First-Principles Lattice Dynamics Method for Strongly Anharmonic Crystals
Tadano, Terumasa; Tsuneyuki, Shinji
2018-04-01
We review our recent development of a first-principles lattice dynamics method that can treat anharmonic effects nonperturbatively. The method is based on the self-consistent phonon theory, and temperature-dependent phonon frequencies can be calculated efficiently by incorporating recent numerical techniques to estimate anharmonic force constants. The validity of our approach is demonstrated through applications to cubic strontium titanate, where overall good agreement with experimental data is obtained for phonon frequencies and lattice thermal conductivity. We also show the feasibility of highly accurate calculations based on a hybrid exchange-correlation functional within the present framework. Our method provides a new way of studying lattice dynamics in severely anharmonic materials where the standard harmonic approximation and the perturbative approach break down.
Heat transport in an anharmonic crystal
Acharya, Shiladitya; Mukherjee, Krishnendu
2018-04-01
We study transport of heat in an ordered, anharmonic crystal in the form of slab geometry in three dimensions. Apart from attaching baths of Langevin type to two extreme surfaces, we also attach baths of same type to the intermediate surfaces of the slab. Since the crystal is uninsulated, it exchanges energy with the intermediate heat baths. We find that both Fourier’s law of heat conduction and the Newton’s law of cooling hold to leading order in anharmonic coupling. The leading behavior of the temperature profile is exponentially falling from high to low temperature surface of the slab. As the anharmonicity increases, profiles fall more below the harmonic one in the log plot. In the thermodynamic limit thermal conductivity remains independent of the environment temperature and its leading order anharmonic contribution is linearly proportional to the temperature change between the two extreme surfaces of the slab. A fast crossover from one-dimensional (1D) to three-dimensional (3D) behavior of the thermal conductivity is observed in the system.
Scattering of Neutrons by an Anharmonic Crystal
Energy Technology Data Exchange (ETDEWEB)
Hoegberg, T; Bohlin, L; Ebbsjoe, I
1967-04-15
Numerical calculations have been performed for the anharmonic effects in neutron scattering. The phonon frequency widths and shifts have been calculated as a function of neutron frequency at different wave numbers and temperatures for a potential with central symmetry and for a face-centered cubic lattice.
Computer Program for Inelastic Neutron Scattering by an Anharmonic Crystal
International Nuclear Information System (INIS)
Bohlin, L.; Ebbsjoe, I.; Hoegberg, T.
1969-02-01
A description is given of the program SAW (Shift and Width), which calculates the energy-dependent shift and width of the intensity peaks obtained for thermal neutrons scattered inelastically by an anharmonic crystal. The program has been coded in FORTRAN IV and may be applied to every solid with a monatomic face-centered cubic lattice where the intermolecular interactions can be described by a centro-symmetrical potential. Interactions beyond third neighbours are neglected
Computer Program for Inelastic Neutron Scattering by an Anharmonic Crystal
Energy Technology Data Exchange (ETDEWEB)
Bohlin, L; Ebbsjoe, I; Hoegberg, T
1969-02-15
A description is given of the program SAW (Shift and Width), which calculates the energy-dependent shift and width of the intensity peaks obtained for thermal neutrons scattered inelastically by an anharmonic crystal. The program has been coded in FORTRAN IV and may be applied to every solid with a monatomic face-centered cubic lattice where the intermolecular interactions can be described by a centro-symmetrical potential. Interactions beyond third neighbours are neglected.
Jacobian elliptic wave solutions in an anharmonic molecular crystal model
International Nuclear Information System (INIS)
Teh, C.G.R.; Lee, B.S.; Koo, W.K.
1997-07-01
Explicit Jacobian elliptic wave solutions are found in the anharmonic molecular crystal model for both the continuum limit and discrete modes. This class of wave solutions include the famous pulse-like and kink-like solitary modes. We would also like to report on the existence of some highly discrete staggered solitary wave modes not found in the continuum limit. (author). 9 refs, 1 fig
Anharmonicity and hydrogen bonding in electrooptic sucrose crystal
Szostak, M. M.; Giermańska, J.
1990-03-01
The polarized absorption spectra of the sucrose crystal in the 5300 - 7300 cm -1 region have been measured. The assignments of all the eight OH stretching overtones are proposed and their mechanical anharmonicities are estimated. The discrepancies from the oriented gas model (OGM) in the observed relative band intensities, especially of the -CH vibrations, are assumed to be connected with vibronic couplings enhanced by the helical arrangement of molecules joined by hydrogen bondings. It seems that this kind of interactions might be important for the second harmonic generation (SHG) by the sucrose crystal.
Cuscó, Ramon; Artús, Luis; Edgar, James H.; Liu, Song; Cassabois, Guillaume; Gil, Bernard
2018-04-01
Hexagonal boron nitride (h -BN) is a layered crystal that is attracting a great deal of attention as a promising material for nanophotonic applications. The strong optical anisotropy of this crystal is key to exploit polaritonic modes for manipulating light-matter interactions in 2D materials. h -BN has also great potential for solid-state neutron detection and neutron imaging devices, given the exceptionally high thermal neutron capture cross section of the boron-10 isotope. A good knowledge of phonons in layered crystals is essential for harnessing long-lived phonon-polariton modes for nanophotonic applications and may prove valuable for developing solid-state 10BN neutron detectors with improved device architectures and higher detection efficiencies. Although phonons in graphene and isoelectronic materials with a similar hexagonal layer structure have been studied, the effect of isotopic substitution on the phonons of such lamellar compounds has not been addressed yet. Here we present a Raman scattering study of the in-plane high-energy Raman active mode on isotopically enriched single-crystal h -BN. Phonon frequency and lifetime are measured in the 80-600-K temperature range for 10B-enriched, 11B-enriched, and natural composition high quality crystals. Their temperature dependence is explained in the light of perturbation theory calculations of the phonon self-energy. The effects of crystal anisotropy, isotopic disorder, and anharmonic phonon-decay channels are investigated in detail. The isotopic-induced changes in the phonon density of states are shown to enhance three-phonon anharmonic decay channels in 10B-enriched crystals, opening the possibility of isotope tuning of the anharmonic phonon decay processes.
Bizarre behavior of heat capacity in crystals due to interplay between two types of anharmonicities.
Yurchenko, Stanislav O; Komarov, Kirill A; Kryuchkov, Nikita P; Zaytsev, Kirill I; Brazhkin, Vadim V
2018-04-07
The heat capacity of classical crystals is determined by the Dulong-Petit value C V ≃ D (where D is the spatial dimension) for softly interacting particles and has the gas-like value C V ≃ D/2 in the hard-sphere limit, while deviations are governed by the effects of anharmonicity. Soft- and hard-sphere interactions, which are associated with the enthalpy and entropy of crystals, are specifically anharmonic owing to violation of a linear relation between particle displacements and corresponding restoring forces. Here, we show that the interplay between these two types of anharmonicities unexpectedly induces two possible types of heat capacity anomalies. We studied thermodynamics, pair correlations, and collective excitations in 2D and 3D crystals of particles with a limited range of soft repulsions to prove the effect of interplay between the enthalpy and entropy types of anharmonicities. The observed anomalies are triggered by the density of the crystal, changing the interaction regime in the zero-temperature limit, and can provide about 10% excess of the heat capacity above the Dulong-Petit value. Our results facilitate understanding effects of complex anharmonicity in molecular and complex crystals and demonstrate the possibility of new effects due to the interplay between different types of anharmonicities.
Crystal anharmonicity in Li(H,D) and Na(H,D) systems
International Nuclear Information System (INIS)
Islam, A.K.M.A.; Haque, E.; Azad, A.S.
1993-05-01
The reliability of our recently developed potential model is tested by extending the study to various anharmonic properties, e.g., third order elastic constants, fourth order elastic constants, Grueneisen parameters, and the pressure derivatives of second order elastic constants of hydrides and deuterides of lithium and sodium. A comparison of the calculated properties with the available experimental results and other theoretical estimates shows the validity and reliability of the derived potential in the study of crystal anharmonicities also. (author). 43 refs, 2 figs, 4 tabs
Neutron scattering by anharmonic crystals and the effect of sublattice displacements
International Nuclear Information System (INIS)
Viswanathan, K.S.; Phillip, Jacob
1979-01-01
A theory has been described for the scattering of neutrons by anharmonic crystals, for which terms of the type Vsup(3) (k 1 j 1 ;-k 1 j 1 ;aj) which contribute to the sublattice displacements are not neglected. It is shown that the sublattice displacements will modify the phase factor arising from the scattering by any atom in the unit cell, and the Debye-Waller factor also gets altered both by the sublattice displacements as well as by higher order terms arising from anharmonicity. (author)
Thermal behaviour of the Debye-Waller factor and the specific heat of anharmonic crystals
International Nuclear Information System (INIS)
Lima, R.A.T. de; Tsallis, C.
1979-08-01
The influence of the cubic and quartic crystalline anharmonicity on the classical and quantum thermal behaviour of the specific heat, Debye temperaturetheta, Debye-Waller factor W, crystalline expansion and phonon spectrum is studied, within the framework of the Variational Method in Statistical Mechanics. The sistems, mainly focalized are the single oscillator, the mono-atomic linear chain and simple cubic crystal. The trial Hamiltonian is an harmonic one, therefore the various anharmonic influences are mainly absorbed into the renormalization of theta(T). Several differences between the classical and quantum results are exhibited. Satisfactory qualitative agreement with experience was obtained in the low-temperature regime, in particular in what concerns the existence of a minimum in theta(T) which has been observed in Cu, Al, Ag, Au and Pb. For the intermediate-temperature regime the customary linear behaviour of W(T) (hence theta(T) almost constant) is reobtained. Finally in the high-temperature regime, the present treatment leads to a √T - dependence for the W-factor, which implies in the wrong curvature with respect to experimental data. A possible explanation of this disagreement might be related to the melting phenomenon, which is not covered by the present theory. (Author) [pt
International Nuclear Information System (INIS)
Audzijonis, A.; Zigas, L.; Vinokurova, I.V.; Farberovic, O.V.; Zaltauskas, R.; Cijauskas, E.; Pauliukas, A.; Kvedaravicius, A.
2006-01-01
The force constants of SbSI crystal have been calculated by the pseudo-potential method. The frequencies and normal coordinates of SbSI vibration modes along the c (z) direction have been determined in harmonic approximation. The potential energies of SbSI normal modes dependence on normal coordinates along the c (z) direction V(z) have been determined in anharmonic approximation, taking into account the interaction between the phonons. It has been found, that in the range of 30-120 cm -1 , the vibrational spectrum is determined by a V(z) double-well normal mode, but in the range of 120-350 cm -1 , it is determined by a V(z) single-well normal mode
Wang, Wei; Sun, Jiafa; Li, Bin; He, Junqi
2017-09-01
First-principles pseudopotential calculations on phonon and electronic properties of β -pyrochlore superconductor KOs2O6 are performed. The imaginary soft-phonon modes with a special double-well potential for the lowest Eu(1) mode and the second lowest T1u(1) mode are reported, which indicates the dynamical instability in KOs2O6. However, the double wells are too small to induce a structural phase transformation in KOs2O6. The strong anharmonicity especially for K T2g(1) phonon mode is got, which is approved to be from the strong electron-phonon coupling that supports the superconductivity in KOs2O6.
Two-qubit gate operations in superconducting circuits with strong coupling and weak anharmonicity
International Nuclear Information System (INIS)
Lü Xinyou; Ashhab, S; Cui Wei; Wu Rebing; Nori, Franco
2012-01-01
We theoretically study the implementation of two-qubit gates in a system of two coupled superconducting qubits. In particular, we analyze two-qubit gate operations under the condition that the coupling strength is comparable with or even larger than the anharmonicity of the qubits. By numerically solving the time-dependent Schrödinger equation under the assumption of negligible decoherence, we obtain the dependence of the two-qubit gate fidelity on the system parameters in the case of both direct and indirect qubit-qubit coupling. Our numerical results can be used to identify the ‘safe’ parameter regime for experimentally implementing two-qubit gates with high fidelity in these systems. (paper)
Energy Technology Data Exchange (ETDEWEB)
Van Hung, Nguyen, E-mail: hungnv@vnu.edu.vn [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Hue, Trinh Thi [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Khoa, Ha Dang [School of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi (Viet Nam); Vuong, Dinh Quoc [Quang Ninh Education & Training Department, Nguyen Van Cu, Ha Long, Quang Ninh (Viet Nam)
2016-12-15
High-order expanded interatomic effective potential and Debye-Waller factors (DWFs) for local vibrational amplitudes in X-ray absorption fine structure (XAFS) of bcc crystals have been studied based on the anharmonic correlated Debye model. DWFs are presented in terms of cumulant expansion up to the fourth order and the many-body effects are taken into account in the present one-dimensional model based on the first shell near neighbor contribution approach used in the derivations of the anharmonic effective potential and XAFS cumulants where Morse potential is assumed to describe the single-pair atomic interaction. Analytical expressions for the dispersion relation, correlated Debye frequency and temperature and four first temperature-dependent XAFS cumulants have been derived based on the many-body perturbation approach. Thermodynamic properties and anharmonic effects in XAFS of bcc crystals described by the obtained cumulants have been in detail discussed. The advantage and efficiency of the present theory are illustrated by good agreement of the numerical results for Mo, Fe and W with experiment.
Strong anharmonicity in the phonon spectra of PbTe and SnTe from first principles
Ribeiro, Guilherme A. S.; Paulatto, Lorenzo; Bianco, Raffaello; Errea, Ion; Mauri, Francesco; Calandra, Matteo
2018-01-01
At room temperature, PbTe and SnTe are efficient thermoelectrics with a cubic structure. At low temperature, SnTe undergoes a ferroelectric transition with a critical temperature strongly dependent on the hole concentration, while PbTe is an incipient ferroelectric. By using the stochastic self-consistent harmonic approximation, we investigate the anharmonic phonon spectra and the occurrence of a ferroelectric transition in both systems. We find that vibrational spectra strongly depend on the approximation used for the exchange-correlation kernel in density-functional theory. If gradient corrections and the theoretical volume are employed, then the calculation of the phonon frequencies as obtained from the diagonalization of the free-energy Hessian leads to phonon spectra in good agreement with experimental data for both systems. In PbTe we evaluate the linear thermal expansion coefficient γ =2.3 ×10-5K-1 , finding it to be in good agreement with experimental value of γ =2.04 ×10-5K-1 . Furthermore, we study the phonon spectrum and we do reproduce the transverse optical mode phonon satellite detected in inelastic neutron scattering and the crossing between the transverse optical and the longitudinal acoustic modes along the Γ X direction. The phonon satellite becomes broader at high temperatures but its energy is essentially temperature independent, in agreement with experiments. We decompose the self-consistent harmonic free energy in second-, third-, and fourth-order anharmonic terms. We find that the third- and fourth-order terms are small. However, treating the third-order term perturbatively on top of the second-order self-consistent harmonic free energy overestimates the energy of the satellite associated with the transverse optical mode. On the contrary, a perturbative treatment on top of the harmonic Hamiltonian breaks down and leads to imaginary phonon frequencies already at 300 K. In the case of SnTe, we describe the occurrence of a ferroelectric
Small Fermi energy, strong electron-phonon effects and anharmonicity in MgB2
International Nuclear Information System (INIS)
Cappelluti, E.; Pietronero, L.
2007-01-01
The investigation of the electron-phonon properties in MgB 2 has attracted a huge interest after the discovery of superconductivity with T c 39 K in this compound. Although superconductivity is often described in terms of the conventional Eliashberg theory, properly generalized in the multiband/multigap scenario, important features distinguish MgB 2 from other conventional strong-coupling superconductors. Most important it is the fact that a large part of the total electron-phonon strength seems to be concentrated here in only one phonon mode, the boron-boron E 2g stretching mode. Another interesting property is the small Fermi energy of the σ bands, which are strongly coupled with the E 2g mode. In this contribution, we discuss how the coexistence of both these features give rise to an unconventional phenomenology of the electron-phonon properties
Manipulating light with strongly modulated photonic crystals
International Nuclear Information System (INIS)
Notomi, Masaya
2010-01-01
Recently, strongly modulated photonic crystals, fabricated by the state-of-the-art semiconductor nanofabrication process, have realized various novel optical properties. This paper describes the way in which they differ from other optical media, and clarifies what they can do. In particular, three important issues are considered: light confinement, frequency dispersion and spatial dispersion. First, I describe the latest status and impact of ultra-strong light confinement in a wavelength-cubic volume achieved in photonic crystals. Second, the extreme reduction in the speed of light is reported, which was achieved as a result of frequency dispersion management. Third, strange negative refraction in photonic crystals is introduced, which results from their unique spatial dispersion, and it is clarified how this leads to perfect imaging. The last two sections are devoted to applications of these novel properties. First, I report the fact that strong light confinement and huge light-matter interaction enhancement make strongly modulated photonic crystals promising for on-chip all-optical processing, and present several examples including all-optical switches/memories and optical logics. As a second application, it is shown that the strong light confinement and slow light in strongly modulated photonic crystals enable the adiabatic tuning of light, which leads to various novel ways of controlling light, such as adiabatic frequency conversion, efficient optomechanics systems, photon memories and photons pinning.
Anharmonicity in nuclear wobbling motion
International Nuclear Information System (INIS)
Oi, M.
2007-01-01
An unexpected strong anharmonicity was observed in the wobbling spectrum in 163 Lu. In an attempt to understand what causes the deviation from the original wobbling model by Bohr and Mottelson, an analysis is presented using several different approaches, such as exact diagonalization, a semiclassical model to deal with anharmonic wobbling motion, and a microscopic method based on the self-consistent cranking calculation
Strong crystal size effect on deformation twinning
DEFF Research Database (Denmark)
Yu, Qian; Shan, Zhi-Wei; Li, Ju
2010-01-01
plasticity. Accompanying the transition in deformation mechanism, the maximum flow stress of the submicrometre-sized pillars was observed to saturate at a value close to titanium’s ideal strength9, 10. We develop a ‘stimulated slip’ model to explain the strong size dependence of deformation twinning......Deformation twinning1, 2, 3, 4, 5, 6 in crystals is a highly coherent inelastic shearing process that controls the mechanical behaviour of many materials, but its origin and spatio-temporal features are shrouded in mystery. Using micro-compression and in situ nano-compression experiments, here we...... find that the stress required for deformation twinning increases drastically with decreasing sample size of a titanium alloy single crystal7, 8, until the sample size is reduced to one micrometre, below which the deformation twinning is entirely replaced by less correlated, ordinary dislocation...
Energy Technology Data Exchange (ETDEWEB)
Palto, S. P., E-mail: palto@online.ru; Barnik, M I; Blinov, L M; Umanskii, B. A., E-mail: umanskii@yahoo.com; Shtykov, N M [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
2010-09-15
Polarization, spectral, and relaxation features of a new electrooptical effect in oriented layers of chiral nematic liquid crystals (LCs) are considered. The physics behind this electrooptical effect is the induction of higher order spatial harmonics in the helical distribution of the director field, which ensures the high speed of electrooptical response. It is shown that the spectral properties of the electrooptical response can be effectively controlled by varying the optical anisotropy of the LC and the pitch of the helical structure.
Strong dielectric liquid crystal polymer (Part 3)
Energy Technology Data Exchange (ETDEWEB)
Kurata, Hideaki; Shibasaki, Akira
1988-11-01
Influence of change of molecular parameters on liquid crystal condition is studied to get the correlation between molecular structure of liquid crystal and phase structure or visco-elastic properties. Eight kinds of biphenyl type liquid crystals with polyacrilate main chain and triphenyl type liquid crystals were used as samples. Followings were found by a ploarizing microscope and X-ray diffraction: Phases are transferred from isotropic phase S/sub A/ phase S/sup *//sub C/ phase S/sub 1/ phase to solid on temperature desending sequence. Degree of polymerization changes only these transfer point but spacer length affects not only transfer points and layer distance but also liquid crystal structure itself. Visco-elasticity of isotropic phase shows Newtonian viscosity and is affected by the main chain length. Macroscopic and microscopic structures influence on viscoelasticity in S/sub A/ phase and S/sup *//sub C/ phase. Two rapid rises of viscoelasticity are found in low molecular weight liquid crystal when S/sub A/ transfer and S/sub A/ to S/sup *//sub C/ transfer occur by temperature desending from the isotropic phase. Viscoelastic behavior is contributed by the properties of domain itself and interaction between domains, and the interaction is changed by polymerization. 6 references, 13 figures, 1 table.
International Nuclear Information System (INIS)
Li, Liang; Wölfel, Alexander; Schönleber, Andreas; Mondal, Swastik; Schreurs, Antoine M. M.; Kroon-Batenburg, Loes M. J.; Smaalen, Sander van
2011-01-01
The superspace maximum entropy method (MEM) density in combination with structure refinements has been used to uncover the modulation in incommensurate Rb 2 ZnCl 4 close to the lock-in transition. Modulated atomic displacement parameters (ADPs) and modulated anharmonic ADPs are found to form an intrinsic part of the modulation. Refined values for the displacement modulation function depend on the presence or absence of modulated ADPs in the model. A combination of structure refinements, analysis of the superspace MEM density and interpretation of difference-Fourier maps has been used to characterize the incommensurate modulation of rubidium tetrachlorozincate, Rb 2 ZnCl 4 , at a temperature of T = 196 K, close to the lock-in transition at T lock-in = 192 K. The modulation is found to consist of a combination of displacement modulation functions, modulated atomic displacement parameters (ADPs) and modulated third-order anharmonic ADPs. Up to fifth-order Fourier coefficients could be refined against diffraction data containing up to fifth-order satellite reflections. The center-of-charge of the atomic basins of the MEM density and the displacive modulation functions of the structure model provide equivalent descriptions of the displacive modulation. Modulations of the ADPs and anharmonic ADPs are visible in the MEM density, but extracting quantitative information about these modulations appears to be difficult. In the structure refinements the modulation parameters of the ADPs form a dependent set, and ad hoc restrictions had to be introduced in the refinements. It is suggested that modulated harmonic ADPs and modulated third-order anharmonic ADPs form an intrinsic part, however small, of incommensurately modulated structures in general. Refinements of alternate models with and without parameters for modulated ADPs lead to significant differences between the parameters of the displacement modulation in these two types of models, thus showing the modulation of ADPs to
Wanser, K. H.
1981-01-01
Silicon has interesting harmonic and anharmonic properties such as the low lying transverse acoustic modes at the X and L points of the Brillouin zone, negative Gruneisen parameters, negative thermal expansion and anomalous acoustic attenuation. In an attempt to understand these properties, a lattice dynamical model employing long range, nonlocal, dipole-dipole interactions was developed. Analytic expression for the Gruneisen parameters of several modes are presented. These expressions explain how the negative Gruneisen parameters arise. This model is applied to the calculation of the thermal expansion of silicon from 5K to 1700K. The thermoelastic contribution to the acoustic attenuation of silicon is computed from 1 to 300 K. Strong attenuation anomalies associated with negative thermal expansion are found in the vicinity of 17K and 125K.
Kinematic anharmonicity of internal rotation of molecules
International Nuclear Information System (INIS)
Bataev, V.A.; Pupyshev, V.I.; Godunov, I.A.
2017-01-01
The methods of analysis the strongly coupled vibrations are proposed for a number of molecules of aromatic and heterocyclic carbonyl (and some others) compounds. The qualitative principles are formulated for molecular systems with a significant kinematic anharmonicity.
Anharmonic oscillator and Bogoliubov transformation
International Nuclear Information System (INIS)
Pattnayak, G.C.; Torasia, S.; Rath, B.
1990-01-01
The anharmonic oscillator occupies a cornerstone in many problems in physics. It was observed that none of the authors have tested Bogoliubov transformation to study anharmonic oscillator. The groundstate energy of the anharmonic oscillator is studied using Bogoliubov transformation and the results presented. (author)
Low-temperature anharmonicity in cesium chloride (CsCl)
Energy Technology Data Exchange (ETDEWEB)
Sist, Mattia; Faerch Fischer, Karl Frederik; Brummerstedt Iversen, Bo [Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University (Denmark); Kasai, Hidetaka [Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University (Denmark); Faculty of Pure and Applied Sciences, TIMS and CiRfSE, University of Tsukuba (Japan)
2017-03-20
Anharmonic lattice vibrations govern heat transfer in materials, and anharmonicity is commonly assumed to be dominant at high temperature. The textbook cubic ionic defect-free crystal CsCl is shown to have an unexplained low thermal conductivity at room temperature (ca. 1 W/(m K)), which increases to around 13 W/(m K) at 25 K. Through high-resolution X-ray diffraction it is unexpectedly shown that the Cs atomic displacement parameter becomes anharmonic at 20 K. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
Energy Technology Data Exchange (ETDEWEB)
Cavaignac, A.L.O. [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão, Imperatriz, MA 65900-410 (Brazil); Lima, R.J.C., E-mail: ricardo.lima.ufma@gmail.com [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão, Imperatriz, MA 65900-410 (Brazil); Façanha Filho, P.F. [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão, Imperatriz, MA 65900-410 (Brazil); Moreno, A.J.D. [Coordenação de Ciências Naturais, Universidade Federal do Maranhão, Bacabal, MA 65700-000 (Brazil); Freire, P.T.C. [Departamento de Física, Universidade Federal do Ceará, Fortaleza, CE 60455-760 (Brazil)
2016-03-01
In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.
International Nuclear Information System (INIS)
Cavaignac, A.L.O.; Lima, R.J.C.; Façanha Filho, P.F.; Moreno, A.J.D.; Freire, P.T.C.
2016-01-01
In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.
RAMAN LIGHT SCATTERING IN PSEUDOSPIN-ELECTRON MODEL AT STRONG PSEUDOSPIN-ELECTRON INTERACTION
Directory of Open Access Journals (Sweden)
T.S.Mysakovych
2004-01-01
Full Text Available Anharmonic phonon contributions to Raman scattering in locally anharmonic crystal systems in the framework of the pseudospin-electron model with tunneling splitting of levels are investigated. The case of strong pseudospin-electron coupling is considered. Pseudospin and electron contributions to scattering are taken into account. Frequency dependences of Raman scattering intensity for different values of model parameters and for different polarization of scattering and incident light are investigated.
Nonadiabatic anharmonic electron transfer
Energy Technology Data Exchange (ETDEWEB)
Schmidt, P. P. [Molecular Physics Research, 6547 Kristina Ursula Court, Falls Church, Virginia 22044 (United States)
2013-03-28
The effect of an inner sphere, local mode vibration on an electron transfer is modeled using the nonadiabatic transition probability (rate) expression together with both the anharmonic Morse and the harmonic oscillator potential. For an anharmonic inner sphere mode, a variational analysis uses harmonic oscillator basis functions to overcome the difficulties evaluating Morse-model Franck-Condon overlap factors. Individual matrix elements are computed with the use of new, fast, robust, and flexible recurrence relations. The analysis therefore readily addresses changes in frequency and/or displacement of oscillator minimums in the different electron transfer states. Direct summation of the individual Boltzmann weighted Franck-Condon contributions avoids the limitations inherent in the use of the familiar high-temperature, Gaussian form of the rate constant. The effect of harmonic versus anharmonic inner sphere modes on the electron transfer is readily seen, especially in the exoergic, inverted region. The behavior of the transition probability can also be displayed as a surface for all temperatures and values of the driving force/exoergicity {Delta}=-{Delta}G. The temperature insensitivity of the transfer rate is clearly seen when the exoergicity equals the collective reorganization energy ({Delta}={Lambda}{sub s}) along a maximum ln (w) vs. {Delta} ridge of the surface. The surface also reveals additional regions for {Delta} where ln (w) appears to be insensitive to temperature, or effectively activationless, for some kinds of inner sphere contributions.
Anharmonic vibrational spectroscopic investigation of malonaldehyde
International Nuclear Information System (INIS)
Alparone, A.; Millefiori, S.
