; Ratner, Mark

    Whenasinglemolecule,oracollectionofmolecules,isplacedbetween two electrodes and voltage is applied, one has a molecular transport junction. We discuss such junctions, their properties, their description, and some of their applications. The discussion is qualitative rather than quantitative, and f...

  14. Molecular electronic junction transport

    DEFF Research Database (Denmark)

    Solomon, Gemma C.; Herrmann, Carmen; Ratner, Mark

    2012-01-01

    Whenasinglemolecule,oracollectionofmolecules,isplacedbetween two electrodes and voltage is applied, one has a molecular transport junction. We discuss such junctions, their properties, their description, and some of their applications. The discussion is qualitative rather than quantitative, and focuses on mechanism, structure/function relations, regimes and mechanisms of transport, some molecular regularities, and some substantial challenges facing the field. Because there are many regimes and m...

  15. Electron transport through molecular junctions

    International Nuclear Information System (INIS)

    At present, metal–molecular tunnel junctions are recognized as important active elements in molecular electronics. This gives a strong motivation to explore physical mechanisms controlling electron transport through molecules. In the last two decades, an unceasing progress in both experimental and theoretical studies of molecular conductance has been demonstrated. In the present work we give an overview of theoretical methods used to analyze the transport properties of metal–molecular junctions as well as some relevant experiments and applications. After a brief general description of the electron transport through molecules we introduce a Hamiltonian which can be used to analyze electron–electron, electron–phonon and spin–orbit interactions. Then we turn to description of the commonly used transport theory formalisms including the nonequilibrium Green’s functions based approach and the approach based on the “master” equations. We discuss the most important effects which could be manifested through molecules in electron transport phenomena such as Coulomb, spin and Frank–Condon blockades, Kondo peak in the molecular conductance, negative differential resistance and some others. Bearing in mind that first principles electronic structure calculations are recognized as the indispensable basis of the theory of electron transport through molecules, we briefly discuss the main equations and some relevant applications of the density functional theory which presently is often used to analyze important characteristics of molecules and molecular clusters. Finally, we discuss some kinds of nanoelectronic devices built using molecules and similar systems such as carbon nanotubes, various nanowires and quantum dots.

  16. Rectification in Y-junctions of Luttinger liquid wires

    OpenAIRE

    Wang, Chenjie; Feldman, D. E.

    2010-01-01

    We investigate rectification of a low-frequency ac bias in Y-junctions of one-channel Luttinger liquid wires with repulsive electron interaction. Rectification emerges due to three scatterers in the wires. We find that it is possible to achieve a higher rectification current in a Y-junction than in a single wire with an asymmetric scatterer at the same interaction strength and voltage bias. The rectification effect is the strongest in the absence of the time-reversal symmetry. In that case, t...

  17. Electron scattering on molecular hydrogen

    International Nuclear Information System (INIS)

    The author considers scattering phenomena which occur when a beam of electrons interacts with a molecular hydrogen gas of low density. Depending on the energy loss of the scattered electrons one can distinguish elastic scattering, excitation and (auto)ionization of the H2-molecule. The latter processes may also lead to dissociation. These processes are investigated in four experiments in increasing detail. (Auth.)

  18. Inelastic transport and low-bias rectification in a single-molecule diode.

    Science.gov (United States)

    Hihath, Joshua; Bruot, Christopher; Nakamura, Hisao; Asai, Yoshihiro; Díez-Pérez, Ismael; Lee, Youngu; Yu, Luping; Tao, Nongjian

    2011-10-25

    Designing, controlling, and understanding rectification behavior in molecular-scale devices has been a goal of the molecular electronics community for many years. Here we study the transport behavior of a single molecule diode, and its nonrectifying, symmetric counterpart at low temperatures, and at both low and high biases to help elucidate the electron-phonon interactions and transport mechanisms in the rectifying system. We find that the onset of current rectification occurs at low biases, indicating a significant change in the elastic transport pathway. However, the peaks in the inelastic electron tunneling (IET) spectrum are antisymmetric about zero bias and show no significant changes in energy or intensity in the forward or reverse bias directions, indicating that despite the change in the elastic transmission probability there is little impact on the inelastic pathway. These results agree with first principles calculations performed to evaluate the IETS, which also allow us to identify which modes are active in the single molecule junction. PMID:21932824

  19. Molecular electronic-structure theory

    CERN Document Server

    Helgaker, Trygve; Olsen, Jeppe

    2014-01-01

    Ab initio quantum chemistry has emerged as an important tool in chemical research and is appliced to a wide variety of problems in chemistry and molecular physics. Recent developments of computational methods have enabled previously intractable chemical problems to be solved using rigorous quantum-mechanical methods. This is the first comprehensive, up-to-date and technical work to cover all the important aspects of modern molecular electronic-structure theory. Topics covered in the book include: * Second quantization with spin adaptation * Gaussian basis sets and molecular-integral evaluati

  20. Silicon-based molecular electronics

    CERN Document Server

    Rakshit, T; Ghosh, A W; Datta, S

    2003-01-01

    Molecular electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport through semiconductor-molecule heterostructures, combining a semi-empirical treatment of the bulk silicon bandstructure with a first-principles description of the molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the molecular levels are driven by an STM potential into the semiconducting band-gap. The peaks appear for positive bias on a p-doped and negative for an n-doped substrate. Charging in these devices is compromised by the RTD action, allowing possible identification of several molecular highest occupied (HOMO) and lowest unoccupied (LUMO) levels. Recent experiments by Hersam et al. [1] support our theoretical predictions.

  1. Thermal rectification in asymmetric U-shaped graphene flakes

    International Nuclear Information System (INIS)

    In this paper, we study the thermal rectification in asymmetric U-shaped graphene flakes by nonequilibrium molecular dynamics simulations. The graphene flakes are composed of a beam and two asymmetric arms. It is found that the heat flux runs preferentially from the wide arm to the narrow arm, which indicates a strong rectification effect. The dependence of the rectification ratio upon the heat flux, the length and the width of the beam and the two arms is studied. It shows that the two asymmetric arms play the central role in thermal rectification and a proper design is needed to obtain the maximum rectification ratio. The result suggests a possible route to manage the heat dissipation in U-shaped graphene based nanoelectronic devices that have recently been fabricated

  2. Electron transport in molecular junctions

    DEFF Research Database (Denmark)

    Jin, Chengjun

    certain image charge position are in quantitative agreement with the experiments, while pure DFT is not. This is the consequence of the accurate energy level alignment, where the DFT+∑ method corrects the self-interaction error in the standard DFT functional and uses a static image charge model to include...... where the lowest unoccupied molecular level (LUMO) of the 44BP molecule hybridizes strongly with Ni 3d orbitals, the gating is auxiliary by the so-called spinterface. Finally, the correlation effect of the image charge beyond the energy level renormalization has been studied. It is shown that the finite......This thesis addresses the electron transport in molecular junctions, focusing on the energy level alignment and correlation effects. Various levels of theory have been applied to study the structural and electronic effects in different molecular junctions, starting from the single particle density...

  3. A gate controlled conjugated single molecule diode: Its rectification could be reversed

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qun, E-mail: zq@nuist.edu.cn

    2014-10-01

    A gate controlled Au/diphenyldipyrimidinyl/Au single molecule diode is simulated by a tight-binding Hamiltonian combined with Green's Function and transport methods. After calculating a number of electronic transport characteristics under various gate voltages, a clear modulation by gate is got and when the positive voltage is high enough, the rectification could be reversed. This is advisable for the designing and building future molecular logic devices and integrated circuits.

  4. Thermal Rectification in Graded Materials

    OpenAIRE

    Wang, Jiao; Pereira, Emmanuel; Casati, Giulio

    2012-01-01

    In order to identify the basic conditions for thermal rectification we investigate a simple model with non-uniform, graded mass distribution. The existence of thermal rectification is theoretically predicted and numerically confirmed, suggesting that thermal rectification is a typical occurrence in graded systems, which are likely to be natural candidates for the actual fabrication of thermal diodes. In view of practical implications, the dependence of rectification on the asymmetry and syste...

  5. Current rectification by molecules with asymmetric tunneling barriers

    OpenAIRE

    Kornilovitch, P.E.; Bratkovsky, A. M.; Williams, R. S.

    2002-01-01

    A simple experimentally accessible realization of current rectification by molecules (molecular films) bridging metal electrodes is described. It is based on the spatial asymmetry of the molecule and requires only one resonant conducting molecular level (pi-orbital). The rectification, which is due to asymmetric coupling of the level to the electrodes by tunnel barriers, is largely independent of the work function difference between the two electrodes. Results of extensive numerical studies o...

  6. EDITORIAL: Focus on Molecular Electronics FOCUS ON MOLECULAR ELECTRONICS

    Science.gov (United States)

    Scheer, Elke; Reineker, Peter

    2008-06-01

    The notion 'molecular electronics' has been used more frequently since the 1970s and summarizes a series of physical phenomena and ideas for their application in connection with organic molecules, oligomers, polymers, organic aggregates and solids. The properties studied in this field were connected to optical and electrical phenomena, such as optical absorption, fluorescence, nonlinear optics, energy transport, charge transfer, electrical conductance, and electron and nuclear spin-resonance. The final goal was and is to build devices which can compete or surpass some aspects of inorganic semiconductor devices. For example, on the basis of organic molecules there exist rectifiers, transistors, molecular wires, organic light emitting diodes, elements for photovoltaics, and displays. With respect to applications, one aspect of the organic materials is their broad variability and the lower effort and costs for their processability. The step from microstructures to the investigation of nanostructures is a big challenge also in this field and has lead to what nowadays is called molecular electronics in its narrow sense. In this field the subjects of the studies are often single molecules, e.g. single molecule optical spectroscopy, electrical conductance, i.e. charge transport through a single molecule, the influence of vibrational degrees of freedom, etc. A challenge here is to provide the techniques for addressing in a reproducible way the molecular scale. In another approach small molecular ensembles are studied in order to avoid artefacts from particular contact situations. The recent development of the field is presented in [1 8]. In this Focus Issue we present new results in the field of 'molecular electronics', both in its broad and specialized sense. One of the basic questions is the distribution of the energy levels responsible for optical absorption on the one hand and for the transport of charge on the other. A still unanswered question is whether the Wannier exciton model applies in which the excitation is distributed over several molecules or whether a good description is given by the Frenkel exciton model with the electron and the whole being localized at the same molecular unit. In organic semiconductors the charge transport usually occurs on the basis of holes because of the presence of many defects giving rise to a localization of the electrons. It is therefore a challenge to produce materials with both positive and negative mobile charge carriers. In the 1990s V M Agranovich introduced the idea of hybrid excitons, i.e. of nanostructured materials consisting of both organic and inorganic semiconductors. At the interface between the organic and inorganic parts new excitons can appear, being a superposition of both Frenkel and Wannier excitons and having both the high oscillator strength of the Frenkel and the large optical nonlinearity of the Wannier exciton. The problem is to find optimum combinations of the organic and inorganic parts to enable the hybrid structure concept to work. Micro-cavities also play an important role in the investigation of organic materials resulting in a new state (polariton) as the superposition of a photon and an exciton because of the large exciton photon interaction. A similar excitation arises because of the interaction between plasmons and photons. A special geometrical shape of a nano-cavity increases the interaction between the electromagnetic radiation and a dipole sitting in the cavity. The interaction between vibronic degrees of freedom and electronic excitations plays an important role for various phenomena such as nonlinear processes, the question of coherence, information on the shape of a potential hypersurface, etc. With the help of femtosecond laser pulses, detailed information on such vibrations can be obtained. Also of great importance is the investigation of the energy transfer in artificial light-harvesting systems, e.g. in dendrimers. Finally the combination of experimental and theoretical investigations allows for a comparison of the spectra of two molecules with the same backbone (tetracene and rubrene). The transport of charge through a molecule occurs possibly in a stationary, but at any rate in a non-equilibrium situation. The study of dissipation in such situations requires special approaches, both in theory and in experiments. One key issue is the understanding of the role of the microscopic phenomena such as the excitation of vibrational modes and their macroscopic outcome, i.e. the dissipation. This topic is addressed in several contributions both theoretically and experimentally. From the theoretical side, for the investigation of the heat production during the electron transfer, non-equilibrium Green's functions have been utilized. In another contribution a combination of the non-equilibrium Green's function technique together with the density functional method has been developed for the calculation of the elastic and inelastic electronic transport. To calculate the transport of indistinguishable particles a path integral Monte Carlo approach has been put forward. In single-molecule transistors the gate-voltage dependence on the Kondo temperature and an accompanying strong Coulomb blockade can be explained by taking into account a strong electron vibron interaction including anharmonicities of the molecular potential surface. The transport of charges is heavily influenced by disorder. The case of static disorder is investigated for linear chains, carbon nanotubes and graphene ribbons. Finally it is shown that the charge transport through a single energy level coupled to a localized vibrational mode and two leads shows hysteretic effects which could possibly be used in a memory device. For applications the control of the current through a molecular junction is considered theoretically. Two possible mechanisms are discussed: the control via coherent destruction using predefined ultrafast laser pulses and the formation of laser pulses using optimal control theory. A group of contributions is dedicated to the study of electronic transport through molecules using various techniques ranging from scanning-tunnelling methods via controllable break-junctions to printing techniques and molecular networks. The molecules under study can be classified into two main groups. On the one hand the functionalization of aromatic or alkane molecules with thiols is used for establishing chemical binding to metal electrodes; in the other set of experiments fullerenes are used as model systems for studying the influence of orientation and heat dissipation. Molecular conducting networks are important under various aspects. Such networks are formed by an array of gold nanoparticles connected by conjugated molecular chains with one or two thiol ends and conduction investigations are performed under various conditions. A careful investigation of the experimental conditions is necessary when comparing conductance measurements using the break junction method. For example there are results demonstrating that several molecular junctions are formed in parallel between the electrodes. Other experiments use different materials for the junctions and measurements are performed at various temperatures. The transport of charge through an alkane-monolayer is investigated using micro-transfer printing to establish contacts without shorts. It is shown that both tunnelling between the electrodes and transport through the states of the molecules contribute to the conductance. C60 plays a role in various fields of molecular electronics. One aspect is the conductance through the molecule as a function of the orientation of the molecule on the surface. It is found that there is a strong orientation dependence of the transport on Au(111) surfaces and that it is almost independent on a Cu(100) surface. A further important phenomenon is the heating and cooling of C60 during charge transport depending on the surface of C60 adsorption. The differences are ascribed to the amount of charge transfer into C60 upon adsorption on different surfaces. In summary, in the field of molecular electronics new materials and structures are developed and investigated, both with respect to a basic understanding of the materials and their compositions and with respect to possible applications in electronics. While in the field of molecular electronics on the microscale the techniques are well established, they still need to be refined in the field of nano-molecular electronics. Nevertheless, both subfields share some of the most challenging questions: e.g. the problems of charge and energy transport, of excitations and the formation of new quasi-particles. Another question is the role of vibrational degrees of freedom, where on the one hand one has to cope with the unavoidable effect of heat dissipation. On the other hand, vibrational excitations are intimately connected to the individual molecule under study and thus offer the possibility to be used in functional devices based on intrinsic molecular properties. This Focus Issue represents a snapshot of the state of the art of this emerging field in the first half of 2008. We expect that the fast development which the research has undergone in recent years will even speed up in the near future. References [1] Pope M and Sweenberg Ch E 1999 Electronic Processes in Organic Crystals and Polymers 2nd edn (Oxford: Oxford University Press) [2] Silinsh E A and Capek V 1994 Organic Molecular Crystals (New York: AIP Press) [3] Agranovich V M and La Rocca G C 2002 Organic Nanostructures: Science and Applications, Proc. Int. School of Physics 'Enrico Fermi', Course CXLIX (Amsterdam: IOS Press) [4] Schwoerer M and Wolf H C 2007 Organic Molecular Solids (Weinheim: Wiley-VCH) [5] Cuniberti G, Fagas G and Richter K (ed) 2005 Introducing Molecular Electronics, Lecture Notes in Physics (Berlin: Springer) [6] Reed M and Lee T 2003 Molecular Nanoelectronics (Stevenson Ranch, CA: American Scientific Publishers) [7] Petty M C 2007 Molecular Electronics, (Weinheim: Wiley-VCH) [8] 2006 Molecular Wires and Nanoscale Conductors Faraday Discuss. 131 1 420 Focus on Molecular Electronics Contents Optical absorption and emission properties of rubrene: insight from a combined experimental and theoretical study T Petrenko, O Krylova, F Neese and M Sokolowski Rapid energy transfer in a dendrimer having ?-conjugated light-harvesting antennas I Akai, K Miyanari, T Shimamoto, A Fujii, H Nakao, A Okada, K Kanemoto, T Karasawa, H Hashimoto, A Ishida, A Yamada, I Katayama, J Takeda and M Kimura Cluster-based density-functional approach to quantum transport through molecular and atomic contacts F Pauly, J K Viljas, U Huniar, M Häfner, S Wohlthat, M Bürkle, J C Cuevas and G Schön Model of mixed Frenkel and charge-transfer excitons in donor acceptor molecular crystals: investigation of vibronic spectra I J Lalov, C Warns and P Reineker Suppressing the current through molecular wires: comparison of two mechanisms GuangQi Li, Michael Schreiber and Ulrich Kleinekathöfer Charge-memory effect in a polaron model: equation-of-motion method for Green functions Pino D'Amico, Dmitry A Ryndyk, Gianaurelio Cuniberti and Klaus Richter Determination of transport levels of organic semiconductors by UPS and IPS S Krause, M B Casu, A Schöll and E Umbach Electrical characterization of alkane monolayers using micro-transfer printing: tunneling and molecular transport C Kreuter, S Bächle, E Scheer and A Erbe Correlated charge transfer along molecular chains L Mühlbacher and J Ankerhold Non-equilibrium Green's functions in density functional tight binding: method and applications A Pecchia, G Penazzi, L Salvucci and A Di Carlo Asymmetric Coulomb blockade and Kondo temperature of single-molecule transistors Florian Elste and Felix von Oppen Electron phonon scattering in molecular electronics: from inelastic electron tunnelling spectroscopy to heating effects Alessio Gagliardi, Giuseppe Romano, Alessandro Pecchia, Aldo Di Carlo, Thomas Frauenheim and Thomas A Niehaus Interlinking Au nanoparticles in 2D arrays via conjugated dithiolated molecules Jianhui Liao, Markus A Mangold, Sergio Grunder, Marcel Mayor, Christian Schönenberger and Michel Calame Conductance values of alkanedithiol molecular junctions M Teresa González, Jan Brunner, Roman Huber, Songmei Wu, Christian Schönenberger and Michel Calame Particularities of surface plasmon exciton strong coupling with large Rabi splitting C Symonds, C Bonnand, J C Plenet, A Bréhier, R Parashkov, J S Lauret, E Deleporte and J Bellessa Excitonic and vibrational nonlinear processes in a polydiacetylene studied by a few-cycle pulse laser T Kobayashi, I Iwakura and A Yabushita Correlations of instantaneous transition energy and intensity of absorption peaks during molecular vibration: toward potential hyper-surface Takayoshi Kobayashi and Zhuan Wang Diffusion and localization in carbon nanotubes and graphene nanoribbons Norbert Nemec, Klaus Richter and Gianaurelio Cuniberti Molecular electronics in junctions with energy disorder Franz J Kaiser, Peter Hänggi and Sigmund Kohler Spatially resolved conductance of oriented C60 G Schull, N Néel, M Becker, J Kröger and R Berndt A design for an optical-nanocavity optimized for use with surface-bound light-emitting materials A M Adawi and D G Lidzey Electronic coupling of optical excitations in organic/inorganic semiconductor hybrid structures S Blumstengel, S Sadofev and F Henneberger The relation between the symmetry of vibrational modes and the potential curve displacement associated with electronic transition studied by using real-time vibrational spectroscopy Takayoshi Kobayashi, Zhuan Wang and Izumi Iwakura Lithographic mechanical break junctions for single-molecule measurements in vacuum: possibilities and limitations Christian A Martin, Dapeng Ding, Herre S J van der Zant and Jan M van Ruitenbeek Strong exciton photon coupling at room temperature in microcavities containing two-dimensional layered perovskite compounds G Lanty, A Bréhier, R Parashkov, J S Lauret and E Deleporte Bipolar transport in organic field-effect transistors: organic semiconductor blends versus contact modification Andreas Opitz, Michael Kraus, Markus Bronner, Julia Wagner and Wolfgang Brütting Resonant heating and substrate-mediated cooling of a single C60 molecule in a tunnel junction Gunnar Schulze, Katharina J Franke and Jose Ignacio Pascual

  7. Fullerene Derived Molecular Electronic Devices

    Science.gov (United States)

    Menon, Madhu; Srivastava, Deepak; Saini, Subbash

    1998-01-01

    The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal grapheme sheet, more complex joints require other mechanisms. In this work we explore structural and electronic properties of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme.

  8. Carbon Nanotubes: Molecular Electronic Components

    Science.gov (United States)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1997-01-01

    The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.

  9. Rectification effect about vacuum separating carbon nanotube bundle predicted by first-principles study

    International Nuclear Information System (INIS)

    For the molecular spintronics transport systems, we propose that the spin current rectifier can be constructed using the nonmagnetic lead. The proposal is confirmed according to the first-principles study of the transport characteristics of a vacuum separating (15,0) carbon nanotube bundle where only one zigzag edge is hydrogenated. The strong rectification effect for spin (charge) current is obtained in the case of the magnetic parallel (anti-parallel) configuration of two zigzag edges. Our investigations indicate that such device can be used as the spin filter and the counterpart of the p–n junction in the field of molecular electronics. -- Highlights: ? We propose that nonmagnetic leads can construct spin current rectifier. ? We propose a spin diode and a filter using CNT. ? The spin and charge current all have the rectification effect in the one-dimensional spin diode.

  10. Rectification of Composition Tableaux

    OpenAIRE

    Bechard, Melissa

    2012-01-01

    In this paper we define an algorithm for rectifying one cell in a composition tableau. We then describe a generalization of this rectification process. The generalization is from one cell in the first column to any number of cells in the first column, provided they are bottom-justified.

  11. Thermal rectification in asymmetric U-shaped graphene flakes

    OpenAIRE

    Cheh, Jigger; Zhao, Hong(Institute of Theoretical Physics, Shanxi University, Taiyuan, Shanxi 030006, China)

    2011-01-01

    In this paper, we study the thermal rectification in asymmetric U-shaped graphene flakes by using nonequilibrium molecular dynamics simulations. The graphene flakes are composed by a beam and two arms. It is found that the heat flux runs preferentially from the wide arm to the narrow arm which indicates a strong rectification effect. The dependence of the rectification ratio upon the heat flux, the length and the width of the beam, the length and width of the two arms are studied. The result ...

  12. Single-molecule diodes with high rectification ratios through environmental control

    Science.gov (United States)

    Capozzi, Brian; Xia, Jianlong; Adak, Olgun; Dell, Emma J.; Liu, Zhen-Fei; Taylor, Jeffrey C.; Neaton, Jeffrey B.; Campos, Luis M.; Venkataraman, Latha

    2015-06-01

    Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40 years ago and consisted of an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule-electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.

  13. Computational Design of Intrinsic Molecular Rectifiers Based on Asymmetric Functionalization of N-Phenylbenzamide.

    Science.gov (United States)

    Ding, Wendu; Koepf, Matthieu; Koenigsmann, Christopher; Batra, Arunabh; Venkataraman, Latha; Negre, Christian F A; Brudvig, Gary W; Crabtree, Robert H; Schmuttenmaer, Charles A; Batista, Victor S

    2015-12-01

    We report a systematic computational search of molecular frameworks for intrinsic rectification of electron transport. The screening of molecular rectifiers includes 52 molecules and conformers spanning over 9 series of structural motifs. N-Phenylbenzamide is found to be a promising framework with both suitable conductance and rectification properties. A targeted screening performed on 30 additional derivatives and conformers of N-phenylbenzamide yielded enhanced rectification based on asymmetric functionalization. We demonstrate that electron-donating substituent groups that maintain an asymmetric distribution of charge in the dominant transport channel (e.g., HOMO) enhance rectification by raising the channel closer to the Fermi level. These findings are particularly valuable for the design of molecular assemblies that could ensure directionality of electron transport in a wide range of applications, from molecular electronics to catalytic reactions. PMID:26642992

  14. Selection-rule blockade and rectification in quantum heat transport

    OpenAIRE

    Ojanen, Teemu

    2009-01-01

    We introduce a new thermal transport phenomenon, a unidirectional selection-rule blockade, and show how it produces unprecedented rectification of bosonic heat flow through molecular or mesoscopic quantum systems. Rectification arises from the quantization of energy levels of the conduction element and selection rules of reservoir coupling operators. The simplest system exhibiting the selection-rule blockade is an appropriately coupled three-level system, providing a candidate for a high-perf...

  15. Unexpected large thermal rectification in asymmetric grain boundary of graphene

    OpenAIRE

    Cao, Hai-Yuan; Xiang, Hongjun; Gong, Xin-Gao

    2011-01-01

    We have investigated the lattice thermal transport across the asymmetric tilt grain boundary between armchair and zigzag graphene by nonequilibrium molecular dynamics (NEMD). We have observed significant temperature drop and ultra-low temperature-dependent thermal boundary resistance. More importantly, we find an unexpected thermal rectification phenomenon. The thermal conductivity and Kapitza conductance is direction-dependent. The effect of thermal rectification could be a...

  16. Giant Thermal Rectification from Polyethylene Nanofiber Thermal Diodes

    OpenAIRE

    ZHANG, Teng; Luo, Tengfei

    2015-01-01

    The realization of phononic computing is held hostage by the lack of high performance thermal devices. Here we show through theoretical analysis and molecular dynamics simulations that unprecedented thermal rectification factors (as large as 1.20) can be achieved utilizing the phase dependent thermal conductivity of polyethylene nanofibers. More importantly, such high thermal rectifications only need very small temperature differences (< 20 oC) across the device, which is a ...

  17. Chaos and rectification of electromagnetic wave in a lateral semiconductor superlattice

    OpenAIRE

    Alekseev, Kirill N.; Pietilainen, Pekka; Zharov, Alexander A.; Feodor V. Kusmartsev

    2001-01-01

    We find the conditions for a rectification of electromagnetic wave in a lateral semiconductor superlattice with a high mobility of electrons. The rectification is assisted by a transition to a dissipative chaos at a very high mobility. We show that mechanism responsible for the rectification is a creation of warm electrons in the superlattice miniband caused by an interplay of the effects of nonlinearity and finite band width.

  18. Effect of proportion on rectification in organic co-oligomer spin rectifiers

    Science.gov (United States)

    Hu, Gui-Chao; Wang, Hui; Ren, Jun-Feng

    2011-07-01

    The rectification behaviours in organic magnetic/nonmagnetic co-oligomer spin rectifiers are investigated theoretically. It is found that both the charge current and the spin current through the device are rectified at the same time. By adjusting the proportion between the magnetic and nonmagnetic components, the threshold voltage and the rectification ratio of the rectifier are modulated. A large rectification ratio is obtained when the two components are equal in length. The intrinsic mechanism is analysed in terms of the asymmetric localization of molecular orbitals under biases. The effect of molecular length on the rectification is also discussed. These results will be helpful in the future design of organic spin diodes.

  19. Collective Current Rectification

    OpenAIRE

    Denisov, S.

    2006-01-01

    We consider a network of coupled underdamped ac-driven dynamical units exposed to a heat bath. The topology of connections defines the absence/presence of certain spatial symmetries, which in turn cause nonzero/zero value of a mean dc-output. We discuss dynamical mechanisms of the rectification and identify dc-current reversals with synchronization/desynchronization transitions in the network dynamics.

  20. Polaron effects on the optical rectification in asymmetrical semi-parabolic quantum wells

    International Nuclear Information System (INIS)

    The effect of the electron-phonon interaction on the optical rectification is investigated theoretically for electrons confined in semi-parabolic quantum wells. We found that the electron-phonon interaction in GaAs/AlGaAs quantum wells increases the optical rectification with up to a factor of 6-13

  1. Aspects of simulation for rectification studies

    Science.gov (United States)

    Mikhail, E. M.; Paderes, F. D., Jr.

    1983-01-01

    The use of mathematical models and simulation is suggested as an aid to rectification. An outline of the factors affecting rectification accuracy is presented along with methods and approaches used for rectifications.

  2. Electronic continuum model for molecular dynamics simulations

    OpenAIRE

    Leontyev, I. V.; Stuchebrukhov, A. A.

    2009-01-01

    A simple model for accounting for electronic polarization in molecular dynamics (MD) simulations is discussed. In this model, called molecular dynamics electronic continuum (MDEC), the electronic polarization is treated explicitly in terms of the electronic continuum (EC) approximation, while the nuclear dynamics is described with a fixed-charge force field. In such a force-field all atomic charges are scaled to reflect the screening effect by the electronic continuum. The MDEC model is rathe...

  3. The merger of electrochemistry and molecular electronics.

    Science.gov (United States)

    McCreery, Richard L

    2012-02-01

    Molecular Electronics has the potential to greatly enhance existing silicon-based microelectronics to realize new functions, higher device density, lower power consumption, and lower cost. Although the investigation of electron transport through single molecules and molecular monolayers in "molecular junctions" is a recent development, many of the relevant concepts and phenomena are derived from electrochemistry, as practiced for the past several decades. The past 10+ years have seen an explosion of research activity directed toward how the structure of molecules affects electron transport in molecular junctions, with the ultimate objective of "rational design" of molecular components with new electronic functions, such as chemical sensing, interactions with light, and low-cost, low-power consumer electronics. In order to achieve these scientifically and commercially important objectives, the factors controlling charge transport in molecules "connected" to conducting contacts must be understood, and methods for massively parallel manufacturing of molecular circuits must be developed. This Personal Account describes the development of reproducible and robust molecular electronic devices, starting with modified electrodes used in electrochemistry and progressing to manufacturable molecular junctions. Although the field faced some early difficulties in reliability and characterization, the pieces are now in place for rapid advances in understanding charge transport at the molecular level. Inherent in the field of Molecular Electronics are many electrochemical concepts, including tunneling, redox exchange, activated electron transfer, and electron coupling between molecules and conducting contacts. PMID:22144404

  4. Molecular Programming Pseudo-code Representation to Molecular Electronics

    CERN Document Server

    Pradhan, Manas Ranjan

    2010-01-01

    This research paper is proposing the idea of pseudo code representation to molecular programming used in designing molecular electronics devices. Already the schematic representation of logical gates like AND, OR, NOT etc.from molecular diodes or resonant tunneling diode are available. This paper is setting a generic pseudo code model so that various logic gates can be formulated. These molecular diodes have designed from organic molecules or Bio-molecules. Our focus is on to give a scenario of molecular computation through molecular programming. We have restricted our study to molecular rectifying diode and logic device as AND gate from organic molecules only.

  5. Electron transmission through molecules and molecular interfaces

    CERN Document Server

    Nitzan, A

    2001-01-01

    Electron transmission through molecules and molecular interfaces has been a subject of intensive research due to recent interest in electron transfer phenomena underlying the operation of the scanning tunneling microscope (STM) on one hand, and in the transmission properties of molecular bridges between conducting leads on the other. In these processes the traditional molecular view of electron transfer between donor and acceptor species give rise to a novel view of the molecule as a current carrying conductor, and observables such as electron transfer rates and yields are replaced by the conductivities, or more generally by current-voltage relationships, in molecular junctions. In this paper I review the current knowledge and understanding of this field, with particular emphasis on theoretical issues. Different approaches to computing the conduction properties of molecules and molecular assemblies are reviewed, and the relationships between them are discussed. Following a detailed discussion of static juncti...

  6. Electronic transport properties of molecular junctions based on the direct binding of aromatic ring to electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Tran Nguyen, E-mail: lantran@ims.ac.jp

    2014-01-15

    Highlights: • Transport properties of molecular junction having direct binding of aromatic ring to electrode have been investigated. • The conductance of junction with sp-type electrode is higher than that of junction with sd-type electrode. • The rectifying mechanism critically depends on the nature of benzene–electrode coupling. • The p–n junction-like can be obtained even without heteroatom doping. • The negative differential resistance effect was observed for the case of sp-type electrode. - Abstract: We have used the non-equilibrium Green’s function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene–electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p–n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of ?-conjugate to electrode will be useful to design the future molecular devices.

  7. Electrons in molecules from basic principles to molecular electronics

    CERN Document Server

    Launay, Jean-Pierre

    2014-01-01

    The purpose of this book is to provide the reader with essential keys to a unified understanding of the rapidly expanding field of molecular materials and devices: electronic structures and bonding, magnetic, electrical and photo-physical properties, and the mastering of electrons in molecular electronics. Chemists will discover how basic quantum concepts allow us to understand the relations between structures, electronic structures, and properties of molecular entities and assemblies, and to design new molecules and materials. Physicists and engineers will realize how the molecular world fits in with their need for systems flexible enough to check theories or provide original solutions to exciting new scientific and technological challenges. The non-specialist will find out how molecules behave in electronics at the most minute, sub-nanosize level. The comprehensive overview provided in this book is unique and will benefit undergraduate and graduate students in chemistry, materials science, and engineering, ...

  8. Electron transport through dipyrimidinyl-diphenyl diblock molecular wire: protonation effect

    CERN Document Server

    Li, Z

    2006-01-01

    Recently, rectifying direction inversion has been observed in dipyrimidinyl-diphenyl (PMPH) diblock molecular wire [J. Am. Chem. Soc. (2005) 127, 10456], and a protonation mechanism was suggested to explain this interesting phenomena. In this paper, we study the protonation effect on transport properties of PMPH molecule by first principles calculations. No significant rectification is found for the pristine diblock molecular wire. Protonation leads to conductance enhancement and rectification. However, for all considered junctions with rectifying effect, the preferential current directions are samely from dipyrimidinyl side to diphenyl side. Effect of molecule-electrode anchoring geometry is studied, and it is not responsible for the discrepancy between experiment and theory.

  9. Electronic transport properties of molecular junctions based on the direct binding of aromatic ring to electrodes

    Science.gov (United States)

    Lan, Tran Nguyen

    2014-01-01

    We have used the non-equilibrium Green's function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene-electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p-n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of ?-conjugate to electrode will be useful to design the future molecular devices.

  10. Giant Thermal Rectification from Polyethylene Nanofiber Thermal Diodes

    CERN Document Server

    Zhang, Teng

    2015-01-01

    The realization of phononic computing is held hostage by the lack of high performance thermal devices. Here we show through theoretical analysis and molecular dynamics simulations that unprecedented thermal rectification factors (as large as 1.20) can be achieved utilizing the phase dependent thermal conductivity of polyethylene nanofibers. More importantly, such high thermal rectifications only need very small temperature differences (< 20 oC) across the device, which is a significant advantage over other thermal diodes which need temperature biases on the order of the operating temperature. Taking this into consideration, we show that the dimensionless temperature-scaled rectification factors of the polymer nanofiber diodes range from 12 to 25 - much larger than other thermal diodes (< 8). The polymer nanofiber thermal diode consists of a crystalline portion whose thermal conductivity is highly phase-sensitive and a cross-linked portion which has a stable phase. Nanoscale size effect can be utilized t...

  11. Electrical gating and rectification in graphene three-terminal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Händel, B. [FG Nanotechnologie, Institut für Mikro- und Nanotechnologien MacroNano and Institut für Mikro- und Nanoelektronik, Postfach 100565, 98684 Ilmenau (Germany); FG Festkörperelektronik, Institut für Mikro- und Nanotechnologien MacroNano and Institut für Mikro- und Nanoelektronik, Technische Universität Ilmenau, Postfach 100565, 98684 Ilmenau (Germany); Hähnlein, B. [FG Nanotechnologie, Institut für Mikro- und Nanotechnologien MacroNano and Institut für Mikro- und Nanoelektronik, Postfach 100565, 98684 Ilmenau (Germany); Göckeritz, R. [FG Nanostrukturierte Materialien, Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale) (Germany); Schwierz, F. [FG Festkörperelektronik, Institut für Mikro- und Nanotechnologien MacroNano and Institut für Mikro- und Nanoelektronik, Technische Universität Ilmenau, Postfach 100565, 98684 Ilmenau (Germany); Pezoldt, J., E-mail: joerg.pezoldt@tu-ilmenau.de [FG Nanotechnologie, Institut für Mikro- und Nanotechnologien MacroNano and Institut für Mikro- und Nanoelektronik, Postfach 100565, 98684 Ilmenau (Germany)

    2014-02-01

    Graphene was grown on semiinsulating silicon carbide at 1800 °C and atmospheric argon pressure. The all carbon T- and Y-shape three terminal junction devices were fabricated using electron beam lithography. All devices featured the negative rectification effect. The exact properties of the devices like the curvature of the output voltage response can be tuned by changing the branch width in the T- and Y-shape devices. Beside the rectification a switching behavior is demonstrated with the same three terminal junctions.

  12. Thermoelectric effect in molecular electronics

    CERN Document Server

    Paulsson, M

    2003-01-01

    We provide a theoretical estimate of the thermoelectric current and voltage over a Phenyldithiol molecule. We also show that the thermoelectric voltage is (1) easy to analyze, (2) insensitive to the detailed coupling to the contacts, (3) large enough to be measured and (4) give valuable information, which is not readily accessible through other experiments, on the location of the Fermi energy relative to the molecular levels. The location of the Fermi-energy is poorly understood and controversial even though it is a central factor in determining the nature of conduction (n- or p-type). We also note that the thermoelectric voltage measured over Guanine molecules with an STM by Poler et al., indicate conduction through the HOMO level, i.e., p-type conduction.

  13. Resonant generation of the rectification electric mode in suddenly created cold lossless magnetized plasma. transversal propagation

    International Nuclear Information System (INIS)

    The nonlinear transformation of the linearly polarized source electromagnetic wave into electron and electromagnetic plasma oscillations, stationary (rectification and space-varying) modes, and traveling electron and electromagnetic plasma waves due to weak nonlinearity has been analyzed by means of the second order perturbation theory with the radio approximation. The efficiency of excitation of the transversal stationary, spatially nonperiodical (rectification) electric mode has been studied for different values of source wave frequency, taking electron cyclotron frequency as a parameter

  14. Studies of Organic Complexes and Thin Films as Materials for Molecular Electronics

    Science.gov (United States)

    Wu, Xiangli

    1995-01-01

    With the continuing miniaturization of electronic devices, a new challenge has arisen, to produce even smaller molecular electronic devices (Chapter 1). Some of the techniques used for studying molecular properties are discussed in Chapter 2: Langmuir-Blodgett (LB) films, attenuated total reflection (ATR) and grazing-angle (GA) Fourier transformed infrared (FTIR), scanning tunneling microscopy (STM), and ellipsometry. Three classes of organic semiconducting materials are discussed in Chapter 3: (1) Two new thiophene-derived annulenes were found to be good electron donors: their complexes with the electron acceptor TCNQF_4 were studied by conductivity measurements, FTIR, FTNIR (Fourier transformed near-infrared), and temperature -dependent EPR (electron paramagnetic resonance) spectroscopy. Both complexes are semiconductors at room temperature. (2) Bifunctional TTF derivatives were studied using the Langmuir -Blodgett technique, FTIR, UV-Vis (Ultraviolet-Visible) and conductivity measurements: Semiconducting LB films were obtained from iodine-doped multilayer films. (3) A record low band gap of 0.65 eV of a novel conducting polymer was determined by in situ spectroelectrochemistry combined with FTNIR. A D-pi-A type molecule of rm C_{16}H_{33 }-Q3CNQ is discussed in Chapter 4: rm C_{16}H_{33} -Q3CNQ was studied by the LB technique, and monolayer films were transferred onto single crystal Au(111) and HOPG (highly oriented pyrolytic graphite). The orientation of the LB monolayers was characterized by grazing-angle FTIR, ellipsometry, and STM. The Electron transfer (rectification) through the monolayers was studied by STS (scanning tunneling spectroscopy), and cyclic voltammetry (CV). Asymmetrical current-voltage response (I-V curves) through the monolayers were observed both in STS and CV. The direction of electron transfer through the molecules was in agreement with the Aviram-Ratner molecular rectifier model.

  15. Progress in molecular precursors for electronic materials

    Energy Technology Data Exchange (ETDEWEB)

    Buhro, W.E. [Washington Univ., St. Louis, MO (United States)

    1996-09-01

    Molecular-precursor chemistry provides an essential underpinning to all electronic-materials technologies, including photovoltaics and related areas of direct interest to the DOE. Materials synthesis and processing is a rapidly developing field in which advances in molecular precursors are playing a major role. This article surveys selected recent research examples that define the exciting current directions in molecular-precursor science. These directions include growth of increasingly complex structures and stoichiometries, surface-selective growth, kinetic growth of metastable materials, growth of size-controlled quantum dots and quantum-dot arrays, and growth at progressively lower temperatures. Continued progress in molecular-precursor chemistry will afford precise control over the crystal structures, nanostructures, and microstructures of electronic materials.

  16. Thermal rectification in quantum graded mass systems

    International Nuclear Information System (INIS)

    We show the existence of thermal rectification in the graded mass quantum chain of harmonic oscillators with self-consistent reservoirs. Our analytical study allows us to identify the ingredients leading to the effect. The presence of rectification in this effective, simple model (representing graded mass materials, systems that may be constructed in practice) indicates that rectification in graded mass quantum systems may be an ubiquitous phenomenon. Moreover, as the classical version of this model does not present rectification, our results show that, here, rectification is a direct result of the quantum statistics.

  17. Projected Quasiparticle Theory for Molecular Electronic Structure

    OpenAIRE

    Scuseria, Gustavo E; Jimenez-Hoyos, Carlos A.; Henderson, Thomas. M.; Samanta, Kousik; Ellis, Jason K.

    2011-01-01

    We derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem. All symmetries (particle number, spin, spatial, and complex conjugation) are deliberately broken and restored in a self-consistent variation-after-projection approach. We show that the resulting method yields a comprehensive black-box treatment of strong correlations with effective one-electron (mean-field) computational cost. The e...

  18. Valve-Less Rectification Pumps.

    Czech Academy of Sciences Publication Activity Database

    Tesa?, Václav

    Heidelberg : Springer Science+Business Media, LLC, 2008 - (Dongqing, L.), s. 2131-2139 ISBN 978-0-387-48998-8 R&D Projects: GA ?R GA101/07/1499 Institutional research plan: CEZ:AV0Z20760514 Keywords : microfluidics * pumps * fluidic rectification Subject RIV: BK - Fluid Dynamics http://www.springer.com/engineering/book/978-0-387-49000-7

  19. Scanning probe methods applied to molecular electronics

    Energy Technology Data Exchange (ETDEWEB)

    Pavlicek, Niko

    2013-08-01

    Scanning probe methods on insulating films offer a rich toolbox to study electronic, structural and spin properties of individual molecules. This work discusses three issues in the field of molecular and organic electronics. An STM head to be operated in high magnetic fields has been designed and built up. The STM head is very compact and rigid relying on a robust coarse approach mechanism. This will facilitate investigations of the spin properties of individual molecules in the future. Combined STM/AFM studies revealed a reversible molecular switch based on two stable configurations of DBTH molecules on ultrathin NaCl films. AFM experiments visualize the molecular structure in both states. Our experiments allowed to unambiguously determine the pathway of the switch. Finally, tunneling into and out of the frontier molecular orbitals of pentacene molecules has been investigated on different insulating films. These experiments show that the local symmetry of initial and final electron wave function are decisive for the ratio between elastic and vibration-assisted tunneling. The results can be generalized to electron transport in organic materials.

  20. Computational Nanotechnology Molecular Electronics, Materials and Machines

    Science.gov (United States)

    Srivastava, Deepak; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    This presentation covers research being performed on computational nanotechnology, carbon nanotubes and fullerenes at the NASA Ames Research Center. Topics cover include: nanomechanics of nanomaterials, nanotubes and composite materials, molecular electronics with nanotube junctions, kinky chemistry, and nanotechnology for solid-state quantum computers using fullerenes.

  1. Fingerprinting Electronic Molecular Complexes in Liquid

    Science.gov (United States)

    Nirmalraj, Peter; La Rosa, Andrea; Thompson, Damien; Sousa, Marilyne; Martin, Nazario; Gotsmann, Bernd; Riel, Heike

    2016-01-01

    Predicting the electronic framework of an organic molecule under practical conditions is essential if the molecules are to be wired in a realistic circuit. This demands a clear description of the molecular energy levels and dynamics as it adapts to the feedback from its evolving chemical environment and the surface topology. Here, we address this issue by monitoring in real-time the structural stability and intrinsic molecular resonance states of fullerene (C60)-based hybrid molecules in the presence of the solvent. Energetic levels of C60 hybrids are resolved by in situ scanning tunnelling spectroscopy with an energy resolution in the order of 0.1 eV at room-temperature. An ultra-thin organic spacer layer serves to limit contact metal-molecule energy overlap. The measured molecular conductance gap spread is statistically benchmarked against first principles electronic structure calculations and used to quantify the diversity in electronic species within a standard population of molecules. These findings provide important progress towards understanding conduction mechanisms at a single-molecular level and in serving as useful guidelines for rational design of robust nanoscale devices based on functional organic molecules.

  2. Fingerprinting Electronic Molecular Complexes in Liquid

    Science.gov (United States)

    Nirmalraj, Peter; La Rosa, Andrea; Thompson, Damien; Sousa, Marilyne; Martin, Nazario; Gotsmann, Bernd; Riel, Heike

    2016-01-01

    Predicting the electronic framework of an organic molecule under practical conditions is essential if the molecules are to be wired in a realistic circuit. This demands a clear description of the molecular energy levels and dynamics as it adapts to the feedback from its evolving chemical environment and the surface topology. Here, we address this issue by monitoring in real-time the structural stability and intrinsic molecular resonance states of fullerene (C60)-based hybrid molecules in the presence of the solvent. Energetic levels of C60 hybrids are resolved by in situ scanning tunnelling spectroscopy with an energy resolution in the order of 0.1 eV at room-temperature. An ultra-thin organic spacer layer serves to limit contact metal-molecule energy overlap. The measured molecular conductance gap spread is statistically benchmarked against first principles electronic structure calculations and used to quantify the diversity in electronic species within a standard population of molecules. These findings provide important progress towards understanding conduction mechanisms at a single-molecular level and in serving as useful guidelines for rational design of robust nanoscale devices based on functional organic molecules. PMID:26743542

  3. Single-Component Molecular Metals for Molecular Electronics

    Science.gov (United States)

    Tanaka, Hisashi; Tokumoto, Madoka; Kobayashi, Hayao; Kobayashi, Akiko

    2004-03-01

    Many organic conductors consist of more than one component, i.e. donor molecules and acceptor molecules, to form charge transfer complexes. In most single-component molecular conductors, "doping" process is necessary to create charge carriers. Both of them require complex or multiple processes for preparation and therefore are not suitable for application as conducting wires or leads in molecular electronics. Therefore, intrinsic single-component molecular metals would be more desirable as molecular wires, in terms of processibility. Recently we have reported that [Ni(tmdt)2] (tmdt=trimethylenetetrathiafulvalenedithiolate) is a new three-dimensional synthetic metallic crystal composed of single-component molecules[1]. The neutral [Ni(tmdt)2] crystal shows a conductivity as high as 400 S/cm at room temperature, and stays metallic down to 0.6 K. Moreover, de Haas-van Alphen oscillations, consistent with the three-dimensional Fermi surface, were observed using AFM micro cantilever[2]. In this presentation, we will report the anisotropy in the electrical conductivity of [Ni(tmdt)2] single crystal, compared with that of three-dimensional molecular stacking. In particular, the difference between single crystal conduction and polycrystalline conduction, as well as a processibility study as wiring material, will be presented. [1] H. Tanaka et al., Science 291, 197 (2001) [2] H. Tanaka et al. to be published.

  4. Electronic transport properties of molecular junctions based on the direct binding of aromatic ring to electrodes

    International Nuclear Information System (INIS)

    Highlights: • Transport properties of molecular junction having direct binding of aromatic ring to electrode have been investigated. • The conductance of junction with sp-type electrode is higher than that of junction with sd-type electrode. • The rectifying mechanism critically depends on the nature of benzene–electrode coupling. • The p–n junction-like can be obtained even without heteroatom doping. • The negative differential resistance effect was observed for the case of sp-type electrode. - Abstract: We have used the non-equilibrium Green’s function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene–electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p–n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of π-conjugate to electrode will be useful to design the future molecular devices

  5. Fullerene-derived molecular electronic devices

    Science.gov (United States)

    Menon, M.; Srivastava, D.; Saini, S.

    1998-08-01

    The carbon nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural and electronic properties of complex three-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme.

  6. Triazatriangulene as binding group for molecular electronics

    DEFF Research Database (Denmark)

    Wei, Zhongming; Wang, Xintai

    2014-01-01

    The triazatriangulene (TATA) ring system was investigated as a binding group for tunnel junctions of molecular wires on gold surfaces. Self-assembled monolayers (SAMs) of TATA platforms with three different lengths of phenylene wires were fabricated, and their electrical conductance was recorded by both conducting probe-atomic force microscopy (CP-AFM) and scanning tunneling microscopy (STM). Similar measurements were performed for phenylene SAMs with thiol anchoring groups as references. It was found that, despite the presence of a sp3 hybridized carbon atom in the conduction path, the TATA platform displays a contact resistance only slightly larger than the thiols. This surprising finding has not been reported before and was analyzed by theoretical computations of the transmission functions of the TATA anchored molecular wires. The relatively low contact resistance of the TATA platform along with its high stability and directionality make this binding group very attractive for molecular electronic measurements and devices. (Figure Presented).

  7. Triazatriangulene as binding group for molecular electronics

    DEFF Research Database (Denmark)

    Wei, Zhongming; Wang, Xintai; Borges, Anders; Santella, Marco; Li, Tao; Sørensen, Jakob Kryger; Vanin, Marco; Hu, Wenping; Liu, Yunqi; Ulstrup, Jens; Solomon, Gemma C.; Chi, Qijin; Bjørnholm, Thomas; Nørgaard, Kasper; Laursen, Bo Wegge

    2014-01-01

    The triazatriangulene (TATA) ring system was investigated as a binding group for tunnel junctions of molecular wires on gold surfaces. Self-assembled monolayers (SAMs) of TATA platforms with three different lengths of phenylene wires were fabricated, and their electrical conductance was recorded ...... with its high stability and directionality make this binding group very attractive for molecular electronic measurements and devices. (Figure Presented).......The triazatriangulene (TATA) ring system was investigated as a binding group for tunnel junctions of molecular wires on gold surfaces. Self-assembled monolayers (SAMs) of TATA platforms with three different lengths of phenylene wires were fabricated, and their electrical conductance was recorded by...... both conducting probe-atomic force microscopy (CP-AFM) and scanning tunneling microscopy (STM). Similar measurements were performed for phenylene SAMs with thiol anchoring groups as references. It was found that, despite the presence of a sp3 hybridized carbon atom in the conduction path, the TATA...

  8. Radar image registration and rectification

    Science.gov (United States)

    Naraghi, M.; Stromberg, W. D.

    1983-01-01

    Two techniques for radar image registration and rectification are presented. In the registration method, a general 2-D polynomial transform is defined to accomplish the geometric mapping from one image into the other. The degree and coefficients of the polynomial are obtained using an a priori found tiepoint data set. In the second part of the paper, a rectification procedure is developed that models the distortion present in the radar image in terms of the radar sensor's platform parameters and the topographic variations of the imaged scene. This model, the ephemeris data and the digital topographic data are then used in rectifying the radar image. The two techniques are then used in registering and rectifying two examples of radar imagery. Each method is discussed as to its benefits, shortcomings and registration accuracy.

  9. Rectification effect in asymmetric Kerr nonlinear medium

    International Nuclear Information System (INIS)

    Based on the transfer matrix method, the recursion of an electromagnetic wave propagating in an asymmetric Kerr nonlinear medium is analytically formulated, from which the rectification effect is clearly presented. The effects on the rectification region of the linear part and nonlinear coefficient of permittivity are both studied, and the energy densities before and after rectification are discussed. We use a rectifying factor to describe the intensity of the rectification effect. The result shows that every transmission peak is divided into two parts when the symmetry is broken, and nonlinear asymmetry has a more significant effect on the rectification effect than the linear asymmetry. The rectification intensity and area will be enlarged when the asymmetry factor is increased in a certain range

  10. Rectification of algebras and modules

    OpenAIRE

    Hinich, V.

    2013-01-01

    Let O be a topological (colored) operad. The Lurie infinity-category of O-algebras with values in (infinity-category of) complexes is compared to the infinity-category underlying the model category of (classical) dg O-algebras. This can be interpreted as a "rectification" result for Lurie operad algebras. A similar result is obtained for modules over operad algebras, as well as for algebras over topological PROPs.

  11. Thermal rectification in quantum graded mass systems

    OpenAIRE

    Pereira, Emmanuel

    2010-01-01

    We show the existence of thermal rectification in the graded mass quantum chain of harmonic oscillators with self-consistent reservoirs. Our analytical study allows us to identify the ingredients leading to the effect. The presence of rectification in this effective, simple model (representing graded mass materials, systems that may be constructed in practice) indicates that rectification in graded mass quantum systems may be an ubiquitous phenomenon. Moreover, as the classical version of thi...

  12. Electron-phonon interactions in molecular electronic devices

    Science.gov (United States)

    Sergueev, Nikolai

    Over the past several decades, semiconductor electronic devices have been miniaturized following the remarkable "Moores law". If this trend is to continue, devices will reach physical size limit in the not too distance future. There is therefore an urgent need to understand the physics of electronic devices at nano-meter scale, and to predict how such nanoelectronics will work. In nanoelectronics theory, one of the most important and difficult problems concerns electron-phonon interactions under nonequilibrium transport conditions. Calculating phonon spectrum, electron-phonon interaction, and their effects to charge transport for nanoelectronic devices including all atomic microscopic details, is a very difficult and unsolved problem. It is the purpose of this thesis to develop a theoretical formalism and associated numerical tools for solving this problem. In our formalism, we calculate electronic Hamiltonian via density functional theory (DFT) within the nonequilibrium Green's functions (NEGF) which takes care of nonequilibrium transport conditions and open device boundaries for the devices. From the total energy of the device scattering region, we derive the dynamic matrix in analytical form within DFT-NEGF and it gives the vibrational spectrum of the relevant atoms. The vibrational spectrum together with the vibrational eigenvector gives the electron-phonon coupling strength at nonequilibrium for various scattering states. A self-consistent Born approximation (SCBA) allows one to determine the phonon self-energy, the electron Green's function, the electronic density matrix and the electronic Hamiltonian, all self-consistently within equal footing. The main technical development of this work is the DFT-NEGF-SCBA formalism and its associated codes. A number of important physics issues are studied in this work. We start with a detailed analysis of transport properties of C60 molecular tunnel junction. We find that charge transport is mediated by resonances due to an alignment of the Fermi level of the electrodes and the lowest unoccupied C60 molecular orbital. We then make a first step toward the problem of analyzing phonon modes of the C60 by examining the rotational and the center-of-mass motions by calculating the total energy. We obtain the characteristic frequencies of the libration and the center-of-mass modes, the latter is quantitatively consistent with recent experimental measurements. Next, we developed a DFT-NEGF theory for the general purpose of calculating any vibrational modes in molecular tunnel junctions. We derive an analytical expression for dynamic matrix within the framework of DFT-NEGF. Diagonalizing the dynamic matrix we obtain the vibrational (phonon) spectrum of the device. Using this technique we calculate the vibrational spectrum of benzenedithiolate molecule in a tunnel junction and we investigate electron-phonon coupling under an applied bias voltage during current flow. We find that the electron-phonon coupling strength for this molecular device changes drastically as the bias voltage increases, due to dominant contributions from the center-of-mass vibrational modes of the molecule. Finally, we have investigated the reverse problem, namely the effect of molecular vibrations on the tunneling current. For this purpose we developed the DFT-NEGF-SCBA formalism, and an example is given illustrating the power of this formalism.

  13. Spin-excited states and rectification in an organic spin rectifier

    Science.gov (United States)

    Zuo, Meng-Ying; Hu, Gui-Chao; Li, Ying; Ren, Jun-Feng; Wang, Chuan-Kui

    2014-08-01

    Spin-excited states in an asymmetric magnetic organic co-oligomer diode are investigated theoretically. The results demonstrate that the structural asymmetry of the co-oligomer is modulated by the spin-excited states, which is embodied in the wave functions of the eigenstates as well as the spin density wave. By calculating the transport property, a robust spin-current rectification concomitant with a charge-current rectification is observed in all spin-excited states. However, the current through the diode is suppressed distinctly by the spin-excited states, while the rectification ratios may be reduced or enhanced depending on the bias and the excited spins. The intrinsic mechanism is analyzed from the spin-dependent transmission combined with the change of molecular eigenstates under bias. Finally, the temperature-induced spin excitation is simulated. Significant rectification behavior is obtained even at room temperature.

  14. Electron and Phonon Transport in Molecular Junctions

    DEFF Research Database (Denmark)

    Li, Qian

    2015-01-01

    Molecular electronics provide the possibility to investigate electron and phonon transport at the smallest imaginable scale, where quantum effects can be investigated and exploited directly in the design. In this thesis, we study both electron transport and phonon transport in molecular junctions. The system we are interested in here are ?-stacked molecules connected with two semi-infinite leads. ?-stacked aromatic rings, connected via ?-? electronic coupling, provides a rather soft mechanical bridge while maintaining high electronic conductivity. We investigate electron transport and the thermoelectric response of five representative ?-stacked systems. We find that the transmission and power factor are both enhanced by increasing the conjugation length or adding substituent groups. The local transmission shows that several extra paths are added by cyano groups, which increases the total transmission at the Fermi energy. We propose and analyze a way of using ?   stacking to design molecular junctions to control heat transport. We develop a simple model system to identify optimal parameter regimes and then use density functional theory (DFT) to extract model parameters for a number of specific ?-stacked systems. It is found that the proposed mechanism can indeed signicantly reduce the phonon conductance but also increase it depending on the specific molecules and stackings used. Furthermore, we study how a molecule's conformation influence phonon transport by mechanically compressing an alkane chain in the junction with graphene leads, using DFT combined with scattering matrix approach. We find that the thermal conductance of the compressed junction drops by half in comparison to the extended junction, making it possible to turn on and o the heat current. The reduced thermal conductance in the compressed junction mainly stems from a large suppression of the transmission coefficients of the longitudinal and the in-plane transverse channels of the leads. Finally, we return and investigate phonon transport through ?-stacked molecules connected to graphene leads including all modes of the system using DFT method. It is found that the thermal conductance of ?-stacked systems can be reduced by 95%, compared with that in a single-molecule junction. Phonon transmission of ?-stacked systems is reduced dramatically in the whole frequency range and the left transmission mainly remains below 5 THz.

  15. Characterization of Hybrid Electronic Materials for Molecular Based Device Electronics

    Science.gov (United States)

    Daniels-Race, Theda

    2008-03-01

    Nanoscale device development, as an exercise in electronic materials fabrication, comes down to essentially one of two approaches---``top-down'' or ``bottom-up.'' In the former, the drive is to retain the macroscopic properties of the materials involved while shrinking toward ever diminishing device geometries. The latter approach attempts to control individual molecules and/or quantum-level structures, during the course of fabrication, in order to ultimately realize device functionality. This bottom-up design and control of molecular assemblies has united device engineers and scientists in testing new combinations of materials, both organic and inorganic. As a result, an entirely new class of nanoscale electronic structures and devices has emerged to create the field of hybrid electronic materials or HEMs^1. HEMs have shown promise as the basis for exciting device applications ranging from quantum computing to unique drug delivery methods. Although theoretical proposals of unimolecular transport began as early as the 1970s, it has been within the last decade in particular that research has yielded significant results in terms of nanoscale electronic applications for HEMs^2. However, many unresolved fundamental issues of electronic materials remain in this field. It is for this reason that in this talk, I will discuss a selection of HEM components (e.g.- self-assembled monolayers of n-alkanethiols, porphyrin molecules), their characterization, and their propensity for future nanoelectronic device development. 1. James R. Heath and Mark A. Ratner, Physics Today, May 2003; 43-49. 2. Mark A. Reed and Takhee Lee (Eds.), ``Molecular Nanoelectronics,'' American Scientific Publishers, Stevenson Ranch, CA, 2003.

  16. Modeling ion sensing in molecular electronics

    Science.gov (United States)

    Chen, Caroline J.; Smeu, Manuel; Ratner, Mark A.

    2014-02-01

    We examine the ability of molecules to sense ions by measuring the change in molecular conductance in the presence of such charged species. The detection of protons (H+), alkali metal cations (M+), calcium ions (Ca2+), and hydronium ions (H3O+) is considered. Density functional theory (DFT) is used within the Keldysh non-equilibrium Green's function framework (NEGF) to model electron transport properties of quinolinedithiol (QDT, C9H7NS2), bridging Al electrodes. The geometry of the transport region is relaxed with DFT. The transport properties of the device are modeled with NEGF-DFT to determine if this device can distinguish among the M+ + QDT species containing monovalent cations, where M+ = H+, Li+, Na+, or K+. Because of the asymmetry of QDT in between the two electrodes, both positive and negative biases are considered. The electron transmission function and conductance properties are simulated for electrode biases in the range from -0.5 V to 0.5 V at increments of 0.1 V. Scattering state analysis is used to determine the molecular orbitals that are the main contributors to the peaks in the transmission function near the Fermi level of the electrodes, and current-voltage relationships are obtained. The results show that QDT can be used as a proton detector by measuring transport through it and can conceivably act as a pH sensor in solutions. In addition, QDT may be able to distinguish among different monovalent species. This work suggests an approach to design modern molecular electronic conductance sensors with high sensitivity and specificity using well-established quantum chemistry.

  17. Projected quasiparticle theory for molecular electronic structure.

    Science.gov (United States)

    Scuseria, Gustavo E; Jiménez-Hoyos, Carlos A; Henderson, Thomas M; Samanta, Kousik; Ellis, Jason K

    2011-09-28

    We derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem. All symmetries (particle number, spin, spatial, and complex conjugation) are deliberately broken and restored in a self-consistent variation-after-projection approach. We show that the resulting method yields a comprehensive black-box treatment of static correlations with effective one-electron (mean-field) computational cost. The ensuing wave function is of multireference character and permeates the entire Hilbert space of the problem. The energy expression is different from regular HFB theory but remains a functional of an independent quasiparticle density matrix. All reduced density matrices are expressible as an integration of transition density matrices over a gauge grid. We present several proof-of-principle examples demonstrating the compelling power of projected quasiparticle theory for quantum chemistry. PMID:21974513

  18. Electron impact dissociation of molecular ions

    Science.gov (United States)

    Bahati, E. M.; Fogle, M. R.; Vane, C. R.; Bannister, M. E.; Zhaunerchyk, V.; Thomas, R. D.

    2006-05-01

    The ORNL Electron-Ion Crossed Beams Experiment is used to determine absolute cross sections for electron-impact dissociation of molecular ions. Investigations have been carried out on DCO^+, CH3^+ , and N2D^+ cations, considered as amongst those species playing important roles in such diverse areas as laboratory plasmas, astrophysics, and thermonuclear fusion. The obtained results on dissociation of DCO^+ resulting in CO^+ fragments are discussed in light of the energy levels and photo-dissociation cross section of HCO^+ predicted by ab initio multi-reference configuration interaction calculations [Koch et al, 1995 Ber. Bunsenges Phys. Chem. 99 (3) 393]. Preliminary results on CH3^+ are compared to the measurements of Lecointre et al [XXIV ICPEAC, Rosario, Argentina, 20 - 26 July 2005; (Poster Session)]. Results for dissociation of N2D^+ producing ND^+ are also presented.

  19. Reversal of Thermal Rectification in Quantum Systems

    OpenAIRE

    Zhang, Lifa; Yan, Yonghong; Wu, Chang-Qin; Wang, Jian-Sheng; Li, Baowen

    2009-01-01

    We study thermal transport in anisotropic Heisenberg spin chains using the quantum master equation. It is found that thermal rectification changes sign when the external homogeneous magnetic field is varied. This reversal also occurs when the magnetic field becomes inhomogeneous. Moreover, we can tune the reversal of rectification by temperatures of the heat baths, the anisotropy and size of the spin chains.

  20. Thermal rectification in nonlinear quantum circuits

    DEFF Research Database (Denmark)

    Ruokola, T.; Ojanen, T.; Jauho, Antti-Pekka

    2009-01-01

    We present a theoretical study of radiative heat transport in nonlinear solid-state quantum circuits. We give a detailed account of heat rectification effects, i.e., the asymmetry of heat current with respect to a reversal of the thermal gradient, in a system consisting of two reservoirs at finite...... rectification changes sign as a function of temperature....

  1. Electron Impact Dissociation of Molecular Ions

    International Nuclear Information System (INIS)

    Electron impact experiments were performed by means of our crossed electron-ion beam set-up. Singly and/or multiply charged ions that results from molecular ion fragmentation are detected individually. Cross-sections for their production are determined from their respective thresholds up to 2.5 keV. The animated crossed beams method is applied to measure: - Absolute inclusive cross sections for electron impact dissociation to individual ionic fragments from the energy threshold up to 2.5 keV. - The contributions from the different reaction channels are separated: single ionization (SI), dissociative excitation (DE) and dissociative ionization (DI). - Kinetic energy release distributions (KERD) of the fragment ions are determined at selected incident electron energies. It allows determination of groups of electronically excited states that contribute to the process considered. - Energy threshold determination allows identification of target initial ground and excited states. 1. Monohydride ions: HeH+, NH+, OH+, and isotopologues XD+: For HeH+, experimental results are available for the production of He+ and He2+. They were analysed taking into account the vibrational population measured in a separate charge transfer experiment (paper in preparation). 2. Polyhydride ions: NH2+, NH3+, OH2+ , OH3+ and isotopologues (unpublished). 3. Hydro(deutero)-carbon ions: C2D3+, C2D4+ and isotopologues C2D3H+, C2D2H2+ (unpublished). Experimental results have been obtained for C2D3+ and C2D4+. The collected data were analysed in detail. 4. Others: C2+ (unpublished). The full analysis of data for electron impact dissociation of C2+ yielding the C+ fragment was performed. These data now need to be published. N2H+, in progress. D3+, D2H+. Dissociation of H3+isotopologues have recently discussed comprehensively, especially as regards isotope effects in the fragmentation. (author)

  2. Energy transformation in molecular electronic systems

    International Nuclear Information System (INIS)

    Our new optical pumping spectroscopy (steady state, and double-laser pulse) allows the production and study of the unstable rare tautomer in its ground and excited states, including picosecond dynamic studies. Molecules under study here included 7-azaindole (model for biological purines), 3-hydroxyflavone (model for plant flavones), lumichrome, and other heterocyclics. New detailed molecular mechanisms for proton transfer are derived, especially with catalytic assisting molecules. A new proton-transfer laser of extraordinary efficiency has become a side dividend, possibly worth of industrial development. The excited and highly reactive singlet molecular oxygen species 1Δ/sub g/) has proven to be ubiquitous in chemical peroxide systems and in physically excited sensitizer-oxygen systems. Hyperbaric oxygen mechanisms in biology probably involve singlet oxygen. We have undertaken a spectroscopic study of tris - dibenzoylmethane chelates of Al, Gd, Eu, and Yb trivalent ions. These chelates offer a variety of electronic behaviors, from Z-effects on π-electron spin-orbital coupling (Al, Gd) to Weissman intramolecular energy transfer to 4f mestable levels (Eu, Gd). Elegant new spectroscopic resolution at 77K permits separation of tautomeric, parasitic self-absorption, dissociation, and cage effects to be resolved. 18 refs., 4 figs

  3. Separation processes, I: Azeotropic rectification

    Directory of Open Access Journals (Sweden)

    Milojevi? Svetomir

    2005-01-01

    Full Text Available In a series of two articles, the problems of azeotrope separation (part I and the design of separation units (part II were analyzed. The basic definition and equations of vapour-liquid equilibria for ideal and non-ideal systems, the importance of the activity coefficient calculation necessary for the analysis of non-ideal equilibrium systems, as well as theoretical aspects of azeotrope rectification and the determination of the optimal third component (modifier or azeotrope agent are presented in the first part.

  4. Electron dynamics in molecular interactions principles and applications

    CERN Document Server

    Hagelberg, Frank

    2013-01-01

    This volume provides a comprehensive introduction to the theory of electronic motion in molecular processes - an increasingly relevant and rapidly expanding segment of molecular quantum dynamics. Emphasis is placed on describing and interpreting transitions between electronic states in molecules as they occur typically in cases of reactive scattering between molecules, photoexcitation or nonadiabatic coupling between electronic and nuclear degrees of freedom. Electron Dynamics in Molecular Interactions aims at a synoptic presentation of some very recent theoretical efforts to solve th

  5. Effect of nanopore geometry on ion current rectification

    International Nuclear Information System (INIS)

    We present the results of systematic studies of ion current rectification performed on artificial asymmetric nanopores with different geometries and dimensions. The nanopores are fabricated by the ion track etching method using surfactant-doped alkaline solutions. By varying the alkali concentration in the etchant and the etching time, control over the pore profile and dimensions is achieved. The pore geometry is characterized in detail using field-emission scanning electron microscopy. The dependence of the ion current rectification ratio on the pore length, tip diameter, and the degree of pore taper is analysed. The experimental data are compared to the calculations based on the Poisson-Nernst-Planck equations. A strong effect of the tip geometry on the diode-like behaviour is confirmed.

  6. Wave rectification in plasma sheaths surrounding electric field antennas

    Science.gov (United States)

    Boehm, M. H.; Carlson, C. W.; Mcfadden, J. P.; Clemmons, J. H.; Ergun, R. E.; Mozer, F. S.

    1994-01-01

    Combined measurements of Langmuir or broadband whistler wave intensity and lower-frequency electric field waveforms, all at 10-microsecond time resolution, were made on several recent sounding rockets in the auroral ionosphere. It is found that Langmuir and whistler waves are partically rectified in the plasma sheaths surrounding the payload and the spheres used as antennas. This sheath rectification occurs whenever the high frequency (HF) potential across the sheath becomes of the same order as the electron temperature or higher, for wave frequencies near or above the ion plasma frequency. This rectification can introduce false low-frequency waves into measurements of electric field spectra when strong high-frequency waves are present. Second harmonic signals are also generated, although at much lower levels. The effect occurs in many different plasma conditions, primarily producing false waves at frequencies that are low enough for the antenna coupling to the plasma to be resistive.

  7. Fitting molecular fragments into electron density

    International Nuclear Information System (INIS)

    A number of techniques for the location of small and medium-sized model fragments in experimentally phased electron-density maps are explored. The application of one of these techniques to automated model building is discussed. Molecular replacement is a powerful tool for the location of large models using structure-factor magnitudes alone. When phase information is available, it becomes possible to locate smaller fragments of the structure ranging in size from a few atoms to a single domain. The calculation is demanding, requiring a six-dimensional rotation and translation search. A number of approaches have been developed to this problem and a selection of these are reviewed in this paper. The application of one of these techniques to the problem of automated model building is explored in more detail, with particular reference to the problem of sequencing a protein main-chain trace

  8. Thermoelectric transport with electron-phonon coupling and electron-electron interaction in molecular junctions

    OpenAIRE

    Ren, Jie; Zhu, Jian-Xin; Gubernatis, James E.; Chen WANG; LI, Baowen

    2011-01-01

    Within the framework of nonequilibrium Green's functions, we investigate the thermoelectric transport in a single molecular junction with electron-phonon and electron-electron interactions. By transforming into a displaced phonon basis, we are able to deal with these interactions non-perturbatively. Then, by invoking the weak tunneling limit, we are able to calculate the thermoelectricity. Results show that at low temperatures, resonances of the thermoelectric figure of meri...

  9. Macroscopic coherent rectification in Andreev interferometers

    International Nuclear Information System (INIS)

    We investigate nonlinear transport through quantum coherent metallic conductors contacted to superconducting components. We find that in certain geometries, the presence of superconductivity generates a large, finite-average rectification effect. Specializing to Andreev interferometers, we show that the direction and magnitude of rectification can be controlled by a magnetic flux tuning the superconducting phase difference at two contacts. In particular, this results in the breakdown of an Onsager reciprocity relation at finite bias. The rectification current is macroscopic in that it scales with the linear conductance, and we find that it exceeds 5% of the linear current at sub-gap biases of a few tens of microelectronvolts. (fast track communication)

  10. Short chain molecular junctions: Charge transport versus dipole moment

    Science.gov (United States)

    Ikram, I. Mohamed; Rabinal, M. K.

    2015-03-01

    The investigation of the influence of dipole moment of short chain organic molecules having three carbon atoms varying in end group on silicon surface was carried on. Here, we use three different molecules of propargyl series varying in dipole moment and its orientation to constitute molecular junctions. The charge transport mechanism in metal-molecules-semiconductor (MMS) junction obtained from current-voltage (I-V) characteristics shows the rectification behavior for two junctions whereas the other junction shows a weak rectification. The electronic properties of the molecules were calculated using Gaussian software package. The observed rectification behavior of these junctions is examined and found to be accounted to the orientation of dipole moment and electron cloud density distribution inside the molecules.

  11. Ion current rectification and rectification inversion in conical nanopores: a perm-selective view

    OpenAIRE

    Momotenko, Dmitry; Cortes Salazar, Fernando; Josserand, Jacques; Liu, Shujuan; Shoa, Yuanuha; Girault, Hubert

    2011-01-01

    Ionic transport in charged conical nanopores is known to give rise to ion current rectification. The present study shows that the rectification direction can be inverted when using electrolyte solutions at very low ionic strengths. To elucidate these phenomena, electroneutral conical nanopores containing a perm-selective region at the tip have been investigated and shown to behave like classical charged nanopores. An analytical model is proposed to account for these rectification processes.

  12. Theory of Vibrationally Inelastic Electron Transport through Molecular Bridges

    OpenAIRE

    Cizek, Martin; Thoss, Michael; Domcke, Wolfgang

    2003-01-01

    Vibrationally inelastic electron transport through a molecular bridge that is connected to two leads is investigated. The study is based on a generic model of vibrational excitation in resonant transmission of electrons through a molecular junction. Employing methods from electron-molecule scattering theory, the transmittance through the molecular bridge can be evaluated numerically exactly. The current through the junction is obtained approximately using a Landauer-type for...

  13. Langmuir-Blodgett Films a unique tool for molecular electronics

    CERN Document Server

    Hussain, Syed Arshad

    2009-01-01

    Molecular electronics is a new, exciting and interdisciplinary field of research. The main concern of the subject is to exploit the organic materials in electronic and optoelectronic devices. On the other hand Langmuir-Blodgett (LB) film deposition technique is one of the best among few methods used to manipulate materials in molecular level. In this article LB film preparation technique has been discussed briefly with an emphasize of its application towards molecular electronics.

  14. Electron Impact Dissociation of Molecular Ions

    International Nuclear Information System (INIS)

    Electron impact experiments were performed by means of our crossed electron-ion beam set-up. Singly and/or multiply charged ions that results from molecular ion fragmentation are detected individually. Cross-sections for their production are determined from their respective thresholds up to 2.5 keV. The animated crossed beams method is applied to measure: - Absolute inclusive cross sections for electron impact dissociation to individual ionic fragments from the energy threshold up to 2.5 keV. - The contributions from the different reaction channels are separated: single ionization (SI) dissociative excitation (DE) and dissociative ionization (DI). - Kinetic energy release distributions (KERD) of the fragment ions are determined at selected incident electron energies. It allows determination of groups of electronically excited states that contribute to the process considered. - Energy threshold determination allows identification of target initial ground and excited states. Molecular species studied in the frame of this CRP are grouped into the five following categories: 1. Light ions: H2+, D2+ and D3+, D2H+: For H2+, the particular importance of the internal energy, the vibrational population, has been underlined. Dissociation of H3+ isotopologues have recently discussed comprehensively in the two following papers, especially as regards isotope effects in the fragmentation. ''Absolute cross sections and kinetic energy release distributions for electron impact dissociation of D3+'' J. Lecointre, M.O. Abdellahi El Ghazaly, J.J. Jureta, D.S. Belic, X. Urbain and P. Defrance, J. Phys. B: At. Mol. Opt. Phys. 42 (2009) 075201 ''Isotope effects in electron impact dissociation of D2H+'' P. Defrance, J.J. Jureta, J. Lecointre and X. Urbain, J. Phys. B: At. Mol. Opt. Phys. 44 (2011) 075202. 2. Hydride ions: HeH+, OH+, OH2+, OH3+ and isotopologues (unpublished). For HeH+, experimental results are available for the production of He+ and He2+. They will be analysed taking into account the vibrational population measured in a separate charge transfer experiment. The reliable collection of the H+ fragment was not possible due to the large KER but this experiment will be considered in a soon future. 3. Hydro(deutero)-carbon ions: C2D3''+, C2D4''+ and isotopologues C2D3H''+, C2D2H2''+ (unpublished). The hydrocarbon and deuterocarbon families (CmHn''+ and CmDn''+) which play a particular role in the plasma studies are systematically investigated in our laboratory. Previous results were published for the methane series (CDn''+, n=1-4), for C2D+ and C2D2+. See number of references in the list here below. Experimental results have been obtained for C2D3+ and C2D4+. The collected data need to be analyzed in detail in order to determine separately the contributions of dissociative excitation and ionization, as well as the associated energy thresholds and KERDs. The standard procedure will be applied to put these data in a form which is suitable for plasma modelling applications. 4. Others: C2+ (unpublished). The full analysis of data for electron impact dissociation of C2+ yielding the C+ fragment was performed. These data now need to be published. 5. Nitrogen: NH+, ND+ and N2+. Dissociation of the nitrogen hydride has recently been made available to the community. In addition, dissociation of N2+was published earlier. ''Electron impact dissociation and ionization of NH+: formation of N+ and N2+'' J. Lecointre, J.J. Jureta and P. Defrance, J. Phys. B: At. Mol. Opt. Phys. 43 (2010) 105202. ''Electron impact dissociation of ND+: formation of D+'' J. Lecointre, D.S. Belic, S. Cherkani-Hassani and P. Defrance, Eur. Phys. J. D 61 (2011) in press. ''Electron Impact dissociation and ionisation of N2+'' E.M. Bahati, J.J. Jureta, D.S. Belic, H. Cherkani-Hassani, M.O. Abdellahi and P. Defrance, J. Phys. B: At. Mol. Opt. Phys. 34 (2001) 2963. (author)

  15. Nanostructured organic-inorganic photodiodes with high rectification ratio

    International Nuclear Information System (INIS)

    High quality organic-inorganic heterojunction photodiodes based on nanostructured copper (II) phthalocyanine (CuPc) and intrinsic zinc oxide (i-ZnO) have been fabricated. The i-ZnO thin films/layers were grown by RF magnetron sputtering on clean indium tin oxide (ITO) coated glass substrates. These films have been characterized by optical absorption and field emission scanning electron microscopy (FESEM). CuPc thin films deposited at room temperature on i-ZnO have exhibited a change in their surface morphology with the post-deposition annealing temperature under normal atmosphere. The electrical dark conductivity and the photoconductivity of ITO/i-ZnO/CuPc/Au sandwich structures have been measured under various photoexcitation intensities using a xenon light source. The devices have shown excellent reproducibility of their electrical characteristics and high rectification ratios. The highest rectification ratio is nearly 831 calculated above the threshold voltage at room temperature for the sample annealed at 250 deg. C (i.e. Pc 250). The effects of the annealing temperature of CuPc on the surface morphology, rectification ratio, and optical properties have been discussed.

  16. Radiative thermal rectification using superconducting materials

    International Nuclear Information System (INIS)

    Thermal rectification can be defined as an asymmetry in the heat flux when the temperature difference between two interacting thermal reservoirs is reversed. In this Letter, we present a far-field radiative thermal rectifier based on high-temperature superconducting materials with a rectification ratio up to 80%. This value is among the highest reported in literature. Two configurations are examined: a superconductor (Tl2Ba2CaCu2O8) exchanging heat with (1) a black body and (2) another superconductor, YBa2Cu3O7 in this case. The first configuration shows a higher maximal rectification ratio. Besides, we show that the two-superconductor rectifier exhibits different rectification regimes depending on the choice of the reference temperature, i.e., the temperature of the thermostat. Presented results might be useful for energy conversion devices, efficient cryogenic radiative insulators engineering, and thermal logical circuits’ development

  17. Single-molecular diodes based on opioid derivatives.

    Science.gov (United States)

    Siqueira, M R S; Corrêa, S M; Gester, R M; Del Nero, J; Neto, A M J C

    2015-12-01

    We propose an efficient single-molecule rectifier based on a derivative of opioid. Electron transport properties are investigated within the non-equilibrium Green's function formalism combined with density functional theory. The analysis of the current-voltage characteristics indicates obvious diode-like behavior. While heroin presents rectification coefficient R>1, indicating preferential electronic current from electron-donating to electron-withdrawing, 3 and 6-acetylmorphine and morphine exhibit contrary behavior, Rrectification rations for heroin diodes show microampere electron current with a maximum of rectification (R=9.1) at very low bias voltage of ?0.6 V and (R=14.3)?1.8 V with resistance varying between 0.4 and 1.5 M ?. Once most of the current single-molecule diodes usually rectifies in nanoampere, are not stable over 1.0 V and present electrical resistance around 10 M. Molecular devices based on opioid derivatives are promising in molecular electronics. PMID:26613894

  18. Optimal rectification by strongly coupled spins

    OpenAIRE

    Werlang, T.; Marchiori, M. A.; Cornelio, M. F.; Valente, D.

    2014-01-01

    We study heat transport in a pair of strongly coupled spins. In particular, we present a condition for optimal rectification, i.e., flow of heat in one direction and complete isolation in the opposite direction. We show that the strong-coupling formalism is necessary for correctly describing heat flow in a wide range of parameters, including moderate to low couplings. We present a situation in which the strong-coupling formalism predicts optimal rectification whereas the phenomenological appr...

  19. Rectification of spin currents in spin chains

    OpenAIRE

    van Hoogdalem, Kevin A.; Loss, Daniel

    2011-01-01

    We study spin transport in nonitinerant one-dimensional quantum spin chains. Motivated by possible applications in spintronics, we consider rectification effects in both ferromagnetic and antiferromagnetic systems. We find that the crucial ingredients in designing a system that displays a nonzero rectification current are an anisotropy in the exchange interaction of the spin chain combined with an offset magnetic field. For both ferromagnetic and antiferromagnetic systems we can exploit the g...

  20. Macroscopic Coherent Rectification in Andreev Interferometers

    OpenAIRE

    Meair, Jonathan; Jacquod, Philippe

    2012-01-01

    We investigate nonlinear transport through quantum coherent metallic conductors contacted to superconducting components. We find that in certain geometries, the presence of superconductivity generates a large, finite-average rectification effect. Specializing to Andreev interferometers, we show that the direction and magnitude of rectification can be controlled by a magnetic flux tuning the superconducting phase difference at two contacts. In particular, this results in the breakdown of an On...

  1. Electroosmotic flow rectification in conical nanopores

    OpenAIRE

    Laohakunakorn, Nadanai; Keyser, Ulrich F

    2015-01-01

    Recent experimental work has suggested that electroosmotic flows (EOF) through conical nanopores exhibit rectification in the opposite sense to the well-studied effect of ionic current rectification. A positive bias voltage generates large EOF and small current, while negative voltages generate small EOF and large current. Here we systematically investigate this effect using finite-element simulations. We find that inside the pore, the electric field and salt concentration are inversely corre...

  2. Projective Rectification with Minimal Geometric Distortion

    OpenAIRE

    Wu, Hsien-Huang P.; Chen, Chih-g

    2007-01-01

    This chapter presented a new way of parameterizing the homography, which leads to a new approach of projective rectification for stereo images. Compared with the previous works, the novelty of this new algorithm is that it uses mean-square distance as minimization criterion which has more well-defined geometric meaning. Furthermore, instead of putting constraint on x-axis disparity, we use shearing transform to achieve a single solution for the projective rectification problem, and greatly re...

  3. High rectification ratios of Fe–porphyrin molecules on Au facets

    International Nuclear Information System (INIS)

    We report room temperature measurements of current vs. voltage (I–V) from self-assembled Fe porphyrin [Fe(III) 5,15-di[4-(s-acetylthio)phenyl]-10,20-diphenyl porphine] molecular layers formed on annealed gold crystal facets on glass substrates. I–V curves were measured using an atomic force microscope with a conductive platinum tip. We observed a rectifier effect that shows asymmetric I–V curves from a monolayer of molecules. The majority rectification ratios at ±1 V obtained from hundreds of I–V lie in between 20 and 200, with the highest up to 9000. This is in contrast to the symmetric I–V curves measured from a few nm thick multilayer molecular islands. We contribute the observed rectification in ultrathin FeP molecular layers from asymmetric Schottky barriers that result from molecules in different bonding strengths to electrodes of gold and platinum. -- Highlights: ? FeP molecular layers or islands of different thickness were self-assembled on Au. ? High rectification ratios up to 9000 observed in sub-nm thick FeP molecular layers. ? Measured current vs. voltage using a conductive AFM tip as one electrode. ? Observed rectification of symmetric molecules using two different electrodes.

  4. High rectification ratios of Fe-porphyrin molecules on Au facets

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaoyu; Wang, Gwo-Ching [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th Street, Troy, NY 12180 (United States); Lewis, Kim M., E-mail: lewisk2@rpi.edu [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th Street, Troy, NY 12180 (United States)

    2012-09-14

    We report room temperature measurements of current vs. voltage (I-V) from self-assembled Fe porphyrin [Fe(III) 5,15-di[4-(s-acetylthio)phenyl]-10,20-diphenyl porphine] molecular layers formed on annealed gold crystal facets on glass substrates. I-V curves were measured using an atomic force microscope with a conductive platinum tip. We observed a rectifier effect that shows asymmetric I-V curves from a monolayer of molecules. The majority rectification ratios at {+-}1 V obtained from hundreds of I-V lie in between 20 and 200, with the highest up to 9000. This is in contrast to the symmetric I-V curves measured from a few nm thick multilayer molecular islands. We contribute the observed rectification in ultrathin FeP molecular layers from asymmetric Schottky barriers that result from molecules in different bonding strengths to electrodes of gold and platinum. -- Highlights: Black-Right-Pointing-Pointer FeP molecular layers or islands of different thickness were self-assembled on Au. Black-Right-Pointing-Pointer High rectification ratios up to 9000 observed in sub-nm thick FeP molecular layers. Black-Right-Pointing-Pointer Measured current vs. voltage using a conductive AFM tip as one electrode. Black-Right-Pointing-Pointer Observed rectification of symmetric molecules using two different electrodes.

  5. Formation of metastable electronic states in polysilylene molecular wire.

    Czech Academy of Sciences Publication Activity Database

    Nešp?rek, Stanislav

    Dresden : MaxPlanckInstitut für Physik komplexer Systeme, 2004. s. C-45. [International Workshop on Advances in Molecular Electronics: From Molecular Materials to Single Molecule Devices.. 23.02.2004-27.02.2004, Dresden] R&D Projects: GA MŠk OC D14.30 Keywords : polysilylene * molecular wire * metastable states Subject RIV: BM - Solid Matter Physics ; Magnetism

  6. Langmuir-Blodgett Films a unique tool for molecular electronics

    OpenAIRE

    Hussain, Syed Arshad

    2009-01-01

    Molecular electronics is a new, exciting and interdisciplinary field of research. The main concern of the subject is to exploit the organic materials in electronic and optoelectronic devices. On the other hand Langmuir-Blodgett (LB) film deposition technique is one of the best among few methods used to manipulate materials in molecular level. In this article LB film preparation technique has been discussed briefly with an emphasize of its application towards molecular electr...

  7. Molecular rectification with identical metal electrodes at low temperatures Thin film deposition; Gold; Molecular electronics; Langmuir- Blodgett; Au/LB/Au structures; Fabrication

    CERN Document Server

    Okazaki, N

    2003-01-01

    A gold deposition technique for the fabrication of Au/LB/Au structures has been developed. The kinetic energy of evaporated gold atoms is reduced by scattering the gold atoms from argon gas. Moreover, the samples are cooled down below 173K (-100 deg C) to avoid the diffusion of gold atoms into the LB films and to fabricate electrically continuous thin gold electrodes (This technique has since been used in fabrication of Au/LB/Au structures even with monolayer LB films (Metzger, et al. (2001)). To measure the current-voltage characteristics of the Au/LB/Au structures at liquid helium temperatures, new junction geometries have been explored. To avoid the direct contact of the Gallium-Indium eutectic onto the LB films, which is the cause of the breakdown of the junction at lower temperatures, a cross electrode junction geometry is used. The problem of poor Langmuir-Blodgett film deposition at the penumbra region of the base electrode is avoided by covering the penumbra region with an insulating omega-tricosenoic...

  8. Thermal conductance and rectification of asymmetric tilt grain boundary in graphene

    CERN Document Server

    Cao, Hai-Yuan; Gong, Xin-Gao

    2011-01-01

    We have investigated the lattice thermal transport across the asymmetry tilt grain boundary between armchair and zigzag grains by using nonequilibrium molecular dynamics (NEMD). We have observed significant temperature drop and ultralow temperature-dependent thermal boundary resistance. Importantly, we find an unexpected thermal rectification phenomenon, i.e, the thermal conductivity and Kapitza conductance is asymmetric with respect to the thermal transport direction. And the effect of thermal rectification could be amplified by increasing the difference of temperature imposed on two sides. Our results propose a new promising kind of thermal rectifier and phonon diodes from polycrystalline graphene without delicate manupulation of the atomic structures.

  9. Mechanical action of infrared light on atoms and molecules through a rectification of the electric force

    International Nuclear Information System (INIS)

    We report the mechanical action of infrared light on atoms and molecules based on the rectification of the electric force. This mechanism is qualitatively different from the conventional ways of controlling photochemistry. The rectification of the electric force originates from the synchronous charge transfer induced by the laser field. This brings about an opportunity to produce a site selective light-induced action, controlled by the tailored intense laser field, on atoms in molecules and clusters. The concept is illustrated by ab initio molecular dynamics simulations of the water hexamer.

  10. Enhanced oscillatory rectification and negative differential resistance in pentamantane diamondoid-cumulene systems.

    Science.gov (United States)

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2016-02-14

    We propose a new functionality for diamondoids in nanoelectronics. Based on the nonequilibrium Green's function formalism and density functional theory, we reveal that when attached to gold electrodes, the pentamantane-cumulene molecular junction exhibits large and oscillatory rectification and negative differential resistance (NDR) - depending on the number of carbon atoms in cumulene (Cn). When n is odd rectification is greatly enhanced where the rectification ratio can reach ?180 and a large negative differential resistance peak current of ?3 ?A. This oscillatory behavior is well rationalised in terms of the occupancy of the carbon 2p states in Cn. Interestingly, different layers of C atoms in the pentamantane molecule have different contributions to transmission. The first and third layers of C atoms in pentamantane have a slight contribution to rectification, and the fifth and sixth layers have a stronger contribution to both rectification and NDR. Thus, our results suggest potential avenues for controlling their functions by chemically manipulating various parts of the diamondoid molecule, thus extending the applications of diamondoids in nanoscale integrated circuits. PMID:26794415

  11. Electron beam irradiation effect on nanostructured molecular sieve catalysts

    International Nuclear Information System (INIS)

    Electron impact can induce chemical changes on particle surfaces of zeolites and molecular sieve catalysts. Some experimental observations of electron irradiation effect on molecular sieve catalysts are presented, e.g., electron-beam-induced growth of bare silver nanowires from zeolite crystallites, formation of vesicles in calcium phosphate, migration of microdomains in iron-oxide doped mesoporous silicas, structural transformation from mesostructured MCM-41 to microporous ZSM-5, etc. The formation mechanisms of the surface structures are discussed

  12. A Quantum Chemical View of Molecular and Nano-Electronics

    OpenAIRE

    Jiang, Jun

    2007-01-01

    This dissertation presents a generalized quantum chemical approach for electron transport in molecular electronic devices based on Green's function scattering theory. It allows to describe both elastic and inelastic electron transport processes at first principles levels of theory, and to treat devices with metal electrodes either chemically or physically bonded to the molecules on equal footing. Special attention has been paid to understand the molecular length dependence of current-voltage ...

  13. Electrical rectification from aligned diodesbased on the donor-(?-bridge)-acceptor molecules

    OpenAIRE

    Chwialkowska, Anna

    2007-01-01

    As traditional devices containing silicon transistors begin to approach their physical limits, new systems composed of organic molecules are being considered for molecularscale devices of the future. The present work reports on the electrical properties of molecular diodes, especially observations of electrical rectification from molecular systems based on donor-(?-bridge)-acceptor molecules. For this purpose three types of molecular assembly were incorporated and their growth ...

  14. Rectification in Tunneling Junctions: 2,2?-Bipyridyl-Terminated n -Alkanethiolates

    OpenAIRE

    Yoon, Hyo Jae; Liao, Kung-ching; Lockett, Matthew R.; Kwok, Sen Wai; Baghbanzadeh, Mostafa; Whitesides, George McClelland

    2014-01-01

    Molecular rectification is a particularly attractive phenomenon to examine in studying structure–property relationships in charge transport across molecular junctions, since the tunneling currents across the same molecular junction are measured, with only a change in the sign of the bias, with the same electrodes, molecule(s), and contacts. This type of experiment minimizes the complexities arising from measurements of current densities at one polarity using replicate junctions. This paper de...

  15. A molecular shift register based on electron transfer.

    Science.gov (United States)

    Hopfield, J J; Onuchic, J N; Beratan, D N

    1988-08-12

    An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a "molecular electronic device" that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density. PMID:17829175

  16. Molecular modeling and multiscaling issues for electronic material applications

    CERN Document Server

    Iwamoto, Nancy; Yuen, Matthew; Fan, Haibo

    Volume 1 : Molecular Modeling and Multiscaling Issues for Electronic Material Applications provides a snapshot on the progression of molecular modeling in the electronics industry and how molecular modeling is currently being used to understand material performance to solve relevant issues in this field. This book is intended to introduce the reader to the evolving role of molecular modeling, especially seen through the eyes of the IEEE community involved in material modeling for electronic applications.  Part I presents  the role that quantum mechanics can play in performance prediction, such as properties dependent upon electronic structure, but also shows examples how molecular models may be used in performance diagnostics, especially when chemistry is part of the performance issue.  Part II gives examples of large-scale atomistic methods in material failure and shows several examples of transitioning between grain boundary simulations (on the atomistic level)and large-scale models including an example ...