2003-01-01
Anharmonic IR spectra of H-bonded and non-H-bonded conformers of malonaldehyde (MA) and its isotopomers MA-D 6 D 8 and MA-D 7 D 9 have been computed by the Vibrational-Self-Consistent-Field (VSCF) and the correlation-corrected-VSCF (CC-VSCF) techniques using ab initio MP2/6-31G*(+p) potential energies. The agreement between the experimental and calculated frequencies is significantly improved to within 2-3%. Anharmonic contributions are substantial especially for νOH of the H-bonded form, by reducing the harmonic value by more than 500 cm -1 . The effect is less important in the non-H-bonded form. The νOH stretching mode is strongly coupled with the ν 3 mode (essentially νCH 7 ) and with the in-plane and out-of-plane OH bending deformations. H-bond formation and deuteration batochromically shift νOH by an amount which is influenced by the anharmonic terms, the major contribution arising from coupling between modes. The comparison with the νOH mode of some other H-bonded systems suggests that anharmonic correction follows H-bonding strength
Strongly-Refractive One-Dimensional Photonic Crystal Prisms
Ting, David Z. (Inventor)
2004-01-01
One-dimensional (1D) photonic crystal prisms can separate a beam of polychromatic electromagnetic waves into constituent wavelength components and can utilize unconventional refraction properties for wavelength dispersion over significant portions of an entire photonic band rather than just near the band edges outside the photonic band gaps. Using a ID photonic crystal simplifies the design and fabrication process and allows the use of larger feature sizes. The prism geometry broadens the useful wavelength range, enables better optical transmission, and exhibits angular dependence on wavelength with reduced non-linearity. The properties of the 1 D photonic crystal prism can be tuned by varying design parameters such as incidence angle, exit surface angle, and layer widths. The ID photonic crystal prism can be fabricated in a planar process, and can be used as optical integrated circuit elements.
Anharmonic Vibrational Spectroscopy on Metal Transition Complexes
Latouche, Camille; Bloino, Julien; Barone, Vincenzo
2014-06-01
Advances in hardware performance and the availability of efficient and reliable computational models have made possible the application of computational spectroscopy to ever larger molecular systems. The systematic interpretation of experimental data and the full characterization of complex molecules can then be facilitated. Focusing on vibrational spectroscopy, several approaches have been proposed to simulate spectra beyond the double harmonic approximation, so that more details become available. However, a routine use of such tools requires the preliminary definition of a valid protocol with the most appropriate combination of electronic structure and nuclear calculation models. Several benchmark of anharmonic calculations frequency have been realized on organic molecules. Nevertheless, benchmarks of organometallics or inorganic metal complexes at this level are strongly lacking despite the interest of these systems due to their strong emission and vibrational properties. Herein we report the benchmark study realized with anharmonic calculations on simple metal complexes, along with some pilot applications on systems of direct technological or biological interest.
Strong crystal field effect in ? - optical absorption study
Gajek, Z.; Krupa, J. C.
1998-12-01
=-1 Results of optical absorption measurements in polarized light on tetravalent neptunium diluted in a 0953-8984/10/50/021/img6 single crystal are reported. The recorded spectra are complex, pointing to the presence of an 0953-8984/10/50/021/img7 impurity. The electronic transitions assigned to the 0953-8984/10/50/021/img8 ion are interpreted in terms of the usual model, following the actual understanding of the neptunium electronic structure and independent theoretical predictions. R.m.s. deviations of the order of 0953-8984/10/50/021/img9 have been obtained for 42 levels fitted with 11 free parameters. The crystal field effect resulting from the fitting is considerably larger than that observed for the uranium ion in the same host.
Pressure measurements of TO-phonon anharmonicity in isotopic ZnS
Energy Technology Data Exchange (ETDEWEB)
Tallman, R.E.; Weinstein, B.A. [SUNY at Buffalo, Department of Physics, Buffalo, NY 14260 (United States); Ritter, T.M. [Dept. of Chemistry and Physics, UNC Pembroke, NC 28372 (United States); Cantarero, A. [Dept. of Physics and Institute of Materials Science, University of Valencia (Spain); Serrano, J.; Lauck, R.; Cardona, M. [Max-Planck-Institut fuer Festkoerperforschung, 70569 Stuttgart (Germany)
2004-03-01
We have measured the dependence on pressure of the line-widths of the TO and LO Raman phonons of {beta}-ZnS. In order to enhance the phenomena observed, and to eliminate possible effects of isotopic disorder, we have measured a nearly isotopically pure crystal, {sup 68}Zn{sup 32}S. The strongly structured pressure effects observed are interpreted on the basis of anharmonic decay and the corresponding two-phonon density of states. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Wave propagation in a strongly nonlinear locally resonant granular crystal
Vorotnikov, K.; Starosvetsky, Y.; Theocharis, G.; Kevrekidis, P. G.
2018-02-01
In this work, we study the wave propagation in a recently proposed acoustic structure, the locally resonant granular crystal. This structure is composed of a one-dimensional granular crystal of hollow spherical particles in contact, containing linear resonators. The relevant model is presented and examined through a combination of analytical approximations (based on ODE and nonlinear map analysis) and of numerical results. The generic dynamics of the system involves a degradation of the well-known traveling pulse of the standard Hertzian chain of elastic beads. Nevertheless, the present system is richer, in that as the primary pulse decays, secondary ones emerge and eventually interfere with it creating modulated wavetrains. Remarkably, upon suitable choices of parameters, this interference "distills" a weakly nonlocal solitary wave (a "nanopteron"). This motivates the consideration of such nonlinear structures through a separate Fourier space technique, whose results suggest the existence of such entities not only with a single-side tail, but also with periodic tails on both ends. These tails are found to oscillate with the intrinsic oscillation frequency of the out-of-phase motion between the outer hollow bead and its internal linear attachment.
Nonlinear (Anharmonic Casimir Oscillator
Directory of Open Access Journals (Sweden)
Habibollah Razmi
2011-01-01
Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.
The anharmonic phonon decay rate in group-III nitrides
International Nuclear Information System (INIS)
Srivastava, G P
2009-01-01
Measured lifetimes of hot phonons in group-III nitrides have been explained theoretically by considering three-phonon anharmonic interaction processes. The basic ingredients of the theory include full phonon dispersion relations obtained from the application of an adiabatic bond charge model and crystal anharmonic potential within the isotropic elastic continuum model. The role of various decay routes, such as Klemens, Ridley, Vallee-Bogani and Barman-Srivastava channels, in determining the lifetimes of the Raman active zone-centre longitudinal optical (LO) modes in BN (zincblende structure) and A 1 (LO) modes in AlN, GaN and InN (wurtzite structure) has been quantified.
Microscopic approach to nuclear anharmonicities
International Nuclear Information System (INIS)
Matsuo, Masayuki; Shimizu, Yoshifumi; Matsuyanagi, Kenichi
1985-01-01
Present status of microscopic study of nuclear anharmonicity phenomena is reviewed from the viewpoint of the time-dependent Hartree-Bogoliubov approach. Both classical- and quantum-mechanical aspects of this approach are discussed. The Bohr-Mottelson-type collective Hamiltonian for anharmonic gamma vibrations is microscopically derived by means of the self-consistent-collective-coordinate method, and applied to the problem of two-phonon states of 168 Er. (orig.)
Light exiting from real photonic band gap crystals is diffuse and strongly directional
Koenderink, A.F.; Vos, Willem L.
2003-01-01
Any photonic crystal is in practice periodic with some inevitable fabricational imperfections. We have measured angle-resolved transmission of photons that are multiply scattered by this disorder in strongly photonic crystals. Peculiar non-Lambertian distributions occur as a function of frequency:
Quantum versus semiclassical description of selftrapping: anharmonic effects
International Nuclear Information System (INIS)
Raghavan, S.; Bishop, A.R.; Kenkre, V.M.
1998-09-01
Selftrapping has been traditionally studied on the assumption that quasiparticles interact with harmonic phonons and that this interaction is linear in the displacement of the phonon. To complement recent semiclassical studies of anharmonicity and nonlinearity in this context, we present below a fully quantum mechanical analysis of a two-site system, where the oscillator is described by a tunably anharmonic potential, with a square well with infinite walls and the harmonic potential as its extreme limits, and wherein the interaction is nonlinear in the oscillator displacement. We find that even highly anharmonic polarons behave similar to their harmonic counterparts in that selftrapping is preserved for long times in the limit of strong coupling, and that the polaronic tunneling time scale depends exponentially on the polaron binding energy. Further, in agreement with earlier results related to harmonic polarons, the semiclassical approximation agrees with the full quantum result in the massive oscillator limit of small oscillator frequency and strong quasiparticle-oscillator coupling. (author)
Strong exciton-photon coupling in organic single crystal microcavity with high molecular orientation
Energy Technology Data Exchange (ETDEWEB)
Goto, Kaname [Department of Electronics, Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Yamashita, Kenichi, E-mail: yamasita@kit.ac.jp [Faculty of Electrical Engineering and Electronics, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Yanagi, Hisao [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Yamao, Takeshi; Hotta, Shu [Faculty of Materials Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan)
2016-08-08
Strong exciton-photon coupling has been observed in a highly oriented organic single crystal microcavity. This microcavity consists of a thiophene/phenylene co-oligomer (TPCO) single crystal laminated on a high-reflection distributed Bragg reflector. In the TPCO crystal, molecular transition dipole was strongly polarized along a certain horizontal directions with respect to the main crystal plane. This dipole polarization causes significantly large anisotropies in the exciton transition and optical constants. Especially the anisotropic exciton transition was found to provide the strong enhancement in the coupling with the cavity mode, which was demonstrated by a Rabi splitting energy as large as ∼100 meV even in the “half-vertical cavity surface emitting lasing” microcavity structure.
Strong exciton-photon coupling in organic single crystal microcavity with high molecular orientation
Goto, Kaname; Yamashita, Kenichi; Yanagi, Hisao; Yamao, Takeshi; Hotta, Shu
2016-08-01
Strong exciton-photon coupling has been observed in a highly oriented organic single crystal microcavity. This microcavity consists of a thiophene/phenylene co-oligomer (TPCO) single crystal laminated on a high-reflection distributed Bragg reflector. In the TPCO crystal, molecular transition dipole was strongly polarized along a certain horizontal directions with respect to the main crystal plane. This dipole polarization causes significantly large anisotropies in the exciton transition and optical constants. Especially the anisotropic exciton transition was found to provide the strong enhancement in the coupling with the cavity mode, which was demonstrated by a Rabi splitting energy as large as ˜100 meV even in the "half-vertical cavity surface emitting lasing" microcavity structure.
Strong exciton-photon coupling in organic single crystal microcavity with high molecular orientation
International Nuclear Information System (INIS)
Goto, Kaname; Yamashita, Kenichi; Yanagi, Hisao; Yamao, Takeshi; Hotta, Shu
2016-01-01
Strong exciton-photon coupling has been observed in a highly oriented organic single crystal microcavity. This microcavity consists of a thiophene/phenylene co-oligomer (TPCO) single crystal laminated on a high-reflection distributed Bragg reflector. In the TPCO crystal, molecular transition dipole was strongly polarized along a certain horizontal directions with respect to the main crystal plane. This dipole polarization causes significantly large anisotropies in the exciton transition and optical constants. Especially the anisotropic exciton transition was found to provide the strong enhancement in the coupling with the cavity mode, which was demonstrated by a Rabi splitting energy as large as ∼100 meV even in the “half-vertical cavity surface emitting lasing” microcavity structure.
Detecting anharmonicity at a glance
International Nuclear Information System (INIS)
Giliberti, M; Stellato, M; Barbieri, S; Cavinato, M; Rigon, E; Tamborini, M
2014-01-01
Harmonic motion is generally presented in such a way that most of the students believe that the small oscillations of a body are all harmonic. Since the situation is not actually so simple, and since the comprehension of harmonic motion is essential in many physical contexts, we present here some suggestions, addressed to undergraduate students and pre-service teachers, that allow one to find out at a glance the anharmonicity of a motion. Starting from a didactically motivated definition of harmonic motion, and stressing the importance of the interplay between mathematics and experiments, we give a four-point criterion for anharmonicity together with some emblematic examples. The role of linear damping is also analysed in relation to the gradual changing of harmonicity into anharmonicity when the ratio between the damping coefficient and the zero-friction angular frequency increases. (paper)
Wang, Hui; Liu, Ju; Wang, Weizhou
2018-02-14
Single-crystal X-ray diffraction reveals that polymorphic ortho-nitrophenyl selenocyanate (o-NSC, crystals 1a and 1b) and monomorphic para-nitrophenyl selenocyanate (p-NSC, crystal 2) crystals are all stabilized mainly by intermolecular and very strong intramolecular C-SeO/N chalcogen bonds, as well as by other different interactions. Thermogravimetric (TG) and differential scanning calorimetry thermogram (DSC) analyses show that the starting decomposition temperatures and melting points of the three crystals are different, following the order 1b > 1a > 2, which is consistent with the structural characteristics of the crystals. In addition, atoms in molecules (AIM) and natural bond orbital (NBO) analyses indicate that the total strengths of the C-SeO and C-SeN chalcogen bonds decrease in the order 1b > 1a > 2. This study could be significant for engineering functional crystals based on robust C-SeO and C-SeN chalcogen bonds, and for designing drugs containing selenium as well as understanding their interaction in biosystems.
arXiv Strong reduction of the effective radiation length in an oriented PWO scintillator crystal
Bandiera, L.; Romagnoni, M.; Argiolas, N.; Bagli, E.; Ballerini, G.; Berra, A.; Brizzolani, C.; Camattari, R.; De Salvador, D.; Haurylavets, V.; Mascagna, V.; Mazzolari, A.; Prest, M.; Soldani, M.; Sytov, A.; Vallazza, E.
We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic field. The data collected at the external lines of CERN SPS were critically compared to Monte Carlo simulations based on the Baier Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of five in case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters/detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments as well as in satellite-borne gamma-telescopes.
Energy Technology Data Exchange (ETDEWEB)
Kong, Tai [Iowa State Univ., Ames, IA (United States)
2016-12-17
Benefiting from unique properties of 4f electrons, rare earth based compounds are known for offering a versatile playground for condensed matter physics research as well as industrial applications. This thesis focuses on three specific examples that further explore the rare earth local moment magnetism and strongly correlated phenomena in various crystal structures.
Redshift of A 1(longitudinal optical) mode for GaN crystals under strong electric field
Gu, Hong; Wu, Kaijie; Zheng, Shunan; Shi, Lin; Zhang, Min; Liu, Zhenghui; Liu, Xinke; Wang, Jianfeng; Zhou, Taofei; Xu, Ke
2018-01-01
We investigated the property of GaN crystals under a strong electric field. The Raman spectra of GaN were measured using an ultraviolet laser, and a remarkable redshift of the A 1(LO) mode was observed. The role of the surface depletion layer was discussed, and the interrelation between the electric field and phonons was revealed. First-principles calculations indicated that, in particular, the phonons that vibrate along the [0001] direction are strongly influenced by the electric field. This effect was confirmed by a surface photovoltage experiment. The results revealed the origin of the redshift and presented the phonon property of GaN under a strong electric field.
Anharmonic phonons and magnons in BiFeO3
Energy Technology Data Exchange (ETDEWEB)
Delaire, Olivier A [ORNL; Ma, Jie [ORNL; Stone, Matthew B [ORNL; Huq, Ashfia [ORNL; Gout, Delphine J [ORNL; Brown, Craig [National Institute of Standards and Technology (NIST); Wang, Kefeng [Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing; Ren, Zhifeng [Boston College, Chestnut Hill
2012-01-01
The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 < T < 750K , using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T-dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large amplitude motions of Bi and O ions observed with neutron diffraction. These results highlight the importance of spin-phonon coupling in this material.
Observation of strong leakage reduction in crystal assisted collimation of the SPS beam
Energy Technology Data Exchange (ETDEWEB)
Scandale, W. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Laboratoire de l' Accelerateur Lineaire (LAL), Universite Paris Sud Orsay, Orsay (France); INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185 Rome (Italy); Arduini, G.; Butcher, M.; Cerutti, F.; Garattini, M.; Gilardoni, S.; Lechner, A.; Losito, R.; Masi, A.; Mereghetti, A.; Metral, E. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Mirarchi, D. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Imperial College, London (United Kingdom); Montesano, S.; Redaelli, S. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Rossi, R. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185 Rome (Italy); Schoofs, P.; Smirnov, G. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Bagli, E.; Bandiera, L.; Baricordi, S. [INFN Sezione di Ferrara, Dipartimento di Fisica, Università di Ferrara, Ferrara (Italy); and others
2015-09-02
In ideal two-stage collimation systems, the secondary collimator–absorber should have its length sufficient to exclude practically the exit of halo particles with large impact parameters. In the UA9 experiments on the crystal assisted collimation of the SPS beam a 60 cm long tungsten bar is used as a secondary collimator–absorber which is insufficient for the full absorption of the halo protons. Multi-turn simulation studies of the collimation allowed to select the position for the beam loss monitor downstream the collimation area where the contribution of particles deflected by the crystal in channeling regime but emerging from the secondary collimator–absorber is considerably reduced. This allowed observation of a strong leakage reduction of halo protons from the SPS beam collimation area, thereby approaching the case with an ideal absorber.
Anharmonic phonons and the isotope effect in superconductivity
International Nuclear Information System (INIS)
Crespi, V.H.; Cohen, M.L.; Penn, D.R.
1991-01-01
Anharmonic interionic potentials are examined in an Einstein model to study the unusual isotope-effect exponents for the high-T c oxides. The mass dependences of the electron-phonon coupling constant λ and the average phonon frequency √ left-angle ω 2 right-angle are computed from weighted sums over the oscillator levels. The isotope-effect exponent is depressed below 1/2 by either a double-well potential or a potential with positive quadratic and quartic parts. Numerical solutions of Schroedinger's equation for double-well potentials produce λ's in the range 1.5--4 for a material with a vanishing isotope-effect parameter α. However, low phonon frequencies limit T c to roughly 15 K. A negative quartic perturbation to a harmonic well can increase α above 1/2. In the extreme-strong-coupling limit, α is 1/2, regardless of anharmonicity
Quantum versus semiclassical description of self-trapping: Anharmonic effects
International Nuclear Information System (INIS)
Raghavan, S.; Bishop, A.R.; Kenkre, V.M.
1999-01-01
Self-trapping has been traditionally studied on the assumption that quasiparticles interact with harmonic phonons and that this interaction is linear in the displacement of the phonon. To complement recent semiclassical studies of anharmonicity and nonlinearity in this context, we present below a fully quantum-mechanical analysis of a two-site system, where the oscillator is described by a tunably anharmonic potential, with a square well with infinite walls and the harmonic potential as its extreme limits, and wherein the interaction is nonlinear in the oscillator displacement. We find that even highly anharmonic polarons behave similar to their harmonic counterparts in that self-trapping is preserved for long times in the limit of strong coupling, and that the polaronic tunneling time scale depends exponentially on the polaron binding energy. Further, in agreement, with earlier results related to harmonic polarons, the semiclassical approximation agrees with the full quantum result in the massive oscillator limit of small oscillator frequency and strong quasiparticle-oscillator coupling. copyright 1999 The American Physical Society
Study of thermophysical and anharmonic properties of fluorite compounds
International Nuclear Information System (INIS)
Singh, R.K.; Pandey, N.K.
1983-01-01
An extensive study is made of thermophysical and anharmonic properties of fluorite compounds using an interionic potential, which consists of a long-range Coulomb and three-body interactions and the short-range overlap repulsion and van der Waals attraction. The agreement achieved between experimental and theoretical results on third-order elastic constants and pressure derivatives of second order elastic constants are generally better than those obtained by others. This potential succeeds in predicting various thermophysical properties, like compressibility and its pressure and temperature derivatives, thermal expansion and Grueneisen parameters of seven crystals of fluorite structure. (author)
Scattering of acoustic waves from a surface in the presence of an anharmonic interface
DEFF Research Database (Denmark)
Kulak, A.; Lodziana, Zbigniew; Srokowski, T.
2002-01-01
Energy transfer coefficient (analogue of LDOS) and aperiodicity index are defined to characterise the nonlinear response and the surface resonances in a thin layer separated from the underlying bulk crystal by an anharmonic interface. Regions of periodic, aperiodic and intermittent motion of the ...
Orientational anharmonicity of interatomic interaction in cubic monocrystals
International Nuclear Information System (INIS)
Belomestnykh, Vladimir N.; Tesleva, Elena P.
2010-01-01
Anharmonicity of interatomic interaction from a position of physical acoustics under the standard conditions is investigated. It is shown that the measure of anharmonicity of interatomic interaction (Grilneisen parameter) is explicitly expressed through velocities of sound. Calculation results of orientation anharmonicity are shown on the example of 116 cubic monocrystals with different lattice structural type and type of chemical bond. Two types of anharmonicity interatomic interaction anisotropy are determined. Keywords: acoustics, orientational anharmonicity, Gruneisen parameter, velocity of sound
Nuclear catalysis mediated by localized anharmonic vibrations
Dubinko, Vladimir
2015-01-01
In many-body nonlinear systems with sufficient anharmonicity, a special kind of lattice vibrations, namely, Localized Anharmonic Vibrations (LAVs) can be excited either thermally or by external triggering, in which the amplitude of atomic oscillations greatly exceeds that of harmonic oscillations (phonons) that determine the system temperature. Coherency and persistence of LAVs may have drastic effect on quantum tunneling due to correlation effects discovered by Schrodinger and Robertson in 1...
Plata, Jose J.; Nath, Pinku; Usanmaz, Demet; Carrete, Jesús; Toher, Cormac; de Jong, Maarten; Asta, Mark; Fornari, Marco; Nardelli, Marco Buongiorno; Curtarolo, Stefano
2017-10-01
One of the most accurate approaches for calculating lattice thermal conductivity, , is solving the Boltzmann transport equation starting from third-order anharmonic force constants. In addition to the underlying approximations of ab-initio parameterization, two main challenges are associated with this path: high computational costs and lack of automation in the frameworks using this methodology, which affect the discovery rate of novel materials with ad-hoc properties. Here, the Automatic Anharmonic Phonon Library (AAPL) is presented. It efficiently computes interatomic force constants by making effective use of crystal symmetry analysis, it solves the Boltzmann transport equation to obtain , and allows a fully integrated operation with minimum user intervention, a rational addition to the current high-throughput accelerated materials development framework AFLOW. An "experiment vs. theory" study of the approach is shown, comparing accuracy and speed with respect to other available packages, and for materials characterized by strong electron localization and correlation. Combining AAPL with the pseudo-hybrid functional ACBN0 is possible to improve accuracy without increasing computational requirements.
Quantum theory of anharmonic oscillators
International Nuclear Information System (INIS)
Yamazaki, K.; Kyoto Univ.
1983-01-01
This in investigation of an anharmonic oscillator characterized by the potential ωsub(o) 2 /2 g 2 + lambda'q 4 . By using the equations of motion and the relations obtained by evaluating where O is an arbitrary operator, H is our total Hamiltonian and |i> and |j> are exact eigenstates of H, we derive an exact recurrence formula. This formula allows us to express tau-functions with a higher power of the variables through tau-functions with a lower power of the variables and energy eigenvalues. In this way we derive several exact relations, which are, in a sense, generalizations of the virial theorem and sum rules. These exact relations are the central equations of this paper. On the basis of these exact relations we propose our 'nearest neighbour level' (N.N.L.) approximation, which seems to provide a good approximation scheme. We can also use our exact relations to test the validity of various approximation methods, and as an example, we discuss the 'New-Tamm-Dancoff' (N.T.D)-type of approximation in detail. (Author)
Energy Technology Data Exchange (ETDEWEB)
Maltseva, Elena; Buma, Wybren Jan [University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Tielens, Alexander G. G. M. [Leiden Observatory, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Huang, Xinchuan; Lee, Timothy J. [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Oomens, Jos, E-mail: w.j.buma@uva.nl, E-mail: petrignani@strw.leidenuniv.nl [Radboud University, Toernooiveld 7, 6525 ED Nijmegen (Netherlands)
2015-11-20
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3-μm CH stretching region of polycyclic aromatic hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (∼4 K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main bands that fall within 0.5% of the experimental frequencies. The implications for the aromatic infrared bands, specifically the 3-μm band, are discussed.
Maltseva, Elena; Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander G. G. M.; Oomens, Jos; Buma, Wybren Jan
2016-01-01
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micrometers CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold ((is) approximately 4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3-m band are discussed.
Bogodaev, N. V.; Zozulya, A. A.; Ivleva, Lyudmila I.; Korshunov, A. S.; Mamaev, A. V.; Polozkov, N. M.
1992-05-01
Most photorefractive crystals suitable for four-wave systems of phase self-conjugation and mutual conjugation have a fairly high level of light-induced scattering (fanning). This may imply that the nonlinearity of a crystal is too strong for optimal operation and a reduction in this nonlinearity would improve the characteristics. This statement is illustrated theoretically and experimentally using the geometry of a loop parametric oscillator as an example.
Anharmonic, dimensionality and size effects in phonon transport
Thomas, Iorwerth O.; Srivastava, G. P.
2017-12-01
We have developed and employed a numerically efficient semi- ab initio theory, based on density-functional and relaxation-time schemes, to examine anharmonic, dimensionality and size effects in phonon transport in three- and two-dimensional solids of different crystal symmetries. Our method uses third- and fourth-order terms in crystal Hamiltonian expressed in terms of a temperature-dependent Grüneisen’s constant. All input to numerical calculations are generated from phonon calculations based on the density-functional perturbation theory. It is found that four-phonon processes make important and measurable contribution to lattice thermal resistivity above the Debye temperature. From our numerical results for bulk Si, bulk Ge, bulk MoS2 and monolayer MoS2 we find that the sample length dependence of phonon conductivity is significantly stronger in low-dimensional solids.
Tang, Liguo; Zhang, Yang; Cao, Wenwu
2016-10-01
Although the self-consistency of the full matrix material constants of a piezoelectric sample obtained by the resonant ultrasonic spectroscopy technique can be guaranteed because all constants come from the same sample, it is a great challenge to determine the constants of a piezoelectric sample with strong anisotropy because it might not be possible to identify enough resonance modes from the resonance spectrum. To overcome this difficulty, we developed a strategy to use two samples of similar geometries to increase the number of easy identifiable modes. Unlike the IEEE resonance methods, sample-to-sample variation here is negligible because the two samples have almost the same dimensions, cut from the same specimen and poled under the same conditions. Using this method, we have measured the full matrix constants of a [011]c poled 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystal, which has 17 independent constants. The self-consistency of the obtained results is checked by comparing the calculated elastic stiffness constants c33 D , c44 D , and c55 D with those directly measured ones using the ultrasonic pulse-echo method.
ANCA: Anharmonic Conformational Analysis of Biomolecular Simulations.
Parvatikar, Akash; Vacaliuc, Gabriel S; Ramanathan, Arvind; Chennubhotla, S Chakra
2018-05-08
Anharmonicity in time-dependent conformational fluctuations is noted to be a key feature of functional dynamics of biomolecules. Although anharmonic events are rare, long-timescale (μs-ms and beyond) simulations facilitate probing of such events. We have previously developed quasi-anharmonic analysis to resolve higher-order spatial correlations and characterize anharmonicity in biomolecular simulations. In this article, we have extended this toolbox to resolve higher-order temporal correlations and built a scalable Python package called anharmonic conformational analysis (ANCA). ANCA has modules to: 1) measure anharmonicity in the form of higher-order statistics and its variation as a function of time, 2) output a storyboard representation of the simulations to identify key anharmonic conformational events, and 3) identify putative anharmonic conformational substates and visualization of transitions between these substates. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Confinement-induced resonances in anharmonic waveguides
Energy Technology Data Exchange (ETDEWEB)
Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Hu Hui; Liu Xiaji; Drummond, Peter D. [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)
2011-10-15
We develop the theory of anharmonic confinement-induced resonances (ACIRs). These are caused by anharmonic excitation of the transverse motion of the center of mass (c.m.) of two bound atoms in a waveguide. As the transverse confinement becomes anisotropic, we find that the c.m. resonant solutions split for a quasi-one-dimensional (1D) system, in agreement with recent experiments. This is not found in harmonic confinement theories. A new resonance appears for repulsive couplings (a{sub 3D}>0) for a quasi-two-dimensional (2D) system, which is also not seen with harmonic confinement. After inclusion of anharmonic energy corrections within perturbation theory, we find that these ACIRs agree extremely well with anomalous 1D and 2D confinement-induced resonance positions observed in recent experiments. Multiple even- and odd-order transverse ACIRs are identified in experimental data, including up to N=4 transverse c.m. quantum numbers.
Kozlovskaya, E. N.; Doroshenko, I. Yu.; Pogorelov, V. E.; Vaskivskyi, Ye. V.; Pitsevich, G. A.