  17. Contactless electronic transport in a bio-molecular junction

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, Faruque M., E-mail: fhossain@unimelb.edu.au; Al-Dirini, Feras; Skafidas, Efstratios [Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville 3010 (Australia); Center for Neural Engineering (CfNE), The University of Melbourne, Parkville 3010 (Australia)

    2014-07-28

    Molecular electronics hold promise for next generation ultra-low power, nano-scale integrated electronics. The main challenge in molecular electronics is to make a reliable interface between molecules and metal electrodes. Interfacing metals and molecules detrimentally affects the characteristics of nano-scale molecular electronic devices. It is therefore essential to investigate alternative arrangements such as contact-less tunneling gaps wherever such configurations are feasible. We conduct ab initio density functional theory and non-equilibrium Green's functions calculations to investigate the transport properties of a biocompatible glycine molecular junction. By analyzing the localized molecular orbital energy distributions and transmission probabilities in the transport-gap, we find a glycine molecule confined between two gold electrodes, without making a contact, is energetically stable and possesses high tunneling current resembling an excellent ohmic-like interface.

  18. Contactless electronic transport in a bio-molecular junction

    International Nuclear Information System (INIS)

    Molecular electronics hold promise for next generation ultra-low power, nano-scale integrated electronics. The main challenge in molecular electronics is to make a reliable interface between molecules and metal electrodes. Interfacing metals and molecules detrimentally affects the characteristics of nano-scale molecular electronic devices. It is therefore essential to investigate alternative arrangements such as contact-less tunneling gaps wherever such configurations are feasible. We conduct ab initio density functional theory and non-equilibrium Green's functions calculations to investigate the transport properties of a biocompatible glycine molecular junction. By analyzing the localized molecular orbital energy distributions and transmission probabilities in the transport-gap, we find a glycine molecule confined between two gold electrodes, without making a contact, is energetically stable and possesses high tunneling current resembling an excellent ohmic-like interface.

  19. A New Full Adder Cell for Molecular Electronics

    Directory of Open Access Journals (Sweden)

    Mehdi Ghasemi

    2011-09-01

    Full Text Available Due to high power consumption and difficulties with minimizing the CMOS transistor size, molecular electronics has been introduced as an emerging technology. Further, there have been noticeable advances in fabrication of molecular wires and switches and also molecular diodes can be used for designing different logic circuits. Considering this novel technology, we use molecules as the active components of the circuit, for transporting electric charge. In this paper, a full adder cell based on molecular electronics is presented. This full adder is consisted of resonant tunneling diodes and transistors which are implemented via molecular electronics. The area occupied by this kind of full adder would be much times smaller than the conventional designs and it can be used as the building block of more complex molecular arithmetic circuits.

  20. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  1. A New Full Adder Cell for Molecular Electronics

    CERN Document Server

    Ghasemi, Mehdi; Navi, Keivan; 10.5121/vlsic.2011.2401

    2012-01-01

    Due to high power consumption and difficulties with minimizing the CMOS transistor size, molecular electronics has been introduced as an emerging technology. Further, there have been noticeable advances in fabrication of molecular wires and switches and also molecular diodes can be used for designing different logic circuits. Considering this novel technology, we use molecules as the active components of the circuit, for transporting electric charge. In this paper, a full adder cell based on molecular electronics is presented. This full adder is consisted of resonant tunneling diodes and transistors which are implemented via molecular electronics. The area occupied by this kind of full adder would be much times smaller than the conventional designs and it can be used as the building block of more complex molecular arithmetic circuits.

  2. A New Full Adder Cell for Molecular Electronics

    Directory of Open Access Journals (Sweden)

    Keivan Navi

    2012-01-01

    Full Text Available Due to high power consumption and difficulties with minimizing the CMOS transistor size, molecular electronics has been introduced as an emerging technology. Further, there have been noticeable advances in fabrication of molecular wires and switches and also molecular diodes can be used for designing different logic circuits. Considering this novel technology, we use molecules as the active components of the circuit, for transporting electric charge. In this paper, a full adder cell based on molecular electronics is presented. This full adder is consisted of resonant tunneling diodes and transistors which are implemented via molecular electronics. The area occupied by this kind of full adder would be much times smaller than the conventional designs and it can be used as the building block of more complex molecular arithmetic circuits.

  3. Molecular Electronics : A Theoretical Study of Electronic Structure of Bulk and Interfaces

    OpenAIRE

    Unge, Mikael

    2006-01-01

    This thesis deals with theoretical studies of the electronic structure of molecules used in the context of molecular electronics. Both studies with model Hamiltonians and first principle calculations have been performed. The materials studied include molecular crystals of pentacene and DNA, which are used as active material in field-effect transistors and as tentative molecular wires, respectively. The molecular magnet compound TCNE and surface modification by means of chemisorption of TDAE o...

  4. Self-assembled nanogaps for molecular electronics

    DEFF Research Database (Denmark)

    Tang, Qingxin; Tong, Yanhong; Jain, Titoo; Hassenkam, Tue; Wan, Qing; Moth-Poulsen, Kasper; Bjørnholm, Thomas

    2009-01-01

    A nanogap for molecular devices was realized using solution-based self-assembly. Gold nanorods were assembled to gold nanoparticle-coated conducting SnO2:Sb nanowires via thiol end-capped oligo(phenylenevinylene)s (OPVs). The molecular gap was easily created by the rigid molecule itself during self-assembly...... conductance measurement confirmed that the self-assembly of the molecules and the subsequent self-assembly of the gold nanorods was a feasible method for the fabrication of the nanogap of the molecular devices....

  5. Effects of cetyltrimethylammonium bromide on redox deposition and rectification properties of silicon oxide thin film

    International Nuclear Information System (INIS)

    Silicon oxide (SiOx) thin film was deposited onto fluorine-doped tin oxide (FTO) and silicon wafer substrate by the reduction of an aqueous solution containing ammonium hexafluorosilicate, dimethylamine borane and cetyltrimethylammonium bromide (CTAB). Characterization of the films by X-ray photoelectron spectroscopic depth profile and infrared spectroscopy proved that the addition of CTAB into the film enhanced the aggregation of silica particles and the growth rate. The SiOx films (resistivity: 3.2 x 108 ? cm) remarkably improved the rectification properties of FTO/SiOx/poly(3,4-ethylenedioxythiophene) derivative diodes. A rectification mechanism based on conduction of electron and ions was investigated.

  6. Rectification effect for spin- and charge-currents in a shuttled molecule transistor

    International Nuclear Information System (INIS)

    We have investigated the spin-dependent electronic transports through a shuttled molecule, a molecule self-excitedly oscillating due to suffering an external electric field. When the shuttled molecule is coupled asymmetrically to a ferromagnetic and a normal metal leads, a pronounced dual rectification effect is predicted for both spin- and charge-currents in the Coulomb blockade regime. As compared to the conventional rectifier based on a static quantum dot, the proposed rectifier based on a movable individual molecule has higher rectification efficiency.

  7. Molecular Spintronics Spin-Dependent Electron Transport in Molecular Wires

    CERN Document Server

    Emberly, E; Emberly, Eldon; Kirczenow, George

    2002-01-01

    We present a theoretical study of spin-dependent transport through molecular wires bridging ferromagnetic metal nanocontacts. We extend to magnetic systems a recently proposed model that provides a em quantitative explanation of the conductance measurements of Reed et al. on Au break-junctions bridged by self-assembled molecular monolayers (SAMs) of 1,4-benzene-dithiolate (BDT) molecules. Based on our calculations, we predict that spin-valve behavior should be observable in nickel break-junctions bridged by SAM's formed from BDT. We also consider spin transport in systems consisting of a clean ferromagnetic nickel STM tip and SAMs of benzene-thiol molecules on gold and nickel substrates. We find that spin-valve behavior should be possible for the Ni substrate. For the case where the substrate is gold, we show that it should be possible to inject a highly spin-polarized current into the substrate.

  8. Energy-Saving in Brew-Rectification

    Directory of Open Access Journals (Sweden)

    N. I. Ulyanau

    2014-06-01

    Full Text Available The paper investigates dynamics of rectification process on one plate of a column. The basic channels controlling brew-rectification process are described in the paper.The paper also considers problems pertaining to synthesis of an adaptive system that controls non-stationary objects with delay. Synthesis of adaptive systems that automatically control product quality and saving on power resources and productivity with the help of the second method of Lyapunov has been carried out in the paper.Industrial introduction of the given automatic control system of technological process shall permit to increase productivity of a rectification (10–15 %, to decrease specific power consumption by (5–10 % while preserving the specified quality of rectified ethyl alcohol and decrease alcohol losses with luting water and malt-residue.

  9. Electroosmotic flow rectification in conical nanopores

    CERN Document Server

    Laohakunakorn, Nadanai

    2015-01-01

    Recent experimental work has suggested that electroosmotic flows (EOF) through conical nanopores exhibit rectification in the opposite sense to the well-studied effect of ionic current rectification. A positive bias voltage generates large EOF and small current, while negative voltages generate small EOF and large current. Here we systematically investigate this effect using finite-element simulations. We find that inside the pore, the electric field and salt concentration are inversely correlated, which leads to the inverse relationship between the magnitudes of EOF and current. Rectification occurs when the pore is driven into states characterized by different salt concentrations depending on the sign of the voltage. The mechanism responsible for this behaviour is concentration polarization, which requires the pore to exhibit the properties of permselectivity and asymmetry.

  10. Electroosmotic flow rectification in conical nanopores

    Science.gov (United States)

    Laohakunakorn, Nadanai; Keyser, Ulrich F.

    2015-07-01

    Recent experimental work has suggested that electroosmotic flows (EOFs) through conical nanopores exhibit rectification in the opposite sense to the well-studied effect of ionic current rectification. A positive bias voltage generates large EOF and small current, while negative voltages generate small EOF and large current. Here we systematically investigate this effect using finite-element simulations. We find that inside the pore, the electric field and salt concentration are inversely correlated, which leads to the inverse relationship between the magnitudes of EOF and current. Rectification occurs when the pore is driven into states characterized by different salt concentrations depending on the sign of the voltage. The mechanism responsible for this behaviour is concentration polarization, which requires the pore to exhibit the properties of permselectivity and asymmetry.

  11. Preparation of high-purity cadmium by rectification

    International Nuclear Information System (INIS)

    Distribution of 21 impurities by cadmium rectification in the column with ten stages of separation is studied. It is shown that impurities content in cadmium decreases more than by 200 times. The program on determination of the basic parameters of rectification columns are developed. Technological parameters of cadmium rectification up to high purity are determined

  12. Controlling molecular fragmentation using low energy electrons

    International Nuclear Information System (INIS)

    We show that functional group dependence exists in dissociative attachment of electrons to molecules and this leads to site and bond selectivity in fragmenting organic molecules at the N-H, O-H and C-H sites using electron energy as a control parameter. This phenomenon is investigated further by measuring the momentum distribution of hydride ions using the newly developed ion momentum imaging technique. We find that while the electron attachment at the O-site leads to a two-body fragmentation, attachment at the C-site leads to few-body fragmentation. Several new phenomena like 'bond orientation dependent electron attachment' and direct screening of one part of the molecule by another part to the incoming electron are unravelled in the very rich momentum distribution data of the hydride ions that we have obtained at various resonances

  13. Theory of Vibrationally Inelastic Electron Transport through Molecular Bridges

    CERN Document Server

    Cizek, M; Domcke, W; Cizek, Martin; Thoss, Michael; Domcke, Wolfgang

    2003-01-01

    Vibrationally inelastic electron transport through a molecular bridge that is connected to two leads is investigated. The study is based on a generic model of vibrational excitation in resonant transmission of electrons through a molecular junction. Employing methods from electron-molecule scattering theory, the transmittance through the molecular bridge can be evaluated numerically exactly. The current through the junction is obtained approximately using a Landauer-type formula. Considering different parameter regimes, which include both the case of a molecular bridge that is weakly coupled to the leads, resulting in narrow resonance structures, and the opposite case of a broad resonance caused by strong interaction with the leads, we investigate the characteristic effects of coherent and dissipative vibrational motion on the electron transport. Furthermore, the validity of widely used approximations such as the wide-band approximation and the restriction to elastic transport mechanisms is investigated in so...

  14. Purification of benzene by extractive rectification

    Energy Technology Data Exchange (ETDEWEB)

    Smoroda, A.I.; Ovsii, A.N.; Kashaba, I.F.; Belitskii, A.N.; Beizer, V.N.; Iliev, V.V.; Pirozhkov, G.P.

    1978-01-01

    Benzene is a very important product, affecting the development of the organic synthesis industry, especially in the production of plastics and synthetic fibers. As a result, the production of benzene is constantly increasing. There is a simultaneous increase in the demands made on its quality. The results from removal of saturated hydrocarbon impurities from benzene by extractive rectification under industrial conditions at the Yasinovka Coke Works are given. The extractive rectification unit was shown to be practical and efficient in operation. The resulting benzene meets the present and expected user requirements.

  15. A thermal diode using phonon rectification

    International Nuclear Information System (INIS)

    A diode is an element blocking flow in one direction, but letting it pass in the other. The most prominent realization of a diode is an electrical rectifier. In this paper, we demonstrate a thermal diode based on standard silicon processing technology using rectification of phonon transport. We use a recently developed detection method to directly visualize the heat flow through such a device fabricated in a thin silicon membrane. The diode consists of an array of differently shaped holes milled into the membrane by focused ion beam processing. In our experiment, we achieve a rectification ratio of the heat current of 1.7 at a temperature of 150 K. (paper)

  16. Thermal rectification in nonlinear quantum circuits

    DEFF Research Database (Denmark)

    Ruokola, T.; Ojanen, T.

    2009-01-01

    We present a theoretical study of radiative heat transport in nonlinear solid-state quantum circuits. We give a detailed account of heat rectification effects, i.e., the asymmetry of heat current with respect to a reversal of the thermal gradient, in a system consisting of two reservoirs at finite temperatures coupled through a nonlinear resonator. We suggest an experimentally feasible superconducting circuit employing the Josephson nonlinearity to realize a controllable low-temperature heat rectifier with a maximal asymmetry of the order of 10%. We also discover a parameter regime where the rectification changes sign as a function of temperature.

  17. Self-assembled nanogaps for molecular electronics

    DEFF Research Database (Denmark)

    Tang, Qingxin; Tong, Yanhong; Jain, Titoo; Hassenkam, Tue; Wan, Qing; Moth-Poulsen, Kasper; Bjørnholm, Thomas

    2009-01-01

    A nanogap for molecular devices was realized using solution-based self-assembly. Gold nanorods were assembled to gold nanoparticle-coated conducting SnO2:Sb nanowires via thiol end-capped oligo(phenylenevinylene)s (OPVs). The molecular gap was easily created by the rigid molecule itself during self-assembly and the gap length was determined by the molecule length. The gold nanorods and gold nanoparticles, respectively covalently bonded at the two ends of the molecule, had very small dimensions, ...

  18. Photoelectrochemical solar conversion systems molecular and electronic aspects

    CERN Document Server

    Munoz, Andres G

    2012-01-01

    Providing new insights into the molecular and electronic processes involved in the conversion of sunlight into chemical products, Photoelectrochemical Solar Conversion Systems: Molecular and Electronic Aspects begins with an historical overview and a survey of recent developments in the electrochemistry of semiconductors and spectroscopic techniques. It then provides a comprehensive introduction to the science of conversion cells, reviews current issues and potential directions, and covers a wide range of materials from organic to inorganic cells.Employing a tutorial organization with balanced

  19. Site-directed deep electronic tunneling through a molecular network

    International Nuclear Information System (INIS)

    Electronic tunneling in a complex molecular network of N(>2) donor/acceptor sites, connected by molecular bridges, is analyzed. The 'deep' tunneling dynamics is formulated using a recursive perturbation expansion, yielding a McConnell-type reduced N-level model Hamiltonian. Applications to models of molecular junctions demonstrate that the donor-bridge contact parameters can be tuned in order to control the tunneling dynamics and particularly to direct the tunneling pathway to either one of the various acceptors

  20. Electron and Phonon Transport in Molecular Junctions

    DEFF Research Database (Denmark)

    Li, Qian

    transmission at the Fermi energy. We propose and analyze a way of using π   stacking to design molecular junctions to control heat transport. We develop a simple model system to identify optimal parameter regimes and then use density functional theory (DFT) to extract model parameters for a number of specific...

  1. Two-electron processes in molecular collisions

    International Nuclear Information System (INIS)

    Orientation effects are reported for the ionization plus excitation of H2 by electron bombardment. The yield of H+-fragment ions as a function of angle relative to the beam direction are reported for angles from 18deg to 90deg and collision energies of 408, 545, and 1089 eV. Comparisons are made between experiment and theoretical predictions based on dipole interactions between projectile and target electrons. (orig.)

  2. Molecular orbital theory and its application to electron spectroscopy

    International Nuclear Information System (INIS)

    The electron spectroscopy developed remarkably in recent years has provided much information on elemental compositions and electronic states of the surface layer. Molecular orbital theories frequently used in analyses of the photoelectron spectra are reviewed. The DV-X? method in which numerical bases are used for estimating the molecular potential in the Hartree-Fock-Slater equation is in excellent agreement with the observations. Example calculations of molecular orbital energies and density of states by this method are presented. Usefulness of the method in other fields is also indicated. (author)

  3. Triazatriangulene as binding group for molecular electronics

    DEFF Research Database (Denmark)

    Wei, Zhongming; Wang, Xintai; Borges, Anders; Santella, Marco; Li, Tao; Sørensen, Jakob Kryger; Vanin, Marco; Hu, Wenping; Liu, Yunqi; Ulstrup, Jens; Solomon, Gemma C.; Chi, Qijin; Bjørnholm, Thomas; Nørgaard, Kasper; Laursen, Bo Wegge

    2014-01-01

    The triazatriangulene (TATA) ring system was investigated as a binding group for tunnel junctions of molecular wires on gold surfaces. Self-assembled monolayers (SAMs) of TATA platforms with three different lengths of phenylene wires were fabricated, and their electrical conductance was recorded by both conducting probe-atomic force microscopy (CP-AFM) and scanning tunneling microscopy (STM). Similar measurements were performed for phenylene SAMs with thiol anchoring groups as references. It was...

  4. Molecular interfaces for plasmonic hot electron photovoltaics.

    Science.gov (United States)

    Pelayo García de Arquer, F; Mihi, Agustín; Konstantatos, Gerasimos

    2015-02-14

    The use of self-assembled monolayers (SAMs) to improve and tailor the photovoltaic performance of plasmonic hot-electron Schottky solar cells is presented. SAMs allow the simultaneous control of open-circuit voltage, hot-electron injection and short-circuit current. To that end, a plurality of molecule structural parameters can be adjusted: SAM molecule's length can be adjusted to control plasmonic hot electron injection. Modifying SAMs dipole moment allows for a precise tuning of the open-circuit voltage. The functionalization of the SAM can also be selected to modify short-circuit current. This allows the simultaneous achievement of high open-circuit voltages (0.56 V) and fill-factors (0.58), IPCE above 5% at the plasmon resonance and maximum power-conversion efficiencies of 0.11%, record for this class of devices. PMID:25578026

  5. High electronic couplings of single mesitylene molecular junctions

    Directory of Open Access Journals (Sweden)

    Yuki Komoto

    2015-12-01

    Full Text Available We report on an experimental analysis of the charge transport properties of single mesitylene (1,3,5-trimethylbenzene molecular junctions. The electronic conductance and the current–voltage characteristics of mesitylene molecules wired into Au electrodes were measured by a scanning tunnelling microscopy-based break-junction method at room temperature in a liquid environment. We found the molecular junctions exhibited two distinct conductance states with high conductance values of ca. 10−1G0 and of more than 10−3G0 (G0 = 2e2/h in the electronic conductance measurements. We further performed a statistical analysis of the current–voltage characteristics of the molecular junctions in the two states. Within a single channel resonant tunnelling model, we obtained electronic couplings in the molecular junctions by fitting the current–voltage characteristics to the single channel model. The origin of the high conductance was attributed to experimentally obtained large electronic couplings of the direct π-bonded molecular junctions (ca. 0.15 eV. Based on analysis of the stretch length of the molecular junctions and the large electronic couplings obtained from the I–V analysis, we proposed two structural models, in which (i mesitylene binds to the Au electrode perpendicular to the charge transport direction and (ii mesitylene has tilted from the perpendicular orientation.

  6. Molecular dynamics simulations of electron irradiated PVDF nanofibers

    Science.gov (United States)

    Miao, Jiayuan; Bhatta, Ram; Kisielowski, Christian; Lolla, Dinesh; Reneker, Darrell; Tsige, Mesfin; Taylor, Philip

    2014-03-01

    High-resolution, aberration corrected transmission electron microscopy was used to observe morphological changes and segmental motion of electrospun poly(vinylidene fluoride) nanofibers in an 80 kilovolt electron beam. Atomic and molecular scale high-resolution images of fibers were made with an aberration corrected electron microscope. Chemical and morphological changes, which include the breaking of the fiber, loss of fluorine atoms and cross-linking of chains, caused by the high-energy electron beam were observed. We present the results of molecular dynamics (MD) simulations of such atomic and molecular level observations. The calculational models include the influence of chain scission, chain recoiling, and torsional defects on the morphology of a nanofiber. The effects of the loss of fluorine atoms and the applied tension on the morphology of the fibers were also investigated. Work supported by the Petroleum Research Fund of the American Chemical Society.

  7. Effect of Intra-molecular Disorder and Inter-molecular Electronic Interactions on the Electronic Structure of Poly-p-Phenylene Vinylene (PPV)

    OpenAIRE

    Yang, Ping; Batista, Enrique R.; Tretiak, Sergei; Saxena, Avadh; Martin, Richard L.; Smith, D. L.

    2007-01-01

    We investigate the role of intra-molecular conformational disorder and inter-molecular electronic interactions on the electronic structure of disorder clusters of poly-p-phenylene vinylene (PPV) oligomers. Classical molecular dynamics is used to determine probable molecular geometries, and first-principle density functional theory (DFT) calculations are used to determine electronic structure. Intra-molecular and inter-molecular effects are disentangled by contrasting results for densely packe...

  8. Energy Transformation in Molecular Electronic Systems

    Energy Technology Data Exchange (ETDEWEB)

    Kasha, Michael

    1999-05-17

    This laboratory has developed many new ideas and methods in the electronic spectroscopy of molecules. This report covers the contract period 1993-1995. A number of the projects were completed in 1996, and those papers are included in the report. The DOE contract was terminated at the end of 1995 owing to a reorganizational change eliminating nationally the projects under the Office of Health and Environmental Research, U. S. Department of Energy.

  9. Laser induced electron diffraction: a tool for molecular orbital imaging

    CERN Document Server

    Peters, Michel; Charron, Eric; Keller, Arne; Atabek, Osman

    2012-01-01

    We explore the laser-induced ionization dynamics of N2 and CO2 molecules subjected to a few-cycle, linearly polarized, 800\\,nm laser pulse using effective two-dimensional single active electron time-dependent quantum simulations. We show that the electron recollision process taking place after an initial tunnel ionization stage results in quantum interference patterns in the energy resolved photo-electron signals. If the molecule is initially aligned perpendicular to the field polarization, the position and relative heights of the associated fringes can be related to the molecular geometrical and orbital structure, using a simple inversion algorithm which takes into account the symmetry of the initial molecular orbital from which the ionized electron is produced. We show that it is possible to extract inter-atomic distances in the molecule from an averaged photon-electron signal with an accuracy of a few percents.

  10. Spin-dependent rectification in the C59N molecule

    Indian Academy of Sciences (India)

    Mahvash Arabi Darehdor; Nasser Shahtahmasebi

    2013-02-01

    Coherent spin-dependent electron transport is investigated in three conditions: (1) a C60 molecule is connected to two ferromagnetic (FM) electrodes symmetrically, (2) a C59N molecule is connected to two FM electrodes symmetrically and (3) a C59N molecule is connected to two FM electrodes asymmetrically. This work is based on a single-band tight-binding model Hamiltonian and the Green’s function approach with the Landauer–Buttiker formalism. Electrodes used in this study are semi-infinite FM electrodes with finite cross-section. Obvious rectification effect is observed in the C59 N molecule which is connected to the FM electrodes asymmetrically. This effect is more in the P alignment of FM electrodes than in AP alignment of FM electrodes. This study indicates that the rectification behaviour is due to the asymmetry in molecule and junctions. Also in this investigation tunnel magnetoresistance (TMR) is calculated for these molecules. Asymmetry is observed in TMR of C59N which is coupled to the electrodes asymmetrically due to asymmetric junctions, but TMR of C60 is symmetric.

  11. Inelastic electron tunneling spectroscopy of molecular transport junctions

    Energy Technology Data Exchange (ETDEWEB)

    Song, Hyunwook [Kyung Hee University, Yongin (Korea, Republic of); Lee, Takhee [Seoul National University, Seoul (Korea, Republic of); Reed, Mark [Yale University, New Haven, CT (United States)

    2014-05-15

    Inelastic electron tunneling spectroscopy (IETS) has become a premier analytical tool in the investigation of nano scale and molecular junctions. The IETS spectrum provides invaluable information about the structure, bonding, and orientation of component molecules in the junctions. One of the major advantages of IETS is its sensitivity and resolution at the level of single molecules. This review discusses how IETS is used to study molecular transport junctions and presents an overview of recent experimental studies.

  12. Ultrafast Molecular Imaging by Laser Induced Electron Diffraction

    CERN Document Server

    Peters, Michel; Cornaggia, Christian; Saugout, Sébastien; Charron, Eric; Keller, Arne; Atabek, Osman

    2010-01-01

    We address the feasibility of imaging geometric and orbital structure of a polyatomic molecule on an attosecond time-scale using the Laser Induced Electron Diffraction, LIED, technique [T. Zuo \\textit{et al.}, Chem. Phys. Lett. \\textbf{259}, 313 (1996)]. We present numerical results obtained for the CO$_2$ molecule using a single active electron model. The molecular geometry (bond-lengths) is determined within 3% of accuracy from a diffraction pattern which also reflects the nodal properties of the initial molecular orbital. Robustness of the structure determination is discussed with respect to vibrational and rotational motions with a complete interpretation of the laser-induced mechanisms.

  13. Predicted Rectification and Negative Differential Spin Seebeck Effect at Magnetic Interfaces

    OpenAIRE

    Ren, Jie

    2013-01-01

    We study the nonequilibrium Seebeck spin transport across metal-magnetic insulator interfaces. The conjugate-converted thermal-spin transport is assisted by the exchange interaction at the interface, between conduction electrons in the metal lead and localized spins in the insulating magnet lead. We predict the rectification and negative differential spin Seebeck effect and resolve their microscopic mechanism, as a consequence of the strongly-fluctuated electronic density of...

  14. Thomas double scattering in electron capture from oriented molecular hydrogen

    International Nuclear Information System (INIS)

    Electron capture from hydrogen molecules by protons is treated using the second-order Born approximation. Differential cross sections in an adiabatic-nuclei approximation for specific molecular orientations and for an equally weighted averaging over all orientations are presented for incident energies of 2.5 and 10 MeV. A Hartree-Fock molecular wave function and linearized-propagator approximation are employed to evaluate the amplitude. An approximate factoring of the amplitude into double scattering and diffraction (arising from the two target nuclei) components is shown to give a poor description of high-velocity molecular capture

  15. Peculiarities of electron excitations decay in ion-molecular crystals

    International Nuclear Information System (INIS)

    Ionic-molecular crystals (IMC) have wide application in various optical devices. Its are using in capacity of solid state dosimetric materials and isolators. Peculiarities of chemical and energetic states of IMC lead to following number of features of electron excitation decay in comparison with alkaline-halogen crystals: - both an electrons and a holes simultaneously could be captured and localized either on anion or on cation complexes; - in-molecular forces arising in result of charge capture could conduct to decay of anion or cation complex; - decay products od anion or cation complex could participate in following reaction of new products formation. All these processes and new products of electron excitation decay exert strong effect on optical, magnetic and electrical characteristics of IMC. Knowledge of way and mechanisms of electron excitation decay in IMC could allow to control of radiation stability of crystals with help of impurities participating in different channels of solid state reactions

  16. The molecular electronic device and the biochip computer: present status.

    OpenAIRE

    Haddon, R.C.; Lamola, A. A.

    1985-01-01

    The idea that a single molecule might function as a self-contained electronic device has been of interest for some time. However, a fully integrated version--the biochip or the biocomputer, in which both production and assembly of molecular electronic components is achieved through biotechnology-is a relatively new concept that is currently attracting attention both within the scientific community and among the general public. In the present article we draw together some of the approaches bei...

  17. The Molecular Electronic Device and the Biochip Computer: Present Status

    Science.gov (United States)

    Haddon, R. C.; Lamola, A. A.

    1985-04-01

    The idea that a single molecule might function as a self-contained electronic device has been of interest for some time. However, a fully integrated version--the biochip or the biocomputer, in which both production and assembly of molecular electronic components is achieved through biotechnology--is a relatively new concept that is currently attracting attention both within the scientific community and among the general public. In the present article we draw together some of the approaches being considered for the construction of such devices and delineate the revolutionary nature of the current proposals for molecular electronic devices (MEDs) and biochip computers (BCCs). With the silicon semiconductor industry already in place and in view of the continuing successes of the lithographic process it seems appropriate to ask why the highly speculative MED or BCC has engendered such interest. In some respects the answer is paradigmatic as much as it is real. It is perhaps best stated as the promise of the realm of the molecular. Thus it is envisioned that devices will be constructed by assembly of individual molecular electronic components into arrays, thereby engineering from small upward rather than large downward as do current lithographic techniques. An important corollary of the construction technique is that the functional elements of such an array would be individual molecules rather than macroscopic ensembles. These two aspects of the MED/BCC--assembly of molecular arrays and individually accessible functional molecular units--are truly revolutionary. Both require scientific breakthroughs and the necessary principles, quite apart from the technology, remain essentially unknown. It is concluded that the advent of the MED/BCC still lies well before us. The twin criteria of utilization of individual molecules as functional elements and the assembly of such elements remains as elusive as ever. Biology engineers structures on the molecular scale but biomolecules do not seem to be imbued with useful electronic properties. Molecular beam epitaxy and thin-film techniques produce electronic devices but they ``engineer down'' and are currently unable to generate individual molecular units. The potential of the MED/BCC field is matched only by the obstacles that must be surmounted for its realization.

  18. Rectification of the Channelrhodopsin Early Conductance

    Science.gov (United States)

    Gradmann, Dietrich; Berndt, André; Schneider, Franziska; Hegemann, Peter

    2011-01-01

    We analyzed the nonlinear current-voltage relationships of the early conducting state of channelrhodopsin-2 expressed in Xenopus oocytes and human embryonic kidney cells with respect to changes of the electrochemical gradients of H+, Na+/K+, and Ca2+/Mg2+. Several models were tested for wild-type ChR2 and mutations at positions E90, E123, H134, and T159. Voltage-gating was excluded as cause for the nonlinearity. However, a general enzyme kinetic model with one predominant binding site yielded good fits throughout. The empty site with an apparent charge number of about ?0.3 and strong external cation binding causes some inward rectification of the uniport function. Additional inward rectification is due to asymmetric competition from outside between the transported ion species. Significant improvement of the fits was achieved by introducing an elastic voltage-divider formed by the voltage-sensitive barriers. PMID:21889442

  19. Rectification of light in the quantum regime

    Science.gov (United States)

    Dai, Jibo; Roulet, Alexandre; Le, Huy Nguyen; Scarani, Valerio

    2015-12-01

    One of the missing elements for realising an integrated optical circuit is a rectifying device playing the role of an optical diode. A proposal based on a pair of two-level atoms strongly coupled to a one-dimensional waveguide showed a promising behavior based on a semiclassical study [Fratini et al., Phys. Rev. Lett. 113, 243601 (2014), 10.1103/PhysRevLett.113.243601]. Our study in the full quantum regime shows that, in such a device, rectification is a purely multiphoton effect. For an input field in a coherent state, rectification reaches up to 70 % for the range of power in which one of the two atoms is excited, but not both.

  20. Research ZCS Synchronous Rectification of Resonant Converter

    OpenAIRE

    Xiao Kui Li

    2014-01-01

    In this study, the application of ZCS synchronous rectification for the IPT resonant converter is researched. A novel control method that AC-DC section of the resonant converter works in ZCS SR state is proposed by using the characteristic of resonant tank current. First, the ZCS working operation of SR is presented, analyzed and equivalent circuits for each operation mode are also given, respectively. Then, the novel control method of ZCS SR for resonant convert...

  1. Rectification Efficiency of Two Harmonically Coupled Particles

    Science.gov (United States)

    Sun, Lian-Xiu

    2009-04-01

    Transportation properties of two harmonically coupled particles moving in a Bashing or rocking ratchet potential are investigated in terms of Langevin simulation. The efficiency for rectification of non-equilibrium fluctuation is calculated by using a new definition. The results show that both the average current and efficiency of two coupled particles in the flashing ratchet are larger than that of a single particle and these quantities are non-monotonous functions of the potential remaining time.

  2. Rectification Efficiency of Two Harmonically Coupled Particles

    International Nuclear Information System (INIS)

    Transportation properties of two harmonically coupled particles moving in a Bashing or rocking ratchet potential are investigated in terms of Langevin simulation. The efficiency for rectification of non-equilibrium fluctuation is calculated by using a new definition. The results show that both the average current and efficiency of two coupled particles in the flashing ratchet are larger than that of a single particle and these quantities are non-monotonous functions of the potential remaining time

  3. Noise rectification in quasigeostrophic forced turbulence

    OpenAIRE

    Álvarez, Alberto; Hernández-García, Emilio; Tintoré, Joaquín

    1998-01-01

    We study the appearance of large-scale mean motion sustained by stochastic forcing on a rotating fluid (in the quasigeostrophic approximation) flowing over topography. We show that the effect is a kind of noise-rectification phenomenon, occurring here in a spatially extended system, and requiring nonlinearity, absence of detailed balance, and symmetry breaking to occur. By application of an analytical coarse-graining procedure, we identify the physical mechanism producing such an effect: It i...

  4. Thermal rectification in nonlinear quantum circuits

    OpenAIRE

    Ruokola, T.; Ojanen, T.; Jauho, Antti-Pekka

    2009-01-01

    We present a theoretical study of radiative heat transport in nonlinear solid-state quantum circuits. We give a detailed account of heat rectification effects, i.e. the asymmetry of heat current with respect to a reversal of the thermal gradient, in a system consisting of two reservoirs at finite temperatures coupled through a nonlinear resonator. We suggest an experimentally feasible superconducting circuit employing the Josephson nonlinearity to realize a controllable low ...

  5. Scene reconstruction and geometrical rectification from stereo images

    OpenAIRE

    Gallego Sánchez, Antonio Javier; Molina Carmona, Rafael; Villagrá Arnedo, Carlos

    2005-01-01

    A system to reconstruct three-dimensional scenes from stereo images is presented. The reconstruction is based on a dense disparity image obtained by a process of window correlation, applying a geometrical rectification before generating a three-dimensional matrix which stores the spatial occupation. The geometrical rectification is essential to correct the conical perspective of the camera and to obtain real scenes. For the geometrical rectification, three approaches are proposed, based on on...

  6. Rectification of radio frequency current in ferromagnetic nanowire

    OpenAIRE

    Yamaguchi, A; Miyajima, H.; Ono, T; Suzuki, Y.; S. Yuasa; Tulapurkar, A.; Nakatani, Y

    2006-01-01

    We report the rectification of a constant wave radio frequency (RF) current by using a single-layer magnetic nanowire; a direct-current voltage is resonantly generated when the RF current flows through the nanowire. The mechanism of the rectification is discussed in terms of the spin torque diode effect reported for magnetic tunnel junction devices and the rectification is shown to be direct attributable to resonant spin wave excitation by the RF current.

  7. Sufficient conditions for thermal rectification in graded materials

    OpenAIRE

    Pereira, Emmanuel

    2011-01-01

    We address a fundamental problem for the advance of phononics: the search of a feasible thermal diode. We establish sufficient conditions for the existence of thermal rectification in general graded materials. By starting from simple assumptions satisfied by the usual anharmonic models that describe heat conduction in solids, we derive an expression for the rectification. The analytical formula shows how to increase the rectification, and the conditions to avoid its decay with the system size...

  8. Effects of elastic anisotropy on acoustic-wave rectification

    Science.gov (United States)

    Tanaka, Yukihiro; Nishiguchi, Norihiko

    2016-01-01

    We investigate numerically the rectification phenomena of bulk acoustic waves in an acoustic-wave rectifier composed of an elastically anisotropic material containing a periodic array of triangular holes. Paying special attention to the effects of elastic anisotropy on phonon mode coupling, we elucidate the rectification performance for quasi-longitudinal and slow transverse waves. We find that elastic anisotropy markedly improves acoustic-wave rectification in comparison with the system composed of isotropic materials, particularly for longitudinal acoustic waves.

  9. EXPERIMENTAL AND THEORETICAL RESULTS OF RECTIFICATION MEASUREMENTS IN AN STM

    OpenAIRE

    Cutler, P.; Feuchtwang, T.; Huang, Z.; Tsong, T.; Nguyen, H.(University of California, Riverside, Riverside, USA); Lucas, A.; Sullivan, T.

    1987-01-01

    Recent measurements of dc current-voltage characteristics of Scanning Tunneling Microscope junctions have confirmed their expected high rectification property. We have exploited this property to study rectification at infrared frequencies. A laser beam of linearly polarized light is focused on an STM junction and the resulting dc bias induced across the junction by the alternating, asymmetrical tunnel current is detected. Results have been obtained that exhibit rectification for W-Si, W-Ni, a...

  10. Thermal Rectification in the Nonequilibrium Quantum-Dot-System

    OpenAIRE

    Chen, T.; Wang, X. B.

    2012-01-01

    Quantum thermal transport in two-quantum-dot system with Dzyaloshinskii-Moriya interaction (DM interaction) has been studied. The sign of thermal rectification can be controlled through changing the energy splitting or the DM interaction strength. The anisotropic term in the system can also affect the sign of rectification. Compared with other proposals [Phys. Rev. B 80, 172301 (2009)], our model can offer larger rectification efficiency and show the potential application in designing the pol...

  11. Thermal rectification properties of multiple-quantum-dot junctions

    OpenAIRE

    Kuo, David M. -T.; Chang, Yia-chung

    2010-01-01

    It is illustrated that semiconductor quantum dots (QDs) embedded into an insulating matrix connected with metallic electrodes and some vacuum space can lead to significant thermal rectification effect. A multilevel Anderson model is used to investigate the thermal rectification properties of the multiple-QD junction. The charge and heat currents in the tunneling process are calculated via the Keldysh Green's function technique. We show that pronounced thermal rectification a...

  12. Excitation of solid electron by proton and hydrogen molecular ions

    International Nuclear Information System (INIS)

    An electric stopping power of solid for hydrogen molecular ion (H2+, H3+) and ion cluster (2H+, 3H+) which lost the bounded electron from the former, were estimated and compared with the value of proton. The spacial distribution of the bounded electron of hydrogen molecular ions such as H2+ and H3+ was assumed by the molecular orbital on the basis of gauss function. In calculating the electric stopping power, a conduction electron is modelled on the free electron gas model and an exitation of bounded electron on the wave packet model. In any cases, the excitation of electron is described by the dielectric function. An effective charge Zeff, the index of the amount of stopping power S, is defined as Zeff = (s/sp)2/1 where Sp represents the stopping power for proton running with the same velocity in the same solid. This effective charge is a useful physical parameter to arrange the stopping power data, because it shows the practical charge number of the injection ion with bounded electron to be reduced to the point charge. The effective charges of H2+ and He+ in low energy field are different depend on the orientations when they transmitted through the carbon film. The effective charge of H2+ was less than 1 if the molecular axis was parallel to the running direction. In high energy field, the dependence of orientation was not observed. The differences of effective charges of H3+ passing through the carbon, aluminium and krypton gas were about 0.2, the small value indicating the small dependence of value on the materials. (S.Y.)

  13. Molecular dynamics simulation of electronically excited polyatomic molecules

    International Nuclear Information System (INIS)

    A computer simulation method is proposed for MD study of the photoinduced intramolecular dynamics in polyatomic molecules electronically excited by ultrashort laser pulses. An efficient, partially analytical procedure for calculation of the absorption (emission) spectra is developed and used for determination of molecular potentials in accordance with the experimental supersonic jets spectra. (author). 21 refs, 4 figs, 1 tab

  14. Quantum information analysis of electronic states at different molecular structures

    OpenAIRE

    Barcza, G; Legeza, Ö.; Marti, K.H.; Reiher, M.

    2010-01-01

    We have studied transition metal clusters from a quantum information theory perspective using the density-matrix renormalization group (DMRG) method. We demonstrate the competition between entanglement and interaction localization. We also discuss the application of the configuration interaction based dynamically extended active space procedure which significantly reduces the effective system size and accelerates the speed of convergence for complicated molecular electronic ...

  15. Variational cellular model of the molecular and crystal electronic structure

    International Nuclear Information System (INIS)

    A variational version of the cellular method is developed to calculate the electronic structure of molecules and crystals. Due to the simplicity of the secular equation, the method is easy to be implemented. Preliminary calculations on the hydrogen molecular ion suggest that it is also accurate and of fast convergence

  16. Fullerene-based Anchoring Groups for Molecular Electronics

    DEFF Research Database (Denmark)

    Martin, Christian A.; Ding, Dapeng; Sørensen, Jakob Kryger; Bjørnholm, Thomas; van Ruitenbeek, Jan M.; van der Zant, Herre

    2008-01-01

    We present results on a new fullerene-based anchoring group for molecular electronics. Using lithographic mechanically controllable break junctions in vacuum we have determined the conductance and stability of single-molecule junctions of 1,4-bis(fullero[c]pyrrolidin-1-yl)benzene. The compound can...

  17. Self assembled monolayers on silicon for molecular electronics

    International Nuclear Information System (INIS)

    We present an overview of various aspects of the self-assembly of organic monolayers on silicon substrates for molecular electronics applications. Different chemical strategies employed for grafting the self-assembled monolayers (SAMs) of alkanes having different chain lengths on native oxide of Si or on bare Si have been reviewed. The utility of different characterization techniques in determination of the thickness, molecular ordering and orientation, surface coverage, growth kinetics and chemical composition of the SAMs has been discussed by choosing appropriate examples. The metal counterelectrodes are an integral part of SAMs for measuring their electrical properties as well as using them for molecular electronic devices. A brief discussion on the variety of options available for the deposition of metal counterelectrodes, that is, soft metal contacts, vapor deposition and soft lithography, has been presented. Various theoretical models, namely, tunneling (direct and Fowler-Nordheim), thermionic emission, Poole-Frenkel emission and hopping conduction, used for explaining the electronic transport in dielectric SAMs have been outlined and, some experimental data on alkane SAMs have been analyzed using these models. It has been found that short alkyl chains show excellent agreement with tunneling models; while more experimental data on long alkyl chains are required to understand their transport mechanism(s). Finally, the concepts and realization of various molecular electronic components, that is, diodes, resonant tunnel diodes, memories and transistors, based on appropriate architecture of SAMs comprising of alkyl chains (?- molecule) and conjugated molecules (?-molecule) have been presented

  18. Theory and Application of Dissociative Electron Capture in Molecular Identification

    CERN Document Server

    Havey, C D; Jones, T; Voorhees, K J; Laramee, J A; Cody, R B; Clougherty, D P; Eberhart, Mark; Voorhees, Kent J.; Laramee, James A.; Cody, Robert B.; Clougherty, Dennis P.

    2006-01-01

    The coupling of an electron monochromator (EM) to a mass spectrometer (MS) has created a new analytical technique, EM-MS, for the investigation of electrophilic compounds. This method provides a powerful tool for molecular identification of compounds contained in complex matrices, such as environmental samples. EM-MS expands the application and selectivity of traditional MS through the inclusion of a new dimension in the space of molecular characteristics--the electron resonance energy spectrum. However, before this tool can realize its full potential, it will be necessary to create a library of resonance energy scans from standards of the molecules for which EM-MS offers a practical means of detection. Here, an approach supplementing direct measurement with chemical inference and quantum scattering theory is presented to demonstrate the feasibility of directly calculating resonance energy spectra. This approach makes use of the symmetry of the transition-matrix element of the captured electron to discriminat...

  19. Electron impact atomic and molecular processes - theoretical and application highlights

    International Nuclear Information System (INIS)

    Electron impact atomic/molecular scattering is an established but ever growing field of multidisciplinary theoretical and experimental research. This is so because the impact processes are found to take place in a wide variety of natural and man-made systems. There has long since been a fundamental as well as applied interest in this area of atomic and molecular Physics. The key quantities employed in interpreting the impact phenomena are cross sections, differential as well as total, which exhibit the characteristics of the target and the collision energy. In this article, the author discussed some aspects of electron -atom and electron - molecule collisions, that result into elastic and various inelastic processes. Theoretical highlights along with a few results are presented here as a preliminary account

  20. Bonding in Molecular Crystals from the Local Electronic Pressure Viewpoint

    CERN Document Server

    Tsirelson, Vladimir G; Tokatly, Ilya V

    2015-01-01

    The spatial distribution of the internal pressure of an electron fluid, which spontaneously arises at the formation of a molecule or a crystal, is linked to the main features of chemical bonding in molecular crystals. The local pressure is approximately expressed in terms of the experimental electron density and its derivatives using the density functional formalism and is applied to identify the bonding features in benzene, formamide and chromium hexacarbonyl. We established how the spatial regions of compression and stretching of the electron fluid in these solids reflect the typical features of chemical bonds of different types. Thus, the internal electronic pressure can serve as a bonding descriptor, which has a clear physical meaning and reveals the specific features of variety of the chemical bonds expressing them in terms of the electron density.

  1. Fulleropyrrolidine end-capped molecular wires for molecular electronics--synthesis, spectroscopic, electrochemical, and theoretical characterization

    DEFF Research Database (Denmark)

    Sørensen, Jakob Kryger; Fock, Jeppe; Pedersen, Anders Holmen; Petersen, Asger B; Jennum, Karsten; Bechgaard, Klaus; Kilså, Kristine; Geskin, Victor; Cornil, Jérôme; Bjørnholm, Thomas; Nielsen, Mogens Brøndsted

    2011-01-01

    In continuation of previous studies showing promising metal-molecule contact properties a variety of C(60) end-capped "molecular wires" for molecular electronics were prepared by variants of the Prato 1,3-dipolar cycloaddition reaction. Either benzene or fluorene was chosen as the central wire, and synthetic protocols for derivatives terminated with one or two fullero[c]pyrrolidine "electrode anchoring" groups were developed. An aryl-substituted aziridine could in some cases be employed directly...

  2. Renormalized molecular levels in a Sc3N@C-80 molecular electronic device

    DEFF Research Database (Denmark)

    Larade, Brian; Taylor, Jeremy Philip; Zheng, Q. R.; Mehrez, Hatem; Pomorski, Pawel; Guo, Hong

    2001-01-01

    We address several general questions about quantum transport through molecular systems by an ab initio analysis of a scandium-nitrogen doped C-80 metallofullerene device. Charge transfer from the Sc3N is found to drastically change the current-voltage characteristics: the current through the Sc3N @ C-80 device is double that through a bare C-80 device. We provide strong evidence that transport in such molecular devices is mediated by molecular electronic states which have been renormalized by th...

  3. III - V semiconductor structures for biosensor and molecular electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Luber, S.M.