2018-01-01
Previously calculated multidimensional potential-energy surfaces of the MeOH monomer and dimer, water dimer, malonaldehyde, formic acid dimer, free pyridine-N-oxide/trichloroacetic acid complex, and protonated water dimer were analyzed. The corresponding harmonic potential-energy surfaces near the global minima were constructed for series of clusters and complexes with hydrogen bonds of different strengths based on the behavior of the calculated multidimensional potential-energy surfaces. This enabled the introduction of an obvious anharmonicity parameter for the calculated potential-energy surfaces. The anharmonicity parameter was analyzed as functions of the size of the analyzed area near the energy minimum, the number of points over which energies were compared, and the dimensionality of the solved vibrational problem. Anharmonicity parameters for potential-energy surfaces in complexes with strong, medium, and weak H-bonds were calculated under identical conditions. The obtained anharmonicity parameters were compared with the corresponding diagonal anharmonicity constants for stretching vibrations of the bridging protons and the lengths of the hydrogen bridges.
Theory of a quantum anharmonic oscillator
International Nuclear Information System (INIS)
Carusotto, S.
1988-01-01
The time evolution of a quantum single-quartic anharmonic oscillator is considered. The study is carried on in operational form by use of the raising and lowering operators of the oscillator. The equation of motion is solved by application of a new integration method based on iteration techniques, and the rigorous solutions that describe the time development of the displacement and momentum operators of the oscillator are obtained. These operators are presented as a Laplace transform and a subsequent inverse Laplace transform of suitable functionals. Finally, the results are employed to describe the time evolution of a quasiclassical anharmonic oscillator
Kinks in systems with cubic and quartic anharmonicity
International Nuclear Information System (INIS)
Kashcheev, V.N.
1988-01-01
For a classical system of interacting particles with on-site cubic or quartic anharmonicity explicit analytic solutions of the d'Alembert equation are obtained in the form of kinks in the presence of dissipation (viscous or Rayleigh) and a constant force. These kinks will be asymptotically stable in the case of quartic anharmonicity and unstable in the case cubic anharmonicity
Hydrogen atom in a uniform electromagnetic field as an anharmonic oscillator
International Nuclear Information System (INIS)
Kibler, M.; Negadi, T.
1984-01-01
This work establishes, by means of the Kustaanheimo-Stiefel transformation, a connection between two branches of theoretical physics which are, in present times, the object of numerous studies: the quantum mechanics of anharmonic oscillators and of the hydrogen atom in a (strong) homogeneous and constant electromagnetic field
Phonon anharmonicity and Gruneisen parameters of alpha-plutonium
International Nuclear Information System (INIS)
Filanovich, A.N.; Povzner, A.A.
2015-01-01
A self-consistent thermodynamic model of alpha-phase of plutonium is constructed. The calculations of thermal and elastic properties of α-Pu, carried out within this model, demonstrate that anomalously strong temperature dependence of the bulk modulus and unusually high value of the coefficient of thermal expansion of α-Pu are caused by its strong lattice anharmonicity. The isothermal and isobaric Gruneisen parameters of α-Pu and δ-Pu Pu_0_._9_6Ga_0_._0_4 are calculated. It is shown that wide spread of the values of Gruneisen parameter of α-Pu, obtained previously from different experimental data, is explained by the dependence of Gruneisen parameter of α-Pu on temperature. - Highlights: • A self-consistent thermodynamic model of alpha-plutonium is developed. • Thermal and elastic properties of alpha-plutonium are calculated. • The reason of spread in the values of Gruneisen parameter of alpha-Pu is established. • Different types of phonon anharmonicity in alpha-Pu and delta-Pu are revealed.
Phonon density of states and anharmonicity of UO2
Pang, Judy W. L.; Chernatynskiy, Aleksandr; Larson, Bennett C.; Buyers, William J. L.; Abernathy, Douglas L.; McClellan, Kenneth J.; Phillpot, Simon R.
2014-03-01
Phonon density of states (PDOS) measurements have been performed on polycrystalline UO2 at 295 and 1200 K using time-of-flight inelastic neutron scattering to investigate the impact of anharmonicity on the vibrational spectra and to benchmark ab initio PDOS simulations performed on this strongly correlated Mott insulator. Time-of-flight PDOS measurements include anharmonic linewidth broadening, inherently, and the factor of ˜7 enhancement of the oxygen spectrum relative to the uranium component by the increased neutron sensitivity to the oxygen-dominated optical phonon modes. The first-principles simulations of quasiharmonic PDOS spectra were neutron weighted and anharmonicity was introduced in an approximate way by convolution with wave-vector-weighted averages over our previously measured phonon linewidths for UO2, which are provided in numerical form. Comparisons between the PDOS measurements and the simulations show reasonable agreement overall, but they also reveal important areas of disagreement for both high and low temperatures. The discrepancies stem largely from a ˜10 meV compression in the overall bandwidth (energy range) of the oxygen-dominated optical phonons in the simulations. A similar linewidth-convoluted comparison performed with the PDOS spectrum of Dolling et al. obtained by shell-model fitting to their historical phonon dispersion measurements shows excellent agreement with the time-of-flight PDOS measurements reported here. In contrast, we show by comparisons of spectra in linewidth-convoluted form that recent first-principles simulations for UO2 fail to account for the PDOS spectrum determined from the measurements of Dolling et al. These results demonstrate PDOS measurements to be stringent tests for ab inito simulations of phonon physics in UO2 and they indicate further the need for advances in theory to address the lattice dynamics of UO2.
Self-pumped passive ring mirror in crystals with strong fanning
Bogodaev, Nickolai V.; Ivleva, Ludmila I.; Korshunov, A. S.; Mamaev, A. V.; Polozkov, N. N.; Zozulya, Aleksei A.
1992-12-01
Most photorefractive crystals, suitable for the realization of self-pumped four-wave mixing phase conjugation and mutual conjugation geometries, are characterized by the high level of fanning. In some cases it may mean that the nonlinearity of these crystals is already too large to be good and a decrease in the value of a nonlinear coupling coefficient may result in an improved performance of these geometries. This point is illustrated using geometry of a self- pumped ring mirror.
Proof of Nishida's Conjecture on Anharmonic Lattices
Rink, Bob
2006-02-01
We prove Nishida's 1971 conjecture stating that almost all low-energetic motions of the anharmonic Fermi-Pasta-Ulam lattice with fixed endpoints are quasi-periodic. The proof is based on the formal computations of Nishida, the KAM theorem, discrete symmetry considerations and an algebraic trick that considerably simplifies earlier results.
Comparative study of quantum anharmonic potentials
International Nuclear Information System (INIS)
Amore, Paolo; Aranda, Alfredo; De Pace, Arturo; Lopez, Jorge A.
2004-01-01
We perform a study of various anharmonic potentials using a recently developed method. We calculate both the wave functions and the energy eigenvalues for the ground and first excited states of the quartic, sextic and octic potentials with high precision, comparing the results with other techniques available in the literature
DEFF Research Database (Denmark)
Nikolaev, Ivan S.; Lodahl, Peter; van Driel, A. Floris
2007-01-01
We observe experimentally that ensembles of quantum dots in three-dimensional 3D photonic crystals reveal strongly nonexponential time-resolved emission. These complex emission decay curves are analyzed with a continuous distribution of decay rates. The log-normal distribution describes the decays...... parameter. This interpretation qualitatively agrees with the calculations of the 3D projected local density of states. We therefore conclude that fluorescence decay of ensembles of quantum dots is highly nonexponential to an extent that is controlled by photonic crystals....
Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.
2004-01-01
We present new results regarding the features of high energy photon emission by an electron beam of 178 GeV penetrating a 1.5 cm thick single Si crystal aligned at the Strings-Of-Strings (SOS) orientation. This concerns a special case of coherent bremsstrahlung where the electron interacts with the strong fields of successive atomic strings in a plane and for which the largest enhancement of the highest energy photons is expected. The polarization of the resulting photon beam was measured by the asymmetry of electron-positron pair production in an aligned diamond crystal analyzer. By the selection of a single pair the energy and the polarization of individual photons could be measured in an the environment of multiple photons produced in the radiator crystal. Photons in the high energy region show less than 20% linear polarization at the 90% confidence level.
F-center and self-trapped exciton formation in strongly excited alkali halide crystals
International Nuclear Information System (INIS)
Kravchenko, V.A.; Yakovlev, V.Yu.
1988-01-01
Method of luminescent and absorption spectroscopy with time resolution was used to study the effect of density of electron pulse excitation (t p =10 -8 s, P=(10 5 -10 8 ) WXcm -2 ) on efficiency of η ε two-halide autolocalized exciton (TALE) and F-centers (η F ) formation in CsI, CsBr, KBr, KI alkali halide crystals. It was established that for all studied systems the elevation of P power of electron beam (EB) from 10 5 up to 5X10 7 WXcm -2 resulted to sufficient decrease of production efficiency and yield of TALE luminescence. In the case when F-centers of colour are induced predominantly by pulsed irradiation in crystals, F-center yield is independent of P. If F-centers and TALE are produced in comparable amounts (CsBr crystals, T=80 K), η ε decrease with P growth is accompanied by η F growth
Theoretical modeling of infrared spectra of the hydrogen and deuterium bond in aspirin crystal
Ghalla, Houcine; Rekik, Najeh; Michta, Anna; Oujia, Brahim; Flakus, Henryk T.
2010-01-01
An extended quantum theoretical approach of the ν IR lineshape of cyclic dimers of weakly H-bonded species is proposed. We have extended a previous approach [M.E.-A. Benmalti, P. Blaise, H.T. Flakus, O. Henri-Rousseau, Chem. Phys. 320 (2006) 267] by accounting for the anharmonicity of the slow mode which is described by a "Morse" potential in order to reproduce the polarized infrared spectra of the hydrogen and deuterium bond in acetylsalicylic acid (aspirin) crystals. From comparison of polarized IR spectra of isotopically neat and isotopically diluted aspirin crystals it resulted that centrosymmetric aspirin dimer was the bearer of the crystal main spectral properties. In this approach, the adiabatic approximation is performed for each separate H-bond bridge of the dimer and a strong non-adiabatic correction is introduced into the model via the resonant exchange between the fast mode excited states of the two moieties. Within the strong anharmonic coupling theory, according to which the X-H→⋯Y high-frequency mode is anharmonically coupled to the H-bond bridge, this model incorporated the Davydov coupling between the excited states of the two moieties, the quantum direct and indirect dampings and the anharmonicity for the H-bond bridge. The spectral density is obtained within the linear response theory by Fourier transform of the damped autocorrelation functions. The evaluated spectra are in fairly good agreement with the experimental ones by using a minimum number of independent parameters. The effect of deuteration has been well reproduced by reducing simply the angular frequency of the fast mode and the anharmonic coupling parameter.
Diehl, Stefan; Bremer, Daniel; Brinkmann, Kai-Thomas; Dormenev, Valery; Eissner, Tobias; Novotny, Rainer W.; Rosenbaum, Christoph; Zaunick, Hans-Georg; PANDA Collaboration
2017-06-01
The uniformity of the light collection is a crucial parameter for detectors based on inorganic scintillation crystals to guarantee a response proportional to the deposited energy. Especially in case of tapered crystals, like they are widely used to realize a 4π geometry of electromagnetic calorimeters (EMC) in high energy physics experiments, a strong non-uniformity is introduced by an additional focusing of the scintillation light due to the tapered geometry. The paper will discuss the determination and the reduction of the non-uniformity in strongly tapered lead tungstate crystals as used for the construction of the electromagnetic calorimeter of the PANDA detector at the future Facility for Antiproton and Ion Research (FAIR). Among different concepts for an uniformization a single de-polished lateral side face provided the optimum result with a remaining non-uniformity below 5% in good agreement with similar studies for the CMS ECAL at LHC. The impact on the achievable energy resolution in the energy regime of photons below 800 MeV is discussed in detail in comparison to GEANT4 simulations. The comparison of the response of two arrays with polished and de-polished crystals, respectively, shows in the latter case a significant improvement of the constant term of the parametrization of the energy resolution down to 0.5% accompanied by only very slight increase of the statistical term.
Energy Technology Data Exchange (ETDEWEB)
Diehl, Stefan; Bremer, Daniel; Brinkmann, Kai-Thomas; Dormenev, Valery; Eissner, Tobias; Novotny, Rainer W.; Rosenbaum, Christoph; Zaunick, Hans-Georg
2017-06-11
The uniformity of the light collection is a crucial parameter for detectors based on inorganic scintillation crystals to guarantee a response proportional to the deposited energy. Especially in case of tapered crystals, like they are widely used to realize a 4π geometry of electromagnetic calorimeters (EMC) in high energy physics experiments, a strong non-uniformity is introduced by an additional focusing of the scintillation light due to the tapered geometry. The paper will discuss the determination and the reduction of the non-uniformity in strongly tapered lead tungstate crystals as used for the construction of the electromagnetic calorimeter of the PANDA detector at the future Facility for Antiproton and Ion Research (FAIR). Among different concepts for an uniformization a single de-polished lateral side face provided the optimum result with a remaining non-uniformity below 5% in good agreement with similar studies for the CMS ECAL at LHC. The impact on the achievable energy resolution in the energy regime of photons below 800 MeV is discussed in detail in comparison to GEANT4 simulations. The comparison of the response of two arrays with polished and de-polished crystals, respectively, shows in the latter case a significant improvement of the constant term of the parametrization of the energy resolution down to 0.5% accompanied by only very slight increase of the statistical term.
International Nuclear Information System (INIS)
Savel'ev, Sergey; Rakhmanov, A.L.; Nori, Franco
2006-01-01
Josephson plasma waves are scattered by the Josephson vortex lattice. This scattering results in a strong dependence, on the in-plane magnetic-field H ab , of the reflection and transmission of THz radiation propagating in layered superconductors. In particular, a tunable band-gap structure (THz photonic crystal) occurs in such a medium. These effects can be used, by varying H ab , for the selective frequency-filtering of THz radiation
Mukhopadhyay, Saikat; Bansal, Dipanshu; Delaire, Olivier; Perrodin, Didier; Bourret-Courchesne, Edith; Singh, David J.; Lindsay, Lucas
2017-09-01
Strongly anharmonic phonon properties of CuCl are investigated with inelastic neutron-scattering measurements and first-principles simulations. An unusual quasiparticle spectral peak emerges in the phonon density of states with increasing temperature, in both simulations and measurements, emanating from exceptionally strong coupling between conventional phonon modes. Associated with this strong anharmonicity, the lattice thermal conductivity of CuCl is extremely low and exhibits anomalous, nonmonotonic pressure dependence. We show how this behavior arises from the structure of the phonon dispersions augmenting the phase space available for anharmonic three-phonon scattering processes, and contrast this mechanism with common arguments based on negative Grüneisen parameters. These results demonstrate the importance of considering intrinsic phonon-dispersion structure toward understanding scattering processes and designing new ultralow thermal conductivity materials.
Anisotropic Light Diffraction by Ultrasound in Crystals with Strong Acoustic Anisotropy
Voloshin, Andrey S.; Balakshy, Vladimir I.
In modern acousto-optics, crystalline materials are used predominantly for manufacturing acousto-optic instruments. Among these materials, such crystals as paratellurite, tellurium, calomel, TAS and some others occupy a prominent place, which are distinguished by exceptionally large anisotropy of acoustic properties. In this work, the influence of acoustic beam energy walk-off on characteristics of Bragg diffraction of light is studied by the example of tellurium crystal. It is shown that the walk-off can substantially change angular and frequency ranges, resulting in their narrowing or broadening subject to position of the operating point in the Bragg angle frequency characteristic. Coefficients of broadening are introduced for characterization of this effect.
Quantum anharmonic oscillator: The airy function approach
Energy Technology Data Exchange (ETDEWEB)
Maiz, F., E-mail: fethimaiz@gmail.com [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia); University of Cartage, Nabeul Engineering Preparatory Institute, Merazka, 8000 Nabeul (Tunisia); AlFaify, S. [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia)
2014-05-15
New and simple numerical method is being reported to solve anharmonic oscillator problems. The method is setup to approach the real potential V(x) of the anharmonic oscillator system as a piecewise linear potential u(x) and to solve the Schrödinger equation of the system using the Airy function. Then, solutions continuity conditions lead to the energy quantification condition, and consequently, the energy eigenvalues. For testing purpose, the method was applied on the sextic and octic oscillators systems. The proposed method is found to be realistic, computationally simple, and having high degrees of accuracy. In addition, it can be applied to any form of potential. The results obtained by the proposed method were seen closely agreeing with results reached by other complicated methods.
Energy Technology Data Exchange (ETDEWEB)
Leys, Jan; Glorieux, Christ; Thoen, Jan [Laboratorium voor Akoestiek en Thermische Fysica, Departement Natuurkunde en Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D-bus 2416, B-3001 Leuven (Belgium)], E-mail: jan.leys@fys.kuleuven.be, E-mail: jan.thoen@fys.kuleuven.be
2008-06-18
Dielectric spectroscopy has often been used to study confinement effects in alkylcyanobiphenyl liquid crystals. In this paper, we highlight some of the effects that have been discovered previously and add new data and interpretation. Aerosil nanoparticles form a hydrogen bonded random porous network. In dispersions of alkylcyanobiphenyls with aerosils, an additional slow process arises, that we ascribe to the relaxation of liquid crystal molecules in close interaction with these nanoparticles. Their relaxation is retarded by a hydrogen bond interaction between the cyano group of the liquid crystals and an aerosil surface hydroxyl group. A similar surface process is also observed in Vycor porous glass, a random rigid structure with small pores. A comparison of the temperature dependence of the relaxation times of the surface processes in decylcyanobiphenyl and isopentylcyanobiphenyl is made, both for Vycor and aerosil confinement. In decylcyanobiphenyl, the temperature dependence for the bulk and surface processes is Arrhenius (in a limited temperature range above the melting point), except in Vycor, where it is a Vogel-Fulcher-Tamman dependence (over a much broader temperature range). In bulk and confined isopentylcyanobiphenyl, the molecular processes have a Vogel-Fulcher-Tamman dependence, whereas the surface processes have an Arrhenius one. Another effect is the acceleration of the rotation around the short molecular axis in confinement, and particularly in aerosil dispersions. This is a consequence of the disorder introduced in the liquid crystalline phase. The disorder drives the relaxation time towards a more isotropic value, resulting in an acceleration for the short axis rotation.
Anharmonic thermal vibrations of be metal found in the MEM nuclear density map
International Nuclear Information System (INIS)
Takata, Masaki; Sakata, Makoto; Larsen, F.K.; Kumazawa, Shintaro; Iversen, B.B.
1993-01-01
A direct observation of the thermal vibrations of Be metal was performed by the Maximum Entropy Method (MEM) using neutron single crystal data. In the previous study, the existence of the small but significant cubic anharmonicity of Be has been found by the conventional least squares refinement of the observed structure factors [Larsen, Lehmann and Merisalo (1980) Acta Cryst. A36, 159-163]. In the present study, the same data were used for the MEM analysis which are comprised of 48 reflections up to sinθ/λ = 1.41A -1 in order to obtain the high resolution nuclear density of Be without using any thermal vibrational model. It was directly visible in the MEM map that not only the cubic terms but also quartic anharmonicities exist in the thermal vibrations of Be nuclei. In order to evaluate thermal parameters of Be including anharmonic terms quantitatively, the least squares refinement of the effective one-particle potential (OPP) parameters up to quartic term was carried out by using the MEM nuclear densities around atomic sites as the data set to be fitted. It was found that the present treatment has a great advantage to decide the most appropriate model of OPP by visually comparing the model with MEM density map. As a result of the least squares refinement, the anharmonic thermal parameters are obtained as α 33 = -0.340(5)[eV/A 3 ], α 40 = 0, β 20 = 9.89(1)[eV/A 4 ] and γ 00 = 0. No other anharmonic term was significant. (author)
Voloshinov, Vitaly; Polikarpova, Nataliya; Ivanova, Polina; Khorkin, Vladimir
2018-04-01
Peculiar cases of acoustic wave propagation and reflection may be observed in strongly anisotropic acousto-optical crystals. A tellurium dioxide crystal serves as a prime example of such media, since it possesses record indexes of acoustic anisotropy. We studied one of the unusual scenarios of acoustic incidence and reflection from a free crystal-vacuum boundary in paratellurite. The directions of the acoustic waves in the (001) plane of the crystal were determined, and their basic characteristics were calculated. The carried-out acousto-optic experiment at the wavelength of light 532 nm and the acoustic frequency 73 MHz confirmed the theoretical predictions. The effects examined in the paper include the acoustic wave propagation with the record walkoff angle 74°. We also observed the incidence of the wave on the boundary at the angle exceeding 90°. Finally, we registered the close-to-back reflection of acoustic energy following the incidence. One of the stunning aspects is the distribution of energy between the incident and the back-reflected wave. The unusual features of the acoustic wave reflections pointed out in the paper are valuable for their possible applications in acousto-optic devices.
Infrared and Raman Spectra of and Isotopomers: A DFT-PT2 Anharmonic Study
Directory of Open Access Journals (Sweden)
Andrea Alparone
2013-01-01
Full Text Available IR and Raman spectra of selenophene and of its perdeuterated isotopomer have been obtained in gas phase through density-functional theory (DFT computations. Vibrational wavenumbers have been calculated using harmonic and anharmonic second-order perturbation theory (PT2 procedures with the B3LYP method and the 6-311 basis set. Anharmonic overtones have been determined by means of the PT2 method. The introduction of anharmonic terms decreases the harmonic wavenumbers, giving a significantly better agreement with the experimental data. The most significant anharmonic effects occur for the C–H and C–D stretching modes, the observed H/D isotopic wavenumber redshifts being satisfactorily reproduced by the PT2 computations within 6–20 cm−1 (1–3%. In the spectral region between 500 cm−1 and 1500 cm−1, the IR spectra are dominated by the out-of-plane C–H (C–D bending transition, whereas the Raman spectra are mainly characterized by a strong peak mainly attributed to the C=C + C–C bonds stretching vibration with the contribution of the in-plane C–H (C–D bending deformation. The current results confirm that the PT2 approach combined with the B3LYP/6-311 level of calculation is a satisfactory choice for predicting vibrational spectra of cyclic molecules.
Zhou, Xue; Li, Mingzhu; Wang, Kang; Li, Huizeng; Li, Yanan; Li, Chang; Yan, Yongli; Zhao, Yongsheng; Song, Yanlin
2018-03-25
Stimulated emission in perovskite-embedded polymer opal structures is investigated. A polymer opal structure is filled with a perovskite, and perovskite photonic crystals are prepared. The spontaneous emission of the perovskite embedded in the polymer opal structures exhibits clear signatures of amplified spontaneous emission (ASE) via gain modulation. The difference in refractive-index contrast between the perovskite and the polymer opal is large enough for retaining photonic-crystals properties. The photonic band gap has a strong effect on the fluorescence emission intensity and lifetime. The stimulated emission spectrum exhibits a narrow ASE rather than a wide fluorescence peak in the thin film. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Long-wave model for strongly anisotropic growth of a crystal step.
Khenner, Mikhail
2013-08-01
A continuum model for the dynamics of a single step with the strongly anisotropic line energy is formulated and analyzed. The step grows by attachment of adatoms from the lower terrace, onto which atoms adsorb from a vapor phase or from a molecular beam, and the desorption is nonnegligible (the "one-sided" model). Via a multiscale expansion, we derived a long-wave, strongly nonlinear, and strongly anisotropic evolution PDE for the step profile. Written in terms of the step slope, the PDE can be represented in a form similar to a convective Cahn-Hilliard equation. We performed the linear stability analysis and computed the nonlinear dynamics. Linear stability depends on whether the stiffness is minimum or maximum in the direction of the step growth. It also depends nontrivially on the combination of the anisotropy strength parameter and the atomic flux from the terrace to the step. Computations show formation and coarsening of a hill-and-valley structure superimposed onto a long-wavelength profile, which independently coarsens. Coarsening laws for the hill-and-valley structure are computed for two principal orientations of a maximum step stiffness, the increasing anisotropy strength, and the varying atomic flux.
Mootha, A.; Takanezawa, Y.; Iwasaka, M.
2018-05-01
The present study focused on the vibration of micro crystal particles of guanine due to Brownian motion. The organic particle has a refractive index of 1.83 and caused a flickering of light. To test the possibility of using magnetic properties under wet conditions, changes in the frequency of particle vibration by applying magnetic fields were investigated. At first, we found that the exposure at 5 T inhibited the flickering light intensities and the particle vibration slightly decreased. Next, we carried out a high speed camera measurement of the Brownian motion of the particle with a time resolution of 100 flame per second (fps) with and without magnetic field exposures. It was revealed that the vibrational speed of synthetic particles was enhanced at 500 mT. Detailed analyses of the particle vibration by changing the direction of magnetic fields versus the light source revealed that the Brownian motion's vibrational frequency was entrained under magnetic fields at 500 mT, and an increase in vibration speed to 20Hz was observed. Additional measurements of light scattering fluctuation using photo-detector and analyses on auto-correlation also confirmed this speculation. The studied Brownian vibration may be influenced by the change in mechanical interactions between the vibration particles and surrounding medium. The discovered phenomena can be applied for molecular and biological interactions in future studies.
Directory of Open Access Journals (Sweden)
Sawrab Chowdhury
2017-04-01
Full Text Available In this article, porous core porous cladding photonic crystal fiber (P-PCF has been proposed for aqueous analytes sensing applications. Guiding properties of the proposed P-PCF has been numerically investigated by utilizing the full vectorial finite element method (FEM. The relative sensitivity and confinement loss are obtained by varying distinct geometrical parameters like the diameter of air holes, a pitch of the core and cladding region over a wider range of wavelength. The proposed P-PCF is organized with five rings air hole in the cladding and two rings air hole in a core territory which maximizes the relative sensitivity expressively and minimizes confinement loss depressively compare with the prior-PCF structures. After completing all investigations, it is also visualized that the relative sensitivity is increasing with the increment of the wavelength of communication band (O + E + S + C + L + U. Higher sensitivity is gained by using higher band for all applied liquids. Finally the investigating effects of different structural parameters of the proposed P-PCF are optimized which shows the sensitivity of 60.57%, 61.45% and 61.82%; the confinement loss of 8.71 × 10−08 dB/m, 1.41 × 10−10 dB/m and 6.51 × 10−10 dB/m for Water (n = 1.33, Ethanol (n = 1.354 and Benzene (n = 1.366 respectively at 1.33 μm wavelength. The optimized P-PCF with higher sensitivity and lower confinement loss has high impact in the area of the chemical as well as gas sensing purposes. Keywords: Porous shaped PCF, Sensitivity, Optical sensing, Liquid sensor, Confinement loss
Realization of collective strong coupling with ion Coulomb crystals in an optical cavity
DEFF Research Database (Denmark)
Herskind, Peter Fønss; Dantan, Aurélien; Marler, Joan
2009-01-01
Cavity quantum electrodynamics (CQED) focuses on understanding the interactions between matter and the electromagnetic field in cavities at the quantum level 1, 2 . In the past years, CQED has attracted attention 3, 4, 5, 6, 7, 8, 9 especially owing to its importance for the field of quantum...... information 10 . At present, photons are the best carriers of quantum information between physically separated sites 11, 12 and quantum-information processing using stationary qubits 10 is most promising, with the furthest advances having been made with trapped ions 13, 14, 15 . The implementation of complex...... quantum-information-processing networks 11, 12 hence requires devices to efficiently couple photons and stationary qubits. Here, we present the first CQED experiments demonstrating that the collective strong-coupling regime 2 can be reached in the interaction between a solid in the form of an ion Coulomb...
Errea, Ion; Calandra, Matteo; Mauri, Francesco
2013-10-25
Palladium hydrides display the largest isotope effect anomaly known in the literature. Replacement of hydrogen with the heavier isotopes leads to higher superconducting temperatures, a behavior inconsistent with harmonic theory. Solving the self-consistent harmonic approximation by a stochastic approach, we obtain the anharmonic free energy, the thermal expansion, and the superconducting properties fully ab initio. We find that the phonon spectra are strongly renormalized by anharmonicity far beyond the perturbative regime. Superconductivity is phonon mediated, but the harmonic approximation largely overestimates the superconducting critical temperatures. We explain the inverse isotope effect, obtaining a -0.38 value for the isotope coefficient in good agreement with experiments, hydrogen anharmonicity being mainly responsible for the isotope anomaly.