    2007-01-15

    The present work reports on the employment of III-V semiconductor structures to biosensor and molecular electronics applications. In the first part a sensor based on a surface-near two dimensional electron gas for a use in biological environment is studied. Such a two dimensional electron gas inherently forms in a molecular beam epitaxy (MBE) grown, doped aluminum gallium arsenide - gallium arsenide (AlGaAs-GaAs) heterostructure. Due to the intrinsic instability of GaAs in aqueous solutions the device is passivated by deposition of a monolayer of 4'-substituted mercaptobiphenyl molecules. The influence of these molecules which bind to the GaAs via a sulfur group is investigated by Kelvin probe measurements in air. They reveal a dependence of GaAs electron affinity on the intrinsic molecular dipole moment of the mercaptobiphenyls. Furthermore, transient surface photovoltage measurements are presented which demonstrate an additional influence of mercaptobiphenyl chemisorption on surface carrier recombination rates. As a next step, the influence of pH-value and salt concentration upon the sensor device is discussed based on the results obtained from sensor conductance measurements in physiological solutions. A dependence of the device surface potential on both parameters due to surface charging is deduced. Model calculations applying Poisson-Boltzmann theory reveal as possible surface charging mechanisms either the adsorption of OH- ions on the surface, or the dissociation of OH groups in surface oxides. A comparison between simulation settings and physical device properties indicate the OH- adsorption as the most probable mechanism. In the second part of the present study the suitability of MBE grown III-V semiconductor structures for molecular electronics applications is examined. In doing so, a method to fabricate nanometer separated, coplanar, metallic electrodes based on the cleavage of a supporting AlGaAs-GaAs heterostructure is presented. This is followed by a thorough topographical and electrical characterization of fabricated devices which includes the electrostatic trapping of single gold nanoclusters between the electrodes. A first application to molecular electronics is presented by conductance measurements on a molecular layer of oligophenylenvinylene derivatives. Simulations on model molecules applying extended Hueckel theory and the nonequilibrium Greens function formalism reveal a good qualitative agreement between theory and experiment. Furthermore, promising extensions to the present fabrication method are discussed. These include the processing and characterization of broken T-shaped electrodes suitable for measurements on single molecules, and the transition to pure semiconductor electrodes based on indium arsenide. (orig.)

  4. Low-energy electron-collision processes in molecular chlorine

    International Nuclear Information System (INIS)

    The results of close-coupling calculations using the complex Kohn variational method are reported for a variety of low-energy electron-collision processes involving molecular chlorine. We report cross sections for elastic scattering and momentum transfer, as well as dissociative excitation of the five lowest electronically excited states (1,3?u, 1,3?g, 3?u+) which are formed by promoting an occupied valence electron into an antibonding (5?u) orbital. We also report cross sections for the excitation of the lowest bound optically allowed states in Cl2. The cross sections, especially at very low energies, are found to depend sensitively on both target polarization and a proper balance of correlation effects in the N- and (N+1)-electron systems. Comparison is made between the results of this study and the limited body of experimental results available for this system

  5. Special issue on ultrafast electron and molecular dynamics

    Science.gov (United States)

    Martin, Fernando; Hishikawa, Akiyoshi; Vrakking, Marc

    2014-06-01

    In the last few years, the advent of novel experimental and theoretical approaches has made possible the investigation of (time-resolved) molecular dynamics in ways not anticipated before. Experimentally, the introduction of novel light sources such as high-harmonic generation (HHG) and XUV/x-ray free electron lasers, and the emergence of novel detection strategies, such as time-resolved electron/x-ray diffraction and the fully coincident detection of electrons and fragment ions in reaction microscopes, has significantly expanded the arsenal of available techniques, and has taken studies of molecular dynamics into new domains of spectroscopic, spatial and temporal resolution, the latter including first explorations into the attosecond domain, thus opening completely new avenues for imaging electronic and nuclear dynamics in molecules. Along the way, particular types of molecular dynamics, e.g., dynamics around conical intersections, have gained an increased prominence, sparked by the realization of the essential role that this dynamics plays in relaxation pathways in important bio-molecular systems. In the short term, this will allow one to uncover and control the dynamics of elementary chemical processes such as, e.g., ultrafast charge migration, proton transfer, isomerization or multiple ionization, and to address new key questions about the role of attosecond coherent electron dynamics in chemical reactivity. The progress on the theoretical side has been no less impressive. Novel generations of supercomputers and a series of novel computational strategies have allowed nearly exact calculations in small molecules, as well as highly successful approximate calculations in large, polyatomic molecules, including biomolecules. Frequent and intensive collaborations involving both theory and experiment have been essential for the progress that has been accomplished. The special issue 'Ultrafast electron and molecular dynamics' seeks to provide an overview of the current developments, as well as new concepts that are emerging in this field when studying molecular dynamics at attosecond or few-femtosecond time-scales. It also aims at indicating how such studies are likely to evolve in the coming years. In this context, the present special issue contains contributions from recognized experts on HHG, free electron lasers, attosecond and femtosecond pump-probe spectroscopy, electron and x-ray diffraction methods, photoionization and theoretical methods specially designed for the analysis of experiments in this field. Seven review articles report on the present status of some selected topics, namely, table-top and free-electron lasers operating in the XUV and x-ray wavelength regimes to investigate ultrafast molecular dynamics, imaging methods to visualize electron and nuclear dynamics, nonlinear optics applications, and recent theoretical developments. These and other topics are covered by 32 research papers, in which new exciting results show the path for future developments in this field.

  6. Interplay between electron-electron and electron-vibration interactions on the thermoelectric properties of molecular junctions

    OpenAIRE

    Perroni, C. A.; Ninno, D.; Cataudella, V.

    2014-01-01

    The linear thermoelectric properties of molecular junctions are theoretically studied close to room temperature within a model including electron-electron and electron-vibration interactions on the molecule. A nonequilibrium adiabatic approach is generalized to include large Coulomb repulsion through a self-consistent procedure and applied to the investigation of large molecules, such as fullerenes, within the Coulomb blockade regime. The focus is on the phonon thermal condu...

  7. Molecular electronics an introduction to theory and experiment

    CERN Document Server

    Cuevas, Juan Carlos

    2010-01-01

    This book provides a comprehensive overview of the rapidly developing field of molecular electronics. It focuses on our present understanding of the electrical conduction in single-molecule circuits and provides a thorough introduction to the experimental techniques and theoretical concepts. It will also constitute as the first textbook-like introduction to both the experiment and theory of electronic transport through single atoms and molecules. In this sense, this publication will prove invaluable to both researchers and students interested in the field of nanoelectronics and nanoscience in

  8. Rectification of niobium and tantalum pentachlorides in packed columns

    International Nuclear Information System (INIS)

    Experimentally determined are mass transfer characteristics of the packed column - the height of the transfer units at rectification separation of mixtures of niobium and tantalum pentachlorides. Experimental data on corrosion resistance and rectification kinetics confirmed the expediency of the use of packed columns for separation and purification of niobium and tantalum pentachlorides

  9. Deep purification of NbCl5 by rectification

    International Nuclear Information System (INIS)

    The results of experiments on rectification of niobium pentachloride on a quartz apparatus are described. It is shown that by means of such rectification a substantial amount of impurities can be removed from NbCl5 down to a level well below the sensitivity threshold of the existing analysis techniques, i.e. to 10-5 to 10-6%

  10. Ballistic thermal rectification in nanoscale three-terminal junctions

    OpenAIRE

    Zhang, Lifa; Wang, Jian-Sheng; Li, Baowen

    2010-01-01

    We study ballistic thermal transport in three-terminal atomic nanojunctions by the nonequilibrium Green's function method. We find that there is ballistic thermal rectification in asymmetric three-terminal structures because of the incoherent phonon scattering from the control terminal. With spin-phonon interaction, we also find the ballistic thermal rectification even in symmetric three-terminal paramagnetic structures.

  11. Electron densities and the excitation of CN in molecular clouds

    Science.gov (United States)

    Black, John H.; Van Dishoeck, Ewine F.

    1991-01-01

    In molecular clouds of modest density and relatively high fractional ionization, the rotational excitation of CN is controlled by a competition among electron impact, neutral impact and the interaction with the cosmic background radiation. The degree of excitation can be measured through optical absorption lines and millimeter-wave emission lines. The available, accurate data on CN in diffuse and translucent molecular clouds are assembled and used to determine electron densities. The derived values, n(e) = roughly 0.02 - 0.5/cu cm, imply modest neutral densities, which generally agree well with determinations by other techniques. The absorption- and emission-line measurements of CN both exclude densities higher than n(H2) = roughly 10 exp 3.5/cu cm on scales varying from 0.001 to 60 arcsec in these clouds.

  12. Electron densities and the excitation of CN in molecular clouds

    Energy Technology Data Exchange (ETDEWEB)

    Black, J.H.; Van Dishoeck, E.F. (Onsala Rymdobservatorium (Sweden) Steward Observatory, Tucson, AZ (USA) California Institute of Technology, Pasadena (USA) Leiden Rijksuniversiteit, Sterrewacht (Netherlands))

    1991-03-01

    In molecular clouds of modest density and relatively high fractional ionization, the rotational excitation of CN is controlled by a competition among electron impact, neutral impact and the interaction with the cosmic background radiation. The degree of excitation can be measured through optical absorption lines and millimeter-wave emission lines. The available, accurate data on CN in diffuse and translucent molecular clouds are assembled and used to determine electron densities. The derived values, n(e) = roughly 0.02 - 0.5/cu cm, imply modest neutral densities, which generally agree well with determinations by other techniques. The absorption- and emission-line measurements of CN both exclude densities higher than n(H2) = roughly 10 exp 3.5/cu cm on scales varying from 0.001 to 60 arcsec in these clouds. 32 refs.

  13. Electron densities and the excitation of CN in molecular clouds

    International Nuclear Information System (INIS)

    In molecular clouds of modest density and relatively high fractional ionization, the rotational excitation of CN is controlled by a competition among electron impact, neutral impact and the interaction with the cosmic background radiation. The degree of excitation can be measured through optical absorption lines and millimeter-wave emission lines. The available, accurate data on CN in diffuse and translucent molecular clouds are assembled and used to determine electron densities. The derived values, n(e) = roughly 0.02 - 0.5/cu cm, imply modest neutral densities, which generally agree well with determinations by other techniques. The absorption- and emission-line measurements of CN both exclude densities higher than n(H2) = roughly 10 exp 3.5/cu cm on scales varying from 0.001 to 60 arcsec in these clouds. 32 refs

  14. Electronic kinetics of molecular nitrogen and molecular oxygen in high-latitude lower thermosphere and mesosphere

    Directory of Open Access Journals (Sweden)

    A. S. Kirillov

    2010-01-01

    Full Text Available Total quenching rate coefficients of Herzberg states of molecular oxygen and three triplet states of molecular nitrogen in the collisions with O2 and N2 molecules are calculated on the basis of quantum-chemical approximations. The calculated rate coefficients of electronic quenching of O2* and N2* molecules show a good agreement with available experimental data. An influence of collisional processes on vibrational populations of electronically excited N2 and O2 molecules is studied for the altitudes of high-latitude lower thermosphere and mesosphere during auroral electron precipitation. It is indicated that molecular collisions of metastable nitrogen N2(A3?u* with O2 molecules are principal mechanism in electronic excitation of both Herzberg states c1?u&minus, A'3?u, A3?u+ and high vibrational levels of singlet states a1?g and b1?g+ of molecular oxygen O2 at these altitudes.

  15. Reversal of thermal rectification in one-dimensional nonlinear composite system

    International Nuclear Information System (INIS)

    Using nonequilibrium molecular dynamics simulations, a comprehensive study of the asymmetric heat conduction in the composite system consisting of the Frenkel—Kontorova (FK) model and Fermi—Pasta—Ulam (FPU) model is conducted. The calculated results show that in a larger system, the rectifying direction can be reversed only by adjusting the thermal bias. Moreover, the rectification reversal depends critically on the system size and the properties of the interface. The mechanisms of the two types of asymmetric heat conduction induced by nonlinearity are discussed. Considering the novel asymmetric heat conduction in the system, it may possess possible applications to manage the thermal rectification in situ directionally without re-building the structure. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  16. Electron dopable molecular wires based on the extended viologens.

    Czech Academy of Sciences Publication Activity Database

    Kolivoška, Viliam; Gál, Miroslav; Pospíšil, Lubomír; Valášek, Michal; Hromadová, Magdaléna

    2011-01-01

    Ro?. 13, ?. 23 (2011), s. 11422-11429. ISSN 1463-9076 R&D Projects: GA ?R GA203/08/1157; GA ?R GA203/09/0705; GA AV ?R IAA400400802; GA MŠk(CZ) MEB041006 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506 Keywords : electron transfer * spectroelectrochemistry * molecular wires Subject RIV: CG - Electrochemistry Impact factor: 3.573, year: 2011

  17. Ab Initio Molecular Dynamics on the Electronic Boltzmann Equilibrium Distribution

    OpenAIRE

    Alonso J.L.; Castro A.; Echenique P.; Polo V.; Rubio A.; Zueco D.

    2010-01-01

    We prove that for a combined system of classical and quantum particles, it is possible to write a dynamics for the classical particles that incorporates in a natural way the Boltzmann equilibrium population for the quantum subsystem. In addition, these molecular dynamics do not need to assume that the electrons immediately follow the nuclear motion (in contrast to any adiabatic approach), and do not present problems in the presence of crossing points between different potent...

  18. Fast Electron Repulsion Integrals for Molecular Coulomb Sturmians

    DEFF Research Database (Denmark)

    Avery, James Emil

    2013-01-01

    A new method is presented for calculating interelectron repulsion integrals for molecular Coulomb Sturmian basis sets. This makes use of an expansion of densities in terms of 2k-Sturmians, and the interelectron repulsion integrals are then calculated by a method based on the theory of hyperspherical harmonics. A rudimentary software library has been implemented and preliminary benchmarks indicate very good performance: On average 40 ns, or approximately 80 clock cycles, per electron repulsion in...

  19. Research ZVS Synchronous Rectification of Resonant Converter

    OpenAIRE

    Xiao Kui Li

    2014-01-01

    In order to expand the application of synchronous rectification, the technology using ZVS synchronous rectifier is studied which is based on the IPT resonant converter. By using its own resonant characteristic, a novel control method that AC-DC section of the resonant converter works in ZVS SR state is proposed in this study. First of all, the ZVS working operation of SR is analyzed and equivalent circuits for each operation mode are also given. On that basis, the novel control method is prop...

  20. Recycled Noise Rectification: A Dumb Maxwell's Daemon

    CERN Document Server

    Borromeo, M; Marchesoni, F

    2006-01-01

    The one dimensional motion of a massless Brownian particle on a symmetric periodic substrate can be rectified by re-injecting its driving noise through a realistic recycling procedure. If the recycled noise is multiplicatively coupled to the substrate, the ensuing feed-back system works like a passive Maxwell's daemon, capable of inducing a net current that depends on both the delay and the autocorrelation times of the noise signals. Extensive numerical simulations show that the underlying rectification mechanism is a resonant nonlinear effect: The observed currents can be optimized for an appropriate choice of the recycling parameters with immediate application to the design of nanodevices for particle transport.

  1. Microwave power engineering generation, transmission, rectification

    CERN Document Server

    Okress, Ernest C

    1968-01-01

    Microwave Power Engineering, Volume 1: Generation, Transmission, Rectification considers the components, systems, and applications and the prevailing limitations of the microwave power technology. This book contains four chapters and begins with an introduction to the basic concept and developments of microwave power technology. The second chapter deals with the development of the main classes of high-power microwave and optical frequency power generators, such as magnetrons, crossed-field amplifiers, klystrons, beam plasma amplifiers, crossed-field noise sources, triodes, lasers. The third

  2. Precision Rectification of Airborne SAR Image

    DEFF Research Database (Denmark)

    Dall, Jørgen; Liao, M.; Zhang, Zhe; Frederiksen, P.

    A simple and direct procedure for the rectification of a certain class of airborne SAR data is presented. The relief displacements of SAR data are effectively removed by means of a digital elevation model and the image is transformed to the ground coordinate system. SAR data from the Danish EMISAR......([7]) is used. The EMISAR produces data with a geometrical resolution of 2.0 meters. The corrected image is tested against photogrammetric control measurements and an accuracy better than 0.5 pixel corresponding to 0.75 meters is obtained. The results indicate promising possibilities for the...

  3. Renormalized molecular levels in a Sc3N@C-80 molecular electronic device

    DEFF Research Database (Denmark)

    Larade, Brian; Taylor, Jeremy Philip

    2001-01-01

    We address several general questions about quantum transport through molecular systems by an ab initio analysis of a scandium-nitrogen doped C-80 metallofullerene device. Charge transfer from the Sc3N is found to drastically change the current-voltage characteristics: the current through the Sc3N @ C-80 device is double that through a bare C-80 device. We provide strong evidence that transport in such molecular devices is mediated by molecular electronic states which have been renormalized by the device environment, such as the electrodes and external bias V-b. The renormalized molecular levels and main transmission features shift in energy corresponding to half the applied bias voltage. This is also consistent with our finding that the voltage drops by V-b/2 at each molecule/electrode contact.

  4. Electron momentum spectroscopy of 1-butene: a theoretical analysis using molecular dynamics and molecular quantum similarity.

    Science.gov (United States)

    Shojaei, S H Reza; Vandenbussche, Jelle; Deleuze, Michael S; Bultinck, Patrick

    2013-09-01

    The results of experimental studies of the valence electronic structure of 1-butene by means of electron momentum spectroscopy (EMS) have been reinterpreted on the basis of molecular dynamical simulations in conjunction with the classical MM3 force field. The computed atomic trajectories demonstrate the importance of thermally induced nuclear dynamics in the electronic neutral ground state, in the form of significant deviations from stationary points on the potential energy surface and considerable variations of the C-C-C-C dihedral angle. These motions are found to have a considerable influence on the computed spectral bands and outer-valence electron momentum distributions. Euclidean distances between spherically averaged electron momentum densities confirm that thermally induced nuclear motions need to be fully taken into account for a consistent interpretation of the results of EMS experiments on conformationally flexible molecules. PMID:23902590

  5. A molecularly based theory for electron transfer reorganization energy

    Science.gov (United States)

    Zhuang, Bilin; Wang, Zhen-Gang

    2015-12-01

    Using field-theoretic techniques, we develop a molecularly based dipolar self-consistent-field theory (DSCFT) for charge solvation in pure solvents under equilibrium and nonequilibrium conditions and apply it to the reorganization energy of electron transfer reactions. The DSCFT uses a set of molecular parameters, such as the solvent molecule's permanent dipole moment and polarizability, thus avoiding approximations that are inherent in treating the solvent as a linear dielectric medium. A simple, analytical expression for the free energy is obtained in terms of the equilibrium and nonequilibrium electrostatic potential profiles and electric susceptibilities, which are obtained by solving a set of self-consistent equations. With no adjustable parameters, the DSCFT predicts activation energies and reorganization energies in good agreement with previous experiments and calculations for the electron transfer between metallic ions. Because the DSCFT is able to describe the properties of the solvent in the immediate vicinity of the charges, it is unnecessary to distinguish between the inner-sphere and outer-sphere solvent molecules in the calculation of the reorganization energy as in previous work. Furthermore, examining the nonequilibrium free energy surfaces of electron transfer, we find that the nonequilibrium free energy is well approximated by a double parabola for self-exchange reactions, but the curvature of the nonequilibrium free energy surface depends on the charges of the electron-transferring species, contrary to the prediction by the linear dielectric theory.

  6. Machine Learning of Molecular Electronic Properties in Chemical Compound Space

    CERN Document Server

    Montavon, Grégoire; Gobre, Vivekanand; Vazquez-Mayagoitia, Alvaro; Hansen, Katja; Tkatchenko, Alexandre; Müller, Klaus-Robert; von Lilienfeld, O Anatole

    2013-01-01

    The combination of modern scientific computing with electronic structure theory can lead to an unprecedented amount of data amenable to intelligent data analysis for the identification of meaningful, novel, and predictive structure-property relationships. Such relationships enable high-throughput screening for relevant properties in an exponentially growing pool of virtual compounds that are synthetically accessible. Here, we present a machine learning (ML) model, trained on a data base of \\textit{ab initio} calculation results for thousands of organic molecules, that simultaneously predicts multiple electronic ground- and excited-state properties. The properties include atomization energy, polarizability, frontier orbital eigenvalues, ionization potential, electron affinity, and excitation energies. The ML model is based on a deep multi-task artificial neural network, exploiting underlying correlations between various molecular properties. The input is identical to \\emph{ab initio} methods, \\emph{i.e.} nucle...

  7. Collision processes of electrons with molecular hydrogen ions

    International Nuclear Information System (INIS)

    Collision processes of electrons with trapped ions of mass numbers 1, 2, 3, 5, 7, 10, 14 and 20 are investigated in the concentric electron-beam device. Trapping characteristics are measured and lead to the conclusion that all the ions in the trap are hydrogenic. Cross section functions for the electron impact dissociation of H2+, H3+ and H5+ are measured. the shape of the H2+ dissociation function indicates that the molecular ions are trapped for a sufficiently long time for vibrational decay to upsilon = 0 to occur. There is good agreement between the present low energy H3+ dissociation data and previous work. Dissociation cross sections for H5+ and the temperature dependence of the e-H5+ recombination rate are measured. The latter is in good agreement with previous room temperature data and facilitates the prediction of the recombination rate in the Jovian ionosphere. (author)

  8. Automated rectification and geocoding of SAR imagery

    Science.gov (United States)

    Kwok, R.; Curlander, J. C.

    1987-01-01

    An automated post-processing system has been developed for rectification and geocoding of SAR (Synthetic Aperture Radar) imagery. The system uses as input a raw uncorrected image from the operational SAR correlator, and produces as a standard output a rectified and geocoded product. The accurate geolocation of SAR image pixels is provided by a spatial transformation model which maps the slant range-azimuth SAR image pixels into their location on a prespecified map grid. This model predicts the geodetic location of each pixel by utilizing: the sensor platform position; a geoid model; the parameters of the data collection system and the processing parameters used in the SAR correlator. Based on their geodetic locations, the pixels are mapped by using the desired cartographic projection equations. This rectification and geocoding technique has been tested with Seasat and SIR-B images. The test results demonstrate absolute location uncertainty of less than 50 m and relative distortion (scale factor and skew) of less than 0.1 percent relative to local variations from the assumed geoid.

  9. Mesoscopic rectification in a quantum dot with spin-orbit interaction

    International Nuclear Information System (INIS)

    We investigate the conductance of an open quantum dot in which uniform Rashba spin-orbit interaction (SOI) is present in the cavity region. The dot has a central triangular stopper (CTS) whose rotation angle controls the symmetry of the whole system. For a Fermi wavelength comparable to the linear dimension of the CTS, the SOI-dependence of the conductance is sensitive to both the direction of bias and the rotation angle of the CTS. We propose a quantum ratchet which generates the directed current against AC bias with time-average zero by using spin-polarized electron injection. The relationship between the symmetry of the dot and the rectification effect is revealed, and is used as a mechanism for charge rectification

  10. Analysis on THz Radiation Generation Efficiency in Optical Rectification by Tilted-Pulse-Front Pumping

    Science.gov (United States)

    Meng, Qinglong; Ye, Rong; Zhong, Zheqiang; Yu, Junli; Zhang, Bin

    2015-09-01

    Optical rectification is one of the most important techniques for efficient terahertz (THz) radiation generation. However, the strong THz absorption caused by the free electrons in nonlinear crystal limits the further increasing of the THz radiation generation efficiency. The interaction mechanism between the femtosecond laser and the nonlinear crystal has been analyzed and the related theoretical model has been built up. And the theoretical model of the THz radiation generation efficiency in optical rectification by tilted-pulse-front pumping has also been built. On the basis, the influence of the central wavelength, the pulse duration, and the temperature on the THz radiation generation efficiency has been analyzed quantitatively. The results show that the THz radiation generation efficiency increases first and then decreases with the increasing of the intensity of pump pulse. In addition, the maximum THz radiation generation efficiency can be achieved by cryogenic temperatures and the optimized parameters of the pump pulses and the nonlinear crystal.

  11. Fulleropyrrolidine end-capped molecular wires for molecular electronics--synthesis, spectroscopic, electrochemical, and theoretical characterization

    DEFF Research Database (Denmark)

    SØrensen, Jakob Kryger; Fock, Jeppe

    2011-01-01

    In continuation of previous studies showing promising metal-molecule contact properties a variety of C(60) end-capped "molecular wires" for molecular electronics were prepared by variants of the Prato 1,3-dipolar cycloaddition reaction. Either benzene or fluorene was chosen as the central wire, and synthetic protocols for derivatives terminated with one or two fullero[c]pyrrolidine "electrode anchoring" groups were developed. An aryl-substituted aziridine could in some cases be employed directly as the azomethine ylide precursor for the Prato reaction without the need of having an electron-withdrawing ester group present. The effect of extending the p-system of the central wire from 1,4-phenylenediamine to 2,7-fluorenediamine was investigated by absorption, fluorescence, and electrochemical methods. The central wire and the C(60) end-groups were found not to electronically communicate in the ground state. However, the fluorescence of C(60) was quenched by charge transfer from the wire to C(60). Quantum chemical calculations predict and explain the collapse of coherent electronic transmission through one of the fulleropyrrolidine-terminated molecular wires.

  12. Growth, modification and integration of carbon nanotubes into molecular electronics

    Science.gov (United States)

    Moscatello, Jason P.

    Molecules are the smallest possible elements for electronic devices, with active elements for such devices typically a few Angstroms in footprint area. Owing to the possibility of producing ultra-high density devices, tremendous effort has been invested in producing electronic junctions by using various types of molecules. The major issues for molecular electronics include (1) developing an effective scheme to connect molecules with the present micro- and nano-technology, (2) increasing the lifetime and stabilities of the devices, and (3) increasing their performance in comparison to the state-of-the-art devices. In this work, we attempt to use carbon nanotubes (CNTs) as the interconnecting nanoelectrodes between molecules and microelectrodes. The ultimate goal is to use two individual CNTs to sandwich molecules in a cross-bar configuration while having these CNTs connected with microelectrodes such that the junction displays the electronic character of the molecule chosen. We have successfully developed an effective scheme to connect molecules with CNTs, which is scalable to arrays of molecular electronic devices. To realize this far reaching goal, the following technical topics have been investigated. (1) Synthesis of multi-walled carbon nanotubes (MWCNTs) by thermal chemical vapor deposition (T-CVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques (Chapter 3). We have evaluated the potential use of tubular and bamboo-like MWCNTs grown by T-CVD and PE-CVD in terms of their structural properties. (2) Horizontal dispersion of MWCNTs with and without surfactants, and the integration of MWCNTs to microelectrodes using deposition by dielectrophoresis (DEP) (Chapter 4). We have systematically studied the use of surfactant molecules to disperse and horizontally align MWCNTs on substrates. In addition, DEP is shown to produce impurityfree placement of MWCNTs, forming connections between microelectrodes. We demonstrate the deposition density is tunable by both AC field strength and AC field frequency. (3) Etching of MWCNTs for the impurity-free nanoelectrodes (Chapter 5). We show that the residual Ni catalyst on MWCNTs can be removed by acid etching; the tip removal and collapsing of tubes into pyramids enhances the stability of field emission from the tube arrays. The acid-etching process can be used to functionalize the MWCNTs, which was used to make our initial CNT-nanoelectrode glucose sensors. Finally, lessons learned trying to perform spectroscopic analysis of the functionalized MWCNTs were vital for designing our final devices. (4) Molecular junction design and electrochemical synthesis of biphenyl molecules on carbon microelectrodes for all-carbon molecular devices (Chapter 6). Utilizing the experience gained on the work done so far, our final device design is described. We demonstrate the capability of preparing patterned glassy carbon films to serve as the bottom electrode in the new geometry. However, the molecular switching behavior of biphenyl was not observed by scanning tunneling microscopy (STM), mercury drop or fabricated glassy carbon/biphenyl/MWCNT junctions. Either the density of these molecules is not optimum for effective integration of devices using MWCNTs as the nanoelectrodes, or an electroactive contaminant was reduced instead of the ionic biphenyl species. (5) Self-assembly of octadecanethiol (ODT) molecules on gold microelectrodes for functional molecular devices (Chapter 7). We have realized an effective scheme to produce Au/ODT/MWCNT junctions by spanning MWCNTs across ODT-functionalized microelectrodes. A percentage of the resulting junctions retain the expected character of an ODT monolayer. While the process is not yet optimized, our successful junctions show that molecular electronic devices can be fabricated using simple processes such as photolithography, self-assembled monolayers and dielectrophoresis.

  13. Electron collisions and internal excitation in stored molecular ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Buhr, H.

    2006-07-26

    In storage ring experiments the role, which the initial internal excitation of a molecular ion can play in electron collisions, and the effect of these collisions on the internal excitation are investigated. Dissociative recombination (DR) and inelastic and super-elastic collisions are studied in the system of He{sup +}{sub 2}. The DR rate coefficient at low energies depends strongly on the initial vibrational excitation in this system. Therefore changes in the DR rate coefficient are a very sensitive probe for changes in the vibrational excitation in He{sup +}{sub 2}, which is used to investigate the effects of collisions with electrons and residual gas species. The low-energy DR of HD{sup +} is rich with resonances from the indirect DR process, when certain initial rotational levels in the molecular ion are coupled to levels in neutral Rydberg states lying below the ion state. Using new procedures for high-resolution electron-ion collision spectroscopy developed here, these resonances in the DR cross section can be measured with high energy sensitivity. This allows a detailed comparison with results of a MQDT calculation in an effort to assign some or all of the resonances to certain intermediate Rydberg levels. (orig.)

  14. Electron collisions and internal excitation in stored molecular ion beams

    International Nuclear Information System (INIS)

    In storage ring experiments the role, which the initial internal excitation of a molecular ion can play in electron collisions, and the effect of these collisions on the internal excitation are investigated. Dissociative recombination (DR) and inelastic and super-elastic collisions are studied in the system of He+2. The DR rate coefficient at low energies depends strongly on the initial vibrational excitation in this system. Therefore changes in the DR rate coefficient are a very sensitive probe for changes in the vibrational excitation in He+2, which is used to investigate the effects of collisions with electrons and residual gas species. The low-energy DR of HD+ is rich with resonances from the indirect DR process, when certain initial rotational levels in the molecular ion are coupled to levels in neutral Rydberg states lying below the ion state. Using new procedures for high-resolution electron-ion collision spectroscopy developed here, these resonances in the DR cross section can be measured with high energy sensitivity. This allows a detailed comparison with results of a MQDT calculation in an effort to assign some or all of the resonances to certain intermediate Rydberg levels. (orig.)

  15. Molecular Electronic Angular Motion Transducer Broad Band Self-Noise

    Directory of Open Access Journals (Sweden)

    Dmitry Zaitsev

    2015-11-01

    Full Text Available Modern molecular electronic transfer (MET angular motion sensors combine high technical characteristics with low cost. Self-noise is one of the key characteristics which determine applications for MET sensors. However, until the present there has not been a model describing the sensor noise in the complete operating frequency range. The present work reports the results of an experimental study of the self-noise level of such sensors in the frequency range of 0.01–200 Hz. Based on the experimental data, a theoretical model is developed. According to the model, self-noise is conditioned by thermal hydrodynamic fluctuations of the operating fluid flow in the frequency range of 0.01–2 Hz. At the frequency range of 2–100 Hz, the noise power spectral density has a specific inversely proportional dependence of the power spectral density on the frequency that could be attributed to convective processes. In the high frequency range of 100–200 Hz, the noise is conditioned by the voltage noise of the electronics module input stage operational amplifiers and is heavily reliant to the sensor electrical impedance. The presented results allow a deeper understanding of the molecular electronic sensor noise nature to suggest the ways to reduce it.

  16. Inelastic Electron Tunneling Spectroscopy in Molecular Electronic Devices from First-Principles

    Science.gov (United States)

    Ji, Tao

    In this thesis, we present the first-principle calculations of inelastic electron tunneling spectroscopy(IETS) in single molecular break junctions. In a two-probe electrode-molecule-electrode setup, density functional theory(DFT) is used for the construction of the Hamiltonian and the Keldysh non-equilibrium Green's function(NEGF) technique will be employed for determining the electron density in non-equilibrium system conditions. Total energy functional, atomic forces and Hessian matrix can be obtained in the DFT-NEGF formalism and self-consistent Born approximation(SCBA) is used to integrate the molecular vibrations (phonons) into the framework once the phonon spectra and eigenvectors are calculated from the dynamic matrix. Geometry optimization schemes will also be discussed as an indispensable part of the formalism as the equilibrium condition is crucial to correctly calculate the phonon properties of the system. To overcome the numerical difficulties, especially the large computational time demand of the electron-phonon coupling problem, we develop a numerical approximation for the electron self-energy due to phonons and the error is controlled within numerical precision. Besides, a direct IETS second order I-V derivative expression is derived to reduce the error of numerical differentiation under reasonable assumptions. These two approximations greatly reduce the computation requirement and make the calculation feasible within current numerical capability. As the application of the DFT-NEGF-SCBA formalism, we calculate the IETS of the gold-octanedithiol(ODT) molecular junction. The I-V curve, conductance and IETS from ab-inito calculations are compared directly to experiments. A microscopic understanding of the electron-phonon coupling mechanism in the molecular tunneling junctions is explained in this example. In addition, comparisons of the hydrogen-dissociative and hydrogen-non-dissociative ODT junctions as well as the different charge transfer behaviors are presented to show the effects of thiol formation in the ODT molecular junction.

  17. Effect of interfacial coupling on rectification in organic spin rectifiers

    Science.gov (United States)

    Hu, Gui-Chao; Zuo, Meng-Ying; Li, Ying; Zhang, Zhao; Ren, Jun-Feng; Wang, Chuan-Kui

    2015-07-01

    The effect of interfacial coupling on rectification in an organic co-oligomer spin diode is investigated theoretically by considering spin-independent and spin-resolved couplings respectively. In the case of spin-independent coupling, an optimal interfacial coupling strength with a significant enhanced rectification ratio is found, whose value depends on the structural asymmetry of the molecule. In the case of spin-resolved coupling, we found that only the variation of the interfacial coupling with specific spin is effective to modulate the rectification, which is due to the spin-filtering property of the central asymmetric magnetic molecule. A transition of the spin-current rectification between parallel spin-current rectification and antiparallel spin-current rectification may be observed with the variation of the spin-resolved interfacial coupling. The interfacial effect on rectification is further analyzed from the spin-dependent transmission spectrum at different biases. Project supported by the National Natural Science Foundation of China (Grant No. 1374195), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AM017), and the Excellent Young Scholars Research Fund of Shandong Normal University, China.

  18. Gold nanoparticle assisted assembly of a heme protein for enhancement of long-range interfacial electron transfer

    DEFF Research Database (Denmark)

    Jensen, Palle Skovhus; Chi, Qijin; Grumsen, Flemming Bjerg; Abad, J.M.; Horsewell, Andy; Schiffrin, D.J.; Ulstrup, Jens

    2007-01-01

    Interfacial electron transfer (ET) of biological macromolecules such as metalloproteins is the key process in bioelectrochemistry, enzymatic electrocatalysis, artificial ET chains, single-molecule electronic amplification and rectification, and other phenomena associated with the area of bioelectronics. A key challenge in molecular bioelectronics is to improve the efficiency of long-range charge transfer. The present work shows that this can be achieved by nanoparticle (NP) assisted assembly of ...

  19. Electron Spin Resonance Study of Electrons Trapped in Solid Molecular Hydrogen Films

    Science.gov (United States)

    Sheludiakov, S.; Ahokas, J.; Järvinen, J.; Vainio, O.; Lehtonen, L.; Zvezdov, D.; Khmelenko, V.; Lee, D. M.; Vasiliev, S.

    2015-12-01

    We report on the measurements of electrons trapped in solid molecular films of H2 , HD, and D2 . A narrow ESR line associated with the trapped electrons was detected with g=2.00233(5) , which turned out to be shifted by - 0.3 G from the free electron resonance. Comparison is made with earlier measurements where a similar line has been seen. In addition, for a D2{:}H2 mixture, after raising the temperature above 1 K, we observe a strong line at the location of the electron cyclotron resonance. The line amplitude is dependent on temperature and has an activation energy of 26 K. We believe that at elevated temperatures, electrons diffuse from the bulk of the film to the surface.

  20. Vibrational excitations in molecular layers probed by ballistic electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kajen, Rasanayagam Sivasayan; Chandrasekhar, Natarajan [Institute of Materials Research and Engineering, 3 Research Link, 117602 (Singapore); Feng Xinliang; Muellen, Klaus [Max-Planck-Institut fuer Polymerforschung, Postfach 3148, D-55021 Mainz (Germany); Su Haibin, E-mail: n-chandra@imre.a-star.edu.sg, E-mail: muellen@mpip-mainz.mpg.de, E-mail: hbsu@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

    2011-10-28

    We demonstrate the information on molecular vibrational modes via the second derivative (d{sup 2}I{sub B}/dV{sup 2}) of the ballistic electron emission spectroscopy (BEES) current. The proposed method does not create huge fields as in the case of conventional derivative spectroscopy and maintains a zero bias across the device. BEES studies carried out on three different types of large polycyclic aromatic hydrocarbon (PAH) molecular layers show that the d{sup 2}I{sub B}/dV{sup 2} spectra consist of uniformly spaced peaks corresponding to vibronic excitations. The peak spacing is found to be identical for molecules within the same PAH family though the BEES onset voltage varies for different molecules. In addition, injection into a particular orbital appears to correspond to a specific vibrational mode as the manifestation of the symmetry principle.

  1. Ab initio molecular dynamics on the electronic Boltzmann equilibrium distribution

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, J L; Echenique, P [Departamento de Fisica Teorica, Universidad de Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza (Spain); Castro, A; Polo, V [Institute for Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, Mariano Esquillor s/n, E-50018 Zaragoza (Spain); Rubio, A [Nano-Bio Spectroscopy group and ETSF Scientific Development Centre, Departamento de Fisica de Materiales, Universidad del PaIs Vasco, Centro de Fisica de Materiales, CSIC-UPV/EHU-MPC and DIPC, E-20018 San Sebastian (Spain); Zueco, D, E-mail: dzueco@unizar.e [Instituto de Ciencia de Materiales de Aragon and Departamento de Fisica de la Materia Condensada, CSIC-Universidad de Zaragoza, E-50009 Zaragoza (Spain)

    2010-08-15

    We prove that for a combined system of classical and quantum particles, it is possible to describe a dynamics for the classical particles that incorporates in a natural way the Boltzmann equilibrium population for the quantum subsystem. In addition, these molecular dynamics (MD) do not need to assume that the electrons immediately follow the nuclear motion (in contrast to any adiabatic approach) and do not present problems in the presence of crossing points between different potential energy surfaces (conical intersections or spin-crossings). A practical application of this MD to the study of the effect of temperature on molecular systems presenting (nearly) degenerate states-such as the avoided crossing in the ring-closure process of ozone-is presented.

  2. Ab initio molecular dynamics on the electronic Boltzmann equilibrium distribution

    International Nuclear Information System (INIS)

    We prove that for a combined system of classical and quantum particles, it is possible to describe a dynamics for the classical particles that incorporates in a natural way the Boltzmann equilibrium population for the quantum subsystem. In addition, these molecular dynamics (MD) do not need to assume that the electrons immediately follow the nuclear motion (in contrast to any adiabatic approach) and do not present problems in the presence of crossing points between different potential energy surfaces (conical intersections or spin-crossings). A practical application of this MD to the study of the effect of temperature on molecular systems presenting (nearly) degenerate states-such as the avoided crossing in the ring-closure process of ozone-is presented.

  3. Platinum(II)-Based Metallo-Supramolecular Polymer with Controlled Unidirectional Dipoles for Tunable Rectification.

    Science.gov (United States)

    Chakraborty, Chanchal; Pandey, Rakesh K; Hossain, Md Delwar; Futera, Zdenek; Moriyama, Satoshi; Higuchi, Masayoshi

    2015-09-01

    A platinum(II)-based, luminescent, metallo-supramolecular polymer (PolyPtL1) having an inherent dipole moment was synthesized via complexation of Pt(II) ions with an asymmetric ligand L1, containing terpyridyl and pyridyl moieties. The synthesized ligand and polymer were well characterized by various NMR techniques, optical spectroscopy, and cyclic voltammetry studies. The morphological study by atomic force microscopy revealed the individual and assembled polymer chains of 1-4 nm height. The polymer was specifically attached on Au-electrodes to produce two types of film (films 1 and 2) in which the polymer chains were aligned with their dipoles in opposite directions. The Au-surface bounded films were characterized by UV-vis, Raman spectroscopy, cyclic voltammetry, and atomic force microscopy study. The quantum mechanical calculation determined the average dipole moment for each monomer unit in PolyPtL1 to be about 5.8 D. The precise surface derivatization permitted effective tuning of the direction dipole moment, as well as the direction of rectification of the resulting polymer-attached molecular diodes. Film 1 was more conductive in positive bias region with an average rectification ratio (RR = I(+4 V)/I(-4 V)) ? 20, whereas film 2 was more conducting in negative bias with an average rectification ratio (RR = I(-4 V)/I(+4 V)) ? 18. PMID:26285226

  4. Stretched exponential relaxation in molecular and electronic glasses

    International Nuclear Information System (INIS)

    Stretched exponential relaxation, exp[-(t/?)?], fits many relaxation processes in disordered and quenched electronic and molecular systems, but it is widely believed that this function has no microscopic basis, especially in the case of molecular relaxation. For electronic relaxation the appearance of the stretched exponential is often described in the context of dispersive transport, where ? is treated as an adjustable parameter, but in almost all cases it is generally assumed that no microscopic meaning can be assigned to 0g, a glass transition temperature. We show that for molecular relaxation ?(Tg) can be understood, providing that one separates extrinsic and intrinsic effects, and that the intrinsic effects are dominated by two magic numbers, ?SR=3/5 for short-range forces, and ?K=3/7 for long-range Coulomb forces, as originally observed by Kohlrausch for the decay of residual charge on a Leyden jar. Our mathematical model treats relaxation kinetics using the Lifshitz-Kac-Luttinger diffusion to traps depletion model in a configuration space of effective dimensionality, the latter being determined using axiomatic set theory and Phillips-Thorpe constraint theory. The experiments discussed include ns neutron scattering experiments, particularly those based on neutron spin echoes which measure S(Q, t) directly, and the traditional linear response measurements which span the range from s to s, as collected and analysed phenomenologically by Angell, Ngai, Boehmer and others. The electronic materials discussed include a-Si:H, granular C60, semiconductor nanocrystallites, charge density waves in TaS3, spin glasses, and vortex glasses in high-temperature semiconductors. The molecular materials discussed include polymers, network glasses, electrolytes and alcohols, Van der Waals supercooled liquids and glasses, orientational glasses, water, fused salts, and heme proteins. In the intrinsic cases the theory of ?(Tg) is often accurate to 2%, which is often better than the quoted experimental accuracies ?5%. The extrinsic cases are identified by explicit structural signatures which are discussed at length. The discussion also includes recent molecular dynamical simulations for metallic glasses, spin glasses, quasicrystals and polymers which have achieved the intermediate relaxed Kohlrausch state and which have obtained values of ? in excellent agreement with the prediction of the microscopic theory. (author)

  5. Patterning molecular scale paramagnets at Au Surface: A root to Magneto-Molecular-Electronics

    CERN Document Server

    Messina, Paul C; Sorace, L; Rovai, D; Caneschi, A; Gatteschi, Dante; Messina, Paolo; Mannini, Matteo; Sorace, Lorenzo; Rovai, Donella; Caneschi, Andrea; Gatteschi, Dante

    2004-01-01

    Few examples of the exploitation of molecular magnetic properties in molecular electronics are known to date. Here we propose the realization of Self assembled monolayers (SAM) of a particular stable organic radical. This radical is meant to be used as a standard molecule on which to prove the validity of a single spin reading procedure known as ESR-STM. We demonstrate here that the radical is chemically anchored at the surface, preserves its magnetic functionality and can be imaged by STM. STM and ESR investigations of the molecular film is reported. We also discuss a range of possible applications, further than ESR-STM, of magnetic monolayers of simple purely organic magnetic molecule.

  6. Scan-Rate-Dependent Ion Current Rectification and Rectification Inversion in Charged Conical Nanopores

    OpenAIRE

    Momotenko, Dmitry; Hubert H. Girault*

    2011-01-01

    Herein we report a theoretical study of diode-like behavior of negatively charged (e.g., glass or silica) nanopores at different potential scan rates (1-1000 V center dot s(-1)). Finite element simulations were used to determine current-voltage characteristics of conical nanop ores at various electrolyte concentrations. This study demonstrates that significant changes in rectification behavior can be observed at high scan rates because the mass transport of ionic species appears sluggish on t...

  7. Electronic and magnetic structure of vivianite: cluster molecular orbital calculations

    Science.gov (United States)

    Grodzicki, M.; Amthauer, G.

    The electronic and magnetic structure of the octahydrophosphate vivianite, Fe3(PO4)2.8H2O, has been investigated by cluster molecular orbital calculations in local spin density approximation. Optical and Mössbauer spectra are well reproduced by the calculations, and the differences between the two iron sites can be correlated with differences in the geometrical structure of the first coordination sphere. The spin structure within the crystallographic ac plane is derived and explained on the basis of different superexchange pathways via edges of the phosphate tetrahedra. The calculations demonstrate that quite large clusters (up to 118 atoms) are necessary to arrive at reliable results.

  8. Molecular Electronics: Insight from First-Principles Transport Simulations

    DEFF Research Database (Denmark)

    Paulsson, Magnus; Frederiksen, Thomas; Brandbyge, Mads

    2010-01-01

    the electronic transport. Here we describe key computational ingredients and discuss these in relation to simulations for scanning tunneling microscopy (STM) experiments with C-60 molecules where the experimental geometry is well characterized. We then show how molecular dynamics simulations may be......Conduction properties of nanoscale contacts can be studied using first-principles simulations. Such calculations give insight into details behind the conductance that is not readily available in experiments. For example, we may learn how the bonding conditions of a molecule to the electrodes affect...

  9. Thermal rectification features: a study starting from local assumptions

    International Nuclear Information System (INIS)

    In the present work, addressing the investigation of thermal rectification in asymmetric models (in particular, graded systems), we generalize a previously developed approach based on the features of the local thermal conductivities. We study the behavior of the predicted rectification as the gradient of temperature into the system increases, and, considering a small chain, we give indications of a big rectification factor in very asymmetric models, a result which makes these graded materials genuine candidates for the construction of thermal diodes. Moreover, our results allow us to understand the details which determine the direction of the bigger heat flow. (paper)

  10. Electronic structure calculations on molecular photo-FET.

    Czech Academy of Sciences Publication Activity Database

    Kratochvílová, Irena; Pavelka, Mat?j; Nešp?rek, Stanislav; Sworakowski, J.; Záliš, Stanislav

    Leiden : Bell Academic Publishers, 2006 - (Simos, T.; Maroulis, G.), s. 1547-1549 ISBN 978-90-04-15542-8. ISSN 1573-4196. - (Lecture Ser. Computer and Computational Sci.. 7b). [International Conference on Computational Methods in Science and Engineering. Chania (GR), 27.10.2006-01.11.2006] R&D Projects: GA MŠk OC 137; GA AV ?R KAN401770651; GA AV ?R 1ET400400413; GA MŠk OC 139 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40400503; CEZ:AV0Z40500505 Keywords : molecular electronics * photochromic molecules * electronic structure * DFT calculations Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. Probing ultrafast electronic and molecular dynamics with free-electron lasers

    International Nuclear Information System (INIS)

    Molecular dynamics is an active area of research, focusing on revealing fundamental information on molecular structures and photon–molecule interaction and with broad impacts in chemical and biological sciences. Experimental investigation of molecular dynamics has been advanced by the development of new light sources and techniques, deepening our understanding of natural processes and enabling possible control and modification of chemical and biomolecular processes. Free-electron lasers (FELs) deliver unprecedented intense and short photon pulses in the vacuum ultraviolet and x-ray spectral ranges, opening a new era for the study of electronic and nuclear dynamics in molecules. This review focuses on recent molecular dynamics investigations using FELs. We present recent work concerning dynamics of molecular interaction with FELs using an intrinsic clock within a single x-ray pulse as well as using an external clock in a pump–probe scheme. We review the latest developments on correlated and coincident spectroscopy in FEL-based research and recent results revealing photo-induced interaction dynamics using these techniques. We also describe new instrumentations to conduct x-ray pump–x-ray probe experiments with spectroscopy and imaging detectors. (review article)

  12. Fragmentation of molecular ions in slow electron collisions

    International Nuclear Information System (INIS)

    The fragmentation of positively charged hydrogen molecular ions by the capture of slow electrons, the so called dissociative recombination (DR), has been investigated in storage ring experiments at the TSR, Heidelberg, where an unique twin-electron-beam arrangement was combined with high resolution fragment imaging detection. Provided with well directed cold electrons the fragmentation kinematics were measured down to meV collision energies where pronounced rovibrational Feshbach resonances appear in the DR cross section. For thermally excited HD+ the fragmentation angle and the kinetic energy release were studied at variable precisely controlled electron collision energies on a dense energy grid from 10 to 80 meV. The anisotropy described for the first time by Legendre polynomials higher 2nd order and the extracted rotational state contributions were found to vary on a likewise narrow energy scale as the rotationally averaged DR rate coefficient. Ro-vibrationally resolved DR experiments were performed on H2+ produced in distinct internal excitations by a novel ion source. Both the low-energy DR rate as well as the fragmentation dynamics at selected resonances were measured individually in the lowest two vibrational and first three excited rotational states. State-specific DR rates and angular dependences are reported. (orig.)