Superconductivity mediated by anharmonic phonons: application to β-pyrochlore oxides
Hattori, Kazumasa; Tsunetsugu, Hirokazu
2010-03-01
We investigate three dimensional anharmonic phonons under tetrahedral symmetry and superconductivity mediated by these phonons. Three dimensional anharmonic phonon spectra are calculated directly by solving Schr"odinger equation and the superconducting transition temperature is determined by using the theory of strong coupling superconductivity assuming an isotropic gap function. With increasing the third order anharmonicity b of the tetrahedral potential, we find a crossover in the energy spectrum to a quantum tunneling regime. We obtain strongly enhanced transition temperatures around the crossover point. The first order transition observed in KOs2O6 is discussed in terms of the first excited state energy δ, and the coupling constant λ in the strong coupling theory of superconductivity. Our results suggest that the decrease of λ and increase of δ below the first order transition temperature. We point out that the change in the oscillation amplitude and characterizes this isomorphic transition. The chemical trends of the superconducting transition temperature, λ, and δ in the β-pyrochlore compounds are also discussed.
Properties of one-dimensional anharmonic lattice solitons
Szeftel, Jacob; Laurent-Gengoux, Pascal; Ilisca, Ernest; Hebbache, Mohamed
2000-12-01
The existence of bell- and kink-shaped solitons moving at constant velocity while keeping a permanent profile is studied in infinite periodic monoatomic chains of arbitrary anharmonicity by taking advantage of the equation of motion being integrable with respect to solitons. A second-order, non-linear differential equation involving advanced and retarded terms must be solved, which is done by implementing a scheme based on the finite element and Newton's methods. If the potential has a harmonic limit, the asymptotic time-decay behaves exponentially and there is a dispersion relation between propagation velocity and decay time. Inversely if the potential has no harmonic limit, the asymptotic regime shows up either as a power-law or faster than exponential. Excellent agreement is achieved with Toda's model. Illustrative examples are also given for the Fermi-Pasta-Ulam and sine-Gordon potentials. Owing to integrability an effective one-body potential is worked out in each case. Lattice and continuum solitons differ markedly from one another as regards the amplitude versus propagation velocity relationship and the asymptotic time behavior. The relevance of the linear stability analysis when applied to solitons propagating in an infinite crystal is questioned. The reasons preventing solitons from arising in a diatomic lattice are discussed.
Anharmonic potential in the oscillator representation
International Nuclear Information System (INIS)
Dineykhan, M.; Efimov, G.V.
1994-01-01
In the non relativistic and relativized Schroedinger equation the Wick ordering method called the oscillator representation is proposed to calculate the energy spectrum for a wide class of potentials allowing the existence of a bound state. The oscillator representation method gives a unique regular way to describe and calculate the energy levels of ground as well as orbital and radial excitation states for a wide class of potentials. The results of the zeroth approximation oscillator representation are in good agreement with the exact values for the anharmonic potentials. The oscillator representation method was applied to the relativized Schroedinger equation too. The perturbation series converges fairly fast, i.e., the highest perturbation corrections over the interaction Hamiltonian are small enough. 29 refs.; 4 tabs. (author)
Directory of Open Access Journals (Sweden)
Adela Rodríguez-Romero
2017-06-01
Full Text Available The first part of this research was devoted to investigating the effect of alternate current (AC using four different types of wave modes (pulse-wave at 2 Hz on the crystal growth of lysozyme in solution. The best results, in terms of size and crystal quality, were obtained when protein crystals were grown under the influence of electric fields in a very specific wave mode (“breathing” wave, giving the highest resolution up to 1.34 Å in X-ray diffraction analysis compared with controls and with those crystals grown in gel. In the second part, we evaluated the effect of a strong magnetic field of 16.5 Tesla combined with radiofrequency pulses of 0.43 μs on the crystal growth in gels of tetragonal hen egg white (HEW lysozyme. The lysozyme crystals grown, both in solution applying breathing-wave and in gel under the influence of this strong magnetic field with pulses of radio frequencies, produced the larger-in-size crystals and the highest resolution structures. Data processing and refinement statistics are very good in terms of the resolution, mosaicity and Wilson B factor obtained for each crystal. Besides, electron density maps show well-defined and distinctly separated atoms at several selected tryptophan residues for the crystal grown using the “breathing wave pulses”.
Time evolution of gibbs states for an anharmonic lattice
Energy Technology Data Exchange (ETDEWEB)
Marchioro, C; Pellegrinotti, A; Suhov, Y [Camerino Univ. (Italy). Istituto di Matematica; Pulvirenti, M [L' Aquila Univ. (Italy). Istituto di Matematica; Rome Univ. (Italy). Istituto di Matematica)
1979-01-01
In this paper we study the time evolution of a regular class of states of an infinite classical system of anharmonic oscillators. The conditional probabilities are investigated and an explicit form for these is given.
Dynamic of cold-atom tips in anharmonic potentials
Menold, Tobias; Federsel, Peter; Rogulj, Carola; Hölscher, Hendrik; Fortágh, József
2016-01-01
Background: Understanding the dynamics of ultracold quantum gases in an anharmonic potential is essential for applications in the new field of cold-atom scanning probe microscopy. Therein, cold atomic ensembles are used as sensitive probe tips to investigate nanostructured surfaces and surface-near potentials, which typically cause anharmonic tip motion. Results: Besides a theoretical description of this anharmonic tip motion, we introduce a novel method for detecting the cold-atom tip dynamics in situ and real time. In agreement with theory, the first measurements show that particle interactions and anharmonic motion have a significant impact on the tip dynamics. Conclusion: Our findings will be crucial for the realization of high-sensitivity force spectroscopy with cold-atom tips and could possibly allow for the development of advanced spectroscopic techniques such as Q-control. PMID:28144505
Time evolution of gibbs states for an anharmonic lattice
International Nuclear Information System (INIS)
Marchioro, C.; Pellegrinotti, A.; Suhov, Y.; Pulvirenti, M.; Rome Univ.
1979-01-01
In this paper we study the time evolution of a regular class of states of an infinite classical system of anharmonic oscillators. The conditional probabilities are investigated and an explicit form for these is given. (orig.) [de
Shen, Tonghao; Su, Neil Qiang; Wu, Anan; Xu, Xin
2014-03-05
In this work, we first review the perturbative treatment of an oscillator with cubic anharmonicity. It is shown that there is a quantum-classical correspondence in terms of mean displacement, mean-squared displacement, and the corresponding variance in the first-order perturbation theory, provided that the amplitude of the classical oscillator is fixed at the zeroth-order energy of quantum mechanics EQM (0). This correspondence condition is realized by proposing the extended Langevin dynamics (XLD), where the key is to construct a proper driving force. It is assumed that the driving force adopts a simple harmonic form with its amplitude chosen according to EQM (0), while the driving frequency chosen as the harmonic frequency. The latter can be improved by using the natural frequency of the system in response to the potential if its anharmonicity is strong. By comparing to the accurate numeric results from discrete variable representation calculations for a set of diatomic species, it is shown that the present method is able to capture the large part of anharmonicity, being competitive with the wave function-based vibrational second-order perturbation theory, for the whole frequency range from ∼4400 cm(-1) (H2 ) to ∼160 cm(-1) (Na2 ). XLD shows a substantial improvement over the classical molecular dynamics which ceases to work for hard mode when zero-point energy effects are significant. Copyright © 2013 Wiley Periodicals, Inc.
International Nuclear Information System (INIS)
Solontsov, A.
2015-01-01
The paper critically overviews the recent developments of the theory of spatially dispersive spin fluctuations (SF) in itinerant electron magnetism with particular emphasis on spin-fluctuation coupling or spin anharmonicity. It is argued that the conventional self-consistent renormalized (SCR) theory of spin fluctuations is usually used aside of the range of its applicability actually defined by the constraint of weak spin anharmonicity based on the random phase approximation (RPA) arguments. An essential step in understanding SF in itinerant magnets beyond RPA-like arguments was made recently within the soft-mode theory of SF accounting for strong spin anharmonicity caused by zero-point SF. In the present paper we generalize it to apply for a wider range of temperatures and regimes of SF and show it to lead to qualitatively new results caused by zero-point effects. - Highlights: • We review the spin-fluctuation theory of itinerant electron magnets with account of zero-point effects. • We generalize the existing theory to account for different regimes of spin fluctuations. • We show that zero-point spin fluctuations play a crucial role in both low- and high-temperature properties of metallic magnets. • We argue that a new scheme of calculation of ground state properties of magnets is needed including zero-point effects
Effects of hypersonic field and anharmonic interactions on channelling radiation
International Nuclear Information System (INIS)
George, Juby; Pathak, Anand P; Goteti, L N S Prakash; Nagamani, G
2007-01-01
The effects of a hypersonic field on positron channelling radiation are considered. Anharmonic effects of the transverse potential induced by these longitudinal fields are incorporated and the wavefunction of the planar channelled positron is found by the solution of Dirac equation under the resonant influence of hypersound. An expression for the resonant frequency is estimated. The transition probabilities and the intensity of the channelling radiation are also calculated. It is found that the anharmonic effects change the spectral distributions considerably
Ground state energy values and moments of the anharmonic oscillator
International Nuclear Information System (INIS)
Seetharaman, M.; Raghavan, Sekhar; Subba Rao, G.
1981-01-01
It is shown that a very satisfactory estimate of the energy values (for all values of the anharmonicity) and moments of the ground state of the quartic anharmonic oscillator can be obtained in the variational method, by considering trial wavefunctions which have the correct asymptotic properties. The results derived with a single variational parameter are a considerable improvement over the recent results of C.A. Ginsburg and E.W. Montroll (1978). (author)
Current dependent angular magnetoresistance in strongly Pr-doped Y Ba2Cu3O7-δ single crystal
International Nuclear Information System (INIS)
Sandu, V; Gyawali, P; Katuwal, T; Almasan, C C; Taylor, B J; Maple, M B
2009-01-01
We report a strong dependence of the angular magnetoresistance (AMR) on the current density in Y Ba 2 Cu 3 O 7-δ single crystal above the critical temperature T c = 13 K for any applied field up to 14 T. We estimated the current dependence from the angular dependence of the top resistance R top , as measured on the face where the current is applied, and the bottom resistance R bot as measured on the opposite face. At any temperature, both below and above T c , R top decreases as the field becomes parallel to the current and ab-plane with an angle dependence that suggests an important contribution arising from the vortex flow. R bot evolves from a monotonic to nonmonotonic angle dependence with three minima and two maxima in the angle range 0 - 180 deg. as the temperature increases. For less Pr-doped samples, Y 0.58 Pr 0.42 Ba 2 Cu 3 O 7-δ (T c = 39 K) and Y 0.68 rP 0.32 Ba 2 Cu 3 O 7-δ (T c = 55 K), where the interplane resistivity is much lower, both R top and R bot follow the same monotonic angle dependence in all temperature and field range.
Mauri, Francesco
Anharmonic effects can generally be treated within perturbation theory. Such an approach breaks down when the harmonic solution is dynamically unstable or when the anharmonic corrections of the phonon energies are larger than the harmonic frequencies themselves. This situation occurs near lattice-related second-order phase-transitions such as charge-density-wave (CDW) or ferroelectric instabilities or in H-containing materials, where the large zero-point motion of the protons results in a violation of the harmonic approximation. Interestingly, even in these cases, phonons can be observed, measured, and used to model transport properties. In order to treat such cases, we developed a stochastic implementation of the self-consistent harmonic approximation valid to treat anharmonicity in the nonperturbative regime and to obtain, from first-principles, the structural, thermodynamic and vibrational properties of strongly anharmonic systems. I will present applications to the ferroelectric transitions in SnTe, to the CWD transitions in NbS2 and NbSe2 (in bulk and monolayer) and to the hydrogen-bond symmetrization transition in the superconducting hydrogen sulfide system, that exhibits the highest Tc reported for any superconductor so far. In all cases we are able to predict the transition temperature (pressure) and the evolution of phonons with temperature (pressure). This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement No. 696656 GrapheneCore1.
Improved models of dense anharmonic lattices
Energy Technology Data Exchange (ETDEWEB)
Rosenau, P., E-mail: rosenau@post.tau.ac.il; Zilburg, A.
2017-01-15
We present two improved quasi-continuous models of dense, strictly anharmonic chains. The direct expansion which includes the leading effect due to lattice dispersion, results in a Boussinesq-type PDE with a compacton as its basic solitary mode. Without increasing its complexity we improve the model by including additional terms in the expanded interparticle potential with the resulting compacton having a milder singularity at its edges. A particular care is applied to the Hertz potential due to its non-analyticity. Since, however, the PDEs of both the basic and the improved model are ill posed, they are unsuitable for a study of chains dynamics. Using the bond length as a state variable we manipulate its dispersion and derive a well posed fourth order PDE. - Highlights: • An improved PDE model of a Newtonian lattice renders compacton solutions. • Compactons are classical solutions of the improved model and hence amenable to standard analysis. • An alternative well posed model enables to study head on interactions of lattices' solitary waves. • Well posed modeling of Hertz potential.
Anharmonic effects in the quantum cluster equilibrium method
von Domaros, Michael; Perlt, Eva
2017-03-01
The well-established quantum cluster equilibrium (QCE) model provides a statistical thermodynamic framework to apply high-level ab initio calculations of finite cluster structures to macroscopic liquid phases using the partition function. So far, the harmonic approximation has been applied throughout the calculations. In this article, we apply an important correction in the evaluation of the one-particle partition function and account for anharmonicity. Therefore, we implemented an analytical approximation to the Morse partition function and the derivatives of its logarithm with respect to temperature, which are required for the evaluation of thermodynamic quantities. This anharmonic QCE approach has been applied to liquid hydrogen chloride and cluster distributions, and the molar volume, the volumetric thermal expansion coefficient, and the isobaric heat capacity have been calculated. An improved description for all properties is observed if anharmonic effects are considered.
Directory of Open Access Journals (Sweden)
Haribabu Palneedi
2017-03-01
Full Text Available Aimed at developing lead-free magnetoelectric (ME composites with performances as good as lead (Pb-based ones, this study employed (001 and (011 oriented 82BaTiO3-10BaZrO3-8CaTiO3 (BZT–BCT piezoelectric single crystals, fabricated by the cost-effective solid-state single crystal growth (SSCG method, in combination with inexpensive, magnetostrictive base metal Nickel (Ni. The off-resonance, direct ME coupling in the prepared Ni/BZT–BCT/Ni laminate composites was found to be strongly dependent on the crystallographic orientation of the BZT–BCT single crystals, as well as the applied magnetic field direction. Larger and anisotropic ME voltage coefficients were observed for the composite made using the (011 oriented BZT–BCT single crystal. The optimized ME coupling of 1 V/cm Oe was obtained from the Ni/(011 BZT–BCT single crystal/Ni composite, in the d32 mode of the single crystal, when a magnetic field was applied along its [100] direction. This performance is similar to that reported for the Ni/Pb(Mg1/3Nb2/3O3-Pb(Zr,TiO3 (PMN–PZT single crystal/Ni, but larger than that obtained from the Ni/Pb(Zr,TiO3 ceramic/Ni composites. The results of this work demonstrate that the use of lead-free piezoelectric single crystals with special orientations permits the selection of desired anisotropic properties, enabling the realization of customized ME effects in composites.
Exact solutions and ladder operators for a new anharmonic oscillator
International Nuclear Information System (INIS)
Dong Shihai; Sun Guohua; Lozada-Cassou, M.
2005-01-01
In this Letter, we propose a new anharmonic oscillator and present the exact solutions of the Schrodinger equation with this oscillator. The ladder operators are established directly from the normalized radial wave functions and used to evaluate the closed expressions of matrix elements for some related functions. Some comments are made on the general calculation formula and recurrence relation for off-diagonal matrix elements. Finally, we show that this anharmonic oscillator possesses a hidden symmetry between E(r) and E(ir) by substituting r->ir
Spin Wave Theory of Strongly Anisotropic Magnets
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1977-01-01
A strong anisotropy gives rise to a non-spherical precession of the spins with different amplitudes in the x and y directions. The highly anharmonic exchange interaction thereby becomes effectively anisotropic. The possibility of detecting a genuine two-ion anisotropy is discussed, and comments...
Energy Technology Data Exchange (ETDEWEB)
Lewins, C. J., E-mail: c.j.lewins@bath.ac.uk; Le Boulbar, E. D.; Lis, S. M.; Shields, P. A.; Allsopp, D. W. E., E-mail: d.allsopp@bath.ac.uk [Department of Electronic and Electrical Engineering, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)
2014-07-28
We show that arrays of emissive nanorod structures can exhibit strong photonic crystal behavior, via observations of the far-field luminescence from core-shell and quantum disc InGaN/GaN nanorods. The conditions needed for the formation of directional Bloch modes characteristic of strong photonic behavior are found to depend critically upon the vertical shape of the nanorod sidewalls. Index guiding by a region of lower volume-averaged refractive index near the base of the nanorods creates a quasi-suspended photonic crystal slab at the top of the nanorods which supports Bloch modes. Only diffractive behavior could be observed without this region. Slab waveguide modelling of the vertical structure shows that the behavioral regime of the emissive nanorod arrays depends strongly upon the optical coupling between the nanorod region and the planar layers below. The controlled crossover between the two regimes of photonic crystal operation enables the design of photonic nanorod structures formed on planar substrates that exploit either behavior depending on device requirements.
Variational random phase approximation for the anharmonic oscillator
International Nuclear Information System (INIS)
Dukelsky, J.; Schuck, P.
1990-04-01
The recently derived Variational Random Phase Approximation is examined using the anharmonic oscillator model. Special attention is paid to the ground state RPA wave function and the convergence of the proposed truncation scheme to obtain the diagonal density matrix. Comparison with the standard Coupled Cluster method is made
Spherical anharmonic oscillator in self-similar approximation
International Nuclear Information System (INIS)
Yukalova, E.P.; Yukalov, V.I.
1992-01-01
The method of self-similar approximation is applied here for calculating the eigenvalues of the three-dimensional spherical anharmonic oscillator. The advantage of this method is in its simplicity and high accuracy. The comparison with other known analytical methods proves that this method is more simple and accurate. 25 refs
Harmonic and Anharmonic Behaviour of a Simple Oscillator
O'Shea, Michael J.
2009-01-01
We consider a simple oscillator that exhibits harmonic and anharmonic regimes and analyse its behaviour over the complete range of possible amplitudes. The oscillator consists of a mass "m" fixed at the midpoint of a horizontal rope. For zero initial rope tension and small amplitude the period of oscillation, tau, varies as tau is approximately…
Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu
2014-07-01
A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.
Strong crystal field effect in Np{sup 4+}:ThCl{sub 4} - optical absorption study
Energy Technology Data Exchange (ETDEWEB)
Gajek, Z. [Instytut Niskich Temperatur i Badan Strukturalnych, Polska Akademia Nauk, 50-950 Wroclaw 2, Skr. Poczt. 1410 (Poland); Krupa, J.C. [Laboratoire de Radiochimie, Institut de Physique Nucleaire, BP 1, 91406 Orsay Cedex (France)
1998-12-21
Results of optical absorption measurements in polarized light on tetravalent neptunium diluted in a ThCl{sub 4} single crystal are reported. The recorded spectra are complex, pointing to the presence of an Np{sup 3+} impurity. The electronic transitions assigned to the Np{sup 4+} ion are interpreted in terms of the usual model, following the actual understanding of the neptunium electronic structure and independent theoretical predictions. R.m.s. deviations of the order of 36 cm{sup -1} have been obtained for 42 levels fitted with 11 free parameters. The crystal field effect resulting from the fitting is considerably larger than that observed for the uranium ion in the same host. (author)
Bianco, Raffaello; Errea, Ion; Calandra, Matteo; Mauri, Francesco
2018-06-01
We study the structural and vibrational properties of the high-temperature superconducting sulfur trihydride and trideuteride in the high-pressure I m 3 ¯m and R 3 m phases by first-principles density-functional-theory calculations. On lowering pressure, the rhombohedral transition I m 3 ¯m →R 3 m is expected, with hydrogen-bond desymmetrization and occurrence of trigonal lattice distortion. With both Perdew-Burke-Ernzerhof (PBE) and Becke-Lee-Yang-Parr (BLYP) exchange-correlation functional, in hydrostatic conditions we find that, contrary to what is suggested in some recent experiments, if the rhombohedral distortion exists it affects mainly the hydrogen bonds, whereas the resulting cell distortion is minimal. We estimate that the occurrence of a stress anisotropy of approximately 10 % could explain this discrepancy. Assuming hydrostatic conditions, we calculate the critical pressure at which the rhombohedral transition occurs. Quantum and anharmonic effects, which are relevant in this system, are included at nonperturbative level with the stochastic self-consistent harmonic approximation. Within this approach, we determine the transition pressure by calculating the free-energy Hessian, a method that allows to estimate the critical pressure with much higher precision (and much lower computational cost) compared with the free-energy "finite-difference" approach previously used. Using PBE and BLYP, we find that quantum anharmonic effects are responsible for a strong reduction of the critical pressure with respect to the one obtained with the classical harmonic approach. Interestingly, for the two functionals, even if the transition pressures at classical harmonic level differ by 83 GPa, the transition pressures including quantum anharmonic effects differ only by 23 GPa. Moreover, we observe a prominent isotope effect, as we estimate higher transition pressure for D3S than for H3S . Finally, within the stochastic self-consistent harmonic approximation, with PBE
Energy Technology Data Exchange (ETDEWEB)
Williams, Robert W. [Department of Biomedical Informatics, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20815 (United States)], E-mail: bob@bob.usuhs.mil; Schluecker, Sebastian [Institute of Physical Chemistry, University of Wuerzburg, Wuerzburg (Germany); Hudson, Bruce S. [Department of Chemistry, Syracuse University, Syracuse, NY (United States)
2008-01-22
A scaled quantum mechanical harmonic force field (SQMFF) corrected for anharmonicity is obtained for the 23 K L-alanine crystal structure using van der Waals corrected periodic boundary condition density functional theory (DFT) calculations with the PBE functional. Scale factors are obtained with comparisons to inelastic neutron scattering (INS), Raman, and FT-IR spectra of polycrystalline L-alanine at 15-23 K. Calculated frequencies for all 153 normal modes differ from observed frequencies with a standard deviation of 6 wavenumbers. Non-bonded external k = 0 lattice modes are included, but assignments to these modes are presently ambiguous. The extension of SQMFF methodology to lattice modes is new, as are the procedures used here for providing corrections for anharmonicity and van der Waals interactions in DFT calculations on crystals. First principles Born-Oppenheimer molecular dynamics (BOMD) calculations are performed on the L-alanine crystal structure at a series of classical temperatures ranging from 23 K to 600 K. Corrections for zero-point energy (ZPE) are estimated by finding the classical temperature that reproduces the mean square displacements (MSDs) measured from the diffraction data at 23 K. External k = 0 lattice motions are weakly coupled to bonded internal modes.
International Nuclear Information System (INIS)
Williams, Robert W.; Schluecker, Sebastian; Hudson, Bruce S.
2008-01-01
A scaled quantum mechanical harmonic force field (SQMFF) corrected for anharmonicity is obtained for the 23 K L-alanine crystal structure using van der Waals corrected periodic boundary condition density functional theory (DFT) calculations with the PBE functional. Scale factors are obtained with comparisons to inelastic neutron scattering (INS), Raman, and FT-IR spectra of polycrystalline L-alanine at 15-23 K. Calculated frequencies for all 153 normal modes differ from observed frequencies with a standard deviation of 6 wavenumbers. Non-bonded external k = 0 lattice modes are included, but assignments to these modes are presently ambiguous. The extension of SQMFF methodology to lattice modes is new, as are the procedures used here for providing corrections for anharmonicity and van der Waals interactions in DFT calculations on crystals. First principles Born-Oppenheimer molecular dynamics (BOMD) calculations are performed on the L-alanine crystal structure at a series of classical temperatures ranging from 23 K to 600 K. Corrections for zero-point energy (ZPE) are estimated by finding the classical temperature that reproduces the mean square displacements (MSDs) measured from the diffraction data at 23 K. External k = 0 lattice motions are weakly coupled to bonded internal modes
International Nuclear Information System (INIS)
Hayashi, Kouichi; Nakajima, Kazuo; Fujiwara, Kozo; Nishikata, Susumu
2008-01-01
Si and Ge are widely used as analyzing crystals for x-rays. Drastic and accurate shaping of Si or Ge gives significant advance in the x-ray field, although covalently bonded Si or Ge crystals have long been believed to be not deformable to various shapes. Recently, we developed a deformation technique for obtaining strongly and accurately shaped Si or Ge wafers of high crystal quality, and the use of the deformed wafer made it possible to produce fine-focused x-rays. In the present study, we prepared a cylindrical Ge wafer with a radius of curvature of 50 mm, and acquired fluorescent x-rays simultaneously from four elements by combining the cylindrical Ge wafer with a position-sensitive detector. The energy resolution of the x-ray fluorescence spectrum was as good as that obtained using a flat single crystal, and its gain was over 100. The demonstration of the simultaneous acquisition of high-resolution x-ray fluorescence spectra indicated various possibilities of x-ray spectrometry, such as one-shot x-ray spectroscopy and highly efficient wave-dispersive x-ray spectrometers
Carignano, Marcelo Andrés
2017-09-05
We present a systematic study based on first principles molecular dynamics simulations of lead iodide perovskites with three different cations, including methylammonium (MA), formamidinium (FA) and cesium. Using the high temperature perovskite structure as a reference, we investigate the instabilities that develop as the material is cooled down to 370 K. All three perovskites display anharmonicity in the motion of the iodine atoms, with the stronger effect observed for the MAPbI$_3$ and CsPbI$_3$. At high temperature, this behavior can be traced back to the reduced effective size of the Cs$^+$ and MA$^+$ cations. MAPbI$_3$ undergoes a spontaneous phase transition within our simulation model driven by the dipolar interaction between neighboring MA cations as the temperature is decreased from 450 K. The reverse transformation from tetragonal to cubic is also monitored through the large distribution of the octahedral tilting angles accompanied by an increase in the anharmonicity of the iodine atoms motion. Both MA and FA hybrid perovskites show a strong coupling between the molecular orientations and the local lattice deformations, suggesting mixed order-disorder/displacive characters of the high temperature phase transitions.
Non-Gaussian wave packet dynamics in anharmonic potential: Cumulant expansion treatment
International Nuclear Information System (INIS)
Toutounji, Mohamad
2015-01-01
This manuscript utilizes cumulant expansion as an alternative algebraic approach to evaluating integrals and solving a system of nonlinear differential equations for probing anharmonic dynamics in condensed phase systems using Morse oscillator. These integrals and differential equations become harder to solve as the anharmonicity of the system goes beyond that of Morse oscillator description. This algebraic approach becomes critically important in case of Morse oscillator as it tends to exhibit divergent dynamics and numerical uncertainties at low temperatures. The autocorrelation function is calculated algebraically and compared to the exact one for they match perfectly. It is also compared to the approximate autocorrelation function using the differential equations technique reported in Toutounji (2014) for weak and strong electron–phonon coupling cases. It is found that the present cumulant method is more efficient, and easier to use, than the exact expression. Deviation between the approximate autocorrelation function and the exact autocorrelation function starts to arise as the electron–phonon coupling strength increases. The autocorrelation function obtained using cumulants identically matches the exact autocorrelation function, thereby surpassing the approach presented in Toutounji (2014). The advantage of the present methodology is its applicability to various types of electron–phonon coupling cases. Additionally, the herein approach only uses algebraic techniques, thereby avoiding both the divergence integral and solving a set of linear first- and second-order partial differential equations as was done in previous work. Model calculations are presented to demonstrate the accuracy of the herein work
Cooper-pair formation by anharmonic rattling modes in the β-pyrochlore superconductor KOs2O6
Chang, Jun; Eremin, Ilya; Thalmeier, Peter
2009-05-01
We study the influence of anharmonic rattling phonons in the β-pyrochlore superconductor KOs2O6 using the strong-coupling Eliashberg approach. In particular, by analyzing the specific heat data, we find that the rattling phonon frequency changes discontinuously at the critical temperature of the first-order phase transition. Solving the strong-coupling Eliashberg equations with effective temperature-dependent α2F(ω), we investigate the consequence of this first-order phase transition for the anomalous temperature dependence of the superconducting gap. We discuss our results in the context of the recent experimental data.
DEFF Research Database (Denmark)
Yang, X.N.; Zhou, C.; Sun, Q.J.
2014-01-01
We study the fragile-to-strong (F−S) transition of metallic glass-forming liquids (MGFLs) by measuring the thermal response during annealing and dynamic heating of La55Al25Ni5Cu15 glass ribbons fabricated at different cooling rates. We find that the glasses fabricated in the intermediate regime o...
Dirac bound states of anharmonic oscillator in external fields
International Nuclear Information System (INIS)
Hamzavi, Majid; Ikhdair, Sameer M.; Falaye, Babatunde J.
2014-01-01
We explore the effect of the external magnetic and Aharonov–Bohm (AB) flux fields on the energy levels of Dirac particle subjects to mixed scalar and vector anharmonic oscillator field in the two-dimensional (2D) space. We calculate the exact energy eigenvalues and the corresponding un-normalized two-spinor-components wave functions in terms of the chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by using the Nikiforov–Uvarov (NU) method. -- Highlights: • Effect of the external fields on the energy levels of Dirac particle with the anharmonic oscillator is investigated. • The solutions are discussed in view of spin and pseudospin symmetries limits. • The energy levels and wave function are presented by the Nikiforov–Uvarov method
Instantons and Borel resummability for the perturbed supersymmetric anharmonic oscillator
International Nuclear Information System (INIS)
Verbaarschot, J.J.M.; West, P.
1991-01-01
In this paper we give an analytical derivation of the large-order behavior of the perturbation series for both the ground state and the excited states of the supersymmetric anharmonic oscillator and of the anharmonic oscillator obtained from the supersymmetric case by varying the strength of the fermion coupling. The results which are obtained with the help of instanton calculus coincide with those obtained numerically in previous work. The large-order perturbation series of the ground state vanishes in the supersymmetric case, whereas away from the supersymmetric point the perturbation series diverges factorially. The perturbation series of the excited states diverges factorially both at the supersymmetric point and away from this point
Finite-element time evolution operator for the anharmonic oscillator
Milton, Kimball A.
1995-01-01
The finite-element approach to lattice field theory is both highly accurate (relative errors approximately 1/N(exp 2), where N is the number of lattice points) and exactly unitary (in the sense that canonical commutation relations are exactly preserved at the lattice sites). In this talk I construct matrix elements for dynamical variables and for the time evolution operator for the anharmonic oscillator, for which the continuum Hamiltonian is H = p(exp 2)/2 + lambda q(exp 4)/4. Construction of such matrix elements does not require solving the implicit equations of motion. Low order approximations turn out to be extremely accurate. For example, the matrix element of the time evolution operator in the harmonic oscillator ground state gives a results for the anharmonic oscillator ground state energy accurate to better than 1 percent, while a two-state approximation reduces the error to less than 0.1 percent.
Fragility, anharmonicity and anelasticity of silver borate glasses
International Nuclear Information System (INIS)
Carini, Giovanni; Carini, Giuseppe; D'Angelo, Giovanna; Tripodo, Gaspare; Bartolotta, Antonio; Marco, Gaetano Di
2006-01-01
The fragility and the anharmonicity of (Ag 2 O) x (B 2 O 3 ) 1-x borate glasses have been quantified by measuring the change in the specific heat capacity at the glass transition temperature T g and the room-temperature thermodynamic Grueneisen parameter. Increasing the silver oxide content above X = 0.10 leads to an increase of both the parameters, showing that a growing fragility of a glass-forming liquid is predictive of an increasing overall anharmonicity of its glassy state. The attenuation and velocity of ultrasonic waves of frequencies in the range of 10-70 MHz have also been measured in silver borate glasses as a function of temperature between 1.5 and 300 K. The experimental data reveal anelastic behaviours which are governed by (i) quantum-mechanical tunnelling below 20 K (ii) thermally activated relaxations between 20 and 200 K and (iii) vibrational anharmonicity at even higher temperatures. Evaluation of tunnelling (C) and relaxation (C * ) strengths shows that C is independent of the structural changes affecting the borate network with increasing metal oxide content and is at least one order of magnitude smaller than C * . The latter observation implies that only a small fraction of the locally mobile defects are subjected to tunnelling motions
Magnetic structure of RPdSn (R=Tb, Ho) single crystal compounds under strong magnetic field
International Nuclear Information System (INIS)
Andoh, Y.; Kurisu, M.; Nakamoto, G.; Tsutaoka, T.; Kawano, S.
2003-01-01
Rare earth compounds RTX, where R stands for rare earth elements, T for Ni, Pd or Rh, and X for Sn or Ge, crystallize to a rhombic ε-TiNiSi structure. Only rare earth elements R contribute to magnetic properties since T and X atoms are nonmagnetic. The competition between RKKY indirect interaction and large magnetic anisotropy generates many complicated magnetic phases. At a low temperature phase, complicated magnetisms such as meta-magnetism were observed in magnetization curves with many steps. In previous experiments dealing with RPdSn where R means Tb or Ho, some characteristics of magnetic properties of these compounds were deduced from magnetization measurements and neutron diffraction without external magnetic field. In this report, the change of magnetic scattering of neutron diffraction was studied under external magnetic fields in order to reveal the mechanism of the phase transformations of the compounds. The difference between TbPdSn and HoPdSn compounds was observed in magnetic field dependence of the wave vectors of the magnetic scattering. Two independent wave vectors in magnetic scattering existed in HoPdSn compound. (Y. Kazumata)
Suparmi; Cari, C.; Wea, K. N.; Wahyulianti
2018-03-01
The Schrodinger equation is the fundamental equation in quantum physics. The characteristic of the particle in physics potential field can be explained by using the Schrodinger equation. In this study, the solution of 4 dimensional Schrodinger equation for the anharmonic potential and the anharmonic partner potential have done. The method that used to solve the Schrodinger equation was the ansatz wave method, while to construction the partner potential was the supersymmetric method. The construction of partner potential used to explain the experiment result that cannot be explained by the original potential. The eigenvalue for anharmonic potential and the anharmonic partner potential have the same characteristic. Every increase of quantum orbital number the eigenvalue getting smaller. This result corresponds to Bohrn’s atomic theory that the eigenvalue is inversely proportional to the atomic shell. But the eigenvalue for the anharmonic partner potential higher than the eigenvalue for the anharmonic original potential.
Tanigaki, Katsumi; Wu, Jiazhen; Tanabe, Yoichi; Heguri, Satoshi; Shiimotani, Hidekazu; Tohoku University Collaboration
2014-03-01
Clathrates are featured by cage-like polyhedral hosts mainly composed of the IVth group elements of Si, Ge, or Sn and alkali metal or alkaline-earth metal elements can be accommodated inside as a guest atom. One of the most intriguing issues in clathrates is their outstanding high thermoelectric performances thanks to the low thermal conductivity. Being irrespective of good electric conductivity σ, the guest atom motions provide a low-energy lying less-dispersive phonons and can greatly suppress thermal conductivity κ. This makes clathrates close to the concept of ``phonon glass electron crystal: PGEC'' and useful in thermoelectric materials from the viewpoint of the figure of merit. In the present study, we show that the local phonon anharmonicity indicated by the tunneling-term of the endohedral atoms (αT) and the itinerant-electron term (γeT), both of which show T-linear dependences in specific heat Cp, can successfully be separated by employing single crystals with various carrier concentrations in a wide range of temperture experimennts. The factors affecting on the phonon anharmonicity as well as the strength of electron-phonon interactions will be discussed based on our recent experiments. The research was financially supported by Ministry of Education, Science, Sports and Culture, Grant in Aid for Science, and Technology of Japan.
McAneny, M.; Freericks, J. K.
2014-11-01
The Coulomb repulsion between ions in a linear Paul trap gives rise to anharmonic terms in the potential energy when expanded about the equilibrium positions. We examine the effect of these anharmonic terms on the accuracy of a quantum simulator made from trapped ions. To be concrete, we consider a linear chain of Yb171+ ions stabilized close to the zigzag transition. We find that for typical experimental temperatures, frequencies change by no more than a factor of 0.01 % due to the anharmonic couplings. Furthermore, shifts in the effective spin-spin interactions (driven by a spin-dependent optical dipole force) are also, in general, less than 0.01 % for detunings to the blue of the transverse center-of-mass frequency. However, detuning the spin interactions near other frequencies can lead to non-negligible anharmonic contributions to the effective spin-spin interactions. We also examine an odd behavior exhibited by the harmonic spin-spin interactions for a range of intermediate detunings, where nearest-neighbor spins with a larger spatial separation on the ion chain interact more strongly than nearest neighbors with a smaller spatial separation.
Onoda, Masashige; Sato, Takuma
2017-12-01
The crystal structures and electronic properties of β'CuxV2O5 are explored through measurements of X-ray four-circle diffraction, electrical resistivity, thermoelectric power, thermal conductivity, magnetization, and electron paramagnetic resonance. For various compositions with 0.243 ≤ x ≤ 0.587, the crystal structures are redetermined through the anharmonic approach of the copper displacement factors, where the anharmonicity is reduced with increasing Cu concentration. The electron transport for x ≤ 0.45 is nonmetallic due to polaron hopping and the random potential of Cu ions, while for x = 0.60, a correlated Fermi-liquid state appears with a Wilson ratio of 1.3 and a Kadowaki-Woods ratio close to the universal value for heavy-fermion systems. At around x = 0.50, the polaronic bandwidth may broaden so that the Hubbard subbands caused by the electron correlation will overlap. The nonmetallic composition in the proximity of the nonmetal-metal crossover shows a dimensionless thermoelectric power factor of 10-2 at 300 K, partly due to the anharmonic copper oscillation.
International Nuclear Information System (INIS)
Sy Savane, Y.
1995-12-01
The influence of the anharmonicity of the core vibration, on the magnetic transition 11/2 - 1 → 7/2 + 1 in 115 Sn have been investigated in the frame of the quasiparticle-phonon nuclear model. The model wave function includes a ''quasiparticle + two phonons'' component. The performed numerical calculations show that those effects cannot explain the strong reduction of the M2-transition observed in the experiment. A full agreement with the experimental value is obtained with g eff s = 0.42g free s . (author). 10 refs, 2 figs, 1 tab
Carrier relaxation in (In,Ga)As quantum dots with magnetic field-induced anharmonic level structure
Energy Technology Data Exchange (ETDEWEB)
Kurtze, H.; Bayer, M. [Experimentelle Physik 2, TU Dortmund, D-44221 Dortmund (Germany)
2016-07-04
Sophisticated models have been worked out to explain the fast relaxation of carriers into quantum dot ground states after non-resonant excitation, overcoming the originally proposed phonon bottleneck. We apply a magnetic field along the quantum dot heterostructure growth direction to transform the confined level structure, which can be approximated by a Fock–Darwin spectrum, from a nearly equidistant level spacing at zero field to strong anharmonicity in finite fields. This changeover leaves the ground state carrier population rise time unchanged suggesting that fast relaxation is maintained upon considerable changes of the level spacing. This corroborates recent models explaining the relaxation by polaron formation in combination with quantum kinetic effects.
Energy Technology Data Exchange (ETDEWEB)
Goryachev, Maxim; Farr, Warrick G.; Carmo Carvalho, Natalia do; Creedon, Daniel L.; Le Floch, Jean-Michel [ARC Centre of Excellence for Engineered Quantum Systems, University of Western Australia, 35 Stirling Highway, Crawley WA 6009 (Australia); Probst, Sebastian [Physikalisches Institut, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Bushev, Pavel [Experimentalphysik, Universität des Saarlandes, D-66123 Saarbrücken (Germany); Tobar, Michael E., E-mail: michael.tobar@uwa.edu.au [ARC Centre of Excellence for Engineered Quantum Systems, School of Physics, University of Western Australia, Crawley 6009 (Australia)
2015-06-08
Interaction of Whispering Gallery Modes (WGMs) with dilute spin ensembles in solids is an interesting paradigm of Hybrid Quantum Systems potentially beneficial for Quantum Signal Processing applications. Unexpected ion transitions are measured in single crystal Y{sub 2}SiO{sub 5} using WGM spectroscopy with large Zero Field Splittings at 14.7 GHz, 18.4 GHz, and 25.4 GHz, which also feature considerable anisotropy of the g-tensors as well as two inequivalent lattice sites, indicating spins from Iron Group Ion (IGI) impurities. The comparison of undoped and Rare-Earth doped crystals reveal that the IGIs are introduced during co-doping of Eu{sup 3+} or Er{sup 3+} with concentration at much lower levels of order 100 ppb. The strong coupling regime between an ensemble of IGI spins and WGM photons have been demonstrated at 18.4 GHz and near zero field. This approach together with useful optical properties of these ions opens avenues for “spins-in-solids” Quantum Electrodynamics.
Stochastic many-body perturbation theory for anharmonic molecular vibrations
Energy Technology Data Exchange (ETDEWEB)
Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
2014-08-28
A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm{sup −1} and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.
International Nuclear Information System (INIS)
Tsallis, C.; Valle, J.W.F.
1979-01-01
The use of the Variational Method to discuss Quantum Statistical Mechanics of anharmonic systems requires, in order to be able to obtain the correct classical limit, the allowance for renormalization of every operator whose definition depends on the harmonic coefficients. The point is exhibited for a single anharmonic oscillator. In this particular case there is no need for mass renormalization. (Author) [pt
X ray absorption fine structure of systems in the anharmonic limit
Mustredeleon, J.; Conradson, S. D.; Batistic, I.; Bishop, A. R.; Raistrick, I.; Jackson, W. E.; Brown, G. E.
A new approach to the analysis of x-ray absorption fine structure (XAFS) data is presented. It is based on the use of radial distribution functions directly calculated from a single-particle ion Hamiltonian containing model potentials. The starting point of this approach is the statistical average of the XAFS for an atomic pair. This average can be computed using a radial distribution function (RDF), which can be expressed in terms of the eigenvalues and wavefunctions associated with the model potential. The pair potential describing the ionic motion is then expressed in terms of parameters that are determined by fitting this statistical average to the experimental XAFS spectrum. This approach allows the use of XAFS as a tool for mapping near-neighbor interatomic potentials, and allows the treatment of systems which exhibit strongly anharmonic potentials which can be treated by perturbative methods. Using this method we have analyzed the high temperature behavior of the oxygen contributions to the Fe K-edge XAFS in the ferrosilicate minerals andradite (Ca3Fe2Si3O12) and magnesiowustite (Mg(0.9)Fe(0.1)O). Using a temperature dependent anharmonic correction derived from these model compounds, we have found evidence for a local structural change in the Fe-O coordination environment upon melting of the geologically important mineral fayalite (Fe2SiO4). We have also employed this method to the study of the axial oxygen contributions to the polarized Cu K-edge XAFS on oriented samples of YBa2Cu3O7 and related compounds. From this study we find evidence for an axial oxygen-centered lattice distortion accompanying the superconducting phase transition and a correlation between this distortion and Tc. The relation of the observed lattice distortion to mechanisms of superconductivity is discussed.
X-ray absorption fine structure of systems in the anharmonic limit
International Nuclear Information System (INIS)
Mustre de Leon, J.; Conradson, S.D.; Batistic, I.; Bishop, A.R.; Raistrick, I.; Jackson, W.E.; Brown, G.E.
1991-01-01
A new approach to the analysis of x-ray absorption fine structure (XAFS) data is presented. It is based on the use of radial distribution functions directly calculated from a single-particle ion hamiltonian containing model potentials. The starting point of this approach is the statistical average of the XAFS for an atomic pair. This average can be computed using a radial distribution function (RDF), which can be expressed in terms of the eigenvalues and wavefunctions associated with the model potential. The pair potential describing the ionic motion is then expressed in terms of parameters that are determined by fitting this statistical average to the experimental XAFS spectrum. This approach allow the use of XAFS as a tool for mapping near-neighbor interatomic potentials, and allows the treatment of systems which exhibit strongly anharmonic potentials which can be treated by perturbative methods. Using this method we have analyzed the high temperature behavior of the oxygen contributions to the Fe K-edge XAFS in the ferrosilicate minerals andradite (Ca 3 Fe 2 Si 3 O 12 ) and magnesiowustite (Mg 0.9 Fe 0.1 O). Using a temperature dependent anharmonic correction derived from these model compounds, we have found evidence for a local structural change in the Fe-O coordination environment upon melting of the geologically important mineral fayalite (Fe 2 SiO 4 ). We have also employed this method to the study of the axial oxygen contributions to the polarized Cu K-edge XAFS on oriented samples of YBa 2 Cu 3 O 7 and related compounds. From this study we find evidence for an axial oxygen-centered lattice distortion accompanying the superconducting phase transition and a correlation between this distortion and T c . The relation of the observed lattice distortion to mechanisms of superconductivity is discussed. 33 refs., 6 figs
Directory of Open Access Journals (Sweden)
Guohong Zou
2016-04-01
Full Text Available Crystals of congruently melting noncentrosymmetric (NCS mixed alkali metal nitrate, Rb2Na(NO33, have been grown through solid state reactions. The material possesses layers with NaO8 hexagonal bipyramids and NO3 triangular units. Rb+ cations are residing in the interlayer space. Each NaO8 hexagonal bipyramid shares its corners and edges with two and three NO3 units, respectively, in order to fulfill a highly dense stacking in the unit cell. The NaO8 groups share their six oxygen atoms in equatorial positions with three different NO3 groups to generate a NaO6-NO3 layer with a parallel alignment. The optimized arrangement of the NO3 groups and their high density in the structure together produce a strong second-harmonic generation (SHG response. Powder SHG measurements indicate that Rb2Na(NO33 has a strong SHG efficiency of five times that of KH2PO4 (KDP and is type I phase-matchable. The calculated average nonlinear optical (NLO susceptibility of Rb2Na(NO33 turns out to be the largest value among the NLO materials composed of only [NO3]− anion. In addition, Rb2Na(NO33 exhibits a wide transparency region ranging from UV to near IR, which suggests that the compound is a promising NLO material.
Low-lying spectra in anharmonic three-body oscillators with a strong short-range
Czech Academy of Sciences Publication Activity Database
Znojil, Miloslav
2003-01-01
Roč. 36, č. 38 (2003), s. 9929-9941 ISSN 0305-4470 R&D Projects: GA AV ČR IAA1048302 Institutional research plan: CEZ:AV0Z1048901 Keywords : three-body Schrodinger equation * limit * large repulsion Subject RIV: BE - Theoretical Physics Impact factor: 1.357, year: 2003
Ruggiero, Michael T; Zeitler, J Axel
2016-11-17
Anharmonicity has been shown to be an important piece of the fundamental framework that dictates numerous observable phenomena. In particular, anharmonicity is the driving force of vibrational relaxation processes, mechanisms that are integral to the proper function of numerous chemical processes. However, elucidating its origins has proven difficult due to experimental and theoretical challenges, specifically related to separating the anharmonic contributions from other unrelated effects. While no one technique is particularly suited for providing a complete picture of anharmonicity, by combining multiple complementary methods such a characterization can be made. In this study the role of individual atomic interactions on the anharmonic properties of crystalline purine, the building block of many DNA and RNA nucleobases, is studied by experimental terahertz time-domain spectroscopy and first-principles density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD). In particular, the detailed vibrational information provided by the DFT calculations is used to interpret the atomic origins of anharmonic-related effects as determined by the AIMD calculations, which are in good agreement with the experimental data. The results highlight that anharmonicity is especially pronounced in the intermolecular interactions, particularly along the amine hydrogen bond coordinate, and yields valuable insight into what is similarly observed complex biosystems and crystalline solids.
International Nuclear Information System (INIS)
Ahn, Sang Woon; Oh, Se Woung; Ro, Seung Woo
1986-01-01
The NMR chemical shift arising from 4d electron angular momentum and 4d electron angular momentum and 4d electron spin dipolar-nuclear spin angular momentum interactions for a 4d 1 system in a strong crystal field environment of trigonal symmetry, where the threefold axis is chosen to be the axis of quantization axis, has been examined. A general expression using the nonmultipole expansion method (exact method) is derived for the NMR chemical shift. From this expression all the multipolar terms are determined. we observe that along the (100), (010), (110), and (111) axes the NMR chemical shifts are positive while along the (001) axis, it is negative. We observe that the dipolar term (1/R 3 ) is the dominant contribution to the NMR chemical shift except for along the (111) axis. A comparison of the multipolar terms with the exact values shows also that the multipolar results are exactly in agreement with the exact values around R≥0.2 nm. The temperature dependence analysis on the NMR chemical shifts may imply that along the (111) axis the contribution to the NMR chemical shift is dominantly pseudo contact interaction. Separation of the contributions of the Fermi and the pseudo contact interactions would correctly imply that the dipolar interaction is the dominant contribution to the NMR chemical shifts along the (100), (010), (001), and (110) axes, but along the (111) axis the Fermi contact interaction is incorrectly the dominant contribution to the NMR chemical shift. (Author)
Terahertz generation via laser coupling to anharmonic carbon nanotube array
Sharma, Soni; Vijay, A.
2018-02-01
A scheme of terahertz radiation generation employing a matrix of anharmonic carbon nanotubes (CNTs) embedded in silica is proposed. The matrix is irradiated by two collinear laser beams that induce large excursions on CNT electrons and exert a nonlinear force at the beat frequency ω = ω1-ω2. The force derives a nonlinear current producing THz radiation. The THz field is resonantly enhanced at the plasmon resource, ω = ω p ( 1 + β ) / √{ 2 } , where ωp is the plasma frequency and β is a characteristic parameter. Collisions are a limiting factor, suppressing the plasmon resonance. For typical values of plasma parameters, we obtain power conversion efficiency of the order of 10-6.
A quantum anharmonic oscillator model for the stock market
Gao, Tingting; Chen, Yu
2017-02-01
A financially interpretable quantum model is proposed to study the probability distributions of the stock price return. The dynamics of a quantum particle is considered an analog of the motion of stock price. Then the probability distributions of price return can be computed from the wave functions that evolve according to Schrodinger equation. Instead of a harmonic oscillator in previous studies, a quantum anharmonic oscillator is applied to the stock in liquid market. The leptokurtic distributions of price return can be reproduced by our quantum model with the introduction of mixed-state and multi-potential. The trend following dominant market, in which the price return follows a bimodal distribution, is discussed as a specific case of the illiquid market.
Approximation methods for the partition functions of anharmonic systems
International Nuclear Information System (INIS)
Lew, P.; Ishida, T.
1979-07-01
The analytical approximations for the classical, quantum mechanical and reduced partition functions of the diatomic molecule oscillating internally under the influence of the Morse potential have been derived and their convergences have been tested numerically. This successful analytical method is used in the treatment of anharmonic systems. Using Schwinger perturbation method in the framework of second quantization formulism, the reduced partition function of polyatomic systems can be put into an expression which consists separately of contributions from the harmonic terms, Morse potential correction terms and interaction terms due to the off-diagonal potential coefficients. The calculated results of the reduced partition function from the approximation method on the 2-D and 3-D model systems agree well with the numerical exact calculations
Anharmonic effective pair potentials of gold under high pressure and high temperature
Okube, M; Ohtaka, O; Fukui, H; Katayama, Y; Utsumi, W
2002-01-01
In order to examine the effect of pressure on the anharmonicity of Au, extended x-ray absorption fine-structure spectra near the Au L sub 3 edge were measured in the temperature range from 300 to 1100 K under pressures up to 14 GPa using large-volume high-pressure devices and synchrotron radiation. The anharmonic effective pair potentials of Au, V (u) = au sup 2 + bu sup 3 , at 0.1 MPa, 6 and 14 GPa have been calculated. The pressure dependence of the thermal expansion coefficients has also been evaluated. The reliability of the anharmonic correction proposed on the basis of the Anderson scale has been discussed.
DEFF Research Database (Denmark)
Bak, KL; Bludsky, O.; Jorgensen, P
1995-01-01
A priori theory is derived for anharmonic calculations of vibrational circular dichroism (VCD). The anharmonic VCD expression is gauge origin independent and reduce to the magnetic field perturbation theory expression in the double-harmonic approximation. The theory has been implemented using...... for the atomic axial tensors and using second-order Moller-Plesset theory for the atomic polar tensors and the force fields, The changes of the vibrational rotatory strengths from anharmonicities are small, and do not explain the previously observed large discrepancies between the double-harmonic results...
International Nuclear Information System (INIS)
Bordyuk, N.A.; Nikitchuk, V.I.; Voloshin, O.M.
1995-01-01
The force constants of anharmonicity, the total energy, and the force of interaction between structural elements of PVC systems are determined from the values of the quasielastic constants of filled polymer systems
Energy Technology Data Exchange (ETDEWEB)
Dabiri, Zohreh, E-mail: z.dabiri@stu.yazd.ac.ir [Physics Department, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of); Kazempour, Ali [Department of Physics, Payame Noor University, P.O. BOX 119395-3697, Tehran (Iran, Islamic Republic of); Nano Structured Coatings Institute of Yazd Payame Noor University, P.O. Code 89431-74559, Yazd (Iran, Islamic Republic of); Sadeghzadeh, Mohammad Ali [Physics Department, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)
2016-11-15
The strength of phonon anharmonicity is investigated in the framework of the Density Functional Perturbation Theory via an applied constant electric field. In contrast to routine approaches, we have employed the electric field as an effective probe to quest after the quasi-harmonic and anharmonic effects. Two typical tetrahedral semiconductors (diamond and silicon) have been selected to test the efficiency of this approach. In this scheme the applied field is responsible for establishing the perturbation and also inducing the anharmonicity in systems. The induced polarization is a result of changing the electronic density while ions are located at their ground state coordinates or at a specified strain. Employing this method, physical quantities of the semiconductors are calculated in presence of the electron–phonon interaction directly and, phonon–phonon interaction, indirectly. The present approach, which is in good agreement with previous theoretical and experimental studies, can be introduced as a benchmark to simply investigate the anharmonicity and pertinent consequences in materials.
Carignano, Marcelo André s; Aravindh, S. Assa; Roqan, Iman S.; Even, Jacky; Katan, Claudine
2017-01-01
cations as the temperature is decreased from 450 K. The reverse transformation from tetragonal to cubic is also monitored through the large distribution of the octahedral tilting angles accompanied by an increase in the anharmonicity of the iodine atoms
A New Quasi-Exactly Solvable Problem and Its Connection with an Anharmonic Oscillator
International Nuclear Information System (INIS)
Yang Dabao; Zhang Fulin; Chen Jingling
2010-01-01
The two-dimensional hydrogen with a linear potential in a magnetic field is solved by two different methods. Furthermore the connection between the model and an anharmonic oscillator is investigated by methods of KS transformation. (general)
Energy Technology Data Exchange (ETDEWEB)
Jasper, Ahren W. [Chemical Sciences and Engineering; Gruey, Zackery B. [Chemical Sciences and Engineering; Harding, Lawrence B. [Chemical Sciences and Engineering; Georgievskii, Yuri [Chemical Sciences and Engineering; Klippenstein, Stephen J. [Chemical Sciences and Engineering; Wagner, Albert F. [Chemical Sciences and Engineering
2018-02-03
Monte Carlo phase space integration (MCPSI) is used to compute full dimensional and fully anharmonic, but classical, rovibrational partition functions for 22 small- and medium-sized molecules and radicals. Several of the species considered here feature multiple minima and low-frequency nonlocal motions, and efficiently sampling these systems is facilitated using curvilinear (stretch, bend, and torsion) coordinates. The curvilinear coordinate MCPSI method is demonstrated to be applicable to the treatment of fluxional species with complex rovibrational structures and as many as 21 fully coupled rovibrational degrees of freedom. Trends in the computed anharmonicity corrections are discussed. For many systems, rovibrational anharmonicities at elevated temperatures are shown to vary consistently with the number of degrees of freedom and with temperature once rovibrational coupling and torsional anharmonicity are accounted for. Larger corrections are found for systems with complex vibrational structures, such as systems with multiple large-amplitude modes and/or multiple minima.
International Nuclear Information System (INIS)
Thomaz, M.T.; Toledo Piza, A.F.R. de
1994-01-01
We show that the Hartree-Fock-Bogoliubov (alias Gaussian) approximation of the initial condition problem of the Fermionic Anharmonic Oscillator i equivalent to a bosonic Hamiltonian system of two classical spin. (author)
Anharmonic vibrational properties in periodic systems: energy, electron-phonon coupling, and stress
Monserrat, Bartomeu; Drummond, N. D.; Needs, R. J.
2013-01-01
A unified approach is used to study vibrational properties of periodic systems with first-principles methods and including anharmonic effects. Our approach provides a theoretical basis for the determination of phonon-dependent quantities at finite temperatures. The low-energy portion of the Born-Oppenheimer energy surface is mapped and used to calculate the total vibrational energy including anharmonic effects, electron-phonon coupling, and the vibrational contribution to the stress tensor. W...