  13. Vibrational coherence transfer in an electronically decoupled molecular dyad

    Science.gov (United States)

    Schweighöfer, Felix; Dworak, Lars; Braun, Markus; Zastrow, Marc; Wahl, Jan; Burghardt, Irene; Rück-Braun, Karola; Wachtveitl, Josef

    2015-03-01

    The ring opening of a dithienylethene photoswitch incorporated in a bridged boron-dipyrromethene - dithienylethene molecular dyad was investigated with ultrafast spectroscopy. Coherent vibrations in the electronic ground state of the boron-dipyrromethene are triggered after selective photoexcitation of the closed dithienylethene indicating vibrational coupling although the two moieties are electronically isolated. A distribution of short-lived modes and a long-lived mode at 143 cm-1 are observed. Analysis of the theoretical frequency spectrum indicates two modes at 97 cm-1 and 147 cm-1 which strongly modulate the electronic transition energy. Both modes exhibit a characteristic displacement of the bridge suggesting that the mechanical momentum of the initial geometry change after photoexcitation of the dithienylethene is transduced to the boron-dipyrromethene. The relaxation to the dithienylethene electronic ground state is accompanied by significant heat dissipation into the surrounding medium. In the investigated dyad, the boron-dipyrromethene acts as probe for the ultrafast photophysical processes in the dithienylethene.

  14. Fragmentation of molecular ions in slow electron collisions

    Energy Technology Data Exchange (ETDEWEB)

    Novotny, Steffen

    2008-06-25

    The fragmentation of positively charged hydrogen molecular ions by the capture of slow electrons, the so called dissociative recombination (DR), has been investigated in storage ring experiments at the TSR, Heidelberg, where an unique twin-electron-beam arrangement was combined with high resolution fragment imaging detection. Provided with well directed cold electrons the fragmentation kinematics were measured down to meV collision energies where pronounced rovibrational Feshbach resonances appear in the DR cross section. For thermally excited HD{sup +} the fragmentation angle and the kinetic energy release were studied at variable precisely controlled electron collision energies on a dense energy grid from 10 to 80 meV. The anisotropy described for the first time by Legendre polynomials higher 2{sup nd} order and the extracted rotational state contributions were found to vary on a likewise narrow energy scale as the rotationally averaged DR rate coefficient. Ro-vibrationally resolved DR experiments were performed on H{sub 2}{sup +} produced in distinct internal excitations by a novel ion source. Both the low-energy DR rate as well as the fragmentation dynamics at selected resonances were measured individually in the lowest two vibrational and first three excited rotational states. State-specific DR rates and angular dependences are reported. (orig.)

  15. A LANDSAT digital image rectification system

    Science.gov (United States)

    Vanwie, P.; Stein, M.

    1976-01-01

    DIRS is a digital image rectification system for the geometric correction of LANDSAT multispectral scanner digital image data. DIRS removes spatial distortions from the data and brings it into conformance with the Universal Transverse Mercator (UTM) map projection. Scene data in the form of landmarks are used to drive the geometric correction algorithms. Two dimensional least squares polynominal and spacecraft attitude modeling techniques for geometric mapping are provided. Entire scenes or selected quadrilaterals may be rectified. Resampling through nearest neighbor or cubic convolution at user designated intervals is available. The output products are in the form of digital tape in band interleaved, single band or CCT format in a rotated UTM projection. The system was designed and implemented on large scale IBM 360 computers.

  16. Digital deformation model for fisheye image rectification.

    Science.gov (United States)

    Hou, Wenguang; Ding, Mingyue; Qin, Nannan; Lai, Xudong

    2012-09-24

    Fisheye lens can provide a wide view over 180°. It then has prominence advantages in three dimensional reconstruction and machine vision applications. However, the serious deformation in the image limits fisheye lens's usage. To overcome this obstacle, a new rectification method named DDM (Digital Deformation Model) is developed based on two dimensional perspective transformation. DDM is a type of digital grid representation of the deformation of each pixel on CCD chip which is built by interpolating the difference between the actual image coordinate and pseudo-ideal coordinate of each mark on a control panel. This method obtains the pseudo-ideal coordinate according to two dimensional perspective transformation by setting four mark's deformations on image. The main advantages are that this method does not rely on the optical principle of fisheye lens and has relatively less computation. In applications, equivalent pinhole images can be obtained after correcting fisheye lens images using DDM. PMID:23037373

  17. Fabrication of Micro-Gap Electrodes for Molecular Electronics

    Science.gov (United States)

    Edura, Tomohiko; Mizuno, Jun; Tsutsui, Ken; Saito, Mikiko; Tokuda, Masahide; Onozato, Harumasa; Koizumi, Toshiko; Wada, Yasuo; Haemori, Masamitsu; Koinuma, Hideomi

    Recently, organic molecular electrical devices such as molecular thin film transistors have received considerable attentions as possible candidates for next generation electrical and optical devices. This paper reports fabricating technologies of flat metallic electrodes on insulating substrates with micro-gap separation. The key technologies of fabricating the planar type electrodes are liftoff method by the combination of bi-layer photoresist with overhang profile and electron beam evaporation of thin metal (Ti and Au) films and SiO2-CMP (Chemical Mechanical Polishing) method of CVD (Chemical Vapor Deposition) deposited TEOS (Tetraethoxysilane) - SiO2 layer. The raggedness of the electrode/insulator interface and the electrode surface on the micro-gap electrodes were less than 3 nm. The isolation characteristics of fabricated electrodes were in the order of 1013 ohm at room temperature, which is enough for analyzing electronic properties of organic thin film devices. Finally, pentacene FET characteristics are discussed fabricated on the micro-gap flat electrodes. The mobility of this FET was 0.015cm2/Vs, which was almost on the order of the previous results. These results suggest that high performance organic thin film transistors would be realized on these advanced electrode structures.

  18. Failure of single electron descriptions of molecular orbital collision processes. [Electron promotion mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Elston, S.B.

    1978-01-01

    Inner-shell excitation occurring in low and moderate (keV range) energy collisions between light atomic and ionic systems is frequently describable in terms of molecular promotion mechanisms, which were extensively explored both theoretically and experimentally. The bulk of such studies have concentrated on processes understandable through the use of single- and independent-electron models. Nonetheless, it is possible to find cases of inner-shell excitation in relatively simple collision systems which involve nearly simultaneous multiple-electron transitions and transitions induced by inherently two-electron interactions. Evidence for these many- and nonindependent-electron phenomena in inner-shell excitation processes and the importance of considering such effects in the interpretation of collisionally induced excitation spectra is discussed. 13 references.

  19. Electronic absorption spectra and geometry of organic molecules an application of molecular orbital theory

    CERN Document Server

    Suzuki, Hiroshi

    1967-01-01

    Electronic Absorption Spectra and Geometry of Organic Molecules: An Application of Molecular Orbital Theory focuses on electronic absorption spectra of organic compounds and molecules. The book begins with the discussions on molecular spectra, electronic absorption spectra of organic compounds, and practical measures of absorption intensity. The text also focuses on molecular orbital theory and group theory. Molecular state functions; fundamental postulates of quantum theory; representation of symmetry groups; and symmetry operations and symmetry groups are described. The book also dis

  20. Dynamic rectification in a thermal diode based on fluid-solid interfaces: Contrasting behavior of soft materials and fluids

    Science.gov (United States)

    Murad, Sohail; Puri, Ishwar K.

    2014-05-01

    We have used molecular dynamics simulations to demonstrate that significant rectification is possible in nano-devices by manipulating solid-fluid interfaces between a thin solid wall and a soft material. In addition, the nature of the rectification is opposite to that for a solid wall and a simpler polar fluid (e.g., water). This thus opens the possibilities of reversing the direction of rectification in a nano-device which could lead to more precise control of heat transfer rates. Our simulations also show that surface modifications of the type introduced here can lead to over six fold increase in heat transfer rates in nano-devices. Dissipating heat from increasingly miniaturized semi-conductors of the future will become increasingly important since size limitations are often dictated by heat dissipation rates. These results also point to some other exciting practical applications. If the outside wall of a house were made hydrophilic, during hot summer days when the intent is to reduce heat transfer from the ambient (Ta > Tin), a small polar fluid like water could be introduced between the two walls. During nights, in order to cool the house (when Tin > Ta) water could be replaced by a less volatile soft material to enhance heat transfer. Thus, the same wall would demonstrate significant rectification in both cases but with different fluids.

  1. Rectification of light refraction in curved waveguide arrays

    OpenAIRE

    Longhi, S.

    2010-01-01

    An 'optical ratchet' for discretized light in photonic lattices, which enables to observe rectification of light refraction at any input beam conditions, is theoretically presented, and a possible experimental implementation based on periodically-curved zigzag waveguide arrays is proposed.

  2. Regularities of high purification of cadmium by rectification

    International Nuclear Information System (INIS)

    Behaviour of 21 impurities in the process of cadmium vacuum rectification under the pressure of residual gases 6.0x10-4 - 1.0x10-3 mm Hg and at the temperature 740-760 deg C in the column with 10 bubble plates is studied. Applicability of the calculation method for determination of basic parameters of rectification columns is shown

  3. Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions

    OpenAIRE

    2015-01-01

    Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can generate a significant direct-current volt...

  4. Rectification and Flux Reversals for Vortices Interacting with Triangular Traps

    OpenAIRE

    Reichhardt, C. J. Olson; Reichhardt, C.

    2004-01-01

    We simulate vortices in superconductors interacting with two-dimensional arrays of triangular traps. We find that, upon application of an ac drive, a net dc flow can occur which shows current reversals with increasing ac drive amplitude for certain vortex densities, in agreement with recent experiments and theoretical predictions. We identify the vortex dynamics responsible for the different rectification regimes. We also predict the occurrence of a novel transverse rectification effect in wh...

  5. High-frequency rectification in UPt3 point contacts

    International Nuclear Information System (INIS)

    Rectification experiments have been performed on UPt3-UPt3 and on Cu-UPt3 point contacts, using far-infrared radiation of 562 GHz. The voltage dependence of the rectification signal differs significantly from the second derivative d2V/dI2, which is also measured for these point contacts, which demonstrates that the point contacts are not in the ballistic regime. The results are explained with a heating model

  6. Current rectification by asymmetric molecules: An ab initio study

    OpenAIRE

    Zhou, Yan-hong; Zheng, Xiao-hong; Ying XU; Zeng, Zhao Yang

    2006-01-01

    We study current rectification effect in an asymmetric molecule HOOC-C$_6$H$_4$-(CH$_2$)$_n$ sandwiched between two Aluminum electrodes using an {\\sl ab initio} nonequilibrium Green function method. The conductance of the system decreases exponentially with the increasing number $n$ of CH$_2$. The phenomenon of current rectification is observed such that a very small current appears at negative bias and a sharp negative differential resistance at a critical positive bias when $n\\ge 2$. The re...

  7. Thermal rectification in bulk materials with asymmetric shape

    OpenAIRE

    Sawaki, D.; Kobayashi, W. (Wataru); Moritomo, Y.; Terasaki, I.

    2011-01-01

    We investigate thermal rectification in a bulk material with a pyramid shape to elucidate shape dependence of the thermal rectification, and find that rectifying coefficient R is 1.35 for this shape, which is smaller than R=1.43 for a rectangular shape. This result is fully duplicated by our numerical calculation based on Fourier's law. We also apply this calculation to a given shape, and show a possible way to increase R depending on the shape.

  8. Machine learning of molecular electronic properties in chemical compound space

    Science.gov (United States)

    Montavon, Grégoire; Rupp, Matthias; Gobre, Vivekanand; Vazquez-Mayagoitia, Alvaro; Hansen, Katja; Tkatchenko, Alexandre; Müller, Klaus-Robert; Anatole von Lilienfeld, O.

    2013-09-01

    The combination of modern scientific computing with electronic structure theory can lead to an unprecedented amount of data amenable to intelligent data analysis for the identification of meaningful, novel and predictive structure-property relationships. Such relationships enable high-throughput screening for relevant properties in an exponentially growing pool of virtual compounds that are synthetically accessible. Here, we present a machine learning model, trained on a database of ab initio calculation results for thousands of organic molecules, that simultaneously predicts multiple electronic ground- and excited-state properties. The properties include atomization energy, polarizability, frontier orbital eigenvalues, ionization potential, electron affinity and excitation energies. The machine learning model is based on a deep multi-task artificial neural network, exploiting the underlying correlations between various molecular properties. The input is identical to ab initio methods, i.e. nuclear charges and Cartesian coordinates of all atoms. For small organic molecules, the accuracy of such a ‘quantum machine’ is similar, and sometimes superior, to modern quantum-chemical methods—at negligible computational cost.

  9. Machine learning of molecular electronic properties in chemical compound space

    International Nuclear Information System (INIS)

    The combination of modern scientific computing with electronic structure theory can lead to an unprecedented amount of data amenable to intelligent data analysis for the identification of meaningful, novel and predictive structure–property relationships. Such relationships enable high-throughput screening for relevant properties in an exponentially growing pool of virtual compounds that are synthetically accessible. Here, we present a machine learning model, trained on a database of ab initio calculation results for thousands of organic molecules, that simultaneously predicts multiple electronic ground- and excited-state properties. The properties include atomization energy, polarizability, frontier orbital eigenvalues, ionization potential, electron affinity and excitation energies. The machine learning model is based on a deep multi-task artificial neural network, exploiting the underlying correlations between various molecular properties. The input is identical to ab initio methods, i.e. nuclear charges and Cartesian coordinates of all atoms. For small organic molecules, the accuracy of such a ‘quantum machine’ is similar, and sometimes superior, to modern quantum-chemical methods—at negligible computational cost. (paper)

  10. Rigorous theory of molecular orientational nonlinear optics

    Directory of Open Access Journals (Sweden)

    Chong Hoon Kwak

    2015-01-01

    Full Text Available Classical statistical mechanics of the molecular optics theory proposed by Buckingham [A. D. Buckingham and J. A. Pople, Proc. Phys. Soc. A 68, 905 (1955] has been extended to describe the field induced molecular orientational polarization effects on nonlinear optics. In this paper, we present the generalized molecular orientational nonlinear optical processes (MONLO through the calculation of the classical orientational averaging using the Boltzmann type time-averaged orientational interaction energy in the randomly oriented molecular system under the influence of applied electric fields. The focal points of the calculation are (1 the derivation of rigorous tensorial components of the effective molecular hyperpolarizabilities, (2 the molecular orientational polarizations and the electronic polarizations including the well-known third-order dc polarization, dc electric field induced Kerr effect (dc Kerr effect, optical Kerr effect (OKE, dc electric field induced second harmonic generation (EFISH, degenerate four wave mixing (DFWM and third harmonic generation (THG. We also present some of the new predictive MONLO processes. For second-order MONLO, second-order optical rectification (SOR, Pockels effect and difference frequency generation (DFG are described in terms of the anisotropic coefficients of first hyperpolarizability. And, for third-order MONLO, third-order optical rectification (TOR, dc electric field induced difference frequency generation (EFIDFG and pump-probe transmission are presented.

  11. Rigorous theory of molecular orientational nonlinear optics

    Science.gov (United States)

    Kwak, Chong Hoon; Kim, Gun Yeup

    2015-01-01

    Classical statistical mechanics of the molecular optics theory proposed by Buckingham [A. D. Buckingham and J. A. Pople, Proc. Phys. Soc. A 68, 905 (1955)] has been extended to describe the field induced molecular orientational polarization effects on nonlinear optics. In this paper, we present the generalized molecular orientational nonlinear optical processes (MONLO) through the calculation of the classical orientational averaging using the Boltzmann type time-averaged orientational interaction energy in the randomly oriented molecular system under the influence of applied electric fields. The focal points of the calculation are (1) the derivation of rigorous tensorial components of the effective molecular hyperpolarizabilities, (2) the molecular orientational polarizations and the electronic polarizations including the well-known third-order dc polarization, dc electric field induced Kerr effect (dc Kerr effect), optical Kerr effect (OKE), dc electric field induced second harmonic generation (EFISH), degenerate four wave mixing (DFWM) and third harmonic generation (THG). We also present some of the new predictive MONLO processes. For second-order MONLO, second-order optical rectification (SOR), Pockels effect and difference frequency generation (DFG) are described in terms of the anisotropic coefficients of first hyperpolarizability. And, for third-order MONLO, third-order optical rectification (TOR), dc electric field induced difference frequency generation (EFIDFG) and pump-probe transmission are presented.

  12. Rigorous theory of molecular orientational nonlinear optics

    International Nuclear Information System (INIS)

    Classical statistical mechanics of the molecular optics theory proposed by Buckingham [A. D. Buckingham and J. A. Pople, Proc. Phys. Soc. A 68, 905 (1955)] has been extended to describe the field induced molecular orientational polarization effects on nonlinear optics. In this paper, we present the generalized molecular orientational nonlinear optical processes (MONLO) through the calculation of the classical orientational averaging using the Boltzmann type time-averaged orientational interaction energy in the randomly oriented molecular system under the influence of applied electric fields. The focal points of the calculation are (1) the derivation of rigorous tensorial components of the effective molecular hyperpolarizabilities, (2) the molecular orientational polarizations and the electronic polarizations including the well-known third-order dc polarization, dc electric field induced Kerr effect (dc Kerr effect), optical Kerr effect (OKE), dc electric field induced second harmonic generation (EFISH), degenerate four wave mixing (DFWM) and third harmonic generation (THG). We also present some of the new predictive MONLO processes. For second-order MONLO, second-order optical rectification (SOR), Pockels effect and difference frequency generation (DFG) are described in terms of the anisotropic coefficients of first hyperpolarizability. And, for third-order MONLO, third-order optical rectification (TOR), dc electric field induced difference frequency generation (EFIDFG) and pump-probe transmission are presented

  13. Theory of nonlinear electromagnetic rectification in a BCS superconductor

    International Nuclear Information System (INIS)

    Within the framework of the BCS pairing approximation, a theory of nonlinear electromagnetic rectification in a Cooper-paired jellium is established. It is pointed out that the electromagnetic rectification phenomenon, inevitably present as the many-body system's reaction in a second-harmonic generation process, is of special interest in a superconductor where induced dc currents flow without resistance. Based on a density-matrix approach the nonlinear response tensor is derived and discussed. The importance of nonlocality for the rectification process in centrosymmetric media is stressed. A simple expression for the response tensor is derived in the limit in which the nonlocal pairing effects are included to lowest order. It is demonstrated that electromagnetic rectification occurs only when the nonlinear response has a diamagnetic part. By considering the electromagnetic-rectification phenomenon as a nonlinear-dynamical Meissner effect, the relation to the linear Meissner effect is emphasized. A qualitative discussion of the rectification process at a superconductor-vacuum interface is undertaken. An integrodifferential equation describing, on the basis of the semiclassical infinite-barrier model, the diamagnetic screening of the nonlinear dc magnetic field is set up and discussed

  14. Electronic transport of molecular nanowires by considering of electron hopping energy between the second neighbors

    Directory of Open Access Journals (Sweden)

    H Rabani

    2015-07-01

    Full Text Available In this paper, we study the electronic conductance of molecular nanowires by considering the electron hopping between the first and second neighbors with the help Green’s function method at the tight-binding approach. We investigate three types of structures including linear uniform and periodic chains as well as poly(p-phenylene molecule which are embedded between two semi-infinite metallic leads. The results show that in the second neighbor approximation, the resonance, anti-resonance and Fano phenomena occur in the conductance spectra of these structures. Moreover, a new gap is observed at edge of the lead energy band wich its width depends on the value of the electron hopping energy between the second neighbors. In the systems including intrinsic gap, this hopping energy shifts the gap in the energy spectra.

  15. Mapping molecular motions leading to charge delocalization with ultrabright electrons

    Science.gov (United States)

    Sciaini, German

    2014-05-01

    Ultrafast diffraction has broken the barrier to atomic exploration by combining the atomic spatial resolution of diffraction techniques with the temporal resolution of ultrafast spectroscopy. X-ray free electron lasers, slicing techniques and femtosecond laser-driven X-ray and electron sources have been successfully applied for the study of ultrafast structural dynamics in a variety of samples. Yet, the application of fs-diffraction to the study of rather sensitive organic molecular crystals remains unexplored. Organic crystals are composed by weak scattering centres, often present low melting points, poor heat conductivity and are, typically, radiation sensitive. Low repetition rates (about tens of Hertz) are therefore required to overcome accumulative heating effects from the laser excitation that can degrade the sample and mask the structural dynamics. This imparts tremendous constraints on source brightness to acquire enough diffraction data before adverse photo-degradation effects have played a non-negligible role in the crystalline structure. We implemented ultra-bright femtosecond electron diffraction to obtain a movie of the relevant molecular motions driving the photo-induced insulator-to-metal phase transition in the organic charge-transfer salt (EDO-TTF)2PF6. On the first few picoseconds (0 - 10 ps) the structural evolution, well-described by three main reaction coordinates, reaches a transient intermediate state (TIS). Model structural refinement calculations indicate that fast sliding of flat EDO-TTF molecules with consecutive motion of PF6 counter-ions drive the formation of TS instead of the expected flattening of initially bent EDO-TTF moieties which seems to evolve through a slower thermal pathway that brings the system into a final high temperature-type state. These findings establish the potential of ultrabright femtosecond electron sources for probing the primary processes governing structural dynamics with atomic resolution in labile systems relevant to chemistry and biology. For more information vide-infra Gao et al., Funding for this project was provided by the Natural Sciences and Engineering Research Council of Canada and the Canada Foundation for Innovation and Grant Agencies in Japan, vide infra Nature reference for more details.

  16. Spin Polarized Electron Transport in a Magnetically Coupled Molecular Wire

    Science.gov (United States)

    Senapati, L.

    2005-03-01

    Nanostructured materials present new opportunities for spintronics and for coherent applications such as quantum information processing. In order to make progress in these areas, new materials that are optimized for spin transfer are required. We will present theoretical studies of electronic structure and transport in magnetically coupled bridging molecules that reveal how coherent spin transport between nanostructures may be enhanced by suitable molecular design. We will present a study on a bridge consisting of two molecules coupled by a vanadium atom and sandwiched by two magnetic contacts (Ni) at both ends. Our first-principles density functional calculations suggest that by controlling the spin of the vanadium atom, one can control the spin polarized transport through the magnetically coupled molecules. The ground state of the magnetically coupled molecular bridge when sandwiched between similar magnetic cluster contacts at both ends (e.g. magnetic clusters such as Ni), prefers anti-parallel to parallel spin configurations. Control of the vanadium spin could be implemented by magnetic STM tips. The large difference in resistance between the two spin configuration states of such a system could be used to make GMR like devices.

  17. Molecularly imprinted polymers as recognition materials for electronic tongues.

    Science.gov (United States)

    Huynh, Tan-Phat; Kutner, Wlodzimierz

    2015-12-15

    For over three decades now, molecularly imprinted polymers (MIPs) have successfully been used for selective chemical sensing because the shape and size of their imprinted molecular cavities perfectly matched those of the target analyte molecules. Moreover, orientation of recognizing sites of these cavities corresponded to those of the binding sites of the template molecules. In contrast, electronic tongue (e-tongue) is usually an array of low-affinity recognition units. Its selectivity is based on recognition pattern or multivariate analysis. Merging these two sensing devices led to a synergetic hybrid sensor, an MIP based e-tongue. Fabrication of these e-tongues permitted simultaneous sensing and discriminating several analytes in complex solutions of many components so that these arrays compensated for limitation in cross-reactivity of MIPs. Apparently, analytical signals generated by MIP-based e-tongues, compared to those of ordinary sensor arrays, were more reliable where a unique pattern or 'fingerprint' for each analyte was generated. Additionally, several transduction platforms (from spectroscopic to electrochemical) engaged in constructing MIP-based e-tongues, found their broad and flexible applications. The present review critically evaluates achievements in recent developments of the MIP based e-tongues for chemosensing. PMID:26233642

  18. On electric-quadrupole and magnetic-dipole contributions to optical rectification in isotropic media near optical resonance

    OpenAIRE

    Zawodny, Roman

    2007-01-01

    Abstract A molecular theory of resonant optical rectification via the second-order electric-dipole polarizability related to magnetic-dipole and electric-quadrupole interaction of an electromagnetic radiation with atoms and molecules of an isotropic medium is presented. The magnetic-dipole and electric-quadrupole contributions to Dc electric-dipole polarization can be produced by arbitrarily polarized light which has to be at resonance with a molecule. Th...

  19. Elastic electron scattering cross sections for molecular hydrogen

    Science.gov (United States)

    Khakoo, M. A.; Trajmar, S.

    1986-01-01

    Using an electron-beam - molecular-beam apparatus and employing the relative flow technique, ratios of the differential elastic scattering cross sections (DCSs of H2 to He were measured at incident electron energies of 15-100 eV and over the angular range of 10-125 degrees. From these ratios, the absolute elastic DCSs for H2 were determined by normalization to accurate, available elastic DCSs of He. Since pure rotational structure was not resolved in this work, the DCSs reported are the sum of elastic and rotational excitations of H2 at room temperature. The reliability of the relative flow normalization to He was checked at each energy and angle by performing similar elastic DCS measurements on Ne (for which the cross sections are known). The resulting absolute Ne DCSs were found to be in good agreement (within 10 percent with the Ne elastic DCSs measured previously (Register and Trajmar, 1984). From the DCSs, integral and momentumtransfer cross sections were calculated. The present results are compared with other recent measurements.

  20. Determination of molecular parameters by electron collisions and laser techniques

    International Nuclear Information System (INIS)

    In this work a general procedure to study diatomic molecules in intermediate coupling scheme has been developed. This study allows to obtain expressions to calculate molecular line strengths and rotational transition intensities. These results are used in a numerical program to synthetize vibrational and rotational band spectra of any diatomic molecule. With this technique the experimental spectra of the first negative system of N2+ and the fist positive system of N2 are reproduced theoretically and it is possible to deduce its electronic transition moments values by comparison. Also the method has been applied to compare the synthetized bands with the experimental spectra of the B Ou+-- x1?g+ system of Au2 and the A2?--- x 2? system of OH. From these comparison band intensities and electronic moments can be deduced. The branching ratio method to measure the relative spectral response in the 1100-1560 Ao=wavelength range of a vacuum uv monochromator has been used. Relative intensity of rotational lines with origine in a common upper vibrational-rotational level of Warner and Lyman systems of H2, have been measured. Also in this work, the deexcitation of the B3?+(0+u), v'=14 level of I2 after pulsed laser excitation has been studied. The quenching cross sections by collisions with I2, H2, CO2 and CH4 have been determin-ed. (Author)

  1. Ionic fragmentation channels in electron collisions of small molecular ions

    International Nuclear Information System (INIS)

    Dissociative Recombination (DR) is one of the most important loss processes of molecular ions in the interstellar medium (IM). Ion storage rings allow to investigate these processes under realistic conditions. At the Heidelberg test storage ring TSR a new detector system was installed within the present work in order to study the DR sub-process of ion pair formation (IPF). The new detector expands the existing electron target setup by the possibility to measure strongly deflected negative ionic fragments. At the TSR such measurements can be performed with a uniquely high energy resolution by independently merging two electron beams with the ion beam. In this work IPF of HD+, H3+ and HF+ has been studied. In the case of HD+ the result of the high resolution experiment shows quantum interferences. Analysis of the quantum oscillations leads to a new understanding of the reaction dynamics. For H3+ it was for the first time possible to distinguish different IPF channels and to detect quantum interferences in the data. Finally the IPF of HF+ was investigated in an energy range, where in previous experiments no conclusive results could be obtained. (orig.)

  2. Ionic fragmentation channels in electron collisions of small molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Jens

    2009-01-28

    Dissociative Recombination (DR) is one of the most important loss processes of molecular ions in the interstellar medium (IM). Ion storage rings allow to investigate these processes under realistic conditions. At the Heidelberg test storage ring TSR a new detector system was installed within the present work in order to study the DR sub-process of ion pair formation (IPF). The new detector expands the existing electron target setup by the possibility to measure strongly deflected negative ionic fragments. At the TSR such measurements can be performed with a uniquely high energy resolution by independently merging two electron beams with the ion beam. In this work IPF of HD{sup +}, H{sub 3}{sup +} and HF{sup +} has been studied. In the case of HD{sup +} the result of the high resolution experiment shows quantum interferences. Analysis of the quantum oscillations leads to a new understanding of the reaction dynamics. For H{sub 3}{sup +} it was for the first time possible to distinguish different IPF channels and to detect quantum interferences in the data. Finally the IPF of HF{sup +} was investigated in an energy range, where in previous experiments no conclusive results could be obtained. (orig.)

  3. Molecular orbital calculations of two-electron states for P donor solid-state spin qubits

    OpenAIRE

    Kettle, L. M.; Goan, Hsi-Sheng; Smith, Sean C.

    2005-01-01

    We theoretically study the Hilbert space structure of two neighbouring P donor electrons in silicon-based quantum computer architectures. To use electron spins as qubits, a crucial condition is the isolation of the electron spins from their environment, including the electronic orbital degrees of freedom. We provide detailed electronic structure calculations of both the single donor electron wave function and the two-electron pair wave function. We adopted a molecular orbita...

  4. Research ZVS Synchronous Rectification of Resonant Converter

    Directory of Open Access Journals (Sweden)

    Xiao Kui Li

    2014-01-01

    Full Text Available In order to expand the application of synchronous rectification, the technology using ZVS synchronous rectifier is studied which is based on the IPT resonant converter. By using its own resonant characteristic, a novel control method that AC-DC section of the resonant converter works in ZVS SR state is proposed in this study. First of all, the ZVS working operation of SR is analyzed and equivalent circuits for each operation mode are also given. On that basis, the novel control method is proposed. Then, according to the differential equations of equivalent circuit, the state space model is established. In order to make full-bridge SR network of the secondary circuit work in ZVS state, the ZVS operating point can be obtained by solving the fixed point function which is based on the state space model and stroboscopic mapping method. Moreover, operating principle of control circuit for ZVS SR is also presented. Finally, experimental results verify the effectiveness of control method proposed in this study.

  5. Research ZCS Synchronous Rectification of Resonant Converter

    Directory of Open Access Journals (Sweden)

    Xiao Kui Li

    2014-01-01

    Full Text Available In this study, the application of ZCS synchronous rectification for the IPT resonant converter is researched. A novel control method that AC-DC section of the resonant converter works in ZCS SR state is proposed by using the characteristic of resonant tank current. First, the ZCS working operation of SR is presented, analyzed and equivalent circuits for each operation mode are also given, respectively. Then, the novel control method of ZCS SR for resonant converter is proposed. According to the ZCS working operation of SR and the differential equations of equivalent circuit, a steady-state mathematical model of the circuit is established. On that basis, the calculation method for ZCS operating point of SR is deduced by solving the fixed point function about resonant tank current. Moreover, the specific flow chart for calculating ZCS operating point of SR and the steady-state waveforms of each state variable is also presented and operating principle of control circuit for ZCS SR is described in detail. Finally, experimental results verify the effectiveness of control method proposed in this study.

  6. Detection and Rectification of Distorted Fingerprints.

    Science.gov (United States)

    Xuanbin Si; Jianjiang Feng; Jie Zhou; Yuxuan Luo

    2015-03-01

    Elastic distortion of fingerprints is one of the major causes for false non-match. While this problem affects all fingerprint recognition applications, it is especially dangerous in negative recognition applications, such as watchlist and deduplication applications. In such applications, malicious users may purposely distort their fingerprints to evade identification. In this paper, we proposed novel algorithms to detect and rectify skin distortion based on a single fingerprint image. Distortion detection is viewed as a two-class classification problem, for which the registered ridge orientation map and period map of a fingerprint are used as the feature vector and a SVM classifier is trained to perform the classification task. Distortion rectification (or equivalently distortion field estimation) is viewed as a regression problem, where the input is a distorted fingerprint and the output is the distortion field. To solve this problem, a database (called reference database) of various distorted reference fingerprints and corresponding distortion fields is built in the offline stage, and then in the online stage, the nearest neighbor of the input fingerprint is found in the reference database and the corresponding distortion field is used to transform the input fingerprint into a normal one. Promising results have been obtained on three databases containing many distorted fingerprints, namely FVC2004 DB1, Tsinghua Distorted Fingerprint database, and the NIST SD27 latent fingerprint database. PMID:26353261

  7. Probing flexible conformations in molecular junctions by inelastic electron tunneling spectroscopy

    International Nuclear Information System (INIS)

    The probe of flexible molecular conformation is crucial for the electric application of molecular systems. We have developed a theoretical procedure to analyze the couplings of molecular local vibrations with the electron transportation process, which enables us to evaluate the structural fingerprints of some vibrational modes in the inelastic electron tunneling spectroscopy (IETS). Based on a model molecule of Bis-(4-mercaptophenyl)-ether with a flexible center angle, we have revealed and validated a simple mathematical relationship between IETS signals and molecular angles. Our results might open a route to quantitatively measure key geometrical parameters of molecular junctions, which helps to achieve precise control of molecular devices

  8. Compressed look-up-table based real-time rectification hardware

    OpenAIRE

    Akin, Abdulkadir; Baz, Ipek; Gaemperle, Luis Manuel; Schmid, Alexandre; Leblebici, Yusuf

    2013-01-01

    Stereo image rectification is a pre-processing step of disparity estimation intended to remove image distortions and to enable stereo matching along an epipolar line. A real-time disparity estimation system needs to perform real-time rectification which requires solving the models of lens distortions, image translations and rotations. Look-up-table based rectification algorithms allow image rectification without demanding high complexity operations. However, they require an external memory to...

  9. Laser-induced currents along molecular wire junctions

    CERN Document Server

    Franco, Ignacio; Brumer, Paul

    2008-01-01

    The treatment of the previous paper is extended to molecular wires. Specifically, the effect of electron-vibrational interactions on the electronic transport induced by femtosecond $\\omega+2\\omega$ laser fields along unbiased molecular nanojunctions is investigated. For this, the photoinduced vibronic dynamics of trans-polyacetylene oligomers coupled to macroscopic metallic leads is followed in a mean-field mixed quantum-classical approximation. A reduced description of the dynamics is obtained by introducing projective lead-molecule couplings and deriving an effective Schr\\"odinger equation satisfied by the orbitals in the molecular region. Two possible rectification mechanisms are identified and investigated. The first one relies on near-resonance photon-absorption and is shown to be fragile to the ultrafast electronic decoherence processes introduced by the wire's vibrations. The second one employs the dynamic Stark effect and is demonstrated to be highly efficient and robust to electron-vibrational intera...

  10. Quantum mechanical simulations of polymers for molecular electronics and photonics

    International Nuclear Information System (INIS)

    Ab initio quantum mechanical studies can play an important role in obtaining a detailed understanding of the electronic structure of existing materials, and in predicting the properties of new ones. In this article the authors give a general outline of their research activity in two areas dealing with new materials, specifically, conducting polymers and polymers with non-linear optical properties. The authors present the strategy followed for the study of these molecular systems, and an overview of their findings concerning the structure of the prototypical conducting polymer, i.e. pure and doped polyacetylene (PA). They focused attention on vibrational spectra and infrared and Raman intensities. The results of self-consistent-field (SCF) calculations on charged soliton-like molecules are consistent with experimental observation. In particular, they show that the theoretically established accidental mutual exclusion of infrared and Raman bands invalidates the requirement formulated on the basis of the interpretation of experimental data, that defects in PA must have local C/sub 2h/ symmetry. These conclusions are derived from extensive calculations for which supercomputer performance was imperative and carried out on the parallel supercomputer assembled at IBM-Kingston as a loosely coupled array of processors (LCAP). The authors briefly describe this computer system which has proven to be ideally suited to the methods of ab initio quantum chemistry

  11. Rapid characterizing of ferromagnetic materials using spin rectification

    International Nuclear Information System (INIS)

    Spin rectification is a powerful tool for dc electric detections of spin dynamics and electromagnetic waves. Technically, elaborately designed on-chip microwave devices are needed in order to realize that effect. In this letter, we propose a rapid characterizing approach based on spin rectification. By directly sending dynamic current into ferromagnetic films with stripe shape, resonant dc voltages can be detected along the longitudinal or transversal directions. As an example, Fe (010) films with precise crystalline structure and magnetic parameters were used to testify the reliability of such method. We investigated not only the dynamic parameters and the precise anisotropy constants of the Fe crystals but also the principle of spin rectification in this method

  12. Rapid characterizing of ferromagnetic materials using spin rectification

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xiaolong, E-mail: fanxiaolong@lzu.edu.cn; Wang, Wei; Wang, Yutian; Zhou, Hengan; Rao, Jinwei; Zhao, Xiaobing; Gao, Cunxu; Xue, Desheng [The Key Lab for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Gui, Y. S.; Hu, C.-M. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

    2014-12-29

    Spin rectification is a powerful tool for dc electric detections of spin dynamics and electromagnetic waves. Technically, elaborately designed on-chip microwave devices are needed in order to realize that effect. In this letter, we propose a rapid characterizing approach based on spin rectification. By directly sending dynamic current into ferromagnetic films with stripe shape, resonant dc voltages can be detected along the longitudinal or transversal directions. As an example, Fe (010) films with precise crystalline structure and magnetic parameters were used to testify the reliability of such method. We investigated not only the dynamic parameters and the precise anisotropy constants of the Fe crystals but also the principle of spin rectification in this method.

  13. Graphene spin diode: Strain-modulated spin rectification

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yunhua; Wang, B., E-mail: stslyl@mail.sysu.edu.cn, E-mail: wangbiao@mail.sysu.edu.cn [Sino-French Institute of Nuclear Engineering and Technology, School of Physics and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China); Liu, Yulan, E-mail: stslyl@mail.sysu.edu.cn, E-mail: wangbiao@mail.sysu.edu.cn [School of Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

    2014-08-04

    Strain effects on spin transport in a ferromagnetic/strained/normal graphene junction are explored theoretically. It is shown that the spin-resolved Fermi energy range can be controlled by the armchair direction strain because the strain-induced pseudomagnetic field suppresses the current. The spin rectification effect for the bias reversal occurs because of a combination of ferromagnetic exchange splitting and the broken spatial symmetry of the junction. In addition, the spin rectification performance can be tuned remarkably by manipulation of the strains. In view of this strain-modulated spin rectification effect, we propose that the graphene-based ferromagnetic/strained/normal junction can be used as a tunable spin diode.

  14. Graphene spin diode: Strain-modulated spin rectification

    International Nuclear Information System (INIS)

    Strain effects on spin transport in a ferromagnetic/strained/normal graphene junction are explored theoretically. It is shown that the spin-resolved Fermi energy range can be controlled by the armchair direction strain because the strain-induced pseudomagnetic field suppresses the current. The spin rectification effect for the bias reversal occurs because of a combination of ferromagnetic exchange splitting and the broken spatial symmetry of the junction. In addition, the spin rectification performance can be tuned remarkably by manipulation of the strains. In view of this strain-modulated spin rectification effect, we propose that the graphene-based ferromagnetic/strained/normal junction can be used as a tunable spin diode

  15. Thermal rectification in non-linear structures with bulk losses

    Science.gov (United States)

    Schmidt, Martin; Kottos, Tsampikos

    2013-03-01

    A mechanism for thermal rectification based on the interplay between non-uniform bulk losses with nonlinearity is presented. We theoretically analyze the phenomenon using an anharmonic array of coupled oscillators coupled to the left and right with two Langevin reservoirs. A third probe thermostat (with temperature TB) is placed in an asymmetric position in the bulk of the lattice thus breaking the translational symmetry and leading to rectification of heat flow. We note that for TB = 0 this Langevin term is equivalent to a simple friction. We find that an increase of the friction strength can increase both the asymmetry and heat flux. Visiting Student from Germany

  16. Mechanism of Enhanced Rectification in Unimolecular Borromean Ring Devices

    CERN Document Server

    Scott, G D; Peters, A J; Cantrill, S J; Stoddart, J F; Jiang, H W

    2006-01-01

    We have studied charge transport through individual Borromean Ring complexes, both with and without anchor groups, in gated double barrier tunneling junctions (DBTJs) formed using the electrical breakjunction technique on gold nanowires. While common single molecule device characteristics can be observed with either form of the Borromean Rings, the complexes with anchor groups show strong rectification of conduction in a relatively high percentage of samples. We present our data along with a simple model underlining the mechanism by which the arrangement and composition of the weakly bonding anchor groups attached to the electroactive element may promote a device configuration resulting in rectification.

  17. Vortex-induced rectification in type II superconductors

    International Nuclear Information System (INIS)

    The authors report a large rectification effect in superconducting films in a parallel magnetic field. This rectification effect is manifested in two features in current-voltage characteristics: The critical current, Ic, is found to differ by as much as 40% for negative and positive currents, and beyond Ic, the magnitude of the voltage is different for positive and negative currents, |V(+I)|?|V(-I)|. Futhermore, the critical current difference |Ic+|-|Ic+| shows complicated behavior, changing sign as temperature and magnetic field are varied. The authors discuss a model based on the Bean-Livingston surface barrier and inhomogeneous bulk pinning that accounts for all observed behavior

  18. Spin current rectification from a spin-biased quantum dot

    OpenAIRE

    Ivanov, T. I.

    2012-01-01

    We compute the spin current rectification coefficient of a non-equilibrium quantum dot subject to a spin bias and an {\\it ac} charge bias with small amplitude. As a function of the position of the resonant level the spin current rectification coefficient shows a set of three peaks around the gate voltage at which the resonant or the upper level of the dot is in the vicinity of the equilibrium Fermi level in the leads. The peak heights can be related to the average number of the quantum dot el...

  19. Digital image transformation and rectification of spacecraft and radar images

    Science.gov (United States)

    Wu, S. S. C.

    1985-01-01

    The application of digital processing techniques to spacecraft television pictures and radar images is discussed. The use of digital rectification to produce contour maps from spacecraft pictures is described; images with azimuth and elevation angles are converted into point-perspective frame pictures. The digital correction of the slant angle of radar images to ground scale is examined. The development of orthophoto and stereoscopic shaded relief maps from digital terrain and digital image data is analyzed. Digital image transformations and rectifications are utilized on Viking Orbiter and Lander pictures of Mars.

  20. Recovery of enriched uranium hexafluoride on pilot rectification plant

    International Nuclear Information System (INIS)

    A description and schematic diagram of a rectification facility for separating uranium hexafluoride with different degrees of enrichment from process mixtures produced in separation operations at the Industrial Association Ehlektrokhimicheskij Zavod are presented. The results of operation of the facility over the period from the third quarter of 1971 to the third quarter of 1972 are reported. Different regimes for distilling mixtures, depending on the initial composition, are discussed. It is shown that there is promise in replacing hydrolysis of process mixtures of highly enriched uranium hexafluoride by rectification fractional distillation

  1. Rectification and flux reversals for vortices interacting with triangular traps

    International Nuclear Information System (INIS)

    We simulate vortices in superconductors interacting with two-dimensional arrays of triangular traps. We find that, upon application of an ac drive, a net dc flow can occur which shows current reversals with increasing ac drive amplitude for certain vortex densities, in agreement with recent experiments and theoretical predictions. We identify the vortex dynamics responsible for the different rectification regimes. We also predict the occurrence of a novel transverse rectification effect in which a dc flow appears that is transverse to the direction of the applied ac drive

  2. Theoretical study of molecular vibrations in electron momentum spectroscopy experiments on furan: An analytical versus a molecular dynamical approach

    International Nuclear Information System (INIS)

    The influence of thermally induced nuclear dynamics (molecular vibrations) in the initial electronic ground state on the valence orbital momentum profiles of furan has been theoretically investigated using two different approaches. The first of these approaches employs the principles of Born-Oppenheimer molecular dynamics, whereas the so-called harmonic analytical quantum mechanical approach resorts to an analytical decomposition of contributions arising from quantized harmonic vibrational eigenstates. In spite of their intrinsic differences, the two approaches enable consistent insights into the electron momentum distributions inferred from new measurements employing electron momentum spectroscopy and an electron impact energy of 1.2 keV. Both approaches point out in particular an appreciable influence of a few specific molecular vibrations of A1 symmetry on the 9a1 momentum profile, which can be unravelled from considerations on the symmetry characteristics of orbitals and their energy spacing

  3. Theoretical study of molecular vibrations in electron momentum spectroscopy experiments on furan: an analytical versus a molecular dynamical approach.