Harding, Lawrence B; Georgievskii, Yuri; Klippenstein, Stephen J
2017-06-08
Full-dimensional analytic potential energy surfaces based on CCSD(T)/cc-pVTZ calculations have been determined for 48 small combustion-related molecules. The analytic surfaces have been used in Diffusion Monte Carlo calculations of the anharmonic zero-point energies. The resulting anharmonicity corrections are compared to vibrational perturbation theory results based both on the same level of electronic structure theory and on lower-level electronic structure methods (B3LYP and MP2).
E x circle epsilon Jahn-Teller anharmonic coupling for an octahedral system
Avram, N M; Kibler, M R
2001-01-01
The coupling between doubly degenerate electronic states and doubly degenerate vibrations is analyzed for an octahedral system on the basis of the introduction of an anharmonic Morse potential for the vibronic part. The vibrations are described by anharmonic coherent states and their linear coupling with the electronic states is considered. The matrix elements of the vibronic interaction are built and the energy levels corresponding to the interaction Hamiltonian are derived.
The aim of this experiment is to measure the influence of strong fields on QED-processes like: Emission of coherent radiation and pair-production when multi-hundred GeV electrons/positrons and photons penetrate single crystals near axial/planar directions. The targets will be diamond, Si, Ge and W crystals.\\\\\\\\ QED is a highly developed theory and has been investigated experimentally in great detail. In recent years it has become technically possible to investigate QED-processes in very strong electromagnetic fields around the characteristic strong field E$_{0}$ = m$^{2}$c$^{3}$/eh = 1.32.10$^{16}$ V/cm. The work of such a field over the Compton length equals the electron mass. The theoretical description of QED in such fields is beyond the framework of perturbation theory. Such fields are only obtained in laboratories for a) heavy ion collisions b) interactions of multi-GeV electrons with extremely intense laser fields and in oriented crystals. In fact it turns out that crystals are unique for this type of e...
Reconsidering harmonic and anharmonic coherent states: Partial differential equations approach
Energy Technology Data Exchange (ETDEWEB)
Toutounji, Mohamad, E-mail: Mtoutounji@uaeu.ac.ae
2015-02-15
This article presents a new approach to dealing with time dependent quantities such as autocorrelation function of harmonic and anharmonic systems using coherent states and partial differential equations. The approach that is normally used to evaluate dynamical quantities involves formidable operator algebra. That operator algebra becomes insurmountable when employing Morse oscillator coherent states. This problem becomes even more complicated in case of Morse oscillator as it tends to exhibit divergent dynamics. This approach employs linear partial differential equations, some of which may be solved exactly and analytically, thereby avoiding the cumbersome noncommutative algebra required to manipulate coherent states of Morse oscillator. Additionally, the arising integrals while using the herein presented method feature stability and high numerical efficiency. The correctness, applicability, and utility of the above approach are tested by reproducing the partition and optical autocorrelation function of the harmonic oscillator. A closed-form expression for the equilibrium canonical partition function of the Morse oscillator is derived using its coherent states and partial differential equations. Also, a nonequilibrium autocorrelation function expression for weak electron–phonon coupling in condensed systems is derived for displaced Morse oscillator in electronic state. Finally, the utility of the method is demonstrated through further simplifying the Morse oscillator partition function or autocorrelation function expressions reported by other researchers in unevaluated form of second-order derivative exponential. Comparison with exact dynamics shows identical results.
Anharmonicity Rise the Thermal Conductivity in Amorphous Silicon
Lv, Wei; Henry, Asegun
We recently proposed a new method called Direct Green-Kubo Modal Analysis (GKMA) method, which has been shown to calculate the thermal conductivity (TC) of several amorphous materials accurately. A-F method has been widely used for amorphous materials. However, researchers have found out that it failed on several different materials. The missing component of A-F method is the harmonic approximation and considering only the interactions of modes with similar frequencies, which neglect interactions of modes with large frequency difference. On the contrary, GKMA method, which is based on molecular dynamics, intrinsically includes all types of phonon interactions. In GKMA method, each mode's TC comes from both mode self-correlations (autocorrelations) and mode-mode correlations (crosscorrelations). We have demonstrated that the GKMA predicted TC of a-Si from Tersoff potential is in excellent agreement with one of experimental results. In this work, we will present the GKMA applications on a-Si using multiple potentials and gives us more insight of the effect of anharmonicity on the TC of amorphous silicon. This research was supported Intel grant AGMT DTD 1-15-13 and computational resources by NSF supported XSEDE resources under allocations DMR130105 and TG- PHY130049.
Microwave dielectric tangent losses in KDP and DKDP crystals
Indian Academy of Sciences (India)
By adding cubic and quartic phonon anharmonic interactions in the pseudospin lattice coupled mode (PLCM) model for KDP-type crystals and using double-time temperature dependent Green's function method, expressions for soft mode frequency, dielectric constant and dielectric tangent loss are obtained. Using model ...
Czech Academy of Sciences Publication Activity Database
Brauer, B.; Gerber, R. B.; Kabeláč, Martin; Hobza, Pavel; Bakker, J. M.; Abo-Riziq, A.; Vries de, M. S.
2005-01-01
Roč. 109, - (2005), s. 6974-6984 ISSN 1089-5639 Grant - others:NSF(US) CHE-0244341 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleic acids bases * vibrational spectrum * frequencies anharmonicity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.898, year: 2005
Insight into structural phase transitions from the decoupled anharmonic mode approximation.
Adams, Donat J; Passerone, Daniele
2016-08-03
We develop a formalism (decoupled anharmonic mode approximation, DAMA) that allows calculation of the vibrational free energy using density functional theory even for materials which exhibit negative curvature of the potential energy surface with respect to atomic displacements. We investigate vibrational modes beyond the harmonic approximation and approximate the potential energy surface with the superposition of the accurate potential along each normal mode. We show that the free energy can stabilize crystal structures at finite temperatures which appear dynamically unstable at T = 0. The DAMA formalism is computationally fast because it avoids statistical sampling through molecular dynamics calculations, and is in principle completely ab initio. It is free of statistical uncertainties and independent of model parameters, but can give insight into the mechanism of a structural phase transition. We apply the formalism to the perovskite cryolite, and investigate the temperature-driven phase transition from the P21/n to the Immm space group. We calculate a phase transition temperature between 710 and 950 K, in fair agreement with the experimental value of 885 K. This can be related to the underestimation of the interaction of the vibrational states. We also calculate the main axes of the thermal ellipsoid and can explain the experimentally observed increase of its volume for the fluorine by 200-300% throughout the phase transition. Our calculations suggest the appearance of tunneling states in the high temperature phase. The convergence of the vibrational DOS and of the critical temperature with respect of reciprocal space sampling is investigated using the polarizable-ion model.
Absorption spectra of CsNd(MoO4)2 and CsGd(MoO4)2-Nd3+ crystals in strong magnetic fields
International Nuclear Information System (INIS)
Gorban', I.S.; Kozeeva, L.P.; Slobodyanyuk, A.V.; Shevchenko, V.A.
1987-01-01
The comparison of the electronic structure of Nd 3+ in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 - Nd 3+ crystals is made. It is established that in these crystals the activator centers, mainly, of the certain type with the symmetry of the local environment C 2 are formed. The absorption spectra of self-activated CsNd(MoO 4 ) 2 crystal differ from spectra of CsGd(MoO 4 ) 2 - Nd 3+ by the presence of the vibrating structure. The Stark splittings of energy levels of Nd 3+ in the investigated crystalline matrices are more sensitive to the environment effect than the Zeeman ones. The ground state of Nd 3+ ion in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 molybdates is characterized by the similar values of g-factors
Czech Academy of Sciences Publication Activity Database
Zhu, Y.; Bise, R. T.; Kaňka, Jiří; Peterka, Pavel; Du, H.
Vol. 281, No. 1 (2008), s. 55-60 ISSN 0030-4018 R&D Projects: GA ČR GA102/05/0995 Grant - others:US National Science Foundation(US) ECS-0404002 Institutional research plan: CEZ:AV0Z20670512 Keywords : photonic crystals * fibre optic sensors * optic al fibres Subject RIV: BH - Optic s, Masers, Lasers Impact factor: 1.552, year: 2008
Danecek, Petr; Kapitán, Josef; Baumruk, Vladimír; Bednárová, Lucie; Kopecký, Vladimír; Bour, Petr
2007-06-14
The difference spectroscopy of the Raman optical activity (ROA) provides extended information about molecular structure. However, interpretation of the spectra is based on complex and often inaccurate simulations. Previously, the authors attempted to make the calculations more robust by including the solvent and exploring the role of molecular flexibility for alanine and proline zwitterions. In the current study, they analyze the IR, Raman, and ROA spectra of these molecules with the emphasis on the force field modeling. Vibrational harmonic frequencies obtained with 25 ab initio methods are compared to experimental band positions. The role of anharmonic terms in the potential and intensity tensors is also systematically explored using the vibrational self-consistent field, vibrational configuration interaction (VCI), and degeneracy-corrected perturbation calculations. The harmonic approach appeared satisfactory for most of the lower-wavelength (200-1800 cm(-1)) vibrations. Modern generalized gradient approximation and hybrid density functionals, such as the common B3LYP method, provided a very good statistical agreement with the experiment. Although the inclusion of the anharmonic corrections still did not lead to complete agreement between the simulations and the experiment, occasional enhancements were achieved across the entire region of wave numbers. Not only the transitional frequencies of the C-H stretching modes were significantly improved but also Raman and ROA spectral profiles including N-H and C-H lower-frequency bending modes were more realistic after application of the VCI correction. A limited Boltzmann averaging for the lowest-frequency modes that could not be included directly in the anharmonic calculus provided a realistic inhomogeneous band broadening. The anharmonic parts of the intensity tensors (second dipole and polarizability derivatives) were found less important for the entire spectral profiles than the force field anharmonicities (third
Mishra, Karuna Kara; Bevara, Samatha; Ravindran, T. R.; Patwe, S. J.; Gupta, Mayanak K.; Mittal, Ranjan; Krishnan, R. Venkata; Achary, S. N.; Tyagi, A. K.
2018-02-01
Herein we reported structural stability, vibrational and thermal properties of K2Ce[PO4]2, a relatively underexplored complex phosphate of tetravalent Ce4+ from in situ high-pressure Raman spectroscopic investigations up to 28 GPa using a diamond anvil cell. The studies identified the soft phonons that lead to a reversible phase transformation above 8 GPa, and a phase coexistence of ambient (PI) and high pressure (PII) phases in a wider pressure region 6-11 GPa. From a visual representation of the computed eigen vector displacements, the Ag soft mode at 82 cm-1 is assigned as a lattice mode of K+ cation. Pressure-induced positional disorder is apparent from the substantial broadening of internal modes and the disappearance of low frequency lattice and external modes in phase PII above 18 GPa. Isothermal mode Grüneisen parameters γi of the various phonon modes are calculated and compared for several modes. Using these values, thermal properties such as average Grüneisen parameter, and thermal expansion coefficient are estimated as 0.47, and 2.5 × 10-6 K-1, respectively. The specific heat value was estimated from all optical modes obtained from DFT calculations as 314 J-mol-1 K-1. Our earlier reported temperature dependence of phonon frequencies is used to decouple the "true anharmonic" (explicit contribution at constant volume) and "quasi harmonic" (implicit contribution brought out by volume change) contributions from the total anharmonicity. In addition to the 81 cm-1 Ag lattice mode, several other lattice and external modes of PO43- ions are found to be strongly anharmonic.
Rotational states of Bose gases with attractive interactions in anharmonic traps
International Nuclear Information System (INIS)
Lundh, Emil; Collin, Anssi; Suominen, Kalle-Antti
2004-01-01
A rotated and harmonically trapped Bose gas with attractive interactions is expected to either remain stationary or escape from the trap. Here we report that, on the contrary, in an anharmonic trapping potential the Bose gas with attractive interactions responds to external rotation very differently, namely, through center-of-mass motion or by formation of vortices
Internal oscillation frequencies and anharmonic effects for the double sine-Gordon kink
DEFF Research Database (Denmark)
Salerno, M.; Samuelsen, Mogens Rugholm
1989-01-01
A simple derivation of the small oscillation frequency around 4π-kink solutions of the double sine-Gordon equation is presented. Small corrections to these frequencies due to anharmonic effects are also numerically and analytically investigated. The analysis is based on energetic considerations...
Anharmonicities of coupled β and γ vibrations discussed in a simple model
International Nuclear Information System (INIS)
Piepenbring, R.; Silvestre-Brac, B.; Szymanski, Z.
1984-01-01
The multiphonon method based on β and γ phonons is tested in a simple model allowing an exact solution for a many body fermion system where pairing and quadrupole forces are acting. The properties exhibiting the anharmonicities of the lowest-lying vibrational states of positive parity are nicely reproduced by this method. (orig.)
Anharmonicities of coupled β and γ vibrations discussed in a simple model
International Nuclear Information System (INIS)
Piepenbring, R.; Silvestre-Brac, B.; Szymanski, Z.
1983-11-01
The multiphonon method based on β and γ phonons is tested in a simple model allowing an exact solution for a many body fermion system where pairing and quadrupole forces are acting. The properties exhibiting the anharmonicities of the lowest-lying vibrational states of positive parity are nicely reproduced by this method
International Nuclear Information System (INIS)
Rezende, J.
1983-01-01
We give a simple proof of Feynman's formula for the Green's function of the n-dimensional harmonic oscillator valid for every time t with Im t<=0. As a consequence the Schroedinger equation for the anharmonic oscillator is integrated and expressed by the Feynman path integral on Hilbert space. (orig.)
Anharmonic solution of Schrödinger time-independent equation
Indian Academy of Sciences (India)
243–261. Anharmonic solution of Schrödinger time-independent equation. MOHAMMED ASHRAFUL ISLAM1,2,∗ and JAMAL NAZRUL ISLAM1. 1Research Centre for Mathematical and Physical Sciences, University of Chittagong, Chittagong,. Bangladesh. 2Department of Mathematics, University of Chittagong, Chittagong, ...
Anharmonic Vibrations of an "Ideal" Hooke's Law Oscillator
Thomchick, John; McKelvey, J. P.
1978-01-01
Presents a model describing the vibrations of a mass connected to fixed supports by "ideal" Hooke's law springs which may serve as a starting point in the study of the properties of irons in a crystal undergoing soft mode activated transition. (SL)
International Nuclear Information System (INIS)
Giricheva, N.I.; Girichev, G.V.; Smorodin, S.V.
2007-01-01
Scanning of potential energy surface in the LaI 3 molecule along normal coordinates are realized using the B3LYP/SDD,SDD method. The most anharmonicity is shown to have a potential function of non-planar oscillation ν 2 (A 2 ''). Effect of anharmonicity on the value of mean-square oscillation amplitudes and oscillation spectrum of the molecule is established. It is noted that the account of anharmonicity of potential functions leads to decreasing mean-square oscillation amplitudes [ru
Zhou, Cai; Shen, Lvkang; Liu, Ming; Gao, Cunxu; Jia, Chenglong; Jiang, Changjun
2018-01-01
The ability to manipulate the magnetism on interfacing ferromagnetic and ferroelectric materials via electric fields to achieve an emergent multiferroic response has enormous potential for nanoscale devices with novel functionalities. Herein, a strong electric-field control of the magnetism modulation is reported for a single-crystal Co (14 nm )/(001 )Pb (Mg1/3Nb2/3) 0.7Ti0.3O3 (PMN-PT) heterostructure by fabricating an epitaxial Co layer on a PMN-PT substrate. Electric-field-tuned ferromagnetic resonance exhibits a large resonance field shift, with a 120-Oe difference between that under positive and negative remanent polarizations, which demonstrates nonvolatile electric-field control of the magnetism. Further, considering the complexity of the twofold symmetry magnetic anisotropy, the linear change of the fourfold symmetry magnetic anisotropy, relating to the single-crystal cubic magnetocrystal anisotropy of the Co thin film, is resolved and quantified to exert a magnon-driven, strong direct magnetoelectric effect on the Co /PMN -PT interface. These results are promising for future multiferroic devices.
Kim, H; Lipscomb, W N
1990-06-12
O-[[(1R)-[[N-(Phenylmethoxycarbonyl)-L-alanyl]amino]ethyl] hydroxyphosphinyl]-L-3-phenyllacetate [ZAAP(O)F], an analogue of (benzyloxycarbonyl)-Ala-Ala-Phe or (benzyloxycarbonyl)-Ala-Ala-phenyllactate, binds to carboxypeptidase A with great affinity (Ki = 3 pM). Similar phosphonates have been shown to be transition-state analogues of the CPA-catalyzed hydrolysis [Hanson, J. E., Kaplan, A. P., & Bartlett, P. A. (1989) Biochemistry 28, 6294-6305]. In the present study, the structure of the complex of this phosphonate with carboxypeptidase A has been determined by X-ray crystallography to a resolution of 2.0 A. The complex crystallizes in the space group P2(1)2(1)2(1) with cell dimensions a = 61.9 A, b = 67.2 A, and c = 76.2 A. The structure of the complex was solved by molecular replacement. Refinement of the structure against 20,776 unique reflections between 10.0 and 2.0 A yields a crystallographic residual of 0.193, including 140 water molecules. The two phosphinyl oxygens of the inhibitor bind to the active-site zinc at 2.2 A on the electrophilic (Arg-127) side and 3.1 A on the nucleophilic (Glu-270) side. Various features of the binding mode of this phosphonate inhibitor are consistent with the hypothesis that carboxypeptidase A catalyzed hydrolysis proceeds through a general-base mechanism in which the carbonyl carbon of the substrate is attacked by Zn-hydroxyl (or Zn-water). An unexpected feature of the bound inhibitor, the cis carbamoyl ester bond at the benzyloxycarbonyl linkage to alanine, allows the benzyloxycarbonyl phenyl ring of the inhibitor to interact favorably with Tyr-198. This complex structure is compared with previous structures of carboxypeptidase A, including the complexes with the potato inhibitor, a hydrated keto methylene substrate analogue, and a phosphonamidate inhibitor. Comparisons are also made with the complexes of thermolysin with some phosphonamidate inhibitors.
Terrill, Kasia; Nesbitt, David J
2010-08-01
Ab initio anharmonic transition frequencies are calculated for strongly coupled (i) asymmetric and (ii) symmetric proton stretching modes in the X-H(+)-X linear ionic hydrogen bonded complexes for OCHCO(+) and N(2)HN(2)(+). The optimized potential surface is calculated in these two coordinates for each molecular ion at CCSD(T)/aug-cc-pVnZ (n = 2-4) levels and extrapolated to the complete-basis-set limit (CBS). Slices through both 2D surfaces reveal a relatively soft potential in the asymmetric proton stretching coordinate at near equilibrium geometries, which rapidly becomes a double minimum potential with increasing symmetric proton acceptor center of mass separation. Eigenvalues are obtained by solution of the 2D Schrödinger equation with potential/kinetic energy coupling explicity taken into account, converged in a distributed Gaussian basis set as a function of grid density. The asymmetric proton stretch fundamental frequency for N(2)HN(2)(+) is predicted at 848 cm(-1), with strong negative anharmonicity in the progression characteristic of a shallow "particle in a box" potential. The corresponding proton stretch fundamental for OCHCO(+) is anomalously low at 386 cm(-1), but with a strong alternation in the vibrational spacing due to the presence of a shallow D(infinityh) transition state barrier (Delta = 398 cm(-1)) between the two equivalent minimum geometries. Calculation of a 2D dipole moment surface and transition matrix elements reveals surprisingly strong combination and difference bands with appreciable intensity throughout the 300-1500 cm(-1) region. Corrected for zero point (DeltaZPE) and thermal vibrational excitation (DeltaE(vib)) at 300 K, the single and double dissociation energies in these complexes are in excellent agreement with thermochemical gas phase ion data.
Anomalous Behavior of Electronic Heat Capacity of Strongly Correlated Iron Monosilicide
Povzner, A. A.; Volkov, A. G.; Nogovitsyna, T. A.
2018-04-01
The paper deals with the electronic heat capacity of iron monosilicide FeSi subjected to semiconductor-metal thermal transition during which the formation of its spintronic properties is observed. The proposed model which considers pd-hybridization of strongly correlated d-electrons with non-correlated p-electrons, demonstrates a connection of their contribution to heat capacity in the insulator phase with paramagnon effects and fluctuations of occupation numbers for p- and d-states. In a slitless state, the temperature curve of heat capacity is characterized by a maximum appeared due to normalization of the electron density of states using fluctuating exchange fields. At higher temperatures, a linear growth in heat capacity occurs due to paramagnon effects. The correlation between the model parameters and the first-principles calculation provides the electron contribution to heat capacity, which is obtained from the experimental results on phonon heat capacity. Anharmonicity of phonons is connected merely with the thermal expansion of the crystal lattice.
International Nuclear Information System (INIS)
Chung, N. N.; Chew, L. Y.
2007-01-01
We have generalized the two-step approach to the solution of systems of N coupled quantum anharmonic oscillators. By using the squeezed vacuum state of each individual oscillator, we construct the tensor product state, and obtain the optimal squeezed vacuum product state through energy minimization. We then employ this optimal state and its associated bosonic operators to define a basis set to construct the Heisenberg matrix. The diagonalization of the matrix enables us to obtain the energy eigenvalues of the coupled oscillators. In particular, we have applied our formalism to determine the eigenenergies of systems of two coupled quantum anharmonic oscillators perturbed by a general polynomial potential, as well as three and four coupled systems. Furthermore, by performing a first-order perturbation analysis about the optimal squeezed vacuum product state, we have also examined into the squeezing properties of two coupled oscillator systems
Two-step approach to the dynamics of coupled anharmonic oscillators
International Nuclear Information System (INIS)
Chung, N. N.; Chew, L. Y.
2009-01-01
We have further extended the two-step approach developed by Chung and Chew [N. N. Chung and L. Y. Chew, Phys. Rev. A 76, 032113 (2007)] to the solution of the quantum dynamics of general systems of N-coupled anharmonic oscillators. The idea is to employ an optimized basis set to represent the dynamical quantum states of these oscillator systems. The set is generated via the action of the optimized Bogoliubov transformed bosonic operators on the optimal squeezed vacuum product state. The procedure requires (i) applying the two-step approach to the eigendecomposition of the time evolution operator and (ii) transforming the representation of the initial state from the original to the optimal bases. We have applied the formalism to examine the dynamics of squeezing and entanglement of several anharmonic oscillator systems.
Raman scattering study of the anharmonic effects in CeO2-y nanocrystals
Popović, Z. V.; Dohčević-Mitrović, Z.; Cros, A.; Cantarero, A.
2007-12-01
We have studied the temperature dependence of the F2g Raman mode phonon frequency and broadening in CeO2-y nanocrystals. The phonon softening and phonon linewidth are calculated using a model which takes into account the three-and four-phonon anharmonic processes. A detailed comparison of the experimental data with theoretical calculations revealed the predominance of four-phonon anharmonic processes in the temperature dependence of the phonon energy and broadening of the nanocrystals. On the other hand, three-phonon processes dominate the temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokes peak intensity ratio was also investigated and found to be smaller for nanosized CeO2 powders than in the bulk counterpart.
Raman scattering study of the anharmonic effects in CeO2-y nanocrystals
International Nuclear Information System (INIS)
Popovic, Z V; Dohcevic-Mitrovic, Z; Cros, A; Cantarero, A
2007-01-01
We have studied the temperature dependence of the F 2g Raman mode phonon frequency and broadening in CeO 2-y nanocrystals. The phonon softening and phonon linewidth are calculated using a model which takes into account the three-and four-phonon anharmonic processes. A detailed comparison of the experimental data with theoretical calculations revealed the predominance of four-phonon anharmonic processes in the temperature dependence of the phonon energy and broadening of the nanocrystals. On the other hand, three-phonon processes dominate the temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokes peak intensity ratio was also investigated and found to be smaller for nanosized CeO 2 powders than in the bulk counterpart
Raman scattering study of the anharmonic effects in CeO{sub 2-y} nanocrystals
Energy Technology Data Exchange (ETDEWEB)
Popovic, Z V [Center for Solid State Physics and New Materials, Institute of Physics, Pregrevica 118, 11080 Belgrade (Serbia); Dohcevic-Mitrovic, Z [Center for Solid State Physics and New Materials, Institute of Physics, Pregrevica 118, 11080 Belgrade (Serbia); Cros, A [Materials Science Institute, University of Valencia, P O Box 22085, E-46071, Valencia (Spain); Cantarero, A [Materials Science Institute, University of Valencia, P O Box 22085, E-46071, Valencia (Spain)
2007-12-12
We have studied the temperature dependence of the F{sub 2g} Raman mode phonon frequency and broadening in CeO{sub 2-y} nanocrystals. The phonon softening and phonon linewidth are calculated using a model which takes into account the three-and four-phonon anharmonic processes. A detailed comparison of the experimental data with theoretical calculations revealed the predominance of four-phonon anharmonic processes in the temperature dependence of the phonon energy and broadening of the nanocrystals. On the other hand, three-phonon processes dominate the temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokes peak intensity ratio was also investigated and found to be smaller for nanosized CeO{sub 2} powders than in the bulk counterpart.
International Nuclear Information System (INIS)
Kowalenko, V.; Rawlinson, A.A.
1998-01-01
We introduce the numerical technique of Mellin-Barnes regularization, which can be used to evaluate both convergent and divergent series. The technique is shown to be numerically equivalent to the corresponding results obtained by Borel summation. Both techniques are then applied to the Bender-Wu formula, which represents an asymptotic expansion for the energy levels of the anharmonic oscillator. We find that this formula is unable to give accurate values for the ground state energy, particularly when the coupling is greater than 0.1. As a consequence, the inability of the Bender-Wu formula to yield exact values for the energy level of the anharmonic oscillator cannot be attributed to its asymptotic nature. (authors)
Two new types of solvability of the one-dimensional anharmonic oscillators
International Nuclear Information System (INIS)
Znojil, M.
1989-01-01
In the Schroedinger picture, we propose a new modification of the so-called Hill-determinant technique. It is shown to guarantee a proper matching of the two underlying power series Ψ(x) at x=0. In the Heisenberg picture, an evolution of the same one-dimensional polynomially anharmonic oscillator is considered. A modified Peano-Baker method is applied and shown to define the explicit solutions by recurrences. 11 refs
Large time asymptotics of solutions to the anharmonic oscillator model from nonlinear optics
Jochmann, Frank
2005-01-01
The anharmonic oscillator model describing the propagation of electromagnetic waves in an exterior domain containing a nonlinear dielectric medium is investigated. The system under consideration consists of a generally nonlinear second order differential equation for the dielectrical polarization coupled with Maxwell's equations for the electromagnetic field. Local decay of the electromagnetic field for t to infinity in the charge free case is shown for a large class of potentials. (This pape...
Czech Academy of Sciences Publication Activity Database
Daněček, Petr; Kapitán, Josef; Baumruk, V.; Bednárová, Lucie; Kopecký, V.; Bouř, Petr
2007-01-01
Roč. 126, č. 22 (2007), s. 224513-1 ISSN 0021-9606 R&D Projects: GA ČR GA203/06/0420; GA ČR GA202/07/0732; GA AV ČR IAA400550702 Institutional research plan: CEZ:AV0Z40550506 Keywords : IR * Raman * ROA spectra * Anharmonic effects Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.044, year: 2007
Šebek, Jiří; Pele, Liat; Potma, Eric O; Gerber, R Benny
2011-07-28
First-principles anharmonic vibrational calculations are carried out for the Raman spectrum of the C-H stretching bands in dodecane, and for the C-D bands in the deuterated molecule. The calculations use the Vibrational Self-Consistent Field (VSCF) algorithm. The results are compared with liquid-state experiments, after smoothing the isolated-molecule sharp-line computed spectra. Very good agreement between the computed and experimental results is found for the two systems. The combined theoretical and experimental results provide insights into the spectrum, elucidating the roles of symmetric and asymmetric CH(3) and CH(2) hydrogenic stretches. This is expected to be very useful for the interpretation of spectra of long-chain hydrocarbons. The results show that anharmonic effects on the spectrum are large. On the other hand, vibrational degeneracy effects seem to be rather modest at the resolution of the experiments. The degeneracy effects may have more pronounced manifestations in higher-resolution experiments. The results show that first-principles anharmonic vibrational calculations for hydrocarbons are feasible, in good agreement with experiment, opening the way for applications to many similar systems. The results may be useful for the analysis of CARS imaging of lipids, for which dodecane is a representative molecule. It is suggested that first-principles vibrational calculations may be useful also for CARS imaging of other systems. This journal is © the Owner Societies 2011
Lee, Y.; Bescond, M.; Logoteta, D.; Cavassilas, N.; Lannoo, M.; Luisier, M.