    Science.gov (United States)

    Morini, Filippo; Deleuze, Michael S; Watanabe, Noboru; Takahashi, Masahiko

    2015-03-01

    The influence of thermally induced nuclear dynamics (molecular vibrations) in the initial electronic ground state on the valence orbital momentum profiles of furan has been theoretically investigated using two different approaches. The first of these approaches employs the principles of Born-Oppenheimer molecular dynamics, whereas the so-called harmonic analytical quantum mechanical approach resorts to an analytical decomposition of contributions arising from quantized harmonic vibrational eigenstates. In spite of their intrinsic differences, the two approaches enable consistent insights into the electron momentum distributions inferred from new measurements employing electron momentum spectroscopy and an electron impact energy of 1.2 keV. Both approaches point out in particular an appreciable influence of a few specific molecular vibrations of A1 symmetry on the 9a1 momentum profile, which can be unravelled from considerations on the symmetry characteristics of orbitals and their energy spacing. PMID:25747082

  4. Dihydroazulene Photochromism:Synthesis, Molecular Electronics and Hammett Correlations

    DEFF Research Database (Denmark)

    Broman, SØren Lindbæk

    2013-01-01

    This thesis describes the development of a versatile synthetic protocol for preparation of a large selection of dihydroazulenes (DHAs) with both electron withdrawing and donating groups. By UV-Vis and NMR spectroscopies and even in a single-molecule junction, their ability to undergo a light-induced ring-opening reaction to vinylheptafulvenes (VHFs) and a thermally induced back-reaction (VHF ? DHA) were studied in detail. The first chapter briefly introduces photoswitches with focus, in particular, on the most well-known photoswitches. Then, the synthesis and properties of the DHA/VHF system will be discussed in detail. The second chapter describes the design and synthesis of DHA/VHFs intended for use in molecular electronics and their solution and single-molecule junction switching properties. By the expansion of the recently reported procedure for functionalization of this system by Suzuki cross-coupling reactions, systems with either one or two “molecular alligator clips” were prepared. These were studied in solution by UV-Vis absorption spectroscopy and in a single-molecule junction, the latter by the group of Danilov and Kubatkin at the Chalmers University of Technology. A single-molecule device was prepared in which reversible switching between states of conductance could be accomplished by either light/heat or light/bias. The third chapter describes the synthesis of a large number of donor and/or acceptor functionalized DHA/VHFs and the systematic dependence of the rate of the thermally induced back-reaction (VHF ? DHA), studied by UV-Vis absorption spectroscopy. In seven different model systems, the rate of back-reaction was found to obey a Hammett correlation when plotting ln(k) against the appropriate ?-values. These plots were used to estimate the ?-value of substituents which have not yet been determined such as heteroaromatics (furan, thiophene, and 1,2,3-triazole) and alkynes (triisopropylsilylethyne, trimethylsilyl- 1,3-butadiyne, and 1,3-butadiyne). It was also shown that the absorption maximum of the VHF and the rate of back-reaction can be conveniently fine-tuned by these donor or acceptor groups. The fourth chapter describes the synthesis and study of a VHF containing two sites for ring-closure in an attempt to overcome the problem of the VHF taking an unreactive conformation which was speculated to cause the relatively slow back-reaction (VHF ? DHA). The study showed that the rate of back-reaction was increased with close to a factor of 2 which is only the statistical improvement of having two possible sites for back-reaction as supposed to just one. The fifth chapter describes, in short, my contributions to an additional seven papers published. Figure 1. Structure of proposed transition state (TS) for the thermally induced ring-closure (VHF ? DHA). This strongly polarized TS is responsible for substituent-dependency of this reaction (left). Reversible switching between the states of the DHA/VHF trapped in a silver nano-gap (right).

  5. Electronic properties of single-molecule junction: Effect of the molecular distortion

    International Nuclear Information System (INIS)

    For a model system consisting of a benzenedithio (BDT) molecule sandwiched between two Au plates, the electronic properties as a function of different BDT geometry are investigated using density functional theory. The distorted BDT structures are got through stretching the electrode distance. The corresponding electronic properties, including the spatial distribution of the frontier orbits, the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital levels and density of states at the Fermi energy are determined. It reveals that the molecular distortion essentially determines electronic structures. The result should be beneficial to understand the stress-dependent or structure-dependent transport mechanism of electrons of the BDT junction.

  6. First-Principles Based Matrix-Green's Function Approach to Molecular Electronic Devices General Formalism

    CERN Document Server

    Xue, Y; Ratner, M A; Xue, Yongqiang; Datta, Supriyo; Ratner, Mark A.

    2001-01-01

    Transport in molecular electronic devices is different from that in semiconductor mesoscopic devices in two important aspects: (1) the effect of the electronic structure and (2) the effect of the interface to the external contact. A rigorous treatment of molecular electronic devices will require the inclusion of these effects in the context of an open system exchanging particle and energy with the external environment. This calls for combining the theory of quantum transport with the theory of electronic structure starting from the first-principles. We present a rigorous yet tractable matrix Green's function approach for studying transport in molecular electronic devices, based on the Non-Equilibrium Green's Function Formalism of quantum transport and the density-functional theory of electronic structure using local orbital basis sets. By separating the device rigorously into the molecular region and the contact region, we can take full advantage of the natural spatial locality associated with the metallic sc...

  7. Electron spin resonance study on lignin molecular mobility

    International Nuclear Information System (INIS)

    Molecular mobility of grinded wood lignin is studied in the wide temperature range using the recombination-kinetic method. Macroradicals formed during low-temperature ?-radiolysis of lignin, are used as a molecular probe. Analysis of curves of stage-by-stage heating of specimens confirms microheterogeneity of lignin

  8. A scheme for automatic text rectification in real scene images

    Science.gov (United States)

    Wang, Baokang; Liu, Changsong; Ding, Xiaoqing

    2015-03-01

    Digital camera is gradually replacing traditional flat-bed scanner as the main access to obtain text information for its usability, cheapness and high-resolution, there has been a large amount of research done on camera-based text understanding. Unfortunately, arbitrary position of camera lens related to text area can frequently cause perspective distortion which most OCR systems at present cannot manage, thus creating demand for automatic text rectification. Current rectification-related research mainly focused on document images, distortion of natural scene text is seldom considered. In this paper, a scheme for automatic text rectification in natural scene images is proposed. It relies on geometric information extracted from characters themselves as well as their surroundings. For the first step, linear segments are extracted from interested region, and a J-Linkage based clustering is performed followed by some customized refinement to estimate primary vanishing point(VP)s. To achieve a more comprehensive VP estimation, second stage would be performed by inspecting the internal structure of characters which involves analysis on pixels and connected components of text lines. Finally VPs are verified and used to implement perspective rectification. Experiments demonstrate increase of recognition rate and improvement compared with some related algorithms.

  9. Symmetry and environment effects on rectification mechanisms in quantum pumps

    OpenAIRE

    Arrachea, Liliana

    2005-01-01

    We consider a paradigmatic model of quantum pumps and discuss its rectification properties in the framework of a symmetry analysis proposed for ratchet systems. We discuss the role of the environment in breaking time-reversal symmetry and the possibility of a finite directed current in the Hamiltonian limit of annular systems.

  10. Terahertz pulse generation via optical rectification in photonic crystal microcavities

    OpenAIRE

    Di Falco, Andrea; Conti, Claudio; Assanto, Gaetano

    2005-01-01

    Using a 3D fully-vectorial nonlinear time-domain analysis we numerically investigate the generation of terahertz radiation by pumping a photonic crystal microcavity out of resonance. High quality factors and a quadratic susceptibility lead to few-cycle terahertz pulses via optical rectification. Material dispersion as well as linear and nonlinear anisotropy is fully accounted for.

  11. Purification of vanadium tetrachloride by the method of rectification

    International Nuclear Information System (INIS)

    Study of liquid-vapor equilibrium in dilute solutions of vanadium oxytrichloride in vanadium tetrachloride showed that the system exhibits positive deviations from Raoult's law. The separation factor is 2.7+-0.08 at 400. The separation coefficients, calculated by the statistical method, for solutions of microimpurities (the chlorides of boron, tin, germanium, carbon, titanium, silicon, and arsenic, and vanadium oxytrichloride) in vanadium tetrachloride at 400 are 81.6, 4.4, 16.1, 14.9, 1.86, 31.4, 1.48, and 2.70. Chlorine can be removed effectively fron vanadium tetrachloride by rectification. If the rectification is conducted at 400, the chlorine concentration can be lowered to 1.6.10-7 mole%. Rectification gave vanadium tetrachloride with the following impurity content, silicon, titanium, and aluminium less than or equal to 5.10-4 wt.%, copper, zinc, boron, and magnesium xx wt.%, and antimony, arsenic, and cadmium less than 5.10-6 wt.%. The contents of carbon chloride, vanadium, oxytrichloride, and chlorine can be lowered by rectification to 5.10-7, and 1.6.10-7 mole%, respectively

  12. Geometric rectification of radar imagery using digital elevation models

    Science.gov (United States)

    Naraghi, M.; Stromberg, W.; Daily, M.

    1983-01-01

    Geologic analysis of radar imagery requires accurate spatial rectification to allow rock type discrimination and meaningful exploitation of multisensor data files. A procedure is described which removes distortions produced by most sources including the heretofore elusive problem of terrain induced effects. Rectified imagery is presented which displays geologic features not apparent in the distorted data.

  13. RECTIFICATION OF BORIC ACID IN NUCLEAR TOWER PLANTS

    Directory of Open Access Journals (Sweden)

    Kazimierz Brodowicz

    1979-01-01

    Full Text Available The paper presents some experimental results of rectification of aqueous solution of boric acid, in the range of parameters used in nuclear power planta, She values of plate efficiency has been obtained experimentally. The concentration distribution has been calculates in case of 3 plate column. Some data concerning the thermodynamic equilibrium of the system have been added.

  14. Proceedings of the NASA Workshop on Registration and Rectification

    Science.gov (United States)

    Bryant, N. A. (editor)

    1982-01-01

    Issues associated with the registration and rectification of remotely sensed data. Near and long range applications research tasks and some medium range technology augmentation research areas are recommended. Image sharpness, feature extraction, inter-image mapping, error analysis, and verification methods are addressed.

  15. Ion Current Rectification Behavior at Novel Borosilicate Glass Capillaries.

    Czech Academy of Sciences Publication Activity Database

    Silver, Barry Richard; Holub, Karel; Mare?ek, Vladimír

    Ústí nad Labem : BEST servis, 2012 - (Navrátil, T.; Fojta, M.), s. 120-124 ISBN 978-80-905221-0-7. [Moderní elektrochemické metody /32./. Jet?ichovice (CZ), 21.05.2012-25.05.2012] Institutional support: RVO:61388955 Keywords : ion * rectification * impedance Subject RIV: CG - Electrochemistry

  16. Electron transport coefficients in low current molecular gas discharges

    International Nuclear Information System (INIS)

    The electron transport parameters for both SF6 and O2 have been experimentally determined using the voltage transient method. The electron convective drift velocity (centre-of-mass velocity) We, the longitudinal diffusion coefficient NDL, and the effective ionization coefficient ?'/N were determined for electron swarm energies in SF6 and O2. For SF6, the electron transport parameters were determined within the range 360 Td2, the electron transport parameters were determined within the range 20 Td< E/N<270 Td and at a gas pressure range of 2< p<50 Torr. Here, E is the applied electric field and N is the gas number density

  17. Development of an electron-temperature-dependent interatomic potential for molecular dynamics simulation of tungsten under electronic excitation

    International Nuclear Information System (INIS)

    Irradiation of a metal by lasers or swift heavy ions causes the electrons to become excited. In the vicinity of the excitation, an electronic temperature is established within a thermalization time of 10-100 fs, as a result of electron-electron collisions. For short times, corresponding to less than 1 ps after excitation, the resulting electronic temperature may be orders of magnitude higher than the lattice temperature. During this short time, atoms in the metal experience modified interatomic forces as a result of the excited electrons. These forces can lead to ultrafast nonthermal phenomena such as melting, ablation, laser-induced phase transitions, and modified vibrational properties. We develop an electron-temperature-dependent empirical interatomic potential for tungsten that can be used to model such phenomena using classical molecular dynamics simulations. Finite-temperature density functional theory calculations at high electronic temperatures are used to parametrize the model potential

  18. Molecular rectifying diodes from self-assembly on silicon

    CERN Document Server

    Lenfant, S; Delerue, C; Allan, G

    2003-01-01

    We demonstrate a molecular rectifying junction made from a sequential self-assembly on silicon. The device structure consists of only one conjugated (p) group and an alkyl spacer chain. We obtain rectification ratios up to 37 and threshold voltages for rectification between -0.3V and -0.9V. We show that rectification occurs from resonance through the highest occupied molecular orbital of the p-group in good agreement with our calculations and internal photoemission spectroscopy. This approach allows us to fabricate molecular rectifying diodes compatible with silicon nanotechnologies for future hybrid circuitries.

  19. Rectification And Revival Of Muslim World

    Directory of Open Access Journals (Sweden)

    M azram

    2012-01-01

    Full Text Available The present doldrums position and state of decadence, internal differences, external aggression (geographical and ideological, lack of self-confidence and dependence, illiteracy, political instability, economic disaster, lack of knowledge and wisdom, back benchers in science and technology, education, medicine, trade and business, banking system and defensive incapability of Muslim Ummah prompted me to write this article.  Although most of the Muslim nations got their independence because of their dedicated struggle and historic events and incidents but the old masters remained active for a remote control over the Muslim Ummah.  Their intellectuals and scholars, individually as well as collectively, have propagated and advised their leadership, the tactics and approaches by which Muslim Ummah can again be enslaved.  Writings of S.P. Huntington and F. Fukuyama are clear examples.  They are actively gearing the international institutions so cleverly that Muslim Ummah does not even realize their ill motives and objectives.  They brought their leadership in a confronting position with Muslim Ummah and hence threatening the world peace.  This situation prompted us to look at our principal sources of inspiration, which are, the Qur’an, Sunnah of the Prophet (SAW, and examples of the “enlightened Caliphs” and see if we could work out a seminal guidelines for our rectification  and revival.  We have gathered together some of these impressions; these are all tentative, nothing final about them, but these are here nonetheless. ABSTRAK: Kehadiran situasi kebelungguan dan  keruntuhan, perbezaan dalaman, pencerobohan luar (geografi dan ideologi, kurang keyakinan diri dan pergantungan, buta huruf, ketidakstabilan politik, bencana ekonomi, kekurangan ilmu dan hikmah, ketinggalan dalam sains dan teknologi, pendidikan, perubatan, perdagangan dan perniagaan, sistem perbankan dan ketidakupayaan pertahanan umat Islam mendorong saya untuk menulis artikel ini. Walaupun kebanyakan negara-negara Islam mendapat kemerdekaan mereka kerana perjuangan mereka yang berdedikasi dan peristiwa dan kejadian yang bersejarah tetapi sejarah orang lama yang kekal aktif untuk mengawal kedudukan umat Islam. Keintelektuallan mereka, secara individu dan secara berkumpulan, telah dikembangkan melalui nasihat kepimpinan mereka, taktik dan pendekatan yang Muslim Ummah sekali lagi boleh diperhambakan. Karya SP Huntington dan F. Fukuyama adalah contoh yang jelas. Mereka secara aktif menggerakkan institusi antarabangsa sehingga umat Islam tidak menyedari motif tersirat dan objektif mereka. Mereka telah membawa kepimpinan mereka dalam kedudukan yang dihadapi dengan umat Islam dan dengan itu mengancam keamanan dunia. Keadaan ini mendorong kita untuk melihat sumber-sumber inspirasi utama, iaitu al-Quran, Sunnah Nabi (SAW, dan contoh-contoh "Khalifah pencerahan" dan lihat jika kita boleh merumuskan satu garis panduan pembetulan dan pemulihan. Kami telah berkumpul bersama untuk mengawal perasaan, ini semua tentatif, walau bagaimanapun tiada apa-apa jua yang muktamad tentang mereka.KEYWORDS: SWT (subhana wa taala; pbuh (peace and blessings be upon him; ra (radiallahu anha/u

  20. Computer simulation of electron induced molecular radiation damage

    International Nuclear Information System (INIS)

    The decay of DNA-bound Auger electron emitters causes strongly localized high-LET effects in the immediate surrounding of the radionuclide. For 125I, the most prominent Auger emitter in radiation biology, electron spectra of individual decays are generated by Monte Carlo simulation. The interaction of these electrons with the DNA as well as with the nearest surrounding is simulated. The use of simple assumptions allows the modelling of radiation damages like single and double strand breaks. In this paper, some selected results of these simulations are presented; in particular, the high-LET character of the Auger electrons is emphasized. (orig.)

  1. Poly(3-hexylthiophene)/multiwalled carbon hybrid coaxial nanotubes: nanoscale rectification and photovoltaic characteristics.

    Science.gov (United States)

    Kim, Kihyun; Shin, Ji Won; Lee, Yong Baek; Cho, Mi Yeon; Lee, Suk Ho; Park, Dong Hyuk; Jang, Dong Kyu; Lee, Cheol Jin; Joo, Jinsoo

    2010-07-27

    We fabricate hybrid coaxial nanotubes (NTs) of multiwalled carbon nanotubes (MWCNTs) coated with light-emitting poly(3-hexylthiophene) (P3HT). The p-type P3HT material with a thickness of approximately 20 nm is electrochemically deposited onto the surface of the MWCNT. The formation of hybrid coaxial NTs of the P3HT/MWCNT is confirmed by a transmission electron microscope, FT-IR, and Raman spectra. The optical and structural properties of the hybrid NTs are characterized using ultraviolet and visible absorption, Raman, and photoluminescence (PL) spectra where, it is shown that the PL intensity of the P3HT materials decreases after the hybridization with the MWCNTs. The current-voltage (I-V) characteristics of the outer P3HT single NT show the semiconducting behavior, while ohmic behavior is observed for the inner single MWCNT. The I-V characteristics of the hybrid junction between the outer P3HT NT and the inner MWCNT, for the hybrid single NT, exhibit the characteristics of a diode (i.e., rectification), whose efficiency is clearly enhanced with light irradiation. The rectification effect of the hybrid single NT has been analyzed in terms of charge tunneling models. The quasi-photovoltaic effect is also observed at low bias for the P3HT/MWCNT hybrid single NT. PMID:20533839

  2. Interference-induced thermoelectric switching and heat rectification in quantum Hall junctions

    Science.gov (United States)

    Vannucci, Luca; Ronetti, Flavio; Dolcetto, Giacomo; Carrega, Matteo; Sassetti, Maura

    2015-08-01

    Interference represents one of the most striking manifestations of quantum physics in low-dimensional systems. Despite evidence of quantum interference in charge transport having been known for a long time, signatures of interference-induced thermal properties have been reported only recently, paving the way for the phase-coherent manipulation of heat in mesoscopic devices. In this work we show that anomalous thermoelectric properties and efficient heat rectification can be achieved by exploiting the phase-coherent edge states of quantum Hall systems. By considering a tunneling geometry with multiple quantum point contacts, we demonstrate that the interference paths effectively break the electron-hole symmetry, allowing for a thermoelectric charge current flowing either from hot to cold or vice versa, depending on the details of the tunnel junction. Correspondingly, an interference-induced heat current is predicted, and we are able to explain these results in terms of an intuitive physical picture. Moreover, we show that heat rectification can be achieved by coupling two quantum Hall systems with different filling factors, and that this effect can be enhanced by exploiting the interference properties of the tunnel junction.

  3. Molecular orbital calculations of two-electron states for P donor solid-state spin qubits

    CERN Document Server

    Kettle, L M; Smith, S C; Goan, Hsi-Sheng; Smith, Sean C.

    2005-01-01

    We theoretically study the Hilbert space structure of two neighbouring P donor electrons in silicon-based quantum computer architectures. To use electron spins as qubits, a crucial condition is the isolation of the electron spins from their environment, including the electronic orbital degrees of freedom. We provide detailed electronic structure calculations of both the single donor electron wave function and the two-electron pair wave function. We adopted a molecular orbital method for the two-electron problem, forming a basis with the calculated single donor electron orbitals. Our two-electron basis contains many singlet and triplet orbital excited states, in addition to the two simple ground state singlet and triplet orbitals usually used in the Heitler-London approximation to describe the two-electron donor pair wave function. We determined the excitation spectrum of the two-donor system, and study its dependence on strain, lattice position and inter donor separation. This allows us to determine how isola...

  4. Distinctive character of electronic and vibrational coherences in disordered molecular aggregates

    OpenAIRE

    Butkus, Vytautas; Zigmantas, Donatas; Abramavicius, Darius; Valkunas, Leonas

    2013-01-01

    Coherent dynamics of coupled molecules are effectively characterized by the two-dimensional (2D) electronic coherent spectroscopy. Depending on the coupling between electronic and vibrational states, oscillating signals of purely electronic, purely vibrational or mixed origin can be observed. Even in the "mixed" molecular systems two types of coherent beats having either electronic or vibrational character can be distinguished by analyzing oscillation Fourier maps, construct...

  5. Intense laser effects on nonlinear optical absorption and optical rectification in single quantum wells under applied electric and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Duque, C.A., E-mail: cduque_echeverri@yahoo.es [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia); Kasapoglu, E. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Sakiroglu, S. [Dokuz Eyluel University, Physics Department, 35160 Buca, Izmir (Turkey); Sari, H. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Soekmen, I. [Dokuz Eyluel University, Physics Department, 35160 Buca, Izmir (Turkey)

    2011-01-01

    In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work.

  6. Intense laser effects on nonlinear optical absorption and optical rectification in single quantum wells under applied electric and magnetic field

    International Nuclear Information System (INIS)

    In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga1-xAlxAs quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work.

  7. Electron loss from multiply protonated lysozyme ions in high energy collisions with molecular oxygen

    DEFF Research Database (Denmark)

    Hvelplund, P; Nielsen, SB; Sørensen, M; Andersen, JU; Jørgensen, Thomas J. D.

    2001-01-01

    We report on the electron loss from multiply protonated lysozyme ions Lys-Hn(n)+ (n = 7 - 17) and the concomitant formation of Lys-Hn(n+1)+. in high-energy collisions with molecular oxygen (laboratory kinetic energy = 50 x n keV). The cross section for electron loss increases with the charge state...... of the precursor from n = 7 to n = 11 and then remains constant when n increases further. The absolute size of the cross section ranges from 100 to 200 A2. The electron loss is modeled as an electron transfer process between lysozyme cations and molecular oxygen....

  8. Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions

    Science.gov (United States)

    2016-01-01

    Summary Molecular junctions consisting of 2–20 nm thick layers of organic oligomers oriented between a conducting carbon substrate and a carbon/gold top contact have proven to be reproducible and reliable, and will soon enter commercial production in audio processing circuits. The covalent, conjugated bond between one or both sp2-hybridized carbon contacts and an aromatic molecular layer is distinct from the more common metal/molecule or silicon/molecule structures in many reported molecular junctions. Theoretical observations based on density functional theory are presented here, which model carbon-based molecular junctions as single molecules and oligomers between fragments of graphene. Electronic coupling between the molecules and the contacts is demonstrated by the formation of hybrid orbitals in the model structure, which have significant electron density on both the graphene and the molecule. The energies of such hybrid orbitals correlate with tunneling barriers determined experimentally, and electronic coupling between the two graphene fragments in the model correlates with experimentally observed attenuation of transport with molecular layer thickness. Electronic coupling is affected significantly by the dihedral angle between the planes of the graphene and the molecular π-systems, but is absent only when the two planes are orthogonal. Coupling also results in partial charge transfer between the graphene contacts and the molecular layer, which results in a shift in electrostatic potential which affects the observed tunneling barrier. Although the degree of partial charge transfer is difficult to calculate accurately, it does provide a basis for the “vacuum level shift” observed in many experiments, including transport and ultraviolet photoelectron spectroscopy of molecular layers on conductors. PMID:26925350

  9. An Electronically Non-Adiabatic Generalization of Ring Polymer Molecular Dynamics

    CERN Document Server

    Hele, Timothy J H

    2013-01-01

    In this thesis I generalize Ring Polymer Molecular Dynamics (RPMD) rate theory to electronically non-adiabatic systems, followed by application to two one-dimensional curve crossing models and a multidimensional spin-boson model.

  10. Manipulation of large molecules by low-temperature STM: model systems for molecular electronics

    International Nuclear Information System (INIS)

    The ability of the low-temperature scanning tunneling microscope to manipulate atoms and to build nanostructures with atomic precision can be extended to the manipulation of larger molecules and to selectively modify their internal degrees of freedom. Manipulation experiments on individual molecules show an exciting diversity of physical, chemical, and electronic phenomena. They permit a deeper insight into the quantum electronics of molecular systems and provide important information on the conformational and mechanical properties of single complex molecules. In this article, recent experiments on specially designed molecules will be reviewed, which investigate model systems interesting for the developing of molecular electronics. Starting from the realization of the principle of a molecular switch, going through the possibility of recording the small intramolecular changes inside a complex molecule during its movement, toward the study of the electronic contact between a single molecular wire and a metallic nanoelectrode

  11. Optically induced transport through semiconductor-based molecular electronics

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guangqi; Seideman, Tamar, E-mail: t-seideman@northwestern.edu [Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States); Fainberg, Boris D., E-mail: fainberg@hit.ac.il [Faculty of Science, Holon Institute of Technology, 58102 Holon (Israel); School of Chemistry, Tel-Aviv University, 69978 Tel-Aviv (Israel)

    2015-04-21

    A tight binding model is used to investigate photoinduced tunneling current through a molecular bridge coupled to two semiconductor electrodes. A quantum master equation is developed within a non-Markovian theory based on second-order perturbation theory with respect to the molecule-semiconductor electrode coupling. The spectral functions are generated using a one dimensional alternating bond model, and the coupling between the molecule and the electrodes is expressed through a corresponding correlation function. Since the molecular bridge orbitals are inside the bandgap between the conduction and valence bands, charge carrier tunneling is inhibited in the dark. Subject to the dipole interaction with the laser field, virtual molecular states are generated via the absorption and emission of photons, and new tunneling channels open. Interesting phenomena arising from memory are noted. Such a phenomenon could serve as a switch.

  12. Optically induced transport through semiconductor-based molecular electronics

    International Nuclear Information System (INIS)

    A tight binding model is used to investigate photoinduced tunneling current through a molecular bridge coupled to two semiconductor electrodes. A quantum master equation is developed within a non-Markovian theory based on second-order perturbation theory with respect to the molecule-semiconductor electrode coupling. The spectral functions are generated using a one dimensional alternating bond model, and the coupling between the molecule and the electrodes is expressed through a corresponding correlation function. Since the molecular bridge orbitals are inside the bandgap between the conduction and valence bands, charge carrier tunneling is inhibited in the dark. Subject to the dipole interaction with the laser field, virtual molecular states are generated via the absorption and emission of photons, and new tunneling channels open. Interesting phenomena arising from memory are noted. Such a phenomenon could serve as a switch

  13. Optically induced transport through semiconductor-based molecular electronics

    Science.gov (United States)

    Li, Guangqi; Fainberg, Boris D.; Seideman, Tamar

    2015-04-01

    A tight binding model is used to investigate photoinduced tunneling current through a molecular bridge coupled to two semiconductor electrodes. A quantum master equation is developed within a non-Markovian theory based on second-order perturbation theory with respect to the molecule-semiconductor electrode coupling. The spectral functions are generated using a one dimensional alternating bond model, and the coupling between the molecule and the electrodes is expressed through a corresponding correlation function. Since the molecular bridge orbitals are inside the bandgap between the conduction and valence bands, charge carrier tunneling is inhibited in the dark. Subject to the dipole interaction with the laser field, virtual molecular states are generated via the absorption and emission of photons, and new tunneling channels open. Interesting phenomena arising from memory are noted. Such a phenomenon could serve as a switch.

  14. Coordination compounds for molecular electronics: Synthesis, characterization and electronic transport properties of copper rotaxanes and molecular complexes

    OpenAIRE

    Ponce González, Julia

    2014-01-01

    Esta tesis se centra en el estudio de compuestos de coordinación de interés en el campo de la electrónica molecular. Este campo tiene como objetivo la utilización de unidades moleculares como componentes activos en circuitos electrónicos. Los dispositivos unimoleculares presentan cualidades únicas, inherentes a la nanoescala, que no poseen equivalencia en los componentes convencionales, actualmente basados en el silicio. Además, la síntesis de moléculas dispone de un altísimo grado de control...

  15. The Polarisation of radiation emitted from molecular states excited by polarised electrons and polarised synchrotron radiation

    International Nuclear Information System (INIS)

    Full text: Recent experiments have investigated the transfer of spin angular momentum into molecular systems, using spin-polarised electrons and observing the circular polarisation of the emitted radiation. The results have been interesting since circular polarization has been observed in fluorescence from molecular hydrogen and from atomic fragments created in the photo-dissociation of molecular hydrogen but not in the fluorescence from molecular nitrogen. This paper discusses the way in which angular momentum is shared in molecular systems and compares the results obtained in electron scattering experiments with measurements of the circular polarization obtained from various molecular states in H2 and N2 excited with circularly-polarised synchrotron radiation. Copyright (2005) Australian Institute of Physics

  16. Efficient electronic structure calculation for molecular ionization dynamics at high x-ray intensity

    OpenAIRE

    Hao, Yajiang; Inhester, Ludger; Hanasaki, Kota; Son, Sang-Kil; Santra, Robin

    2015-01-01

    We present the implementation of an electronic-structure approach dedicated to ionization dynamics of molecules interacting with x-ray free-electron laser (XFEL) pulses. In our scheme, molecular orbitals for molecular core-hole states are represented by linear combination of numerical atomic orbitals that are solutions of corresponding atomic core-hole states. We demonstrate that our scheme efficiently calculates all possible multiple-hole configurations of molecules formed ...

  17. Renormalization of Molecular Electronic Levels at Metal-Molecule Interfaces

    CERN Document Server

    Neaton, J B; Louie, S G; Hybertsen, Mark S.; Louie, Steven G.

    2006-01-01

    The electronic structure of benzene on graphite (0001) is computed using the GW approximation for the electron self-energy. The benzene quasiparticle energy gap is predicted to be 7.2 eV on graphite, substantially reduced from its calculated gas-phase value of 10.5 eV. This decrease is caused by a change in electronic correlation energy, an effect completely absent from the corresponding Kohn-Sham gap. For weakly-coupled molecules, this correlation energy change is seen to be well described by a surface polarization effect. A classical image potential model illustrates trends for other conjugated molecules on graphite.

  18. Semiclassical initial value representation for electronically nonadiabatic molecular dynamics

    International Nuclear Information System (INIS)

    The semiclassical initial value representation (SC-IVR), which has recently seen a great deal of interest for treating nuclear dynamics on a single potential energy surface, is generalized to be able to describe electronically nonadiabatic (i.e., multisurface) processes. The essential idea is a quantization of the classical electron-nuclear Hamiltonian of Meyer and Miller [J. Chem. Phys. 70, 3214 (1979)] within the SC-IVR methodology. Application of the approach to a series of test problems suggested by Tully shows it to provide a good description of electronically nonadiabatic dynamics for a variety of situations. copyright 1997 American Institute of Physics

  19. Computational Nanotechnology of Molecular Materials, Electronics, and Actuators with Carbon Nanotubes and Fullerenes

    Science.gov (United States)

    Srivastava, Deepak; Menon, Madhu; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

    2001-01-01

    The role of computational nanotechnology in developing next generation of multifunctional materials, molecular scale electronic and computing devices, sensors, actuators, and machines is described through a brief review of enabling computational techniques and few recent examples derived from computer simulations of carbon nanotube based molecular nanotechnology.

  20. Proceedings of the 2. Latin American Meeting on Atomic, Molecular and Electronic Collisions

    International Nuclear Information System (INIS)

    Annals of the II Latin American Meeting on Atomic, Molecular and Electronic Collisions. Over than 50 people from Latin America participated on this meeting giving talks on different subjects (theoretical and experimental), related to atomic and molecular physics, as well as, nuclear physics. (A.C.A.S.)

  1. Molecular double core-hole electron spectroscopy for chemical analysis

    CERN Document Server

    Tashiro, Motomichi; Fukuzawa, Hironobu; Ueda, Kiyoshi; Buth, Christian; Kryzhevoi, Nikolai V; Cederbaum, Lorenz S

    2010-01-01

    We explore the potential of double core hole electron spectroscopy for chemical analysis in terms of x-ray two-photon photoelectron spectroscopy (XTPPS). The creation of deep single and double core vacancies induces significant reorganization of valence electrons. The corresponding relaxation energies and the interatomic relaxation energies are evaluated by CASSCF calculations. We propose a method how to experimentally extract these quantities by the measurement of single and double core-hole ionization potentials (IPs and DIPs). The influence of the chemical environment on these DIPs is also discussed for states with two holes at the same atomic site and states with two holes at two different atomic sites. Electron density difference between the ground and double core-hole states clearly shows the relaxations accompanying the double core-hole ionization. The effect is also compared with the sensitivity of single core hole ionization potentials (IPs) arising in single core hole electron spectroscopy. We have ...

  2. Secondary-emission electron gun for high pressure molecular lasers

    International Nuclear Information System (INIS)

    A new type of high voltage, large area electron gun is described. Ions are generated in a low pressure ion source, extracted by a grid, and accelerated by a -130-kV continuously biased electrode. By secondary emission, these ions produce electrons which are accelerated toward the grid. They go through the ion source and an electron window (15x5 cm). Electron-beam density profiles display a good uniformity. The current density, limited only by the available power for the discharge, reaches presently 1 mA/cm2. The advantages of this gun over others are moderate vacuum requirements and capability for both low current cw and high current pulsed beams with easy control at ground potential and small energy requirement

  3. A parity function for studying the molecular electronic structure

    DEFF Research Database (Denmark)

    Schmider, Hartmut

    1996-01-01

    Sections through the molecular Wigner function with zero momentum variable are shown to provide important information about the off-diagonal regions of the spinless one-particle reduced density matrix. Since these regions are characteristic for the bonding situation in molecules, the sections are...

  4. Molecular fingerprints in the electronic properties of crystalline organic semiconductors

    DEFF Research Database (Denmark)

    Ciuchi, S.; Hatch, R.C.; Höchst, H.; Faber, C.; Blase, X.; Fratini, S.

    2012-01-01

    bands can be achieved in organic semiconductors provided that one properly accounts for the coupling to molecular vibrational modes and the presence of disorder. Our findings rationalize the growing experimental evidence that even the best band structure theories based on a many-body treatment of...

  5. Molecular double core-hole electron spectroscopy for chemical analysis

    OpenAIRE

    Tashiro, Motomichi; Ehara, Masahiro; Fukuzawa, Hironobu; Ueda, Kiyoshi; Buth, Christian; Kryzhevoi, Nikolai V.; Lorenz S. Cederbaum

    2010-01-01

    We explore the potential of double core hole electron spectroscopy for chemical analysis in terms of x-ray two-photon photoelectron spectroscopy (XTPPS). The creation of deep single and double core vacancies induces significant reorganization of valence electrons. The corresponding relaxation energies and the interatomic relaxation energies are evaluated by CASSCF calculations. We propose a method how to experimentally extract these quantities by the measurement of single an...

  6. Recent advances in molecular electronics based on carbon nanotubes.

    Science.gov (United States)

    Bourgoin, Jean-Philippe; Campidelli, Stéphane; Chenevier, Pascale; Derycke, Vincent; Filoramo, Arianna; Goffman, Marcelo F

    2010-01-01

    Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field. PMID:21137718

  7. Epipolar image rectification through geometric algorithms with unknown parameters

    Science.gov (United States)

    Herráez, José; Denia, José Luis; Navarro, Pablo; Rodríguez, Jaime; Teresa Martín, M.

    2013-10-01

    Image processing in photogrammetry is commonly used for scene reconstruction. Although two-dimensional applications can be solved using isolated images, reconstruction of three-dimensional scenes usually requires the use of multiple images simultaneously. Epipolar image rectification is a common technique for this purpose. It typically requires internal orientation parameters and, therefore, knowledge of camera calibration and relative orientation parameters between images. A reparameterization of the fundamental matrix through a completely geometric algorithm of seven parameters that enables the epipolar image rectification of a photogrammetric stereo pair without introducing any orientation parameters and without premarking ground control points is presented. The algorithm enables the generation of different stereoscopic models with a single photogrammetric pair from unknown cameras, scanned from a book, or frames from video sequences. Stereoscopic models with no parallaxes have been obtained with a standard deviation of <0.5 pixels.

  8. Photovoltaic application of resonance light absorption and rectification

    Science.gov (United States)

    Lin, Guang H.; Bockris, John O'M.

    1997-04-01

    In this paper, we suggest a new concept, direct energy transfer from light to dc electricity by means of resonance light absorption and rectification. The experimental validation of resonance light absorption by a fabricated subnanostructure and high frequency rectification in the range corresponding to that of visible light is reported. The subnanostructure consists of a parallel dipole antenna array. A resonance peak signal of short circuit current was observed. This peak signal appeared only at the polarization of incident light parallel to dipole element. The short circuit peak signal was also observed at a photon energy less than that of the optical bandgap. The peak angle exhibited the predicted relation with the wavelength of the incident light. The possible photovoltaic applications of the experimental observations are discussed.

  9. Nonlinear optical rectification in asymmetric coupled quantum wells

    International Nuclear Information System (INIS)

    The optical rectification (OR) in the asymmetric coupled quantum wells (ACQWs) is calculated theoretically. The dependence of the OR on the width of the right-well and the barrier is studied. The analytical expression of the optical rectification coefficient is obtained by using the compact density-matrix approach and the iterative method, and the numerical calculations are presented for a typical GaAs/AlxGa1-xAs ACQW. The results obtained show that the OR efficient can reach the magnitude of 10-4 m/V in this ACQW system, which is 1-2 orders higher than that in single quantum systems. Moreover, the OR coefficient is strongly dependent on the widths of the barrier and the right-well of the ACQWs. An appropriate choice for the width of the barrier and the right-well of the ACQWs can induce a larger OR coefficient

  10. Rectification of energy transport in nonlinear metamaterials via ratchets

    International Nuclear Information System (INIS)

    The presence of discrete breathers (DBs) has already been described in nonlinear photonic materials, such as ferroelectrics and metamaterials (MMs) by the Klein–Gordon (K–G) approach. Rectification of energy transport in MMs in the presence of an appropriate external field is studied via symmetry breaking leading to directed energy transport or ratchet behaviour. Based on the earlier development of the K–G equation in a MM system with a split-ring resonator for antenna applications, a theoretical model for current density is worked out by symmetry analysis and its violation to characterize the ratchet effect. The time-averaged current shows interesting results against phase shift in the ac driver. These data are further related to various parameters, such as coupling and damping in the system. For MMs, this opens a new application for rectification using ratchets. (paper)

  11. Rectification of the OPAL Cold Neutron Source Cryogenic System

    International Nuclear Information System (INIS)

    The Cold Neutron Source (CNS) at ANSTO's OPAL Reactor had experienced repeated outages since 2009 due to failures in the cryogenic system. An extensive root cause analysis was initiated in May 2012, led by an ANSTO team that also involved knowledgeable external experts. At the conclusion of the investigation, a set of recommendations was released to address the identified contributing causes. A rectification program was established to implement the solutions. Cryogenic operation of the CNS, providing end users with cold neutrons, successfully returned to service in July 2013. Thanks to the unique stand-by operation mode of the CNS, irradiation activities at the reactor, as well as thermal neutron availability, had not been affected during the year-long investigation/rectification process. Some technical and operational aspects of the investigation, testing and engineering modifications are discussed in this presentation

  12. Light-Induced Ion Rectification in Zigzag Nanochannels.

    Science.gov (United States)

    Li, Chuanshuai; Hu, Shimin; Yang, Lei; Fan, Jiajie; Yao, Zhiqiang; Zhang, Yiqiang; Shao, Guosheng; Hu, Junhua

    2015-12-01

    Ion transport through nanoporous systems has attracted broad interest due to its crucial role in physiological processes in living organisms and artificial bionic devices. In this work, a nanochannel system with a zigzag inner surface was fabricated by using a two-step anodizing technique. The rectification performance of the zigzag channels was observed by I-V measurement in KCl solution. Unlike channels with asymmetric geometry, the mechanism was analyzed based on the "point effect" of charge distribution and "shape effect" of the zigzag channel. The current rectification ratio decreases from nearly 3.0 to 1.0 when the KCl concentration increased from 0.1?mm to 100?mm. The fabrication of different nanopore systems and exploration of novel mechanisms will help to develop biomimetic membranes for practical applications. PMID:26255623

  13. Separation and purification of niobium and tantalum by rectification of their pentafluorides

    International Nuclear Information System (INIS)

    Main statistic parameters of the process of rectification separation of niobium and tantalum in the form of their pentafluorides and pentachlorides are calculated. Comparison of the data obtained shows that niobium pentafluoride rectification efficiency is 5 time less according to the value of interstage flow than the rectification of their pentachlorides. To illustrate the possibilities of rectification separation and purification of niobium and tantalum pentafluorides a number of experiments have been carried out. Experiments have grounded that the use of high-efficiency rectification coulomus is necessary for the fine separation of pentafluoride data and for their purification from a number of impurities. Behaviour of impurities during rectification purification of pentafluorides is in correlation with the data on liquid-vapor phase equilibria in studied systems of pentafluorides-impurity (TiF4, AlF3, WF6, WOF4, MoOF4, MoF6)

  14. Formation of stationary electronic states in finite homogeneous molecular chains

    OpenAIRE

    Lakhno, V. D.; Korshunova, A. N.

    2013-01-01

    Evolution of an arbitrary initial distribution of a quantummechanical particle in a uniform molecular chain is simulated by a system of coupled quantumclassical dynamical equations with dissipation. Stability of a uniform distribution of the particle over the chain is studied. An asymptotical expression is obtained for the time in which a localized state is formed. The validity of the expression is checked by direct computational experiments. It is shown that the time of soliton and multisoli...

  15. A Quantum of Solace: molecular electronics of benzodiazepines

    Science.gov (United States)

    Turin, Luca; Horsfield, Andrew; Stoneham, Marshall

    2011-03-01

    Benzodiazepines and related drugs modulate the activity of GABA-A receptors, the main inhibitory receptor of the central nervous system. The prevailing view is that these drugs bind at the interface between two receptor subunits and allosterically modulate the response to GABA. In this talk I shall present evidence that benzodiazepines work instead by facilitating electron transport from the cytoplasm to a crucial redox-sensitive group in the gamma subunit. If this idea is correct, benzodiazepines should not only be regarded as keys fitting into a lock, but also as one-electron chemical field-effect transistors fitting into an electronic circuit. Supported by DARPA Grant N66001-10-1-4062.

  16. Multi-electron coincidence spectroscopy: double photoionization from molecular inner-shell orbitals

    International Nuclear Information System (INIS)

    We have studied double photoionization from molecular inner-shell orbitals and investigated the properties of the resultant double core-hole states in molecules, by multi-electron coincidence spectroscopy with a magnetic bottle electron spectrometer. A brief summary of our previous studies is presented

  17. Terahertz generation by optical rectification in uniaxial birefringent crystals

    OpenAIRE

    Rowley, J.D. (Janet D.); Wahlstrand, J. K.; Zawilski, K. T.; Schunemann, P. G.; Giles, N. C.; Bristow, A. D.

    2012-01-01

    The angular dependence of terahertz (THz) emission from birefringent crystals can differ significantly from that of cubic crystals. Here we consider optical rectification in uniaxial birefringent materials, such as chalcopyrite crystals. The analysis is verified in (110)-cut ZnGeP_2 and compared to (zincblende) GaP. Although the crystals share the same nonzero second-order tensor elements, the birefringence in chalcopyrite crystals cause the pump pulse polarization to evolve as it propagates ...

  18. Thermal rectification effects of multiple semiconductor quantum dot junctions

    OpenAIRE

    Kuo, David M T

    2010-01-01

    Based on the multiple energy level Anderson model, this study theoretically examines the thermoelectric effects of semiconductor quantum dots (QDs) in the nonlinear response regime. The charge and heat currents in the sequential tunneling process are calculated by using the Keldysh Green's function technique. Results show that the thermal rectification effect can be observed in a multiple QD junction system, whereas the tunneling rate, size fluctuation, and location distribution of QD signifi...

  19. Decontamination of nitric acid by distillation or rectification

    International Nuclear Information System (INIS)

    The undesirable active and non-active components were removed from the simulated solution of nitric acid formed in the course of the absorption of NOx liberated during the vitrification of liquid medium-level nuclear power plant waste. Decontamination factor values of 5 for both 137Cs and Na and the reduction of the content of inactive salts below the limits required by the State standard for technical nitric acid were attained by rectification. (author) 1 tab., 4 figs., 5 refs

  20. Rectification of License Plate Images Based on HT and Projection

    OpenAIRE

    Jingsong Tao; Hao Feng,; Qingxin Zhu; Hongyao Deng

    2013-01-01

    It is crucial to segment characters correctly and improve rate of correct character recognition when processing automobile license plates corrections. In this paper, two algorithms are proposed to obtain the horizontal tilt and vertical shear angles. The transformation matrix for images rectification is given and the subpixel issue is solved. Some experiments were done to test the algorithms. Experimental results show that the algorithm is robust, flexible and effective.

  1. Efficient Video Rectification and Stabilisation for Cell-Phones

    OpenAIRE

    Ringaby, Erik; Forssén, Per-Erik

    2012-01-01

    This article presents a method for rectifying and stabilising video from cell-phones with rolling shutter (RS) cameras. Due to size constraints, cell-phone cameras have constant, or near constant focal length, making them an ideal application for calibrated projective geometry. In contrast to previous RS rectification attempts that model distortions in the image plane, we model the 3D rotation of the camera. We parameterise the camera rotation as a continuous curve, with knots distributed acr...

  2. Molecular shock response of explosives: electronic absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mcgrne, Shawn D [Los Alamos National Laboratory; Moore, David S [Los Alamos National Laboratory; Whitley, Von H [Los Alamos National Laboratory; Bolme, Cindy A [Los Alamos National Laboratory; Eakins, Daniel E [Los Alamos National Laboratory

    2009-01-01

    Electronic absorption spectroscopy in the range 400-800 nm was coupled to ultrafast laser generated shocks to begin addressing the question of the extent to which electronic excitations are involved in shock induced reactions. Data are presented on shocked polymethylmethacrylate (PMMA) thin films and single crystal pentaerythritol tetranitrate (PETN). Shocked PMMA exhibited thin film interference effects from the shock front. Shocked PETN exhibited interference from the shock front as well as broadband increased absorption. Relation to shock initiation hypotheses and the need for time dependent absorption data (future experiments) is briefly discussed.

  3. First principles study of the electron transport through cis -polyacetylene based molecular wires

    Science.gov (United States)

    Yao, Jinhuan; Li, Yanwei; Zou, Zhengguang; Yang, Jianwen; Yin, Zhoulan

    2011-10-01

    The electron transport properties of cis-polyacetylene and cis-polyacetylene based molecular wires (oligo(cyclopentadiene), oligo(pyrrole), and oligo(furan)) have been studied theoretically using a combination of density-functional theory and non-equilibrium Green?s functions method. The results demonstrate that the introduction of bridging group X (X=CH 2, NH, and O) in cis-polyacetylene has a profound effect on the electron transport behavior of the molecules. The conductance of the four molecular wires decreases in the order of polyacetylene>oligo(cyclopentadiene)>oligo(furan)>oligo(pyrrole). In particular, the conductances of oligo(furan) and oligo(pyrrole) are much lower than those of polyacetylene and oligo(cyclopentadiene). The mechanism of this difference of electron transport properties of these four molecular systems is analyzed in terms of their geometric structures, electronic structures, transmission spectra, and spatial distribution of frontier orbitals. It is found that the energy levels of frontier molecular orbitals and the evolution of spatial distribution of frontier molecular orbitals with the applied bias are the essential reason for generating this difference of electron transport behaviors of the four molecular systems.

  4. Tunneling of electrons via rotor-stator molecular interfaces: combined ab initio and model study

    CERN Document Server

    Petreska, Irina; Pejov, Ljupco; Kocarev, Ljupco

    2015-01-01

    Tunneling of electrons through rotor-stator anthracene aldehyde molecular interfaces is studied with a combined ab initio and model approach. Molecular electronic structure calculated from first principles is utilized to model different shapes of tunneling barriers. Together with a rectangular barrier, we also consider a sinusoidal shape that captures the effects of the molecular internal structure more realistically. Quasiclassical approach with the Simmons' formula for current density is implemented. Special attention is paid on conformational dependence of the tunneling current. Our results confirm that the presence of the side aldehyde group enhances the interesting electronic properties of the pure anthracene molecule, making it a bistable system with geometry dependent transport properties. We also investigate the transition voltage and we show that confirmation dependent field emission could be observed in these molecular interfaces at realistically low voltages. The present study accompanies our previ...

  5. Calibration and rectification research for fish-eye lens application

    Science.gov (United States)

    Feng, Weijia; Zhang, Baofeng; Cao, Zuoliang; Zong, Xiaoning; Röning, Juha

    2011-01-01

    The purpose of this paper aims to promote the application of fish-eye lens. Accurate parameters calibration and effective distortion rectification of an imaging device is of utmost importance in machine vision. Fish-eye lens produces a hemispherical field of view of an environment, which appears definite significant since its advantage of panoramic sight with a single compact visual scene. But fish-eye lens image has an unavoidable inherent severe distortion. The precise optical center is the precondition for other parameters calibration and distortion correction. Therefore, three different optical center calibration methods have been researched for diverse applications. Support Vector Machine (SVM) and Spherical Equidistance Projection Algorithm (SEPA) are integrated to replace traditional rectification methods. SVM is a machine learning method based on the theory of statistics, which have good capabilities of imitating, regression and classification. In this research, SVM provides a mapping table between the fish-eye image and the standard image for human eyes. Two novel training models have been designed. SEPA has been applied to promote the rectification effect of the edge of fish-eye lens image. The validity and effectiveness of our achievements are demonstrated by processing the real images.

  6. DC Rectification of Microwaves in YIG/Pt/Py Trilayers

    Science.gov (United States)

    Sklenar, Joseph; Ketterson, John; Jungfleisch, Matthias; Jiang, Wanjun; Zhang, Wei; Pearson, John; Hoffmann, Axel; Yang, Qinghui; Wen, Qiye; Zhang, Huaiwu

    2015-03-01

    The DC voltage arising from the rectification of microwaves passing through a ferromagnet/spin Hall metal bilayer structure at ferromagnetic resonance is a powerful tool in understanding spin-orbit torques from spin Hall effects. Rectification mechanisms such as anisotropic magnetoresistance of the ferromagnetic or spin Hall magnetoresistance of the spin Hall metal can contribute depending on whether the ferromagnet is conductive or insulating. For both types of ferromagnets, spin pumping acting in concert with the inverse spin Hall effect can also generate additional DC voltages. We have studied rectification in a trilayer system of YIG/Pt/Py under conditions where both ferromagnets are simultaneously excited. By tipping the DC magnetic field out of the sample plane we can make the resonances of both ferromagnet materials degenerate. In this simultaneous resonance regime we observe an enhancement in the voltage of the YIG lineshape coming at the expense of the Py signal. Furthermore, at arbitrarily tipped out-of-plane tipping angles we observe asymmetries of the Py signal under field reversal. We compare this observation with the behavior of Py/Pt bilayer samples. This work was supported by DOE, Office of Science, Materials Science and Engineering Division.

  7. Unified framework for automatic image stitching and rectification

    Science.gov (United States)

    An, Jaehyun; Kim, Beom Su; Koo, Hyung Il; Cho, Nam Ik

    2015-05-01

    Conventional image stitching methods were developed under the assumption or condition that (1) the optical center of a camera is fixed (fixed-optical-center case) or (2) the camera captures a plane target (plane-target case). Hence, users should know or test which condition is more appropriate for the given set of images and then select a right algorithm or try multiple stitching algorithms. We propose a unified framework for the image stitching and rectification problem, which can handle both cases in the same framework. To be precise, we model each camera pose with six parameters (three for the rotation and three for the translation) and develop a cost function that reflects the registration errors on a reference plane. The designed cost function is effectively minimized via the Levenberg-Marquardt algorithm. For the given set of images, when it is found that the relative camera motions between the images are large, the proposed method performs rectification of images and then composition using the rectified images; otherwise, the algorithm simply builds a visually pleasing result by selecting a viewpoint. Experimental results on synthetic and real images show that our method successfully performs stitching and metric rectification.

  8. Goal-oriented rectification of camera-based document images.

    Science.gov (United States)

    Stamatopoulos, Nikolaos; Gatos, Basilis; Pratikakis, Ioannis; Perantonis, Stavros J

    2011-04-01

    Document digitization with either flatbed scanners or camera-based systems results in document images which often suffer from warping and perspective distortions that deteriorate the performance of current OCR approaches. In this paper, we present a goal-oriented rectification methodology to compensate for undesirable document image distortions aiming to improve the OCR result. Our approach relies upon a coarse-to-fine strategy. First, a coarse rectification is accomplished with the aid of a computationally low cost transformation which addresses the projection of a curved surface to a 2-D rectangular area. The projection of the curved surface on the plane is guided only by the textual content's appearance in the document image while incorporating a transformation which does not depend on specific model primitives or camera setup parameters. Second, pose normalization is applied on the word level aiming to restore all the local distortions of the document image. Experimental results on various document images with a variety of distortions demonstrate the robustness and effectiveness of the proposed rectification methodology using a consistent evaluation methodology that encounters OCR accuracy and a newly introduced measure using a semi-automatic procedure. PMID:20876019

  9. Magnetization dependent current rectification in (Ga,Mn)As magnetic tunnel junctions

    OpenAIRE

    HASHIMOTO, Yoshiaki; Amano, Hiroaki; Iye, Yasuhiro; Katsumoto, Shingo

    2011-01-01

    We have found that the current rectification effect in triple layer (double barrier) (Ga,Mn)As magnetic tunnel junctions strongly depends on the magnetization alignment. The direction as well as the amplitude of the rectification changes with the alignment, which can be switched by bi-directional spin-injection with very small threshold currents. A possible origin of the rectification is energy dependence of the density of states around the Fermi level. Tunneling density of states in (Ga,Mn)A...

  10. Rectification and Phase Locking for Particles on Two Dimensional Periodic Substrates

    OpenAIRE

    Reichhardt, C.; Olson, C. J.; Hastings, M. B.

    2001-01-01

    We show that a novel rectification phenomena is possible for overdamped particles interacting with a 2D periodic substrate and driven with a longitudinal DC drive and a circular AC drive. As a function of DC amplitude, the longitudinal velocity increases in a series of quantized steps with transverse rectification occuring near these transitions. We present a simple model that captures the quantization and rectification behaviors.

  11. Switching and Rectification of a Single Light-sensitive Diarylethene Molecule Sandwiched between Graphene Nanoribbons

    OpenAIRE

    Cai, Yongqing; Zhang, Aihua; Feng, Yuan ping; Zhang, Chun

    2011-01-01

    The 'open' and 'closed' isomers of the diarylethene molecule that can be converted between each other upon photo-excitation are found to have drastically different current-voltage characteristics when sandwiched between two graphene nanoribbons (GNRs). More importantly, when one GNR is metallic and another one is semiconducting, strong rectification behavior of the 'closed' diarylethene isomer with the rectification ratio >10^3 is observed. The surprisingly high rectification ratio originates...

  12. Electrostatics in the Cytoplasmic Pore Produce Intrinsic Inward Rectification in Kir2.1 Channels

    OpenAIRE

    Yeh, Shih-Hao; Chang, Hsueh-Kai; Shieh, Ru-Chi

    2005-01-01

    Inward rectifier K+ channels are important in regulating membrane excitability in many cell types. The physiological functions of these channels are related to their unique inward rectification, which has been attributed to voltage-dependent block. Here, we show that inward rectification can also be induced by neutral and positively charged residues at site 224 in the internal vestibule of tetrameric Kir2.1 channels. The order of extent of inward rectification is E224K mutant > E224G mutant >...

  13. Ballistic switching and rectification in single wall carbon nanotube Y junctions

    International Nuclear Information System (INIS)

    Transport properties of various semiconducting zig-zag carbon nanotube Y junctions are studied for the investigations of rectification and switching. Our results indicate that such junctions, when symmetric, can support both ballistic rectification and/or the ballistic switching operating modes. Although structural symmetry of the Y junction is found to be a necessary condition for rectification, it may not be sufficient in all cases

  14. A quantum-defect theory of molecular electronic polarizability

    International Nuclear Information System (INIS)

    An algorithm based on the quantum defect theory is proposed for computing the dynamic polarizability tensor for polar molecules. The algorithm makes use of ab initio methods developed for ground and lowlying electronic states. The computed refractive index and scattered-light depolarization coefficient for gaseous nitric oxide are in good agreement with experiment

  15. Electron transfer statistics and thermal fluctuations in molecular junctions

    International Nuclear Information System (INIS)

    We derive analytical expressions for probability distribution function (PDF) for electron transport in a simple model of quantum junction in presence of thermal fluctuations. Our approach is based on the large deviation theory combined with the generating function method. For large number of electrons transferred, the PDF is found to decay exponentially in the tails with different rates due to applied bias. This asymmetry in the PDF is related to the fluctuation theorem. Statistics of fluctuations are analyzed in terms of the Fano factor. Thermal fluctuations play a quantitative role in determining the statistics of electron transfer; they tend to suppress the average current while enhancing the fluctuations in particle transfer. This gives rise to both bunching and antibunching phenomena as determined by the Fano factor. The thermal fluctuations and shot noise compete with each other and determine the net (effective) statistics of particle transfer. Exact analytical expression is obtained for delay time distribution. The optimal values of the delay time between successive electron transfers can be lowered below the corresponding shot noise values by tuning the thermal effects

  16. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study.

    Science.gov (United States)

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-28

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]? and Si-[Cr(styrene)]? single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]? system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]?-[Cr(styrene)]? DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires. PMID:26219748

  17. Measuring relative barrier heights in molecular electronic junctions with transition voltage spectroscopy.

    Science.gov (United States)

    Beebe, Jeremy M; Kim, BongSoo; Frisbie, C Daniel; Kushmerick, James G

    2008-05-01

    Though molecular devices exhibiting potentially useful electrical behavior have been demonstrated, a deep understanding of the factors that influence charge transport in molecular electronic junctions has yet to be fully realized. Recent work has shown that a mechanistic transition occurs from direct tunneling to field emission in molecular electronic devices. The magnitude of the voltage required to enact this transition is molecule-specific, and thus measurement of the transition voltage constitutes a form of spectroscopy. Here we determine that the transition voltage for a series of alkanethiol molecules is invariant with molecular length, while the transition voltage of a conjugated molecule depends directly on the manner in which the conjugation pathway has been extended. Finally, by examining the transition voltage as a function of contact metal, we show that this technique can be used to determine the dominant charge carrier for a given molecular junction. PMID:19206478

  18. The role of dimensionality on the molecule-lead coupling in molecular electronic junctions

    Science.gov (United States)

    Zelovich, Tamar; Kronik, Leeor; Hod, Oded

    We present new insights into the role dimensionality plays in the lead-molecule coupling scheme at molecular electronic junctions. A key ingredient of our approach is a transformation of the Hamiltonian matrix from an atomistic to a state representation of the molecular junction. This provides direct access to the different couplings between the molecular states and the energy manifold of the leads, which underlie the transport properties of molecular junctions. We explore several tight-binding junction models and predict the appearance of coupling bands that depend on the dimensionality and shape of the leads. We believe that a similar analysis may contribute to the understanding of many phenomena characteristic to the fields of nano- and molecular-electronics.

  19. Molecular-frame angular distribution of normal and resonant Auger electrons

    Energy Technology Data Exchange (ETDEWEB)

    Rolles, D; Pesic, Z D; Dumitriu, I; Berrah, N [Physics Department, Western Michigan University, Kalamazoo, Michigan 49008 (United States); Pruemper, G; Fukuzawa, H; Liu, X-J; Ueda, K [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Harries, J, E-mail: Daniel.Rolles@asg.mpg.d [Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo 679-5198 (Japan)

    2010-02-01

    Molecular-frame angular distributions (MFADs) of resonant and non-resonant ('normal') Auger electrons were determined using angle-resolved electron-ion coincidence spectroscopy. Here, we concentrate on the MFADs of normal N2 KVV Auger electrons. We conclude that their MFADs are independent of both photon energy and light polarization direction, thus confirming that the two-step model is a good approximation. All threshold and shape-resonance phenomena can be attributed to the absorption process and are irrelevant for the Auger decay in the molecular frame. Distinct differences in the MFADs are found as a function of the Auger final state.

  20. Investigation of the molecular conformations of ethanol using electron momentum spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ning, C G; Luo, Z H; Huang, Y R; Liu, K; Zhang, S F; Deng, J K [Department of Physics and Key Laboratory of Atomic and Molecular NanoSciences of MOE, Tsinghua University, Beijing 100084 (China); Hajgato, B; Morini, F; Deleuze, M S [Research Group of Theoretical Chemistry, Department SBG, Hasselt University, Agoralaan Gebouw D, B-3590 Diepenbeek (Belgium)], E-mail: ningcg@tsinghua.edu.cn, E-mail: djk-dmp@tsinghua.edu.cn, E-mail: michael.deleuze@uhasselt.be

    2008-09-14

    The valence electronic structure and momentum-space electron density distributions of ethanol have been investigated with our newly constructed high-resolution electron momentum spectrometer. The measurements are compared to thermally averaged simulations based on Kohn-Sham (B3LYP) orbital densities as well as one-particle Green's function calculations of ionization spectra and Dyson orbital densities, assuming Boltzmann's statistical distribution of the molecular structure over the two energy minima defining the anti and gauche conformers. One-electron ionization energies and momentum distributions in the outer-valence region were found to be highly dependent upon the molecular conformation. Calculated momentum distributions indeed very sensitively reflect the distortions and topological changes that molecular orbitals undergo due to the internal rotation of the hydroxyl group, and thereby exhibit variations which can be traced experimentally. The B3LYP model Kohn-Sham orbital densities are overall in good agreement with the experimental distributions, and closely resemble benchmark ADC(3) Dyson orbital densities. Both approaches fail to quantitatively reproduce the experimental momentum distributions characterizing the highest occupied molecular orbital. Since electron momentum spectroscopy measurements at various electron impact energies indicate that the plane wave impulse approximation is valid, this discrepancy between theory and experiment is tentatively ascribed to thermal disorder, i.e. large-amplitude and thermally induced dynamical distortions of the molecular structure in the gas phase.

  1. Investigation of the molecular conformations of ethanol using electron momentum spectroscopy

    International Nuclear Information System (INIS)

    The valence electronic structure and momentum-space electron density distributions of ethanol have been investigated with our newly constructed high-resolution electron momentum spectrometer. The measurements are compared to thermally averaged simulations based on Kohn-Sham (B3LYP) orbital densities as well as one-particle Green's function calculations of ionization spectra and Dyson orbital densities, assuming Boltzmann's statistical distribution of the molecular structure over the two energy minima defining the anti and gauche conformers. One-electron ionization energies and momentum distributions in the outer-valence region were found to be highly dependent upon the molecular conformation. Calculated momentum distributions indeed very sensitively reflect the distortions and topological changes that molecular orbitals undergo due to the internal rotation of the hydroxyl group, and thereby exhibit variations which can be traced experimentally. The B3LYP model Kohn-Sham orbital densities are overall in good agreement with the experimental distributions, and closely resemble benchmark ADC(3) Dyson orbital densities. Both approaches fail to quantitatively reproduce the experimental momentum distributions characterizing the highest occupied molecular orbital. Since electron momentum spectroscopy measurements at various electron impact energies indicate that the plane wave impulse approximation is valid, this discrepancy between theory and experiment is tentatively ascribed to thermal disorder, i.e. large-amplitude and thermally induced dynamical distortions of the molecular structure in the gas phase

  2. Self-Assembled Molecular Rafts at Liquid|Liquid Interfaces for Four-Electron Oxygen Reduction

    OpenAIRE

    Olaya, Astrid Johana; Schaming, Delphine Henriette; Brevet, Pierre-François Marie; Nagatani, Hirohisa; Zimmermann, Tomas; Vanicek, Jiri; Xu, Hai-jun; Gros, Claude P.; Barbe, Jean-Michel; Girault, Hubert

    2012-01-01

    The self-assembly of the oppositely charged watersoluble porphyrins, cobalt tetramethylpyridinium porphyrin (CoTMPyP4+) and cobalt tetrasulphonatophenyl porphyrin (CoTPPS4?), at the interface with an organic solvent to form molecular “rafts”, provides an excellent catalyst to perform the interfacial four-electron reduction of oxygen by lipophilic electron donors such as tetrathiafulvalene (TTF). The catalytic activity and selectivity of the self-assembled catalyst toward the four-electron pat...

  3. Electron mobility in gallium arsenide layers obtained by molecular beam epitaxy in hydrogen atmosphere

    International Nuclear Information System (INIS)

    Investigations aimed at determining hydrogen effect on electron mobility value in gallium arsenide layers produced during molecular-radiation epitaxy (MRE) at 300 and 77 K are conducted. Dependences of electron mobility in the epitaxial layers of GaAs on hydrogen pressure are presented. It is shown that in case of treatment in hydrogen plasma at an increased temperature (350 deg C), hydrogen introduction during MRE-growth of GaAs layers leads to photoluminescence intensity and electron mobility

  4. Intense Electron Beams from GaAs Photocathodes as a Tool for Molecular and Atomic Physics

    OpenAIRE

    Krantz, Claude

    2009-01-01

    We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at stable cathode lifetimes of 24 h or more. ...

  5. Electron Transfer Dynamics in Efficient Molecular Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Gerald John

    2014-10-01

    This research provided new mechanistic insights into surface mediated photochemical processes relevant to solar energy conversion. In this past three years our research has focused on oxidation photo-redox chemistry and on the role surface electric fields play on basic spectroscopic properties of molecular-semiconductor interfaces. Although this research as purely fundamental science, the results and their interpretation have relevance to applications in dye sensitized and photogalvanic solar cells as well as in the storage of solar energy in the form of chemical bonds.

  6. Oscillating molecular dipoles require strongly correlated electronic and nuclear motion

    International Nuclear Information System (INIS)

    To create an oscillating electric dipole in an homonuclear diatomic cation without an oscillating driver one needs (i) to break the symmetry of the system and (ii) to sustain highly correlated electronic and nuclear motion. Based on numerical simulations in H2+ we present results for two schemes. In the first one (i) is achieved by creating a superposition of symmetric and antisymmetric electronic states freely evolving, while (ii) fails. In a second scheme, by preparing the system in a dressed state of a strong static field, both conditions hold. We then analyze the robustness of this scheme with respect to features of the nuclear wave function and its intrinsic sources of decoherence. (tutorial)

  7. Molecular aspects of biological energy and electron transport: photosynthesis

    International Nuclear Information System (INIS)

    Pulse radiolysis and flash photolysis have been applied to chemical systems involved in biological energy and electron transport processes. The processes of particular interest are those that take place in mitochondria (i.e. oxidative phosphorylation), in chloroplasts (i.e. photosynthesis) and in photo-receptors (i.e. vision). Pulse radiation techniques can be applied either to the intact biological membranes (see, for example, Witt, Quart. Rev. Biophys.; 4:365 (1971)), or to simple solutions of individual components of the various excitation and electron transport chains. The two approaches are complementary. In this paper a description is given of some data obtained from simple solutions which are helpful in interpreting information similarly gained from intact photosynthetic membranes, and hence in understanding certain aspects of photosynthesis. (author)

  8. Dihydroazulene Photochromism:Synthesis, Molecular Electronics and Hammett Correlations

    DEFF Research Database (Denmark)

    Broman, Søren Lindbæk

    2013-01-01

    This thesis describes the development of a versatile synthetic protocol for preparation of a large selection of dihydroazulenes (DHAs) with both electron withdrawing and donating groups. By UV-Vis and NMR spectroscopies and even in a single-molecule junction, their ability to undergo a light-induced ring-opening reaction to vinylheptafulvenes (VHFs) and a thermally induced back-reaction (VHF ? DHA) were studied in detail. The first chapter briefly introduces photoswitches with focus, in particul...

  9. Tuning intermetallic electronic coupling in polyruthenium systems via molecular architecture

    Indian Academy of Sciences (India)

    Sandeep Ghumaan; Goutam Kumar Lahiri

    2006-11-01

    A large number of polynuclear ruthenium complexes encompassing selective combinations of spacer (bridging ligand, BL) and ancillary (AL) functionalities have been designed. The extent of intermetallic electronic communication in mixed-valent states and the efficacy of the ligand frameworks towards the tuning of coupling processes have been scrutinised via structural, spectroelectrochemical, EPR, magnetic and theoretical investigations. Moreover, the sensitive oxidation state features in the complexes of non-innocent quinonoid bridging moieties have also been addressed.

  10. Dissipative Effects in the Electronic Transport through DNA Molecular Wires

    CERN Document Server

    Gutíerrez, R; Cuniberti, G

    2005-01-01

    We investigate the influence of a dissipative environment which effectively comprises the effects of counterions and hydration shells, on the transport properties of short \\DNA wires. Their electronic structure is captured by a tight-binding model which is embedded in a bath consisting of a collection of harmonic oscillators. Without coupling to the bath a temperature independent gap opens in the electronic spectrum. Upon allowing for electron-bath interaction the gap becomes temperature dependent. It increases with temperature in the weak-coupling limit to the bath degrees of freedom. In the strong-coupling regime a bath-induced {\\it pseudo-gap} is formed. As a result, a crossover from tunneling to activated behavior in the low-voltage region of the $I$-$V$ characteristics is observed with increasing temperature. The temperature dependence of the transmission near the Fermi energy, $t(E_{\\rm F})$, manifests an Arrhenius-like behavior in agreement with recent transport experiments. Moreover, $t(E_{\\rm F})$ sh...

  11. Rectification induced in N2AA-doped armchair graphene nanoribbon device

    International Nuclear Information System (INIS)

    By using non-equilibrium Green function formalism in combination with density functional theory, we investigated the electronic transport properties of armchair graphene nanoribbon devices in which one lead is undoped and the other is N2AA-doped with two quasi-adjacent substitutional nitrogen atoms incorporating pairs of neighboring carbon atoms in the same sublattice A. Two kinds of N2AA-doped style are considered, for N dopants substitute the center or the edge carbon atoms. Our results show that the rectification behavior with a large rectifying ratio can be found in these devices and the rectifying characteristics can be modulated by changing the width of graphene nanoribbons or the position of the N2AA dopant. The mechanisms are revealed to explain the rectifying behaviors.

  12. Rectification induced in N{sub 2}{sup AA}-doped armchair graphene nanoribbon device

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tong; Wang, Ling-Ling, E-mail: llwang@hnu.edu.cn; Luo, Kai-Wu; Xu, Liang [School of Physics and Microelectronic and Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, Hunan University, Changsha 410082 (China); Li, Xiao-Fei, E-mail: xfli@hnu.edu.cn [School of Physics and Microelectronic and Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, Hunan University, Changsha 410082 (China); Department of Electrical and Information Engineering, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2014-07-07

    By using non-equilibrium Green function formalism in combination with density functional theory, we investigated the electronic transport properties of armchair graphene nanoribbon devices in which one lead is undoped and the other is N{sub 2}{sup AA}-doped with two quasi-adjacent substitutional nitrogen atoms incorporating pairs of neighboring carbon atoms in the same sublattice A. Two kinds of N{sub 2}{sup AA}-doped style are considered, for N dopants substitute the center or the edge carbon atoms. Our results show that the rectification behavior with a large rectifying ratio can be found in these devices and the rectifying characteristics can be modulated by changing the width of graphene nanoribbons or the position of the N{sub 2}{sup AA} dopant. The mechanisms are revealed to explain the rectifying behaviors.

  13. Molecular and electronic structure of osmium complexes confined to Au(111) surfaces using a self-assembled molecular bridge

    Science.gov (United States)

    de la Llave, Ezequiel; Herrera, Santiago E.; Adam, Catherine; Méndez De Leo, Lucila P.; Calvo, Ernesto J.; Williams, Federico J.

    2015-11-01

    The molecular and electronic structure of Os(II) complexes covalently bonded to self-assembled monolayers (SAMs) on Au(111) surfaces was studied by means of polarization modulation infrared reflection absorption spectroscopy, photoelectron spectroscopies, scanning tunneling microscopy, scanning tunneling spectroscopy, and density functional theory calculations. Attachment of the Os complex to the SAM proceeds via an amide covalent bond with the SAM alkyl chain 40° tilted with respect to the surface normal and a total thickness of 26 Å. The highest occupied molecular orbital of the Os complex is mainly based on the Os(II) center located 2.2 eV below the Fermi edge and the LUMO molecular orbital is mainly based on the bipyridine ligands located 1.5 eV above the Fermi edge.

  14. Infrared rectification in a nanoantenna-coupled metal-oxide-semiconductor tunnel diode.

    Science.gov (United States)

    Davids, Paul S; Jarecki, Robert L; Starbuck, Andrew; Burckel, D Bruce; Kadlec, Emil A; Ribaudo, Troy; Shaner, Eric A; Peters, David W

    2015-12-01

    Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement. Recently, surface plasmons on heavily doped Si surfaces were investigated as a way of extending surface-mode confinement to the thermal infrared region. Here we combine a nanostructured metallic surface with a heavily doped Si infrared-reflective ground plane designed to confine infrared radiation in an active electronic direct-conversion device. The interplay of strong infrared photon-phonon coupling and electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast electronic tunnelling in metal-oxide-semiconductor (MOS) structures. Infrared dispersion of SiO2 near a longitudinal optical (LO) phonon mode gives large transverse-field confinement in a nanometre-scale oxide-tunnel gap as the wavelength-dependent permittivity changes from 1 to 0, which leads to enhanced electromagnetic fields at material interfaces and a rectified displacement current that provides a direct conversion of infrared radiation into electric current. The spectral and electrical signatures of the nanoantenna-coupled tunnel diodes are examined under broadband blackbody and quantum-cascade laser (QCL) illumination. In the region near the LO phonon resonance, we obtained a measured photoresponsivity of 2.7?mA W(-1) cm(-2) at -0.1?V. PMID:26414194

  15. Infrared rectification in a nanoantenna-coupled metal-oxide-semiconductor tunnel diode

    Science.gov (United States)

    Davids, Paul S.; Jarecki, Robert L.; Starbuck, Andrew; Burckel, D. Bruce; Kadlec, Emil A.; Ribaudo, Troy; Shaner, Eric A.; Peters, David W.

    2015-12-01

    Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement. Recently, surface plasmons on heavily doped Si surfaces were investigated as a way of extending surface-mode confinement to the thermal infrared region. Here we combine a nanostructured metallic surface with a heavily doped Si infrared-reflective ground plane designed to confine infrared radiation in an active electronic direct-conversion device. The interplay of strong infrared photon–phonon coupling and electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast electronic tunnelling in metal–oxide–semiconductor (MOS) structures. Infrared dispersion of SiO2 near a longitudinal optical (LO) phonon mode gives large transverse-field confinement in a nanometre-scale oxide-tunnel gap as the wavelength-dependent permittivity changes from 1 to 0, which leads to enhanced electromagnetic fields at material interfaces and a rectified displacement current that provides a direct conversion of infrared radiation into electric current. The spectral and electrical signatures of the nanoantenna-coupled tunnel diodes are examined under broadband blackbody and quantum-cascade laser (QCL) illumination. In the region near the LO phonon resonance, we obtained a measured photoresponsivity of 2.7?mA W–1 cm–2 at ?0.1?V.

  16. Regularizing the molecular potential in electronic structure calculations. II. Many-body methods

    Energy Technology Data Exchange (ETDEWEB)

    Bischoff, Florian A., E-mail: florian.bischoff@hu-berlin.de [Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin (Germany)

    2014-11-14

    In Paper I of this series [F. A. Bischoff, “Regularizing the molecular potential in electronic structure calculations. I. SCF methods,” J. Chem. Phys. 141, 184105 (2014)] a regularized molecular Hamilton operator for electronic structure calculations was derived and its properties in SCF calculations were studied. The regularization was achieved using a correlation factor that models the electron-nuclear cusp. In the present study we extend the regularization to correlated methods, in particular the exact solution of the two-electron problem, as well as second-order many body perturbation theory. The nuclear and electronic correlation factors lead to computations with a smaller memory footprint because the singularities are removed from the working equations, which allows coarser grid resolution while maintaining the precision. Numerical examples are given.

  17. Molecular and electronic structure of actinide hexa-cyanoferrates

    International Nuclear Information System (INIS)

    The goal of this work is to improve our knowledge on the actinide-ligand bond properties. To this end, the hexacyanoferrate entities have been used as pre-organized ligand. We have synthesized, using mild chemistry, the following series of complexes: AnIV[FeII(CN)6].xH2O (An = Th, U, Np, Pu); AmIII[FeIII(CN)6].xH2O; Pu III[CoIII(CN)6].xH2O and K(H?)AnIII[FeII(CN)6].xH2O (An = Pu, Am). The metal oxidation states have been obtained thanks to the ?CN, stretching vibration and to the actinide LIII absorption edge studies. As Prussian Blue, the AnIV[FeII(CN)6].xH2O (An = Np, Pu) are class II of Robin and Day compounds. X-ray Diffraction has shown besides that these complexes crystallize in the P63/m space group, as the isomorphic LaKFe(CN)6.4H2O complex used as structural model. The EXAFS oscillations at the iron K edge and at the An LIII edge allowed to determine the An-N, An-O, Fe-C and Fe-N distances. The display of the multiple scattering paths for both edges explains the actinide contribution absence at the iron edge, whereas the iron signature is present at the actinide edge. We have shown that the actinide coordination sphere in actinides hexa-cyanoferrates is comparable to the one of lanthanides. However, the actinides typical behavior towards the lanthanides is brought to the fore by the AnIV versus LnIII ions presence in this family of complexes. Contrarily to the 4f electrons, the 5f electrons influence the electronic properties of the compounds of this family. However, the gap between the An-N and Ln-N distances towards the corresponding metals ionic radii do not show any covalence bond evolution between the actinide and lanthanide series. (author)

  18. Molecular Imaging Using X-Ray Free-Electron Lasers

    Science.gov (United States)

    Barty, Anton; Küpper, Jochen; Chapman, Henry N.

    2013-04-01

    The opening of hard X-ray free-electron laser facilities, such as the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory in the United States, has ushered in a new era in structural determination. With X-ray pulse durations down to 10 fs or shorter, and up to 1013 transversely coherent photons per pulse in a narrow spectral bandwidth, focused irradiances of 1018 to 1021 W cm-2 or higher can be produced at X-ray energies ranging from 500 eV to 10 keV. New techniques for determining the structure of systems that cannot be crystallized and for studying the time-resolved behavior of irreversible reactions at femtosecond timescales are now available.

  19. Electronic Properties of Novel Materials - Progress in Molecular Nanostructures. Proceedings

    International Nuclear Information System (INIS)

    These proceedings represent papers presented at the 12th International Winterschool on Electronic Properties of Novel Materials, held in Austria. The main topic of the Winterschool was fullerene nanostructures, their synthesis and applications. Specifically, various preparation and fabrication methods were discussed. Electrical properties including resistivity, thermoelectric power, and superconductivity were discussed. Carbon nanotubes and their varied configurations including ropes, single-walled and multi-walled nanotubes and their properties were presented. Among the applications, hydrogen storage and encapsulation of ferromagnetic metals into carbon nanotubes were elaborated on. Plastic solar cells and fullerenes made an interesting topic at the meeting. There were 113 papers presented at the conference,out of which 5 have been abstracted for the Energy,Science and Technology database

  20. Molecular isotopic effects on coupled electronic and nuclear fluxes

    International Nuclear Information System (INIS)

    A full quantum treatment shows that coupled electronic and nuclear fluxes exhibit a strong sensitivity to a small mass change in a vibrating molecule. This has been exemplified with the existing isotopes of H2+ as well as few fictitious ones. We find that the fluxes undergo a significant change as one goes from one isotope of reduced mass ? to another. Other well-defined observables are likewise affected. It turns out that as a general rule, the heavier the isotope, the larger the flux, the smaller the dispersion, and the longer the revival period. While we were able to confirm analytically that the time at the first turning point scales as ?(?) and that the revival period changes linearly with ?, the mechanism of other observables remains subtle as the result of quantum interference highlighted by the pronounced difference observed on the dispersion pattern.

  1. Electronic and transport properties of a molecular junction with asymmetric contacts

    International Nuclear Information System (INIS)

    Asymmetric molecular junctions have been shown experimentally to exhibit a dual-conductance transport property with a pulse-like current-voltage characteristic, by Reed and co-workers. Using a recently developed first-principles integrated piecewise thermal equilibrium current calculation method and a gold-benzene-1-olate-4-thiolate-gold model molecular junction, this unusual transport property has been reproduced. Analysis of the electrostatics and the electronic structure reveals that the high-current state results from subtle bias induced charge transfer at the electrode-molecule contacts that raises molecular orbital energies and enhances the current-contributing molecular density of states and the probabilities of resonance tunneling of conduction electrons from one electrode to another.

  2. Coupled electron-phonon transport from molecular dynamics with quantum baths

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Wang, J. S.

    2009-01-01

    -classical approximation. Both charge and energy transport and their interplay can be studied. We compare the MD results with those of a fully quantum mechanical nonequilibrium Green's function (NEGF) approach for the electron currents. We find a ballistic to diffusive transition of the electron conduction in one......Based on generalized quantum Langevin equations for the tight-binding wavefunction amplitudes and lattice displacements, electron and phonon quantum transport are obtained exactly using molecular dynamics (MD) in the ballistic regime. The electron-phonon interactions can be handled with a quasi...

  3. NATO Advanced Study Institute on Electronic Structure of Polymers and Molecular Crystals

    CERN Document Server

    Ladik, János

    1975-01-01

    The NATO Advanced Study Institute on "Electronic Structure of Polymers and Molecular Crystals" was held at the Facultes Universi­ taires de Namur (F.U.N.) from September 1st till September 14th, 1974. We wish to express our appreciation to the NATO Scientific Affairs Division whose generous support made this Institute possible and to the Facultes Universitaires de Namur and the Societe Chimique de Belgique which provided fellowships and travel grants to a number of students. This volume contains the main lectures about the basic principles of the field and about different recent developments of the theory of the electronic structure of polymers and molecular crystals. The school started with the presentation of the basic SCF-LCAO theory of the electronic structure of periodic polymers and molecular crystals (contributions by Ladik, Andre & Delhalle) showing how a combination of quantum chemical and solid state physical methods can provide band structures for these systems. The numerical aspects of these ...

  4. Ab initio investigation of electronic properties of the magnesium hydride molecular ion.

    Science.gov (United States)

    Khemiri, Noura; Dardouri, Riadh; Oujia, Brahim; Gadéa, Florent Xavier

    2013-09-12

    In this work, adiabatic potential energy curves, spectroscopic constants, dipole moments, and vibrational levels for numerous electronic states of magnesium hydride molecular ion (MgH(+)) are computed. These properties are determined by the use of an ab initio method involving a nonempirical pseudopotential for the magnesium core (Mg), the core polarization potential (CPP), the l-dependent cutoff functions and the full valence configuration interaction (FCI). The molecular ion is thus treated as a two-electron system. Our calculations on the MgH(+) molecular ion extend previous theoretical works to numerous electronic excited states in the various symmetries. A good agreement with the available theoretical and experimental works is obtained for the spectroscopic constants, the adiabatic potential energy curves, and the dipole moments for the lowest states of MgH(+). PMID:23944679

  5. NATO Advanced Research Workshop on Vectorization of Advanced Methods for Molecular Electronic Structure

    CERN Document Server

    1984-01-01

    That there have been remarkable advances in the field of molecular electronic structure during the last decade is clear not only to those working in the field but also to anyone else who has used quantum chemical results to guide their own investiga­ tions. The progress in calculating the electronic structures of molecules has occurred through the truly ingenious theoretical and methodological developments that have made computationally tractable the underlying physics of electron distributions around a collection of nuclei. At the same time there has been consider­ able benefit from the great advances in computer technology. The growing sophistication, declining costs and increasing accessibi­ lity of computers have let theorists apply their methods to prob­ lems in virtually all areas of molecular science. Consequently, each year witnesses calculations on larger molecules than in the year before and calculations with greater accuracy and more com­ plete information on molecular properties. We can surel...

  6. Molecular volume and electronic and vibrational polarizibilities for amorphous LaAlO3

    International Nuclear Information System (INIS)

    Grazing incidence x-ray reflectivity measurements are used to determine the density of sputter-deposited LaAlO3 and anodized LaAl films. Together with refractive index and dielectric constant measurements, it is demonstrated that a coherent picture emerges explaining the low dielectric constant of the amorphous films (?13) as compared to the single-crystal value (?26). The importance of molecular volume dependence of the electronic and vibrational molecular polarizabilities is underlined

  7. Low-energy Electron collisions with O$_2$: Test of Molecular R-matrix without Diagonalization

    OpenAIRE

    Tarana, Michal; Chris H. Greene

    2013-01-01

    Electron collisions with O$_2$ at scattering energies below 1 eV are studied in the fixed-nuclei approximation for a range of internuclear separations using the ab initio molecular R-matrix method. The $^2\\Pi_g$ scattering eigenphases and quantum defects are calculated. The parameters of the resonance and the energy of the bound negative ion are then extracted. Different models of the target that employ molecular orbitals calculated for the neutral target are compared with m...

  8. Efficient electronic structure calculation for molecular ionization dynamics at high x-ray intensity

    CERN Document Server

    Hao, Yajiang; Hanasaki, Kota; Son, Sang-Kil; Santra, Robin

    2015-01-01

    We present the implementation of an electronic-structure approach dedicated to ionization dynamics of molecules interacting with x-ray free-electron laser (XFEL) pulses. In our scheme, molecular orbitals for molecular core-hole states are represented by linear combination of numerical atomic orbitals that are solutions of corresponding atomic core-hole states. We demonstrate that our scheme efficiently calculates all possible multiple-hole configurations of molecules formed during XFEL pulses. The present method is suitable to investigate x-ray multiphoton multiple ionization dynamics and accompanying nuclear dynamics, providing essential information on the chemical dynamics relevant for high-intensity x-ray imaging.

  9. Electronic absorption spectra and nonlinear optical properties of CO2 molecular aggregates: A quantum chemical study

    Indian Academy of Sciences (India)

    Tarun K Mandal; Sudipta Dutta; Swapan K Pati

    2009-09-01

    We have investigated the structural aspects of several carbon dioxide molecular aggregates and their spectroscopic and nonlinear optical properties within the quantum chemical theory framework. We find that, although the single carbon dioxide molecule prefers to be in a linear geometry, the puckering of angles occur in oligomers because of the intermolecular interactions. The resulting dipole moments reflect in the electronic excitation spectra of the molecular assemblies. The observation of significant nonlinear optical properties suggests the potential application of the dense carbon dioxide phases in opto-electronic devices.

  10. Molecular-scale imaging of unstained deoxyribonucleic acid fibers by phase transmission electron microscopy

    International Nuclear Information System (INIS)

    The molecular structure of deoxyribonucleic acid (DNA) fibers was observed by a phase reconstruction method called three-dimensional Fourier filtering using a 200 kV transmission electron microscope. The characteristic helical structure and the spacing of adjacent base pairs of DNA were partially resolved due to an improved signal-to-noise ratio and resolution enhancement by the phase reconstruction although the molecular structure was damaged by the electron beam irradiation. In the spherical aberration-free phase images, the arrangements of single atom-sized spots forming sinusoidal curves were sometimes observed, which seem to be the contrast originating in the sulfur atoms along the main chains

  11. The roles of electronic and nuclear stopping in the desorption valine negative molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, J.E.; Salehpour, M.; Fishel, D.L.; Tou, J.C.

    1988-01-01

    The yield of valine negative molecular ions has been measured as a function of Xe/sup +/, Kr/sup +/, and Ar/sup +/ primary ion velocity. The electronic and nuclear stopping powers are comparable in magnitude and opposite in slope in the experimental velocity region. The yield data are explained in terms of electronic stopping power alone, with no contribution from nuclear stopping power within the experimental error. Low molecular weight atomic species are found to be best described by a nuclear stopping power related process. 18 refs., 3 figs.

  12. The roles of electronic and nuclear stopping in the desorption valine negative molecular ions

    International Nuclear Information System (INIS)

    The yield of valine negative molecular ions has been measured as a function of Xe+, Kr+, and Ar+ primary ion velocity. The electronic and nuclear stopping powers are comparable in magnitude and opposite in slope in the experimental velocity region. The yield data are explained in terms of electronic stopping power alone, with no contribution from nuclear stopping power within the experimental error. Low molecular weight atomic species are found to be best described by a nuclear stopping power related process. 18 refs., 3 figs

  13. Assessment of delocalized and localized molecular orbitals through electron momentum spectroscopy

    International Nuclear Information System (INIS)

    Recently, there was a hot controversy about the concept of localized orbitals, which was triggered by Grushow's work titled “Is it time to retire the hybrid atomic orbital?” [J. Chem. Educ. 88, 860 (2011)]. To clarify the issue, we assess the delocalized and localized molecular orbitals from an experimental view using electron momentum spectroscopy. The delocalized and localized molecular orbitals based on various theoretical models for CH4, NH3, and H2O are compared with the experimental momentum distributions. Our results show that the delocalized molecular orbitals rather than the localized ones can give a direct interpretation of the experimental (e, 2e) results

  14. Effect of torsion angle on electronic transport through different anchoring groups in molecular junction

    International Nuclear Information System (INIS)

    By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate effect of torsion angle on electronic transport properties of 4,4'-biphenyl molecule connected with different anchoring groups (dithiocarboxylate and thiol group) to Au(111) electrodes. The influence of the HOMO-LUMO gaps and the spatial distributions of molecular orbitals on the quantum transport through the molecular device are discussed. Theoretical results show that the torsion angle plays important role in conducting behavior of molecular devices. By changing the torsion angle between two phenyl rings, namely changing the magnitude of the intermolecular coupling effect, a different transport behavior can be observed in these two systems.

  15. Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge

    Science.gov (United States)

    Guan, W.; Meng, X. F.; Dong, X. M.

    2014-12-01

    Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

  16. The research on rectification and amplification of the image in mobile large container inspection system

    International Nuclear Information System (INIS)

    The author introduces a geometrical rectification algorithm of the image in mobile large container inspection system. The comparison and discussion of the image before and after the rectification have been given. Amplification algorithms of the images are discussed. With all the algorithms, the quality of the images has been improved

  17. Experimental comparison of two processes for rare gas removal by rectification or absorption at low temperature

    International Nuclear Information System (INIS)

    The paper reports the state of work for development and testing of the experimental rectification plant KRETA and the ADAMO system, and of the noble gas scrubbing system TED. A comparative evaluation explains the advantages and drawbacks of the two methods on trial, rectification with O2 preseparation, or pressureless gas scrubbing with CCl2F2. (DG)

  18. 27 CFR 1.82 - Acquiring or receiving distilled spirits in bulk for redistillation, processing, rectification...

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Acquiring or receiving distilled spirits in bulk for redistillation, processing, rectification, warehousing, or warehousing and... bulk for redistillation, processing, rectification, warehousing, or warehousing and bottling....

  19. Electron induced conformational changes of imine-based molecular switches on a Au(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Lotze, Christian; Pascual, Jose Ignacio [Inst. f. Experimentalphysik, Freie Universitaet Berlin (Germany); Luo, Ying; Haag, Rainer [Inst. f. Organische Chemie, Freie Universitaet Berlin (Germany)

    2010-07-01

    Organic molecules exhibiting controllable reversible transitions between isomeric states on surfaces promise an enormous potential in the field of molecular electronics. The reversible cis-trans isomerization of azobenzene-like molecules is often hindered by a strong interaction of the nitrogen lone-pair electrons of the di-azo bridge (-N=N-) with the substrate. In order to improve the isomerization capabilities, the di-azo bridge is substituted by an imine-group (-N=CH-). Here, we use low-temperature scanning tunneling microscopy to investigate a sub-monolayer of the newly designed imine-based molecular switch NPCI on a Au(111) surface. Its carboxylic termination mediates the formation of hydrogen-bonded dimers, which align in rows along the herringbone reconstruction. We were able to induce reversible conformational changes with the tunneling electrons from the STM tip and determine its efficiency as a function of electron energy.

  20. Participation of Low Molecular Weight Electron Carriers in Oxidative Protein Folding

    Directory of Open Access Journals (Sweden)

    József Mandl

    2009-03-01

    Full Text Available Oxidative protein folding is mediated by a proteinaceous electron relay system, in which the concerted action of protein disulfide isomerase and Ero1 delivers the electrons from thiol groups to the final acceptor. Oxygen appears to be the final oxidant in aerobic living organisms, although the existence of alternative electron acceptors, e.g. fumarate or nitrate, cannot be excluded. Whilst the protein components of the system are well-known, less attention has been turned to the role of low molecular weight electron carriers in the process. The function of ascorbate, tocopherol and vitamin K has been raised recently. In vitro and in vivo evidence suggests that these redox-active compounds can contribute to the functioning of oxidative folding. This review focuses on the participation of small molecular weight redox compounds in oxidative protein folding.

  1. Theory of Photoinduced Phase Transitions in Molecular Conductors: Interplay Between Correlated Electrons, Lattice Phonons and Molecular Vibrations

    Directory of Open Access Journals (Sweden)

    Kenji Yonemitsu

    2012-01-01

    Full Text Available Dynamics of photoinduced phase transitions in molecular conductors are reviewed from the perspective of interplay between correlated electrons and phonons. (1 The charge-transfer complex TTF-CA shows a transition from a neutral paraelectric phase to an ionic ferroelectric phase. Lattice phonons promote this photoinduced transition by preparing short-range lattice dimerization as a precursor. Molecular vibrations stabilize the neutral phase so that the ionic phase, when realized, possesses a large ionicity and the Mott character; (2 The organic salts ?-(BEDT-TTF2RbZn(SCN4 and ?-(BEDT-TTF2I3 show transitions from a charge-ordered insulator to a metal. Lattice phonons make this photoinduced transition hard for the former salt only. Molecular vibrations interfere with intermolecular transfers of correlated electrons at an early stage; (3 The organic salt ?-(d-BEDT-TTF2Cu[N(CN2]Br shows a transition from a Mott insulator to a metal. Lattice phonons modulating intradimer transfer integrals enable photoexcitation-energy-dependent transition pathways through weakening of effective interaction and through introduction of carriers.

  2. Molecular structure and electronic structure of 2-pyridine-carbaldehyde thiosemicarbazone

    Energy Technology Data Exchange (ETDEWEB)

    Biyushkin, V.N.; Chumakov, Yu.M.; Samus' , N.M.; Baka, I.D.

    1987-07-01

    In a continuation of research into the relationship between the molecular structure, electronic structure, and antitumor activity of the thiosemicarbazones of ..cap alpha..-(N)-heterocyclic aldehydes an x-ray crystallographic investigation of 2-pyridinecarbaldehyde thiosemicarbazone monohydrate was undertaken, and the electronic structure of the thiosemicarbazone molecule was calculated by a quantum-chemical method. The compound exhibits clearly defined activity against sarcoma 180.

  3. Calculation of low-energy electron dissociative attachment of molecular hydrogen for plasma applications

    International Nuclear Information System (INIS)

    Calculation of rate constants for dissociative electron attachment to molecular hydrogen is reported. The calculation is based on an improved nonlocal resonance model of Cizek, Horacek and Domcke which takes fully into account the nonlocality of the resonance dynamics and uses potentials with correct asymptotic forms. The rate constants are calculated for all quantum numbers ? and J of the target molecules and for electron temperature in the range 0-30 000 K. (author)

  4. Rate coefficients for low-energy electron dissociative attachment to molecular hydrogen

    International Nuclear Information System (INIS)

    Calculation of rate constants for dissociative electron attachment to molecular hydrogen is reported. The calculation is based on an improved nonlocal resonance model of Cizek, Horacek and Domcke which takes fully into account the nonlocality of the resonance dynamics and uses potentials with correct asymptotic forms. The rate constants are calculated for all quantum numbers v and J of the target molecules and for electron temperature in the range 0-30000 K. (author)

  5. Molecular Electronic Level Alignment at Weakly Coupled Organic Film/Metal Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jin; Feng, Min; Dougherty, Daniel B.; Sun, Hao; Petek, Hrvoje

    2014-10-28

    Electronic level alignment at interfaces of molecular materials with inorganic semiconductors and metals controls many interfacial phenomena. How the intrinsic properties of the interacting systems define the electronic structure of their interface remains one of the most important problems in molecular electronics and nanotechnology that can be solved through a combination of surface science experimental techniques and theoretical modeling. In this article, we address this fundamental problem through experimental and computational studies of molecular electronic level alignment of thin films of C6F6 on noble metal surfaces. The unoccupied electronic structure of C6F6 is characterized with single molecule resolution using low-temperature scanning tunneling microscopy-based constant-current distance-voltage spectroscopy. The experiments are performed on several noble metal surfaces with different work functions and distinct surface-normal projected band structures. In parallel, the electronic structures of the quantum wells (QWs) formed by the lowest unoccupied molecular orbital state of the C6F6 monolayer and multilayer films and their alignment with respect to the vacuum level of the metallic substrates are calculated by solving the Schrödinger equation for a semiempirical one-dimensional (1D) potential of the combined system using input from density functional theory. Our analysis shows that the level alignment for C6F6 molecules bound through weak van der Waals interactions to noble metal surfaces is primarily defined by the image potential of metal, the electron affinity of the molecule, and the molecule surface distance. We expect the same factors to determine the interfacial electronic structure for a broad range of molecule/metal interfaces.