2018-05-01
We propose an efficient method to quantum mechanically treat anharmonic interactions in the atomistic nonequilibrium Green's function simulation of phonon transport. We demonstrate that the so-called lowest-order approximation, implemented through a rescaling technique and analytically continued by means of the Padé approximants, can be used to accurately model third-order anharmonic effects. Although the paper focuses on a specific self-energy, the method is applicable to a very wide class of physical interactions. We apply this approach to the simulation of anharmonic phonon transport in realistic Si and Ge nanowires with uniform or discontinuous cross sections. The effect of increasing the temperature above 300 K is also investigated. In all the considered cases, we are able to obtain a good agreement with the routinely adopted self-consistent Born approximation, at a remarkably lower computational cost. In the more complicated case of high temperatures (≫300 K), we find that the first-order Richardson extrapolation applied to the sequence of the Padé approximants N -1 /N results in a significant acceleration of the convergence.
Anharmonic behavior and structural phase transition in Yb2O3
Directory of Open Access Journals (Sweden)
Sugandha Dogra Pandey
2013-12-01
Full Text Available The investigation of structural phase transition and anharmonic behavior of Yb2O3 has been carried out by high-pressure and temperature dependent Raman scattering studies respectively. In situ Raman studies under high pressure were carried out in a diamond anvil cell at room temperature which indicate a structural transition from cubic to hexagonal phase at and above 20.6 GPa. In the decompression cycle, Yb2O3 retained its high pressure phase. We have observed a Stark line in the Raman spectra at 337.5 cm−1 which arises from the electronic transition between 2F5/2 and 2F7/2 multiplates of Yb3+ (4f13 levels. These were followed by temperature dependent Raman studies in the range of 80–440 K, which show an unusual mode hardening with increasing temperature. The hardening of the most dominant mode (Tg + Ag was analyzed in light of the theory of anharmonic phonon-phonon interaction and thermal expansion of the lattice. Using the mode Grüneisen parameter obtained from high pressure Raman measurements; we have calculated total anharmonicity of the Tg + Ag mode from the temperature dependent Raman data.
MORGENSTERN, [No Value; FRICK, M; VONDERLINDEN, W
We present quantum simulation studies for a system of strongly correlated fermions coupled to local anharmonic phonons. The Monte Carlo calculations are based on a generalized version of the Projector Quantum Monte Carlo Method allowing a simultaneous treatment of fermions and dynamical phonons. The
DEFF Research Database (Denmark)
Katajainen, Jyrki
2008-01-01
In this project the goal is to develop the safe * family of containers for the CPH STL. The containers to be developed should be safer and more reliable than any of the existing implementations. A special focus should be put on strong exception safety since none of the existing prototypes available...
International Nuclear Information System (INIS)
Froissart, Marcel
1976-01-01
Strong interactions are introduced by their more obvious aspect: nuclear forces. In hadron family, the nucleon octet, OMEGA - decuplet, and quark triply are successively considered. Pion wave having been put at the origin of nuclear forces, low energy phenomena are described, the force being explained as an exchange of structure corresponding to a Regge trajectory in a variable rotating state instead of the exchange of a well defined particle. At high energies the concepts of pomeron, parton and stratons are introduced, pionization and fragmentation are briefly differentiated [fr
A study of anharmonic al and nonlinear behaviours of vibrations of atomic nuclei
International Nuclear Information System (INIS)
Volpe, M.C.
1997-01-01
Double Giant Resonances, vibrational states in which a Giant Resonance is excited on top of another Giant Resonance, have been in the last years the object of many theories and studies. Whereas the measured energies and widths of these states agree with a theoretical predictions, the measured excitation cross sections on the other hand are almost always larger than the calculated ones. The standard theoretical approaches are based both on a harmonic approximation for the collective motion on the nucleus and on its linear response to an external field. In this work the influence of anharmonicities and non-linearities in the external field on the excitation of Double Giant Resonances are studied. First, an oscillator model and an extension of the Lipkin-Meshkow-Glick model are used to study the effects of anharmonicities and non-linearities on the excitation probabilities. The results show that these terms can influence the excitation probability of the second excited state in a significant way. Secondly, these exactly soluble schematic models are used to study some of the approximations made in microscopic calculations based on boson expansion methods and also some aspects on the time-dependent mean field approach. Finally, a microscopic calculation of the Coulomb excitation cross sections of Double Giant Resonances is presented for several nuclei. It is found that, for 208 Pb, the inclusion of anharmonicities and non-linearities and the consideration of many states that play a role in the excitation process give a satisfactory agreement between calculated and observed cross sections. (author)
Energy Technology Data Exchange (ETDEWEB)
Meier, Patrick; Oschetzki, Dominik; Rauhut, Guntram, E-mail: rauhut@theochem.uni-stuttgart.de [Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany); Berger, Robert [Clemens-Schöpf Institut für Organische Chemie and Biochemie, Technische Universität Darmstadt, Petersenstrasse 22, 64287 Darmstadt (Germany)
2014-05-14
A transformation of potential energy surfaces (PES) being represented by multi-mode expansions is introduced, which allows for the calculation of anharmonic vibrational spectra of any isotopologue from a single PES. This simplifies the analysis of infrared spectra due to significant CPU-time savings. An investigation of remaining deviations due to truncations and the so-called multi-level approximation is provided. The importance of vibrational-rotational couplings for small molecules is discussed in detail. In addition, an analysis is proposed, which provides information about the quality of the transformation prior to its execution. Benchmark calculations are provided for a set of small molecules.
Vibrational spectra and thermal rectification in three-dimensional anharmonic lattices
International Nuclear Information System (INIS)
Lan Jinghua; Li Baowen
2007-01-01
We study thermal rectification in a three-dimensional model consisting of two segments of anharmonic lattices. One segment consists of layers of harmonic oscillator arrays coupled to a substrate potential, which is a three-dimensional Frenkel-Kontorova model, and the other segment is a three-dimensional Fermi-Pasta-Ulam model. We study the vibrational bands of the two lattices analytically and numerically, and find that, by choosing the system parameters properly, the rectification can be as high as a few thousands, which is high enough to be observed in experiment. Possible experiments in nanostructures are discussed
Escuer, Albert; Vicente, Ramon; Kumar, Sujit B.; Solans, Xavier; Font-Bardía, Mercé; Caneschi, Andrea
1996-05-22
The trinuclear complex (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)] was obtained by reaction of basic solutions of nickel(II), Medpt (bis(3aminopropyl)methylamine) and thiocyanate ligand with atmospheric CO(2) or by simple reaction with carbonate anion. (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)] crystallizes in the triclinic system, space group P&onemacr;, with a = 12.107(5) Å, b = 12.535(7) Å, c = 16.169(9) Å, alpha = 102.69(5) degrees, beta = 92.91(5) degrees, gamma = 118.01(4) degrees, Z = 2, and R = 0.043. The three nickel atoms are asymmetrically bridged by one pentadentate carbonato ligand, which shows a novel coordination mode. The (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)] compound shows a very strong antiferromagnetic coupling. Fit as irregular triangular arrangement gave J(1) = -88.4, J(2) = -57.7, and J(3) = -9.6 cm(-)(1), which is the strongest AF coupling observed to date for Ni(3) compounds. The magnetic behavior of the carbonato bridge is discussed.
International Nuclear Information System (INIS)
Kobel, M.
1991-07-01
Using the Crystal ball detector at the e + e - storage ring DORIS II we have measured the branching fraction B μμ to muon pairs of the Υ(1S) and Υ(2S) resonances and for the first time the product of the muonic partial width Γ μμ and the branching fraction B ee to electrons for both resonances. We obtain B μμ (1S)=(2.31±0.12±0.10)%, Γ μμ (1S).B ee (1S)=(31.2±1.6±1.7) eV and B μμ (2S)=(1.22±0.28±0.19)%, Γ μμ (2S).B ee (2S)=(6.5±1.5±1.0) eV, where the errors given are the statistical and systematic uncertainties, respectively. Inserting the present world average value of B ee (1S)=(2.52±0.17)% we measure for the first time the muonic partial width Γ μμ (1S)=(1.24±0.06±0.11) keV. In addition we present the first evidence for the expected interference between μ-pair production in the continuum and in Υ(1S) decays. Using our result on B μμ (1S) we derive a value for the scale parameter Λ of the strong interaction from exploiting the ratio of B μμ to the branching fraction B ggg of the Υ(1S) to three gluons. In the anti Manti S renormalization scheme for the theory of Quantum Chromo Dynamics (QCD) we find for four flavors Λ 4 sub(anti Manti S)=(210±25 -50 +120 ) MeV. We convert this number into a measurement of the strong coupling constant α s sub(anti Manti S)(μ=5 GeV)=0.184±0.006 -0.013 +0.027 . In both results the experimental and the theoretical errors are listed, respectively. The values for the theoretical uncertainties should be taken as an educated guess. Given today's state of the art in QCD, they are in principle unknown. (orig.) [de
Anharmonic properties of Raman modes in double wall carbon nano tubes
Energy Technology Data Exchange (ETDEWEB)
Marquina, J. [Universidad de los Andes, Facultad de Ciencias, Centro de Estudios Avanzados en Optica, 5101 Merida (Venezuela, Bolivarian Republic of); Power, Ch.; Gonzalez, J. [Universidad de los Andes, Facultad de Ciencias, Centro de Estudios en Semiconductores, 5101 Merida (Venezuela, Bolivarian Republic of); Broto, J. M. [Universite de Toulouse, Laboratoire National des Champs Magnetiques Intenses, CNRS UPR 3228, 31400 Toulouse (France); Flahaut, E., E-mail: castella@ula.v [Universite Paul Sabatier, Laboratoire de Chimie des Materiaux Inorganiques, UMR CNRS 5085, 31062 Toulouse (France)
2011-07-01
The temperature dependence of the radial breathing modes (RB Ms) and the zone-center tangential optical phonons (G-bands) of double-walled carbon nano tubes has been investigated between 300 and 700 K using Raman scattering. As expected, with increasing temperature, the frequencies of the Raman peaks, including the RB Ms and G-bands downshift simultaneously. We show here that the temperature dependence of the RB Ms can be fitted by a simple linear dependence and different RB Ms have different frequency shifts. We observe a noticeable nonlinearity in the temperature dependence of the G-band associated with the outer semiconducting tube G+ext (s). The deviation from the linear trend is due to the contribution of the third-order anharmonic term in the lattice potential energy with a pure temperature effect. An estimated value of 1.5 for the Grueneisen parameter of the G+ext (s) band was found. (Author)
Random-phase approximation and its extension for the O(2) anharmonic oscillator
International Nuclear Information System (INIS)
Aouissat, Z.; Martin, C.
2004-01-01
We apply the random-phase approximation (RPA) and its extension called renormalized RPA to the quantum anharmonic oscillator with an O(2) symmetry. We first obtain the equation for the RPA frequencies in the standard and in the renormalized RPAs using the equation-of-motion method. In the case where the ground state has a broken symmetry, we check the existence of a zero frequency in the standard and in the renormalized RPAs. Then we use a time-dependent approach where the standard-RPA frequencies are obtained as small oscillations around the static solution in the time-dependent Hartree-Bogolyubov equation. We draw the parallel between the two approaches. (orig.)
Equidistance of the complex two-dimensional anharmonic oscillator spectrum: the exact solution
International Nuclear Information System (INIS)
Cannata, F; Ioffe, M V; Nishnianidze, D N
2012-01-01
We study a class of quantum two-dimensional models with complex potentials of a specific form. They can be considered as the generalization of a recently studied model with quadratic interaction not amenable to the conventional separation of variables. In the present case, the property of shape invariance provides the equidistant form of the spectrum and the algorithm to construct eigenfunctions analytically. It is shown that the Hamiltonian is non-diagonalizable, and the resolution of identity must also include the corresponding associated functions. In the specific case of anharmonic second plus fourth-order interaction, expressions for the wavefunctions and associated functions are constructed explicitly for the lowest levels, and the recursive algorithm to produce higher level wavefunctions is given. (paper)
Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re σ-phase
Energy Technology Data Exchange (ETDEWEB)
Palumbo, Mauro, E-mail: mauro.palumbo@rub.de; Fries, Suzana G. [ICAMS, Ruhr University Bochum, Universität Str. 150, D-44801 Bochum (Germany); Pasturel, Alain [SIMAP, UMR CNRS-INPG-UJF 5266, BP 75, F-38402 Saint Martin d’Hères (France); Alfè, Dario [Department of Earth Sciences, Department of Physics and Astronomy, London Centre for Nanotechnology and Thomas Young Centre-UCL, University College London, Gower Street, London WC1E 6BT (United Kingdom)
2014-04-14
Using density-functional theory in combination with the direct force method and molecular dynamics we investigate the vibrational properties of a binary Cr-Re σ-phase. In the harmonic approximation, we have computed phonon dispersion curves and density of states, evidencing structural and chemical effects. We found that the σ-phase is mechanically unstable in some configurations, for example, when all crystallographic sites are occupied by Re atoms. By using a molecular-dynamics-based method, we have analysed the anharmonicity in the system and found negligible effects (∼0.5 kJ/mol) on the Helmholtz energy of the binary Cr-Re σ-phase up to 2000 K (∼0.8T{sub m}). Finally, we show that the vibrational contribution has significant consequences on the disordering of the σ-phase at high temperature.
Frequency and Temperature Dependence of Anharmonic Phonon Relaxation Rate in Carbon Nanotubes
International Nuclear Information System (INIS)
Hepplestone, S P; Srivastava, G P
2007-01-01
The relaxation rate of phonon modes in the (10, 10) single wall carbon nanotube undergoing three-phonon interactions at various temperatures has been studied using both qualitative and quantitative approaches based upon Fermi's Golden Rule and a quasi-elastic continuum model for the anharmonic potential. For the quantitative calculations, dispersion relations for the phonon modes were obtained from analytic expressions developed by Zhang et al. The qualitative expressions were derived using simple linear phonon dispersions relations. We show that in the high temperature regime the relaxation rate varies linearly with temperature and with the square of the frequency. In the low temperature regime we show that the relaxation rate varies exponentially with the inverse of temperature. These results have some very interesting implifications for effects for mean free path and thermal conductivity calculations
Anharmonic vibrational modes of chemisorbed H on the Rh(001) surface
International Nuclear Information System (INIS)
Hamann, D.R.; Feibelman, P.J.
1988-01-01
The potential for H atoms in the vicinity of the fourfold hollow chemisorption site on the Rh(001) surface at monolayer coverage is calculated using local-density-functional theory, and the linear-augmented-plane-wave method. The potential is found to contain important anharmonic components, one that couples parallel and perpendicular motion, and another producing azimuthal anisotropy. Variational solutions are found for the ground and low-lying excited states of H and D in this potential. The fundamental asymmetric- and symmetric-stretch H vibrational excitations are found to have energies of 67 and 92 meV. The latter agrees with recent experimental results, and higher-lying experimental modes are interpreted as mixed excitations. Comparisons are made with spring-constant models, calculated potentials for H on Ni and Pd(001), and theories of Bloch states for H on Ni
Random-phase approximation and its extension for the O(2) anharmonic oscillator
Energy Technology Data Exchange (ETDEWEB)
Aouissat, Z. [Institut fuer Kernphysik, Technische Hochschule Darmstadt, Schlossgarten 9, D-64289, Darmstadt (Germany); Martin, C. [Groupe de Physique Theorique, Institut de Physique Nucleaire, F-91406, Orsay Cedex (France)
2004-02-01
We apply the random-phase approximation (RPA) and its extension called renormalized RPA to the quantum anharmonic oscillator with an O(2) symmetry. We first obtain the equation for the RPA frequencies in the standard and in the renormalized RPAs using the equation-of-motion method. In the case where the ground state has a broken symmetry, we check the existence of a zero frequency in the standard and in the renormalized RPAs. Then we use a time-dependent approach where the standard-RPA frequencies are obtained as small oscillations around the static solution in the time-dependent Hartree-Bogolyubov equation. We draw the parallel between the two approaches. (orig.)
Quantum effects in amplitude death of coupled anharmonic self-oscillators
Amitai, Ehud; Koppenhöfer, Martin; Lörch, Niels; Bruder, Christoph
2018-05-01
Coupling two or more self-oscillating systems may stabilize their zero-amplitude rest state, therefore quenching their oscillation. This phenomenon is termed "amplitude death." Well known and studied in classical self-oscillators, amplitude death was only recently investigated in quantum self-oscillators [Ishibashi and Kanamoto, Phys. Rev. E 96, 052210 (2017), 10.1103/PhysRevE.96.052210]. Quantitative differences between the classical and quantum descriptions were found. Here, we demonstrate that for quantum self-oscillators with anharmonicity in their energy spectrum, multiple resonances in the mean phonon number can be observed. This is a result of the discrete energy spectrum of these oscillators, and is not present in the corresponding classical model. Experiments can be realized with current technology and would demonstrate these genuine quantum effects in the amplitude death phenomenon.
International Nuclear Information System (INIS)
Fei Xiang; Snow, W.M.
1999-01-01
Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles
Fei Xiang
1999-01-01
Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles.
Numerical solutions of anharmonic vibration of BaO and SrO molecules
Energy Technology Data Exchange (ETDEWEB)
Pramudito, Sidikrubadi; Sanjaya, Nugraha Wanda [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia); Sumaryada, Tony, E-mail: tsumaryada@ipb.ac.id [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia); Computational Biophysics and Molecular Modeling Research Group (CBMoRG), Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia)
2016-03-11
The Morse potential is a potential model that is used to describe the anharmonic behavior of molecular vibration between atoms. The BaO and SrO molecules, which are two almost similar diatomic molecules, were investigated in this research. Some of their properties like the value of the dissociation energy, the energy eigenvalues of each energy level, and the profile of the wavefunctions in their correspondence vibrational states were presented in this paper. Calculation of the energy eigenvalues and plotting the wave function’s profiles were performed using Numerov method combined with the shooting method. In general we concluded that the Morse potential solved with numerical methods could accurately produce the vibrational properties and the wavefunction behavior of BaO and SrO molecules from the ground state to the higher states close to the dissociation level.
Monge Palacios, Manuel
2018-01-29
We performed a theoretical study on the double hydrogen shift isomerization reaction of a six carbon atom Criegee intermediate (C6-CI), catalyzed by formic acid (HCOOH), to produce vinylhydroperoxide (VHP), C6-CI+HCOOH→VHP+HCOOH. This Criegee intermediate can serve as a surrogate for larger CIs derived from important volatile organic compounds like monoterpenes, whose reactivity is not well understood and are difficult to handle computationally. The reactant HCOOH exerts a pronounced catalytic effect on the studied reaction by lowering the barrier height, but the kinetic enhancement is hindered by the multistructural anharmonicity. First, the rigid ring-structure adopted by the saddle point to facilitate simultaneous transfer of two atoms does not allow formation of as many conformers as those formed by the reactant C6-CI. And second, the flexible carbon chain of C6-CI facilitates the formation of stabilizing intramolecular C–H···O hydrogen bonds; this stabilizing effect is less pronounced in the saddle point structure due to its tightness and steric effects. Thus, the contribution of the reactant C6-CI conformers to the multistructural partition function is larger than that of the saddle point conformers. The resulting low multistructural anharmonicity factor partially cancels out the catalytic effect of the carboxylic acid, yielding in a moderately large rate coefficient, k(298 K) = 4.9·10-13 cm3 molecule-1 s-1. We show that carboxylic acids may promote the conversion of stabilized Criegee intermediates into vinylhydroperoxides in the atmosphere, which generates OH radicals and leads to secondary organic aerosol, thereby affecting the oxidative capacity of the atmosphere and ultimately the climate.
Krasnoshchekov, Sergey V; Stepanov, Nikolay F
2013-11-14
In the theory of anharmonic vibrations of a polyatomic molecule, mixing the zero-order vibrational states due to cubic, quartic and higher-order terms in the potential energy expansion leads to the appearance of more-or-less isolated blocks of states (also called polyads), connected through multiple resonances. Such polyads of states can be characterized by a common secondary integer quantum number. This polyad quantum number is defined as a linear combination of the zero-order vibrational quantum numbers, attributed to normal modes, multiplied by non-negative integer polyad coefficients, which are subject to definition for any particular molecule. According to Kellman's method [J. Chem. Phys. 93, 6630 (1990)], the corresponding formalism can be conveniently described using vector algebra. In the present work, a systematic consideration of polyad quantum numbers is given in the framework of the canonical Van Vleck perturbation theory (CVPT) and its numerical-analytic operator implementation for reducing the Hamiltonian to the quasi-diagonal form, earlier developed by the authors. It is shown that CVPT provides a convenient method for the systematic identification of essential resonances and the definition of a polyad quantum number. The method presented is generally suitable for molecules of significant size and complexity, as illustrated by several examples of molecules up to six atoms. The polyad quantum number technique is very useful for assembling comprehensive basis sets for the matrix representation of the Hamiltonian after removal of all non-resonance terms by CVPT. In addition, the classification of anharmonic energy levels according to their polyad quantum numbers provides an additional means for the interpretation of observed vibrational spectra.
Energy Technology Data Exchange (ETDEWEB)
Inoue, M [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Fujikawa, R [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Baryshev, A [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Khanikaev, A [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Lim, P B [CREST, Japan Science and Technology Agency, Saitama 332-0012, Japan (Japan); Uchida, H [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Aktsipetrov, O [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation); Fedyanin, A [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation); Murzina, T [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation); Granovsky, A [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation)
2006-04-21
When the constitutive materials of photonic crystals (PCs) are magnetic, or even only a defect introduced in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical properties. The strong photon confinement in the vicinity of magnetic defects results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of magnetization in media, and hence they are called magnetophotonic crystals providing the spin-dependent nature in PCs. (topical review)
International Nuclear Information System (INIS)
Inoue, M; Fujikawa, R; Baryshev, A; Khanikaev, A; Lim, P B; Uchida, H; Aktsipetrov, O; Fedyanin, A; Murzina, T; Granovsky, A
2006-01-01
When the constitutive materials of photonic crystals (PCs) are magnetic, or even only a defect introduced in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical properties. The strong photon confinement in the vicinity of magnetic defects results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of magnetization in media, and hence they are called magnetophotonic crystals providing the spin-dependent nature in PCs. (topical review)
Energy Technology Data Exchange (ETDEWEB)
Slenkamp, Karla M.; Lynch, Michael S.; Van Kuiken, Benjamin E.; Brookes, Jennifer F.; Bannan, Caitlin C.; Daifuku, Stephanie L.; Khalil, Munira, E-mail: mkhalil@chem.washington.edu [Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 (United States)
2014-02-28
Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (ν{sub CN}) vibrations found in [(NH{sub 3}){sub 5}Ru{sup III}NCFe{sup II}(CN){sub 5}]{sup −} (FeRu) dissolved in D{sub 2}O and formamide and [(NC){sub 5}Fe{sup II}CNPt{sup IV}(NH{sub 3}){sub 4}NCFe{sup II}(CN){sub 5}]{sup 4−} (FePtFe) dissolved in D{sub 2}O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the ν{sub CN} modes in the electronic ground state. The FTIR spectra of the ν{sub CN} modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic ν{sub CN} modes. The vibrational mode anharmonicities of the individual ν{sub CN} modes range from 14 to 28 cm{sup −1}. The mixed-mode anharmonicities range from 2 to 14 cm{sup −1}. In general, the bridging ν{sub CN} mode is most weakly coupled to the radial ν{sub CN} mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four ν{sub CN} modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D{sub 2}O. The ν{sub CN} modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm{sup −1}. This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the ν{sub CN} modes in cyanide-bridged transition metal mixed valence complexes.
Origin of electronic properties of PbGa2Se4 crystal: Experimental and theoretical investigations
International Nuclear Information System (INIS)
Babuka, T.; Kityk, I.V.; Parasyuk, O.V.; Myronchuk, G.; Khyzhun, O.Y.; Fedorchuk, A.O.; Makowska-Janusik, M.
2015-01-01
Graphical abstract: In the presented work the structural and electronic properties of the PbGa 2 Se 4 single crystal were investigated experimentally as well as theoretically. The XPS spectra, Urbach’s rule and steepness parameters of PbGa 2 Se 4 single crystal have been investigated for the first time. The quantum chemical calculations were also never performed before for the studied structure. The theoretically obtained data help to explain the properties of material. - Highlights: • Urbach’s rule and steepness parameters for PbGa 2 Se 4 crystals explored for the first time. • Non-reactivity of the PbGa 2 Se 4 surface was established by XPS. • DFT approach shows its efficiency to describe electronic properties of PbGa 2 Se 4 . • Electronic parameters are affected by existence of electron–phonon interaction. - Abstract: The PbGa 2 Se 4 crystal is a promising material for optoelectronic applications. It is caused by coexistence of the large polarized Pb cations and a huge contribution of anharmonic phonon subsystem caused by chalcogenide anions. In the present work the electronic and optical properties of the mentioned material were studied theoretically as well as experimentally by optical and X-ray photoelectron spectroscopy methods. The DFT approach has been used for the quantum chemical electronic properties calculations. Urbach rule and steepness parameters of the PbGa 2 Se 4 crystal have been evaluated for the first time. These parameters and Urbach energies increase with increasing temperature of the samples that is typical for the semiconducting materials. The XPS measurements of the investigated crystal reveal that all the spectral features are originated from core-level states of the constituent elements. Simultaneously these results also confirm non-reactivity of the PbGa 2 Se 4 surface. However, the titled single crystal possesses a number of intrinsic structural defects and vacancies thereby affecting its electronic properties. The
Bende, Attila; Muntean, Cristina M
2014-03-01
The theoretical IR and Raman spectra of the guanine-cytosine DNA base pairs in Watson-Crick and Hoogsteen configurations were computed using DFT method with M06-2X meta-hybrid GGA exchange-correlation functional, including the anharmonic corrections and solvent effects. The results for harmonic frequencies and their anharmonic corrections were compared with our previously calculated values obtained with the B3PW91 hybrid GGA functional. Significant differences were obtained for the anharmonic corrections calculated with the two different DFT functionals, especially for the stretching modes, while the corresponding harmonic frequencies did not differ considerable. For the Hoogtseen case the H⁺ vibration between the G-C base pair can be characterized as an asymmetric Duffing oscillator and therefore unrealistic anharmonic corrections for normal modes where this proton vibration is involved have been obtained. The spectral modification due to the anharmonic corrections, solvent effects and the influence of sugar-phosphate group for the Watson-Crick and Hoogsteen base pair configurations, respectively, were also discussed. For the Watson-Crick case also the influence of the stacking interaction on the theoretical IR and Raman spectra was analyzed. Including the anharmonic correction in our normal mode analysis is essential if one wants to obtain correct assignments of the theoretical frequency values as compared with the experimental spectra.
Sokolov, V I; Shirokov, E A; Kislov, A N
2002-01-01
Paper presents the results of investigations into lattice vibrations induced by nickel impurities charged negatively as to the lattice in ZnSe:Ni, ZnO:Ni, ZnS:Ni, CdS:Ni semiconductors. To investigate into vibrations one applies a sensitive technique of field exciton-oscillation spectroscopy. One observes experimentally oscillating reiterations of the impurity exciton head line including the intensive peaks of combined repetitions up to the 8-th order. The experimental results are discussed on the basis of the model estimations of oscillations of a lattice with a charged impurity centre, as well as, on the ground of calculations for oscillations of monoatomic chain with high anharmonicity. Charged impurity centres are shown to induce new oscillations of lattice - impurity anharmonic modes
Mansoori Kermani, Maryam; Dehestani, Maryam
2018-06-01
We modeled a one-dimensional actuator including the Casimir and electrostatic forces perturbed by an external force with fractional damping. The movable electrode was assumed to oscillate by an anharmonic elastic force originated from Murrell-Mottram or Lippincott potential. The nonlinear equations have been solved via the Adomian decomposition method. The behavior of the displacement of the electrode from equilibrium position, its velocity and acceleration were described versus time. Also, the changes of the displacement have been investigated according to the frequency of the external force and the voltage of the electrostatic force. The convergence of the Adomian method and the effect of the orders of expansion on the displacement versus time, frequency, and voltage were discussed. The pull-in parameter was obtained and compared with the other models in the literature. This parameter was described versus the equilibrium position and anharmonicity constant.