  6. Measurement of molecular motion in organic semiconductors by thermal diffuse electron scattering

    OpenAIRE

    Alexander S. Eggeman; Illig, Steffen; Troisi, Alessandro; Sirringhaus, Henning; Paul A. Midgley

    2013-01-01

    Many of the remarkable electrical and optical properties of organic semiconductors are governed by the interaction of electronic excitations with intra- and intermolecular vibrational modes. However, in specific systems this interaction is not understood in detail at a molecular level and this has been due, at least in part, to the lack of easy-to-use and widely available experimental probes of the structural dynamics. Here we demonstrate that thermal diffuse scattering in electron diffractio...

  7. Cluster molecular orbital description of the electronic structures of mixed-valence iron oxides and silicates

    Science.gov (United States)

    Sherman, David M.

    1986-01-01

    A molecular orbital description, based on spin-unrestricted X??-scattered wave calculations, is given for the electronic structures of mixed valence iron oxides and silicates. The cluster calculations show that electron hopping and optical intervalence charge-transger result from weak FeFe bonding across shared edges of FeO6 coordination polyhedra. In agreement with Zener's double exchange model, FeFe bonding is found to stabilize ferromagnetic coupling between Fe2+ and Fe3+ cations. ?? 1986.

  8. Coupled electron-phonon transport from molecular dynamics with quantum baths

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Wang, J. S.

    2009-01-01

    Based on generalized quantum Langevin equations for the tight-binding wavefunction amplitudes and lattice displacements, electron and phonon quantum transport are obtained exactly using molecular dynamics (MD) in the ballistic regime. The electron-phonon interactions can be handled with a quasi-classical approximation. Both charge and energy transport and their interplay can be studied. We compare the MD results with those of a fully quantum mechanical nonequilibrium Green's function (NEGF) appr...

  9. Study of rectification at the metal-cadmium telluride contact

    International Nuclear Information System (INIS)

    The barrier heights at the contact between metals and N or P type cadmium telluride have been determined. Various surface treatments have been used for the semiconductor: lapping, polishing and etching in a bromine in methanol solution. Depending on these preparation differences of about 0.1 eV have been observed for the barrier height which in any case was no more than 0.9 - 1.0 eV. These results can not be explained by only considering the Schottky theory of rectification

  10. Removal of phenol from wastewaters by extractive rectification

    Energy Technology Data Exchange (ETDEWEB)

    Popov, N.T.

    1984-01-01

    A method is described for removing phenol from wastewaters by steam distillation, followed by extractive rectification of the phenol from the steam. The efficiency of 4 separating agents: tetramethylenesulphone, n-formylmorpholene tetraethyleneglycol and diethyleneglycol was examined. Tests were carried out in continuously operating laboratory columns using a model mixture of water with 4% phenol. Results showed that with a ratio of wastewater to circulating steam of 1:1, it was possible to obtain treated water containing 50% less phenol than in the circulating steam.

  11. Digital image processing for the rectification of television camera distortions.

    Science.gov (United States)

    Rindfleisch, T. C.

    1971-01-01

    All television systems introduce distortions into the imagery they record which influence the results of quantitative photometric and geometric measurements. Digital computer techniques provide a powerful approach to the calibration and rectification of these systematic effects. Nonlinear as well as linear problems can be attacked with flexibility and precision. Methods which have been developed and applied for the removal of structured system noises and the correction of photometric, geometric, and resolution distortions in vidicon systems are briefly described. Examples are given of results derived primarily from the Mariner Mars 1969 television experiment.

  12. Geometric registration and rectification of spaceborne SAR imagery

    Science.gov (United States)

    Curlander, J. C.; Pang, S. N.

    1982-01-01

    This paper describes the development of automated location and geometric rectification techniques for digitally processed synthetic aperture radar (SAR) imagery. A software package has been developed that is capable of determining the absolute location of an image pixel to within 60 m using only the spacecraft ephemeris data and the characteristics of the SAR data collection and processing system. Based on this location capability algorithms have been developed that geometrically rectify the imagery, register it to a common coordinate system and mosaic multiple frames to form extended digital SAR maps. These algorithms have been optimized using parallel processing techniques to minimize the operating time. Test results are given using Seasat SAR data.

  13. Geometrical rectification of spin-scan images from Pioneer 11

    Science.gov (United States)

    Strickland, R. N.; Burke, J. J.

    1980-01-01

    Images of Saturn received from Pioneer 11 suffer from geometrical distortions due to the curvilinear scan lines and the unequal sampling intervals in orthogonal directions, which are inherent in spin-scan imaging. In this paper geometrical image rectification by polynomial transformation based on control points is discussed. Factors that affect the accuracy of reconstruction are shown to include the spatial distribution and spatial density of control points, and the order of the polynomial distortion model. A computer implementation of the technique is described.

  14. Application and rectification of the blowing air measuring system

    International Nuclear Information System (INIS)

    This article introduces application of the blowing air measuring in the Pilot Plant, briefly introduces the rectification of measuring parameters of pulsed extraction column. measuring liquid level of stank which contains two phase medium, the blowing air measuring system of mixer-settler, supervising liquid float, alarm of high level, supervising exinanition signals, measuring liquid level in the hot cells, easily crystallized blowing air system. Through the experience of cold-test and thermal-test, it showed that this measuring method was accuracy and reliable in application, meanwhile maintained conveniently. (authors)

  15. Rectification of nanopores in aprotic solvents - transport properties of nanopores with surface dipoles

    Science.gov (United States)

    Plett, Timothy; Shi, Wenqing; Zeng, Yuhan; Mann, William; Vlassiouk, Ivan; Baker, Lane A.; Siwy, Zuzanna S.

    2015-11-01

    Nanopores have become a model system to understand transport properties at the nanoscale. We report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments.Nanopores have become a model system to understand transport properties at the nanoscale. We report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06340j

  16. Large nonlinear optical rectification in atomic hexagonal layers with broken space inversion symmetry

    International Nuclear Information System (INIS)

    Motivated by possible applications in optoelectronics, we consider nonlinear optical rectification (NOR) in two planar hexagonal lattice structures with broken space inversion symmetry—namely, in graphene epitaxially grown on a SiC substrate and in boronitrene (a monolayer of BN). For both structures, we calculate the second-order nonlinear optical susceptibility ?(2)(0;?, ? ?) relevant to the NOR effect and evaluate a bias voltage V0 appearing at the structure terminals under strong laser irradiation. We show that the reason for the ?(2)(0;?, ? ?) being nonvanishing in the examined structures is their sublattice (inversion) asymmetry combined with the trigonal symmetry of their ?-electron energy bands near the corners of the hexagonal Brillouin zone of those structures. In spite of being rather small, the trigonal warping of the energy bands involved is found to provide a remarkably large magnitude of the NOR susceptibility, reaching the order of 5 × 10?4 esu for the graphene/SiC overlayer system when the pump photon energy ?? approaches the bandgap energy EG (?0.26 eV) of the overlying graphene. For a graphene sample of a few microns length, irradiated by a normally incident laser beam with a relatively moderate power density of 10 kW cm?2, the corresponding optical rectification voltage V0 is estimated to be as large as several millivolts. Moreover, the sign of the voltage (i.e., its polarity) can be sharply reversed by sweeping the photon energy through the inter-?-band resonance condition ?? = EG. This frequency-controlled optical switching, if realized, will be a potent technique for graphene-based photonics and optoelectronics. (paper)

  17. Defect-Engineered Heat Transport in Graphene: A Route to High Efficient Thermal Rectification

    Science.gov (United States)

    Zhao, Weiwei; Wang, Yanlei; Wu, Zhangting; Wang, Wenhui; Bi, Kedong; Liang, Zheng; Yang, Juekuan; Chen, Yunfei; Xu, Zhiping; Ni, Zhenhua

    2015-07-01

    Low-dimensional materials such as graphene provide an ideal platform to probe the correlation between thermal transport and lattice defects, which could be engineered at the molecular level. In this work, we perform molecular dynamics simulations and non-contact optothermal Raman measurements to study this correlation. We find that oxygen plasma treatment could reduce the thermal conductivity of graphene significantly even at extremely low defect concentration (˜83% reduction for ˜0.1% defects), which could be attributed mainly to the creation of carbonyl pair defects. Other types of defects such as hydroxyl, epoxy groups and nano-holes demonstrate much weaker effects on the reduction where the sp2 nature of graphene is better preserved. With the capability of selectively functionalizing graphene, we propose an asymmetric junction between graphene and defective graphene with a high thermal rectification ratio of ˜46%, as demonstrated by our molecular dynamics simulation results. Our findings provide fundamental insights into the physics of thermal transport in defective graphene, and two-dimensional materials in general, which could help on the future design of functional applications such as optothermal and electrothermal devices.

  18. Communication: Electrical rectification of C59N: The role of anchoring and doping sites.

    Science.gov (United States)

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2016-01-14

    Based on the nonequilibrium Green's function formalism and density-functional theory, we investigate the onset of electrical rectification in a single C59N molecule in conjunction with gold electrodes. Our calculations reveal that rectification is dependent upon the anchoring of the Au atom on C59N; when the Au electrode is singly bonded to a C atom (labeled here as A), the system does not exhibit rectification, whereas when the electrode is connected to the C-C bridge site between two hexagonal rings (labeled here as B), transmission asymmetry is observed, where the rectification ratio reaches up to 2.62 at ±1 V depending on the N doping site relative to the anchoring site. Our analysis of the transmission mechanism shows that N doping of the B configuration causes rectification because more transmission channels are available for transmission in the B configuration than in the A configuration. PMID:26772547

  19. Communication: Electrical rectification of C59N: The role of anchoring and doping sites

    Science.gov (United States)

    Tawfik, Sherif Abdulkader; Cui, X. Y.; Ringer, S. P.; Stampfl, C.

    2016-01-01

    Based on the nonequilibrium Green's function formalism and density-functional theory, we investigate the onset of electrical rectification in a single C59N molecule in conjunction with gold electrodes. Our calculations reveal that rectification is dependent upon the anchoring of the Au atom on C59N; when the Au electrode is singly bonded to a C atom (labeled here as A), the system does not exhibit rectification, whereas when the electrode is connected to the C-C bridge site between two hexagonal rings (labeled here as B), transmission asymmetry is observed, where the rectification ratio reaches up to 2.62 at ±1 V depending on the N doping site relative to the anchoring site. Our analysis of the transmission mechanism shows that N doping of the B configuration causes rectification because more transmission channels are available for transmission in the B configuration than in the A configuration.

  20. Study on hydrodynamics and kinetics of cesium and rubidium rectification in filled column

    International Nuclear Information System (INIS)

    Some hydrodynamic and mass exchange characteristics of cesium and rubidium rectification in field column are studied. For the experiments cesium with 2.4-3.2 weight % rubidium, rubidium with 0.3-0.7 % cesium and rubidium with 0.1-0.2 % cesium and 10-12 % potassium admixtures have been taken. The main hydraulic and mass exchange characteristics of the field column during cesium and rubidium rectification are determined. The rectification process of heavy alkaline metals does not have any principal differences from rectification of standard systems at moderate temperatures. During rectification of rubidium with an admixture of cesium the maximum separation degree can be achieved in the pressure range of 100-200 mm Hg

  1. Atomic and molecular photoelectron and Auger-electron-spectroscopy studies using synchrotron radiation

    International Nuclear Information System (INIS)

    Electron spectroscopy, combined with synchrotron radiation, was used to measure the angular distributions of photoelectrons and Auger electrons from atoms and molecules as functions of photon energy. The branching ratios and partial cross sections were also measured in certain cases. By comparison with theoretical calculations, the experimental results are interpreted in terms of the characteristic electronic structure and ionization dynamics of the atomic or molecular sample. The time structure of the synchrotron radiation source was used to record time-of-flight (TOF) spectra of the ejected electrons. The double-angle-TOF method for the measurement of photoelectron angular distributions is discussed. This technique offers the advantages of increased electron collection efficiency and the elimination of certain systematic errors. An electron spectroscopy study of inner-shell photoexcitation and ionization of Xe, photoelectron angular distributions from H2 and D2, and photoionization cross sections and photoelectron asymmetries of the valence orbitals of NO are reported

  2. Interaction of hydrogen molecular ions with thin foils. I. Convoy electrons

    International Nuclear Information System (INIS)

    Doubly differential electron spectra from thin carbon foils (2 to 20 ?g/cm2) bombarded with 0.8 MeV/amu H+, H2+, H3+, and 3He+ ion beams have been measured in the angular range 150 to 300. A predominant group of electrons whose velocities are centered about the ion velocity (convoy electrons) is observed even at these large angles, for thinner foils with molecular ions H2+ and H3+. The yield of convoy electrons for H3+ is always larger than that for H2+ and both yields are strongly dependent on foil thickness. Our results for H2+ and H3+ are consistent with the model that the electron loss process is the dominant mechanism for producing convoy electrons

  3. Electronic structure of a spiropyran derived molecular switch in direct contact with the Au(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Bronner, Christopher; Schulze, Gunnar; Franke, Katharina J.; Pascual, Jose Ignacio; Tegeder, Petra [Freie Universitaet Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin (Germany)

    2011-07-01

    As nanometer scale phenomena advance into the grasp of technological application, the potential building blocks of molecular electronics and sensorics are studied in detail. Surface-bound molecular switches are of particular interest, since the functionality of the substrate/adsorbate system can be switched by an external stimulus. We present combined two-photon photoemission (2PPE) and scanning tunneling spectroscopy (STS) investigations of a nitro-spiropyran derivative's occupied and unoccupied electronic states at the Au(111) surface in both its open and closed form. Both forms exhibit significant differences in the electronic structure which allows following a potential ring-opening/closure reaction. Resonant electron tunneling from the STM tip into the LUMO of the adsorbate molecule induced ring-opening, while the corresponding photon driven process via transfer of electrons from the substrate to the adsorbate turned out to be inefficient. The loss of the molecule's functionality is attributed to a strong electronic coupling between adsorbate and metallic substrate and accordingly to short lifetimes of molecular excited states.

  4. Holstein-Hubbard model approach to electronic conduction through molecular quantum dots

    CERN Document Server

    Walczak, K

    2006-01-01

    Here we study the nonlinear transport properties of a molecular device in which electron-electron and electron-phonon interactions are present. The considered device is composed of vibrating molecular bridge weakly connected to two metallic electrodes. Molecule itself is treated as a quantum dot with discrete energy levels, while its connection to the electrodes is described within the wide-band approximation. Nonperturbative computational scheme, used in this work, is based on the Green's function theory within the framework of mapping technique (GFT-MT). This method transforms the many-body electron-phonon interaction problem into a one-body multi-channel single-electron scattering problem with occupation of particular quasi-levels calculated in a self-consistent way. It is shown that transport in the presence of phonons is mediated via polaron propagation, while the combined effect of electron-electron and electron-phonon coupling is to reduce the current flowing through the device and to induce the negati...

  5. The influence of finite lifetime of electronic states on the vibrational structure of molecular electronic spectra

    International Nuclear Information System (INIS)

    A general theory describing the effect of finite lifetime of electronic states on the vibrational structure of electronic spectra is developed. A proper description of the decay of the excited state involved in the transition is achieved by summing the perturbation series for the T matrix to infinte order in the interaction responsible for the decay. An effective non-hermitian Hamiltonian is obtained which describes the vibrational motion in the short-lived electronic state. The finite lifetime influences the spectra in a different way, depending whether the short-lived state is the final or the initial state of the electronic transition. In the former case the spectrum given by an incoherent superposition of lorentzian lines, while in the latter case there are interferences between the vibrational levels of the short-lived electronic state which modify the vibrational structure in a characteristic manner. The theory is applied to various spectra of CO and N2 involving the excitation of K-shell electrons. (Auth.)

  6. Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

    International Nuclear Information System (INIS)

    We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

  7. Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, Claude

    2009-10-28

    We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

  8. IR-MALDI OF LOW MOLECULAR WEIGHT COMPOUNDS USING A FREE ELECTRON LASER.

    Science.gov (United States)

    Initial experiments on infrared matrix-assisted laser desorption/ionization mass spectrometry (IR-MALDI) using a free electron laser in the analysis of low-molecular-weight compounds are reported. Mass spectra from samples of ethylenediaminetetraacetic acid (EDTA), nitrilotriacet...

  9. Electronic structure and correlations in pristine and potassium doped Cu-Phthalocyanine molecular crystals

    CERN Document Server

    Giovannetti, G; Van den Brink, J; Giovannetti, Gianluca; Brocks, Geert; Brink, Jeroen van den

    2006-01-01

    We investigate the changes in the electronic structure of copper phthalocyanine (CuPc) crystals that is caused by intercalation with potassium. This is done by means of {\\it ab initio} LSDA and LSDA+U calculations of the electronic structure of these molecular crystals. Pristine CuPc is found to be an insulator with local magnetic moments and a Pc-derived valence band with a width of 0.32 eV. In the intercalated compound $\\rm K_2CuPc$ the additional electrons that are introduced by potassium are fully transferred to the $e_g$ states of the Pc-ring. A molecular low spin state results, preserving, however, the local magnetic moment on the copper ions. The degeneracy of the $e_g$ levels is split by a crystal field that quenches the orbital degeneracy and gives rise to a band splitting of 110 meV. Molecular electronic Coulomb interactions enhance this splitting in $\\rm K_2CuPc$ to a charge gap of 1.4 eV. The bandwidth of the conduction band is 0.56 eV, which is surprisingly large for a molecular solid. This is li...

  10. Reduction of the Glauber amplitude for electron impact rotational excitation of quadrupolar molecular ions

    International Nuclear Information System (INIS)

    A reduction of the Glauber amplitude for the rotational excitation of pure quadrupolar molecular ions by electron impact is presented in a form suitable for numerical evaluation. The differential cross-section is expressed in terms of one dimensional integrals over impact parameter. (author)

  11. Influence of the electron-phonon iinteraction on phonon heat conduction in a molecular nanowire

    Directory of Open Access Journals (Sweden)

    Galovi? Slobodanka P.

    2006-01-01

    Full Text Available A model for phonon heat conduction in a molecular nanowire is developed. The calculation takes into account modification of the acoustic phonon dispersion relation due to the electron-phonon interaction. The results obtained are compared with models based upon a simpler, Callaway formula.

  12. Electron-molecular cation reactive collisions: from channel mixing to competitive processes

    International Nuclear Information System (INIS)

    The competition between dissociative recombination, vibrational excitation, and dissociative excitation of molecular cations in electron-impact collisions is discussed within the formalism of the Multichannel Quantum Defect Theory. Illustrative results are given for the HD+/HD and CO+/CO systems.

  13. Molecular dynamics simulations of ions in electron plasmas at strong coupling

    International Nuclear Information System (INIS)

    Molecular dynamic (MD) computer simulations are used to investigate the stopping of heavy ions in strongly coupled electron plasmas. Our results show, that in this regime collisions between the electrons as well as non-linear screening effects yield at low ion velocities a dependence of the stopping power on the ion charge Z which scales like Z1.43 instead of the usual Z2 ln(const/Z)-scaling for weak coupling. This is connected with an enhanced local density of electrons around a highly charged, slow ion. (orig.)

  14. Secondary electron emission from Au by medium energy atomic and molecular ions

    CERN Document Server

    Itoh, A; Obata, F; Hamamoto, Y; Yogo, A

    2002-01-01

    Number distributions of secondary electrons emitted from a Au metal surface have been measured for atomic and molecular ions of H sup + , He sup + , C sup + , N sup + , O sup + , H sup + sub 2 , H sup + sub 3 , HeH sup + , CO sup + and O sup + sub 2 in the energy range 0.3-2.0 MeV. The emission statistics obtained are described fairly well by a Polya function. The Polya parameter b, determining the distribution shape, is found to decrease monotonously with increasing emission yield gamma, revealing a surprising relationship of b gamma approx 1 over the different projectile species and impact energies. This finding supports certainly the electron cascading model. Also we find a strong negative molecular effect for heavier molecular ions, showing a significant reduction of gamma compared to the estimated values using constituent atomic projectile data.

  15. Have we been here before? Inorganic precursors for collective electronic behaviour of molecular crystals

    International Nuclear Information System (INIS)

    The community focused on collective electronic properties of organic and metal-organic molecular crystals sometimes assumes that these are uniquely a consequence of the fact that the lattice is composed of molecular building blocks. However, quantum mechanics has a wider horizon and precursors for some of the phenomena currently occupying our field were observed and investigated a while ago in various inorganic lattices. We recall some of the latter, which serve to highlight what really is unique to the molecular solid state. We also recall a simplified classification scheme to correlate crystal structures and physical properties. Examples from magnetism include one- and two-dimensional ferromagnetism and complex magnetic lattice topologies; from electron transport we mention low-dimensional superconductors incorporating localized magnetic moments

  16. Secondary electron emission from Au by medium energy atomic and molecular ions

    International Nuclear Information System (INIS)

    Number distributions of secondary electrons emitted from a Au metal surface have been measured for atomic and molecular ions of H+, He+, C+, N+, O+, H+2, H+3, HeH+, CO+ and O+2 in the energy range 0.3-2.0 MeV. The emission statistics obtained are described fairly well by a Polya function. The Polya parameter b, determining the distribution shape, is found to decrease monotonously with increasing emission yield ?, revealing a surprising relationship of b??1 over the different projectile species and impact energies. This finding supports certainly the electron cascading model. Also we find a strong negative molecular effect for heavier molecular ions, showing a significant reduction of ? compared to the estimated values using constituent atomic projectile data

  17. Ultrafast Electron Transfer at Organic Semiconductor Interfaces: Importance of Molecular Orientation

    KAUST Repository

    Ayzner, Alexander L.

    2015-01-02

    © 2014 American Chemical Society. Much is known about the rate of photoexcited charge generation in at organic donor/acceptor (D/A) heterojunctions overaged over all relative arrangements. However, there has been very little experimental work investigating how the photoexcited electron transfer (ET) rate depends on the precise relative molecular orientation between D and A in thin solid films. This is the question that we address in this work. We find that the ET rate depends strongly on the relative molecular arrangement: The interface where the model donor compound copper phthalocyanine is oriented face-on with respect to the fullerene C60 acceptor yields a rate that is approximately 4 times faster than that of the edge-on oriented interface. Our results suggest that the D/A electronic coupling is significantly enhanced in the face-on case, which agrees well with theoretical predictions, underscoring the importance of controlling the relative interfacial molecular orientation.

  18. Computer Simulations of Molecular Electronic Devices in Vacuum and in Organic Solvents

    Science.gov (United States)

    Wang, Huachuan

    The main aim of this dissertation is to study the structure and dynamics of molecular electronic devices in vacuum and in solvent environment, with special focus on the mechanical properties and cross-section geometries of the break-junction down to the atomic level. The problem statement relies on how to overcome the limitations of observations from experiments, to interpret and reduce the gap between experiential measurements and theoretical studies. In order to reach this goal, a molecular system involving gold nano-electrodes, organic dithiol molecules and a driving-spring model has been built based on the experimental set-up of the break junction (BJ) technique. This technique can be classified as the mechanical controllable break junction (MCBJ) and scanning tunneling / atomic force microscope break junction (STM/AFM-BJ). We then generated self-assembled monolayers and molecular junctions by combining grand-canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation. These approaches allow us to calibrate the structure and dynamics of molecular junctions under multiple environmental factors simultaneously. In the final stage, conductance calculations are performed using the density functional theory (DFT) in combination with the Green's function techniques. The intermediate molecular junction structures could be used to perform electronic transport calculations to eventually close the force-structure-conductance loop.

  19. Recent Advances in Photoinduced Electron Transfer Processes of Fullerene-Based Molecular Assemblies and Nanocomposites

    Directory of Open Access Journals (Sweden)

    Osamu Ito

    2012-05-01

    Full Text Available Photosensitized electron-transfer processes of fullerenes hybridized with electron donating or other electron accepting molecules have been surveyed in this review on the basis of the recent results reported mainly from our laboratories. Fullerenes act as photo-sensitizing electron acceptors with respect to a wide variety of electron donors; in addition, fullerenes in the ground state also act as good electron acceptors in the presence of light-absorbing electron donors such as porphyrins. With single-wall carbon nanotubes (SWCNTs, the photoexcited fullerenes act as electron acceptor. In the case of triple fullerene/porphyrin/SWCNT architectures, the photoexcited porphyrins act as electron donors toward the fullerene and SWCNT. These mechanisms are rationalized with the molecular orbital considerations performed for these huge supramolecules. For the confirmation of the electron transfer processes, transient absorption methods have been used, in addition to time-resolved fluorescence spectral measurements. The kinetic data obtained in solution are found to be quite useful to predict the efficiencies of photovoltaic cells.

  20. Asymmetry-induced electric current rectification in permselective systems.

    Science.gov (United States)

    Green, Yoav; Edri, Yaron; Yossifon, Gilad

    2015-09-01

    For a symmetric ion permselective system, in terms of geometry and bulk concentrations, the system response is also symmetric under opposite electric field polarity. In this work we derive an analytical solution for the concentration distribution, electric potential, and current-voltage response for a four-layered system comprised of two microchambers connected by two permselective regions of varying properties. It is shown that any additional asymmetry in the system, in terms of the geometry, bulk concentration, or surface charge property of the permselective regions, results in current rectification. Our work is divided into two parts: when both permselective regions have the same surface charge sign and the case of opposite signs. For the same sign case we are able to show that the system behaves as a dialytic battery while accounting for field-focusing effects. For the case of opposite signs (i.e., bipolar membrane), our system exhibits the behavior of a bipolar diode where the magnitude of the rectification can be of order 10^{2}-10^{3}. PMID:26465567

  1. Stereo Calibration and Rectification for Omnidirectional Multi-camera Systems

    Directory of Open Access Journals (Sweden)

    Yanchang Wang

    2012-10-01

    Full Text Available Stereo vision has been studied for decades as a fundamental problem in the field of computer vision. In recent years, computer vision and image processing with a large field of view, especially using omnidirectional vision and panoramic images, has been receiving increasing attention. An important problem for stereo vision is calibration. Although various kinds of calibration methods for omnidirectional cameras are proposed, most of them are limited to calibrate catadioptric cameras or fish?eye cameras and cannot be applied directly to multi?camera systems. In this work, we propose an easy calibration method with closed?form initialization and iterative optimization for omnidirectional multi?camera systems. The method only requires image pairs of the 2D target plane in a few different views. A method based on the spherical camera model is also proposed for rectifying omnidirectional stereo pairs. Using real data captured by Ladybug3, we carry out some experiments, including stereo calibration, rectification and 3D reconstruction. Statistical analyses and comparisons of the experimental results are also presented. As the experimental results show, the calibration results are precise and the effect of rectification is promising.

  2. Rectification effects in superconductors with magnetic pinning centers

    International Nuclear Information System (INIS)

    We investigate the dynamics and pinning properties of vortices in superconducting Al films deposited on top of a close-packed array of Py microsized loops by electrical transport measurements. The micromagnets have an in-plane magnetic moment that can be set in different magnetic states by applying an external field parallel to the plane of the pattern. When the loops are set in the magnetic vortex-state, for which the stray field is the smallest, a weaker pinning in comparison with the polarized states (i.e. strong stray field) is observed. In addition, a clear influence of the chosen magnetic state of the Py rings on the dynamics of the vortex motion under an ac-excitations is obtained. When the magnetic elements are in the as-grown state a rectification signal which reverses sign when the field changes polarity is observed. In contrast to that, when the array of loops is magnetized the observed rectification effect is independent of the field polarity and can be reversed by reorienting the magnetization of the micromagnets

  3. Toward optimizing the electronic structure and properties of large-area molecular junctions

    International Nuclear Information System (INIS)

    Full text: Large area molecular electronic junctions that contain ensembles of >1012 molecules sandwiched between two conducting contacts are complex devices with many possible molecule-contact configurations. Several different types of molecules (e.g., nitroazobenzene, biphenyl, nitrobiphenyl, fluorene) and contacts (e.g., pyrolyzed photo resist films or PPF, C, Au, Ag, Cu) have been employed in the construction of these devices. In these devices, often the molecular layer is covalently bonded to one of the electrodes and physisorbed on the other. Electronic structure modeling is very important for understanding the behaviour of these complex systems. We investigate the covalent bonding of molecules to Au (111), Ag (111), Cu (111), Cu (001), Cu (011), and graphene electrodes, and employ advanced concepts, such as binding energy, bond order, DOS, molecular orbital energy level and spatial distribution, to analyze the efficiency of electronic interaction. The physisorption of molecules to metal surfaces is also explored, e.g. nitrobenzene/Cu system. For calculation of the current-voltage dependence and understanding of electron transport, we intend to employ the tandem of ab initio electronic structure methods and non-equilibrium Green functions technique. (author)

  4. Measuring the Density of a Molecular Cluster Injector via Visible Emission from an Electron Beam

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, D. P.; Kaita, R.; Majeski, R. M.; Stotler, D. P.

    2010-06-28

    A method to measure the density distribution of a dense hydrogen gas jet is pre- sented. A Mach 5.5 nozzle is cooled to 80K to form a flow capable of molecular cluster formation. A 250V, 10mA electron beam collides with the jet and produces H? emission that is viewed by a fast camera. The high density of the jet, several 1016cm-3, results in substantial electron depletion, which attenuates the H? emission. The attenuated emission measurement, combined with a simplified electron-molecule collision model, allows us to determine the molecular density profile via a simple iterative calculation.

  5. Photoelectron and electron momentum spectroscopy of tetrahydrofuran from a molecular dynamical perspective.

    Science.gov (United States)

    Shojaei, S H Reza; Morini, Filippo; Deleuze, Michael S

    2013-03-01

    The results of experimental studies of the valence electronic structure of tetrahydrofuran employing He I photoelectron spectroscopy as well as Electron Momentum Spectroscopy (EMS) have been reinterpreted on the basis of Molecular Dynamical simulations employing the classical MM3 force field and large-scale quantum mechanical simulations employing Born-Oppenheimer Molecular Dynamics in conjunction with the dispersion corrected ?B97XD exchange-correlation functional. Analysis of the produced atomic trajectories demonstrates the importance of thermal deviations from the lowest energy path for pseudorotation, in the form of considerable variations of the ring-puckering amplitude. These deviations are found to have a significant influence on several outer-valence electron momentum distributions, as well as on the He I photoelectron spectrum. PMID:23387306

  6. X-ray diffraction and electron spectroscopy of epitaxial molecular C sub 60 films

    Energy Technology Data Exchange (ETDEWEB)

    Tong, W.M.; Ohlberg, D.A.A.; You, H.K.; Williams, R.S.; Anz, S.J.; Alvarez, M.M.; Whetten, R.L.; Rubin, Y.; Diederich, F.N. (Univ. of California, Los Angeles (United States))

    1991-06-13

    Films of the new carbon allotrope, molecular C{sub 60}, also known as Buckminsterfullerene, have been grown on Si(111) substrates by molecular beam epitaxy. The films have been characterized with X-ray 2{theta} diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and electron energy loss spectroscopy. The diffraction data from oriented films show that close-packed planes of C{sub 60} molecules are stacked parallel to the substrate surface but that the correlation length for X-ray scattering is less than 200 {angstrom}. The electron spectroscopic data show that the C atoms of C{sub 60} are essentially sp{sup 2}-bonded, but there are significant differences with respect to graphite.

  7. Benchmark values for molecular two-electron integrals arising from the Dirac equation.

    Science.gov (United States)

    Ba?c?, A; Hoggan, P E

    2015-02-01

    The two-center two-electron Coulomb and hybrid integrals arising in relativistic and nonrelativistic ab initio calculations on molecules are evaluated. Compact, arbitrarily accurate expressions are obtained. They are expressed through molecular auxiliary functions and evaluated with the numerical Global-adaptive method for arbitrary values of parameters in the noninteger Slater-type orbitals. Highly accurate benchmark values are presented for these integrals. The convergence properties of new molecular auxiliary functions are investigated. The comparison for two-center two-electron integrals is made with results obtained from single center expansions by translation of the wave function to a single center with integer principal quantum numbers and results obtained from the Cuba numerical integration algorithm, respectively. The procedures discussed in this work are capable of yielding highly accurate two-center two-electron integrals for all ranges of orbital parameters. PMID:25768632

  8. VUV diagnostic of electron impact processes in low temperature molecular hydrogen plasma

    CERN Document Server

    Komppula, J

    2015-01-01

    Novel methods for diagnostics of molecular hydrogen plasma processes, such as ionization, production of high vibrational levels, dissociation of molecules via excitation to singlet and triplet states and production of metastable states, are presented for molecular hydrogen plasmas in corona equilibrium. The methods are based on comparison of rate coefficients of plasma processes and optical emission spectroscopy of lowest singlet and triplet transitions, i.e. Lyman-band ($B^1\\Sigma^+_u \\rightarrow X^1\\Sigma^+_g$) and molecular continuum ($a^3\\Sigma^+_g \\rightarrow b^3\\Sigma^+_u$), of the hydrogen molecule in VUV wavelength range. Comparison of rate coefficients of spin-allowed and/or spin-forbidden excitations reduces the uncertainty caused by the non-equilibrium distributions of electron energy and molecular vibrational level, which are typically known poorly in plasma sources. The described methods are applied to estimate the rates of various plasma processes in a filament arc discharge.

  9. Secondary electron emission from solid molecular hydrogen under the bombardment by high-energy charged particles

    International Nuclear Information System (INIS)

    The theory has been developed of secondary electron emission from solid molecular hydrogen occurring under the bombardment by high-energy charged particles. The solution of equation of low-energy secondary electrons transfer to the surface, fitting the needed boundary conditions, is found by the methods of transport linear theory. The expression is obtained for flux density of electrons escaping from the surface of the material. The value of the surface potential barrier is calculated at the environment-vacuum interface. It is shown that the expression for the angular and energy distributions of the electrons which escaped from the target comprises two summands. The first summand corresponds to the particles, multiply scattered on hydrogen molecules, the second one corresponds to electrons, which escaped from the material unscattered

  10. Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies.

    Science.gov (United States)

    Lemmetyinen, Helge; Tkachenko, Nikolai V; Efimov, Alexander; Niemi, Marja

    2011-01-14

    The present paper highlights results of a systematic study of photoinduced electron transfer, where the fundamental aspects of the photochemistry occurring in solutions and in artificially or self-assembled molecular systems are combined and compared. In photochemical electron transfer (ET) reactions in solutions the electron donor, D, and acceptor, A, have to be or to diffuse to a short distance, which requires a high concentration of quencher molecules and/or long lifetimes of the excited donor or acceptor, which cannot always be arranged. The problem can partly be avoided by linking the donor and acceptor moieties covalently by a single bond, molecular chain or chains, or rigid bridge, forming D-A dyads. The covalent combination of porphyrin or phthalocyanine donors with an efficient electron acceptor, e.g. fullerene, has a two-fold effect on the electron transfer properties. Firstly, the electronic systems of the D-A pair result in a formation of an exciplex intermediate upon excitation both in solutions and in solid phases. The formation of the exciplex accelerates the ET rate, which was found to be as fast as >10(12) s(-1). Secondly, the total reorganization energy can be as small as 0.3 eV, even in polar solvents, which allows nanosecond lifetimes for the charge separated (CS) state. Molecular assemblies can form solid heterogeneous, but organized systems, e.g. molecular layers. This results in more complex charge separation and recombination dynamics. A distinct feature of the ET in organized assemblies is intermolecular interactions, which open a possibility for a charge migration both in the acceptor and in the donor layers, after the primary intramolecular exciplex formation and charge separation in the D-A dyad. The intramolecular ET is fast (35 ps) and efficient, but the formed interlayer CS states have lifetimes in microsecond or even second time domain. This is an important result considering possible applications. PMID:21031207

  11. Enhancing rectification of a nano-swimmer system by multi-layered asymmetric barriers.

    Science.gov (United States)

    Chen, Yen-Fu; Xiao, Song; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2015-10-21

    The rectification of nano-swimmers in two chambers separated by a strip of funnel gates is explored by dissipative particle dynamics simulations. According to the trajectories of active colloids across the funnel zone, two rectification mechanisms are identified: geometry-assisted diffusion and trap-hindered diffusion. In general, geometry-assisted diffusion dominates at a small active force (Fa) and run time (?) while trap-hindered diffusion governs at a large Fa and ?. The rectification ratio is affected by the funnel shape and various geometries are considered: open/closed triangular, circular and rectangular funnels. The rectification ratio of open funnels is always greater than that of closed funnels. Moreover, the open circular funnel has the best performance while the triangular one has the worst. Rectification can be enhanced as the number of funnel layers is increased. It is found that the rectification ratio of self-propelled colloids can be dramatically augmented by triple-layered funnels to be as high as 30. Our simulation study offers an efficient approach for rectification enhancement. PMID:26394906

  12. Thermal rectification in a polymer-functionalized single-wall carbon nanotube

    International Nuclear Information System (INIS)

    Thermal rectification occurs when heat current through a material is favored in one direction but not in the opposite direction. These materials, often called thermal diodes, have the potential to perform logic calculations with phonons. Rectification obtained with existing material systems is either too minor or too difficult to implement practically. Hence, we present a scheme to enable higher rectification using a single-wall carbon nanotube (SWCNT) that is covalently functionalized near one end with polyacetylene (PA) chains. This composite structure allows rectification R up to 204%, which is higher than the values reported for SWCNTs. Here, R=((J+?J?)/J?)100%, where J+ and J? are the heat currents for forward and reverse bias, respectively. The interatomic interactions in the SWCNT-PA nanocomposite are nonlinear, i.e., they are anharmonic, which is a requirement for thermal rectification. Through atomistic simulations, we identify two additional conditions to accomplish thermal rectification at the nanoscale, namely, (1) structural asymmetry, and (2) that the influence of this asymmetry on thermal transport is temperature dependent. The optimum temperature difference to achieve the highest thermal rectification with the structure is 40–80 K. (paper)

  13. The nonlinear optical rectification of a confined exciton in a quantum dot

    International Nuclear Information System (INIS)

    An exciton in a disc-like quantum dot (QD) with the parabolic confinement, under applied electric field, is studied within the framework of the effective-mass approximation. The nonlinear optical rectification between the ground and the first-excited states has been examined through the computed energies and wave functions in details for the excitons. The results show that the optical rectification susceptibility obtained in a disc-like QD reach the magnitude of 10-2 m/V, which is 3-4 orders of magnitude higher than in one-dimensional QDs. It is found that the second-order nonlinear optical properties of exciton states in a QD are strongly affected by the confinement strength and the electric field. - Research highlights: ? The magnitude of the nonlinear optical rectification of the excitons confined in a disc-like quantum dot may reach 10-2 m/V. It is much higher than that of the other low-dimensional semiconductors, e.g., quantum wells, and one-dimensional semiparabolic quantum dots. ? The nonlinear optical rectification of the excitons confined in a disc-like quantum dot is strongly dependent on the confinement frequency. In order to obtain the larger optical rectification coefficients in quantum dots, we can change the confinement frequency. ? The calculated results also reveal that an applied electric field has a great influence on the nonlinear optical rectification susceptibility. In order to obtain the larger optical rectification coefficients in quantum dots we can induce the electric field.

  14. Enhancing rectification of a nano-swimmer system by multi-layered asymmetric barriers

    Science.gov (United States)

    Chen, Yen-Fu; Xiao, Song; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2015-10-01

    The rectification of nano-swimmers in two chambers separated by a strip of funnel gates is explored by dissipative particle dynamics simulations. According to the trajectories of active colloids across the funnel zone, two rectification mechanisms are identified: geometry-assisted diffusion and trap-hindered diffusion. In general, geometry-assisted diffusion dominates at a small active force (Fa) and run time (?) while trap-hindered diffusion governs at a large Fa and ?. The rectification ratio is affected by the funnel shape and various geometries are considered: open/closed triangular, circular and rectangular funnels. The rectification ratio of open funnels is always greater than that of closed funnels. Moreover, the open circular funnel has the best performance while the triangular one has the worst. Rectification can be enhanced as the number of funnel layers is increased. It is found that the rectification ratio of self-propelled colloids can be dramatically augmented by triple-layered funnels to be as high as 30. Our simulation study offers an efficient approach for rectification enhancement.

  15. Investigation of Terminal Group Effect on Electron Transport Through Open Molecular Structures

    International Nuclear Information System (INIS)

    The effect of terminal groups on the electron transport through metal-molecule-metal system has been investigated using nonequilibrium Green's function (NEGF) formalism combined with extended Huckel theory (EHT). Au-molecule-Au junctions are constructed with borazine and BCN unit structure as core molecule and sulphur (S), oxygen (O), selenium (Se) and cyano-group (CN) as terminal groups. The electron transport characteristics of the borazine and BCN molecular systems are analyzed through the transmission spectra and the current-voltage curve. The results demonstrate that the terminal groups modifying the transport behaviors of these systems in a controlled way. Our result shows that, selenium is the best linker to couple borazine to Au electrode and oxygen is the best one to couple BCN to Au electrode. Furthermore, the results of borazine systems are compared with that of BCN molecular systems and are discussed. Simulation results show that the conductance through BCN molecular systems is four times larger than the borazine molecular systems. Negative differential resistance behavior is observed with borazine-CN system and the saturation feature appears in BCN systems. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Well-ordered monolayers of alkali-doped coronene and picene: Molecular arrangements and electronic structures

    Energy Technology Data Exchange (ETDEWEB)

    Yano, M.; Endo, M.; Hasegawa, Y.; Okada, R.; Yamada, Y., E-mail: yamada@bk.tsukuba.ac.jp; Sasaki, M. [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)

    2014-07-21

    Adsorptions of alkali metals (such as K and Li) on monolayers of coronene and picene realize the formation of ordered phases, which serve as well-defined model systems for metal-intercalated aromatic superconductors. Upon alkali-doping of the monolayers of coronene and picene, scanning tunneling microscopy and X-ray absorption spectroscopy revealed the rearrangement of the entire molecular layer. The K-induced reconstruction of both monolayers resulted in the formation of a structure with a herringbone-like arrangement of molecules, suggesting the intercalation of alkali metals between molecular planes. Upon reconstruction, a shift in both the vacuum level and core levels of coronene was observed as a result of a charge transfer from alkali metals to coronene. In addition, a new density of states near the Fermi level was formed in both the doped coronene and the doped picene monolayers. This characteristic electronic feature of the ordered monolayer has been also reported in the multilayer picene films, ensuring that the present monolayer can model the properties of the metal-intercalated aromatic hydrocarbons. It is suggested that the electronic structure near the Fermi level is sensitive to the molecular arrangement, and that both the strict control and determinations of the molecular structure in the doped phase should be important for the determination of the electronic structure of these materials.

  17. Well-ordered monolayers of alkali-doped coronene and picene: Molecular arrangements and electronic structures

    International Nuclear Information System (INIS)

    Adsorptions of alkali metals (such as K and Li) on monolayers of coronene and picene realize the formation of ordered phases, which serve as well-defined model systems for metal-intercalated aromatic superconductors. Upon alkali-doping of the monolayers of coronene and picene, scanning tunneling microscopy and X-ray absorption spectroscopy revealed the rearrangement of the entire molecular layer. The K-induced reconstruction of both monolayers resulted in the formation of a structure with a herringbone-like arrangement of molecules, suggesting the intercalation of alkali metals between molecular planes. Upon reconstruction, a shift in both the vacuum level and core levels of coronene was observed as a result of a charge transfer from alkali metals to coronene. In addition, a new density of states near the Fermi level was formed in both the doped coronene and the doped picene monolayers. This characteristic electronic feature of the ordered monolayer has been also reported in the multilayer picene films, ensuring that the present monolayer can model the properties of the metal-intercalated aromatic hydrocarbons. It is suggested that the electronic structure near the Fermi level is sensitive to the molecular arrangement, and that both the strict control and determinations of the molecular structure in the doped phase should be important for the determination of the electronic structure of these materials

  18. Tuning electron transport through a single molecular junction by bridge modification

    International Nuclear Information System (INIS)

    The possibility of controlling electron transport in a single molecular junction represents the ultimate goal of molecular electronics. Here, we report that the modification of bridging group makes it possible to improve the performance and obtain new functions in a single cross-conjugated molecular junction, designed from a recently synthesized bipolar molecule bithiophene naphthalene diimide. Our first principles results show that the bipolar characteristic remains after the molecule was modified and sandwiched between two metal electrodes. Rectifying is the intrinsic characteristic of the molecular junction and its performance can be enhanced by replacing the saturated bridging group with an unsaturated group. A further improvement of the rectifying and a robust negative differential resistance (NDR) behavior can be achieved by the modification of unsaturated bridge. It is revealed that the modification can induce a deviation angle about 4° between the donor and the acceptor π-conjugations, making it possible to enhance the communication between the two π systems. Meanwhile, the low energy frontier orbitals of the junction can move close to the Fermi level and encounter in energy at certain biases, thus a transport channel with a considerable transmission can be formed near the Fermi level only at a narrow bias regime, resulting in the improvement of rectifying and the robust NDR behavior. This finding could be useful for the design of single molecular devices.

  19. Modelling the effect of structure and base sequence on DNA molecular electronics

    International Nuclear Information System (INIS)

    DNA is a material that has the potential to be used in nanoelectronic devices as an active component. However, the electronic properties of DNA responsible for its conducting behaviour remain controversial. Here we use a self-consistent quantum molecular dynamics method to study the effect of DNA structure and base sequence on the energy involved when electrons are added or removed from isolated molecules and the transfer of the injected charge along the molecular axis when an electric field is applied. Our results show that the addition or removal of an electron from DNA molecules is most exothermic for poly(dC)-poly(dG) in its B-form and poly(dA)-poly(dT) in its A-form, and least exothermic in its Z-form. Additionally, when an electric field is applied to a charged DNA molecule along its axis, there is electron transfer through the molecule, regardless of the number and sign of the injected charge, the molecular structure and the base sequence. Results from these simulations provide useful information that is hard to obtain from experiments and needs to be considered for further modelling aiming to improve charge transport efficiency in nanoelectronic devices based on DNA

  20. Unexpectedly high pressure for molecular dissociation in liquid hydrogen by a reliable electronic simulation

    CERN Document Server

    Mazzola, Guglielmo; Sorella, Sandro

    2014-01-01

    The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular dynamics based on the quantum Monte Carlo method, which can describe accurately the electronic correlation and treat a large number of hydrogen atoms, allowing a realistic and reliable prediction of thermodynamic roperties. We find that the molecular liquid phase is unexpectedly stable and the transition towards a fully atomic liquid phase occurs at much higher pressure than previously believed. The old standing problem of low temperature atomization is, therefore, still far from experimental reach.