Mansoori Kermani, Maryam; Dehestani, Maryam
2018-03-01
We modeled a one-dimensional actuator including the Casimir and electrostatic forces perturbed by an external force with fractional damping. The movable electrode was assumed to oscillate by an anharmonic elastic force originated from Murrell-Mottram or Lippincott potential. The nonlinear equations have been solved via the Adomian decomposition method. The behavior of the displacement of the electrode from equilibrium position, its velocity and acceleration were described versus time. Also, the changes of the displacement have been investigated according to the frequency of the external force and the voltage of the electrostatic force. The convergence of the Adomian method and the effect of the orders of expansion on the displacement versus time, frequency, and voltage were discussed. The pull-in parameter was obtained and compared with the other models in the literature. This parameter was described versus the equilibrium position and anharmonicity constant.
Quaranta, Vanessa; Hellström, Matti; Behler, Jörg; Kullgren, Jolla; Mitev, Pavlin D.; Hermansson, Kersti
2018-06-01
Unraveling the atomistic details of solid/liquid interfaces, e.g., by means of vibrational spectroscopy, is of vital importance in numerous applications, from electrochemistry to heterogeneous catalysis. Water-oxide interfaces represent a formidable challenge because a large variety of molecular and dissociated water species are present at the surface. Here, we present a comprehensive theoretical analysis of the anharmonic OH stretching vibrations at the water/ZnO(101 ¯ 0) interface as a prototypical case. Molecular dynamics simulations employing a reactive high-dimensional neural network potential based on density functional theory calculations have been used to sample the interfacial structures. In the second step, one-dimensional potential energy curves have been generated for a large number of configurations to solve the nuclear Schrödinger equation. We find that (i) the ZnO surface gives rise to OH frequency shifts up to a distance of about 4 Å from the surface; (ii) the spectrum contains a number of overlapping signals arising from different chemical species, with the frequencies decreasing in the order ν(adsorbed hydroxide) > ν(non-adsorbed water) > ν(surface hydroxide) > ν(adsorbed water); (iii) stretching frequencies are strongly influenced by the hydrogen bond pattern of these interfacial species. Finally, we have been able to identify substantial correlations between the stretching frequencies and hydrogen bond lengths for all species.
Harmonic balance approach to the periodic solutions of the (an)harmonic relativistic oscillator
International Nuclear Information System (INIS)
Belendez, Augusto; Pascual, Carolina
2007-01-01
The first-order harmonic balance method via the first Fourier coefficient is used to construct two approximate frequency-amplitude relations for the relativistic oscillator for which the nonlinearity (anharmonicity) is a relativistic effect due to the time line dilation along the world line. Making a change of variable, a new nonlinear differential equation is obtained and two procedures are used to approximately solve this differential equation. In the first the differential equation is rewritten in a form that does not contain a square-root expression, while in the second the differential equation is solved directly. The approximate frequency obtained using the second procedure is more accurate than the frequency obtained with the first due to the fact that, in the second procedure, application of the harmonic balance method produces an infinite set of harmonics, while in the first procedure only two harmonics are produced. Both approximate frequencies are valid for the complete range of oscillation amplitudes, and excellent agreement of the approximate frequencies with the exact one are demonstrated and discussed. The discrepancy between the first-order approximate frequency obtained by means of the second procedure and the exact frequency never exceeds 1.6%. We also obtained the approximate frequency by applying the second-order harmonic balance method and in this case the relative error is as low 0.31% for all the range of values of amplitude of oscillation A
Vitale, Valerio; Dziedzic, Jacek; Dubois, Simon M-M; Fangohr, Hans; Skylaris, Chris-Kriton
2015-07-14
Density functional theory molecular dynamics (DFT-MD) provides an efficient framework for accurately computing several types of spectra. The major benefit of DFT-MD approaches lies in the ability to naturally take into account the effects of temperature and anharmonicity, without having to introduce any ad hoc or a posteriori corrections. Consequently, computational spectroscopy based on DFT-MD approaches plays a pivotal role in the understanding and assignment of experimental peaks and bands at finite temperature, particularly in the case of floppy molecules. Linear-scaling DFT methods can be used to study large and complex systems, such as peptides, DNA strands, amorphous solids, and molecules in solution. Here, we present the implementation of DFT-MD IR spectroscopy in the ONETEP linear-scaling code. In addition, two methods for partitioning the dipole moment within the ONETEP framework are presented. Dipole moment partitioning allows us to compute spectra of molecules in solution, which fully include the effects of the solvent, while at the same time removing the solvent contribution from the spectra.
Quantum theory of anharmonic oscillators - a variational and systematic general approximation method
International Nuclear Information System (INIS)
Yamazaki, K.; Kyoto Univ.
1984-01-01
The paper investigates the energy levels and wavefunctions of an anharmonic oscillator characterised by the potential 1/2ω 2 q 2 +lambdaq 4 . As a lowest-order approximation an extremely simple formula for energy levels, Esub(i)sup(0) = (i+1/2)1/4(3/αsub(i)+αsub(i)), is derived (i being the quantum number of the energy level). This formula reproduces the exact energy levels within an error of about 1%. Systematically higher orders of the present perturbation theory are developed. The present second-order perturbation theory reduces the errors of the lowest-order results by a factor of about 1/5 in general. Various ranges (large, intermediate, small) of (i, lambda) are investigated and compared with the exact values obtained by other workers. For i = 0, 1, even the fourth-order perturbation calculation can be elaborated explicitly, which reduces the error to about 0.01% for any lambda. For small lambda it gives correct numerical coefficients up to lambda 4 terms, as it should. (author)
Ghatge, Mayur; Tabrizian, Roozbeh
2018-03-01
A matrix of aluminum-nitride (AlN) waveguides is acoustically engineered to realize electrically isolated phase-synchronous frequency references through nonlinear wave-mixing. AlN rectangular waveguides are cross-coupled through a periodically perforated plate that is engineered to have a wide acoustic bandgap around a desirable frequency ( f1≈509 MHz). While the coupling plate isolates the matrix from resonant vibrations of individual waveguide constituents at f1, it is transparent to the third-order harmonic waves (3f1) that are generated through nonlinear wave-mixing. Therefore, large-signal excitation of the f1 mode in a constituent waveguide generates acoustic waves at 3f1 with an efficiency defined by elastic anharmonicity of the AlN film. The phase-synchronous propagation of the third harmonic through the matrix is amplified by a high quality-factor resonance mode at f2≈1529 MHz, which is sufficiently close to 3f1 (f2 ≅ 3f1). Such an architecture enables realization of frequency-multiplied and phase-synchronous, yet electrically and spectrally isolated, references for multi-band/carrier and spread-spectrum wireless communication systems.
International Nuclear Information System (INIS)
Sarkar, P.; Bhattacharyya, S.P.
1995-01-01
The effects of quartic anharmonicity on the quantum dynamics of a linear oscillator with time-dependent force constant (K) or harmonic frequency (ω) are studied both perturbatively and numerically by the time-dependent Fourier grid Hamiltonian method. In the absence of anharmonicity, the ground-state population decreases and the population of an accessible excited state (k = 2.4, 6 ... ) increases with time. However, when anharmonicity is introduced, both the ground- and excited-state populations show typical oscillations. For weak coupling, the population of an accessible excited state at a certain instant of time (short) turns out to be a parabolic function of the anharmonic coupling constant (λ), when all other parameters of the system are kept fixed. This parabolic nature of the excited-state population vs. the λ profile is independent of the specific form of the time dependence of the force constant, K t . However, it depends upon the rate at which K t relaxes. For small anharmonic coupling strength and short time scales, the numerical results corroborate expectations based on the first-order time-dependent perturbative analysis, using a suitably repartitioned Hamiltonian that makes H 0 time-independent. Some of the possible experimental implications of our observations are analyzed, especially in relation to intensity oscillations observed in some charge-transfer spectra in systems in which the dephasing rates are comparable with the time scale of the electron transfer. 21 refs., 7 figs., 1 tab
Analytic properties of the OCP and ionic mixtures in the strongly coupled fluid state
International Nuclear Information System (INIS)
DeWitt, H.E.
1993-01-01
Exact results for the Madelung constants and first order anharmonic energies are given for the inverse power potentials with the Coulomb potential as the softest example. Similar exact results are obtained using the analysis of Rosenfeld on the Γ → ∞ limit for the OCP internal energy, direct correlation function, screening function, and bridge functions. Knowing these exact limits for the fluid phase of the OCP allows one to determine the nature of the thermal corrections to the strongly coupled results. Solutions of the HNC equation modified with the hard sphere bridge function give an example
Beć, Krzysztof B.; Grabska, Justyna; Czarnecki, Mirosław A.
2018-05-01
We investigated near-infrared (7500-4000 cm-1) spectra of n-hexanol, cyclohexanol and phenol in CCl4 (0.2 M) by using anharmonic quantum calculations. These molecules represent three major kinds of alcohols; linear and cyclic aliphatic, and aromatic ones. Vibrational second-order perturbation theory (VPT2) was employed to calculate the first overtones and binary combination modes and to reproduce the experimental NIR spectra. The level of conformational flexibility of these three alcohols varies from one stable conformer of phenol through four conformers of cyclohexanol to few hundreds conformers in the case of n-hexanol. To take into account the most relevant conformational population of n-hexanol, a systematic conformational search was performed. Accurate reproduction of the experimental NIR spectra was achieved and detailed spectra-structure correlations were obtained for these three alcohols. VPT2 approach provides less reliable description of highly anharmonic modes, i.e. OH stretching. In the present work this limitation was manifested in erroneous results yielded by VPT2 for 2νOH mode of cyclohexanol. To study the anharmonicity of this mode we solved the corresponding time-independent Schrödinger equation based on a dense-grid probing of the relevant vibrational potential. These results allowed for significant improvement of the agreement between the calculated and experimental 2νOH band of cyclohexanol. Various important biomolecules include similar structural units to the systems investigated here. A detailed knowledge on spectral properties of these three types of alcohols is therefore essential for advancing our understanding of NIR spectroscopy of biomolecules.
International Nuclear Information System (INIS)
Huveneers, François
2013-01-01
We study the thermal conductivity, at fixed positive temperature, of a disordered lattice of harmonic oscillators, weakly coupled to each other through anharmonic potentials. The interaction is controlled by a small parameter ϵ > 0. We rigorously show, in two slightly different setups, that the conductivity has a non-perturbative origin. This means that it decays to zero faster than any polynomial in ϵ as ϵ → 0. It is then argued that this result extends to a disordered chain studied by Dhar and Lebowitz (2008 Phys. Rev. Lett. 100 134301), and to a classic spin chain recently investigated by Oganesyan, Pal and Huse (2009 Phys. Rev. B 80 115104). (paper)
Tortello, M; Daghero, D; Ummarino, G A; Stepanov, V A; Jiang, J; Weiss, J D; Hellstrom, E E; Gonnelli, R S
2010-12-03
Directional point-contact Andreev-reflection measurements in Ba(Fe(1-x)Co(x))2As2 single crystals (T(c) = 24.5 K) indicate the presence of two superconducting gaps with no line nodes on the Fermi surface. The point-contact Andreev-reflection spectra also feature additional structures related to the electron-boson interaction, from which the characteristic boson energy Ω(b)(T) is obtained, very similar to the spin-resonance energy observed in neutron scattering experiments. Both the gaps and the additional structures can be reproduced within a three-band s ± Eliashberg model by using an electron-boson spectral function peaked at Ω(0) = 12 meV ≃ Ω(b)(0).
Morpurgo, Simone
2007-01-01
The principles of symmetry and group theory are applied to the zero-order wavefunctions associated with the strong-field t[subscript 2g][superscript 2] configuration and their symmetry-adapted linear combinations (SALC) associated with the generated energy terms are derived. This approach will enable students to better understand the use of…
Energy Technology Data Exchange (ETDEWEB)
Sobhani, Hadi; Hassanabadi, Hassan [Shahrood University of Technology, Faculty of Physics, Shahrood (Iran, Islamic Republic of); Chung, Won Sang [Gyeongsang National University, Department of Physics and Research Institute of Natural Science, College of Natural Science, Jinju (Korea, Republic of)
2018-02-15
In this article, we determine the thermodynamical properties of the anharmonic canonical ensemble within the cosmic-string framework. We use the ordinary statistics and the q-deformed superstatistics for this study. The q-deformed superstatistics is derived by modifying the probability density in the original superstatistics. The Schroedinger equation is rewritten in the cosmic-string framework. Next, the anharmonic oscillator is investigated in detail. The wave function and the energy spectrum of the considered system are derived using the bi-confluent Heun functions. In the next step, we first determine the thermodynamical properties for the canonical ensemble of the anharmonic oscillator in the cosmic-string framework using the ordinary statistics approach. Also, these quantities have been obtained in the q-deformed superstatistics. For vanishing deformation parameter, the ordinary results are obtained. (orig.)
Strong Mechanoluminescence from Oxynitridosilicate Phosphors
Energy Technology Data Exchange (ETDEWEB)
Zhang Lin; Xu Chaonan; Yamada, Hiroshi, E-mail: cn-xu@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), 807-1 Shuku, Tosu, Saga 841-0052 (Japan)
2011-10-29
We successfully developed a novel Mechanoluminescence (ML) material with water resistance, oxynitridosilicate; BaSi{sub 2}O{sub 2}N{sub 2}: Eu{sup 2+}. The crystal structure, photoluminescence (PL) and ML properties were characterized. The ML of BaSi{sub 2}O{sub 2}N{sub 2}: Eu{sup 2+} is so strong that the blue-green emission can be observed by the naked eyes clearly. In addition, it shows superior water resistance property. No changes were found in the ML intensities during the total water treatment test.
Why does the martensitic transformation temperature strongly depend on composition?
International Nuclear Information System (INIS)
Ren, X.; Otsuka, K.
2000-01-01
The reason for the strong composition and heat-treatment dependence of the martensitic transformation temperature was investigated by a simple Landau-type model. Assuming the anharmonic and coupling coefficients are insensitive to composition, we obtained an important result martensitic transformation occurs at a critical elastic constant c' and a critical TA 2 phonon energy ω η 2 , which are independent of alloy composition. This result gained support from a large body of experimental data of Cu-based alloys. Since c' and phonon energy are strongly dependent on composition, the constancy of c' at Ms demands that the (transformation) temperature must exhibit an opposite effect to compensate the composition effect. Therefore, the lower the c', the higher the Ms is. Because the temperature dependence of c' is weak (due to the 1 st order nature of the transformation), the big c' change by a slight composition change must be compensated by a large change in temperature. Thus Ms has strong composition dependence. The effect of quench is to increase point defects, being equivalent to a composition change, thus has a strong effect on Ms. From the present study, we can conclude that the strong composition dependence of Ms is mainly a harmonic effect. (orig.)
International Nuclear Information System (INIS)
Pietsch, U.
1982-01-01
X-ray structure amplitudes of elemental and A 3 B 5 semiconductors can be described by means of spherical atomic form factors and an additional scattered particle at the position of the centre of the covalent bond between next neighbours named bond charge. For this analysis anharmonic core vibrations were neglegted. In this note the influence is estimated of anharmonic core vibrations on the total structure amplitudes of some zinc-blende compounds (GaAs, ZnSe, CuBr, InSb, and CuCl)
Directory of Open Access Journals (Sweden)
N. Al Sdran
2016-06-01
Full Text Available The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x = Ax2α + Bx2, (A>0, B<0, with (α = 2 for quadratic, (α =3 for sextic and (α =4 for octic anharmonic oscillators. The Airy function approach is based on the replacement of the real potential V(x by a piecewise-linear potential v(x, while, the Numerov method is based on the discretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It’s found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.
Kolmann, Stephen J.; Jordan, Meredith J. T.
2010-02-01
One of the largest remaining errors in thermochemical calculations is the determination of the zero-point energy (ZPE). The fully coupled, anharmonic ZPE and ground state nuclear wave function of the SSSH radical are calculated using quantum diffusion Monte Carlo on interpolated potential energy surfaces (PESs) constructed using a variety of method and basis set combinations. The ZPE of SSSH, which is approximately 29 kJ mol-1 at the CCSD(T)/6-31G∗ level of theory, has a 4 kJ mol-1 dependence on the treatment of electron correlation. The anharmonic ZPEs are consistently 0.3 kJ mol-1 lower in energy than the harmonic ZPEs calculated at the Hartree-Fock and MP2 levels of theory, and 0.7 kJ mol-1 lower in energy at the CCSD(T)/6-31G∗ level of theory. Ideally, for sub-kJ mol-1 thermochemical accuracy, ZPEs should be calculated using correlated methods with as big a basis set as practicable. The ground state nuclear wave function of SSSH also has significant method and basis set dependence. The analysis of the nuclear wave function indicates that SSSH is localized to a single symmetry equivalent global minimum, despite having sufficient ZPE to be delocalized over both minima. As part of this work, modifications to the interpolated PES construction scheme of Collins and co-workers are presented.
Kolmann, Stephen J; Jordan, Meredith J T
2010-02-07
One of the largest remaining errors in thermochemical calculations is the determination of the zero-point energy (ZPE). The fully coupled, anharmonic ZPE and ground state nuclear wave function of the SSSH radical are calculated using quantum diffusion Monte Carlo on interpolated potential energy surfaces (PESs) constructed using a variety of method and basis set combinations. The ZPE of SSSH, which is approximately 29 kJ mol(-1) at the CCSD(T)/6-31G* level of theory, has a 4 kJ mol(-1) dependence on the treatment of electron correlation. The anharmonic ZPEs are consistently 0.3 kJ mol(-1) lower in energy than the harmonic ZPEs calculated at the Hartree-Fock and MP2 levels of theory, and 0.7 kJ mol(-1) lower in energy at the CCSD(T)/6-31G* level of theory. Ideally, for sub-kJ mol(-1) thermochemical accuracy, ZPEs should be calculated using correlated methods with as big a basis set as practicable. The ground state nuclear wave function of SSSH also has significant method and basis set dependence. The analysis of the nuclear wave function indicates that SSSH is localized to a single symmetry equivalent global minimum, despite having sufficient ZPE to be delocalized over both minima. As part of this work, modifications to the interpolated PES construction scheme of Collins and co-workers are presented.
International Nuclear Information System (INIS)
Caswell, W.E.
1979-01-01
We introduce a generalization of Wick-ordering which maps the anharmonic oscillator (AO) Hamiltonian for mass m and coupling lambda exactly into a ''Wick-ordered'' Hamiltonian with an effective mass M which is a simple analytic function of lambda and m. The effective coupling Λ=lambda/M 3 is bounded. We transform the AO perturbation series in lambda into one in Λ. This series may then be summed using Borel summation methods. We also introduce a new summation method for the AO series (which is a practical necessity to obtain accurate energy levels of the excited states). We obtain a numerical accuracy for (E/sub P/T--E/sub e/xact)/ E/sub e/xact of at least 10 -7 (using 20 orders of perturbation theory) and 10 -3 (using only 2 orders of perturbation theory) for all couplings and all energy levels of the anharmonic oscillator. The methods are applicable also to the double-well potential (DWP, the AO with a negative mass-squared). The only change is that now the effective coupling is unbounded as lambda→0. The series in Λ is, however, still summable. The relative accuracy in the energy levels for 20 orders of perturbation theory varies from 10 -7 for large coupling to 1% at lambda=0.1 and to 10% at lambda=.05. We also present results for the sextic oscillator
DEFF Research Database (Denmark)
Christensen, Claus H.; Schmidt, I.; Carlsson, A.
2005-01-01
A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion....... As representative examples, a metal (Pt), an alloy (PtSn), and a metal carbide (beta-Mo2C) were supported on conventional and mesoporous zeolite carriers, respectively, and the degree of particle dispersion was compared by TEM imaging. On conventional zeolites, the supported material aggregated on the outer surface...
Energy Technology Data Exchange (ETDEWEB)
Land, T A; Dylla-Spears, R; Thorsness, C B
2006-08-29
Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.
Indian Academy of Sciences (India)
2018-05-18
May 18, 2018 ... Abstract. 4-Nitrobenzoic acid (4-NBA) single crystals were studied for their linear and nonlinear optical ... studies on the proper growth, linear and nonlinear optical ..... between the optic axes and optic sign of the biaxial crystal.
Schomaker, Verner; Lingafelter, E. C.
1985-01-01
Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)
Momeni, F.; Naderi, M. H.
2018-05-01
In this paper, we study theoretically a hybrid optomechanical system consisting of a degenerate optical parametric amplifier inside a driven optical cavity with a moving end mirror which is modeled as a stiffening Duffing-like anharmonic quantum mechanical oscillator. By providing analytical expressions for the critical values of the system parameters corresponding to the emergence of the multistability behavior in the steady-state response of the system, we show that the stiffening mechanical Duffing anharmonicity reduces the width of the multistability region while the optical parametric nonlinearity can be exploited to drive the system toward the multistability region. We also show that for appropriate values of the mechanical anharmonicity strength the steady-state mechanical squeezing and the ground-state cooling of the mechanical resonator can be achieved. Moreover, we find that the presence of the nonlinear gain medium can lead to the improvement of the mechanical anharmonicity-induced cooling of the mechanical motion, as well as to the mechanical squeezing beyond the standard quantum limit of 3 dB.
Kermani, Bahram G
2016-07-01
Crystal Genetics, Inc. is an early-stage genetic test company, focused on achieving the highest possible clinical-grade accuracy and comprehensiveness for detecting germline (e.g., in hereditary cancer) and somatic (e.g., in early cancer detection) mutations. Crystal's mission is to significantly improve the health status of the population, by providing high accuracy, comprehensive, flexible and affordable genetic tests, primarily in cancer. Crystal's philosophy is that when it comes to detecting mutations that are strongly correlated with life-threatening diseases, the detection accuracy of every single mutation counts: a single false-positive error could cause severe anxiety for the patient. And, more importantly, a single false-negative error could potentially cost the patient's life. Crystal's objective is to eliminate both of these error types.
Diffusion in Coulomb crystals.
Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K
2011-07-01
Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.
Bipolarons in nonmetallic crystals
International Nuclear Information System (INIS)
Vinetskii, V.L.; Pashitskii, E.A.; Yanchuk, V.A.
1987-01-01
The binding energy of a bipolaron in an ionic crystal increases substantially in the case of strong anisotropy of the effective masses of the free carriers of the easy plane type or easy axis type. In the second case the polaron is cigar-like in shape and the coaxial configuration of bipolarons is energetically favorable. In this case a significant gain in the binding energy and in the width of the region of existence of the bipolaron, with respect to the dielectric constant and the magnitude of the electron-phonon interaction constant, compared with an isotropic crystal, is obtained only for quasi-two-dimensional, or layered, and quasi-one-dimensional, or chainlike, crystals. This work shows that a significant gain in the binding energy can be obtained by taking into account the anisotropy of the dielectric constant of the crystal and localization of the electron wave functions in directions perpendicular to the layers and chains of atoms
Testing strong interaction theories
International Nuclear Information System (INIS)
Ellis, J.
1979-01-01
The author discusses possible tests of the current theories of the strong interaction, in particular, quantum chromodynamics. High energy e + e - interactions should provide an excellent means of studying the strong force. (W.D.L.)
Jiang, Shaolong; Zhao, Liyun; Shi, Yuping; Xie, Chunyu; Zhang, Na; Zhang, Zhepeng; Huan, Yahuan; Yang, Pengfei; Hong, Min; Zhou, Xiebo; Shi, Jianping; Zhang, Qing; Zhang, Yanfeng
2018-05-01
Rhenium diselenide (ReSe2), which bears in-plane anisotropic optical and electrical properties, is of considerable interest for its excellent applications in novel devices, such as polarization-sensitive photodetectors and integrated polarization-controllers. However, great challenges to date in the controllable synthesis of high-quality ReSe2 have hindered its in-depth investigations and practical applications. Herein, we report a feasible synthesis of monolayer single-crystal ReSe2 flakes on the Au foil substrate by using a chemical vapor deposition route. Particularly, we focus on the temperature-dependent Raman spectroscopy investigations of monolayer ReSe2 grown on Au foils, which present concurrent red shifts of Eg-like and Ag-like modes with increasing measurement temperature from 77–290 K. Linear temperature dependences of both modes are revealed and explained from the anharmonic vibration of the ReSe2 lattice. More importantly, the strong interaction of ReSe2 with Au, with respect to that with SiO2/Si, is further confirmed by temperature-dependent Raman characterization. This work is thus proposed to shed light on the optical and thermal properties of such anisotropic two-dimensional three-atom-thick materials.
Monomial Crystals and Partition Crystals
Tingley, Peter
2010-04-01
Recently Fayers introduced a large family of combinatorial realizations of the fundamental crystal B(Λ0) for ^sln, where the vertices are indexed by certain partitions. He showed that special cases of this construction agree with the Misra-Miwa realization and with Berg's ladder crystal. Here we show that another special case is naturally isomorphic to a realization using Nakajima's monomial crystal.
Crystal structure and magnetic susceptibility of UOSe single crystals
International Nuclear Information System (INIS)
Kaczorowski, D.; Muenster Univ.; Poettgen, R.; Jeitschko, W.; Gajek, Z.; Zygmunt, A.
1993-01-01
The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T N =100±2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author)
Crystal structure and magnetic susceptibility of UOSe single crystals
Energy Technology Data Exchange (ETDEWEB)
Kaczorowski, D. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Poettgen, R.; Jeitschko, W. (Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Gajek, Z.; Zygmunt, A. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research)
1993-01-01
The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T[sub N]=100[+-]2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author).
International Nuclear Information System (INIS)
Taneichi, T.; Kobayashi, T.
2007-01-01
Discussion on wavelength dependent 'anharmonic' effects in a pump-probe signal for a system of wavepacket on one- and two-dimensional harmonic potentials was given. The Fourier power spectrum of the signal, calculated for a model composed of a three-state electronic system coupled to a set of displaced harmonic oscillators, depends on the pulse duration. Condition under which the wavepacket motion in the harmonic potential substantially deviates from that of the classical point mass is derived. The Fourier power spectrum has enhanced components with frequencies of harmonics even in a system composed of ideally harmonic potentials. Utility of the Fourier analysis of the spectrum for clarification of the squeezed molecular vibrational state is discussed. Calculated oscillatory behavior in phase of a pump-probe signal, as a function of probe frequency, was discussed in terms of a two-dimensional effect on a pump-probe signal
Seko, Atsuto; Togo, Atsushi; Hayashi, Hiroyuki; Tsuda, Koji; Chaput, Laurent; Tanaka, Isao
2015-11-01
Compounds of low lattice thermal conductivity (LTC) are essential for seeking thermoelectric materials with high conversion efficiency. Some strategies have been used to decrease LTC. However, such trials have yielded successes only within a limited exploration space. Here, we report the virtual screening of a library containing 54 779 compounds. Our strategy is to search the library through Bayesian optimization using for the initial data the LTC obtained from first-principles anharmonic lattice-dynamics calculations for a set of 101 compounds. We discovered 221 materials with very low LTC. Two of them even have an electronic band gap <1 eV , which makes them exceptional candidates for thermoelectric applications. In addition to those newly discovered thermoelectric materials, the present strategy is believed to be powerful for many other applications in which the chemistry of materials is required to be optimized.
Energy Technology Data Exchange (ETDEWEB)
Rath, Biswanath
1988-01-01
An ansatz is developed to find out an analytical expression for energy levels of anharmonic oscillators of the type V(X) X/sup 2//2 + lambdaXsup(2m) (m = 2,3) which is valid for all values of n and all regimes of parameter space. The procedure is extended to find out an analytical expression for the energy levels of the oscillator V(X) X/sup 2//2 + lambda/sub 1/ X/sup 4/ + lambda/sub 2/ X/sup 6/. As a practical application, it has been applied to calculate the characteristics of radiation emitted due to channeling of relativistic positrons between (100) planes in silicon.
Electromagnetic processes in strong crystalline fields
2007-01-01
We propose a number of new investigations on aspects of radiation from high energy electron and positron beams (10-300 GeV) in single crystals and amorphous targets. The common heading is radiation emission by electrons and positrons in strong electromagnetic fields, but as the setup is quite versatile, other related phenomena in radiation emission can be studied as well. The intent is to clarify the role of a number of important aspects of radiation in strong fields as e.g. observed in crystals. We propose to measure trident 'Klein-like' production in strong crystalline fields, 'crystalline undulator' radiation, 'sandwich' target phenomena, LPM suppression of pair production as well as axial and planar effects in contributions of spin to the radiation.
Golden, Barbara L.; Kundrot, Craig E.
2003-01-01
RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.
Crystallization mechanisms of acicular crystals
Puel, François; Verdurand, Elodie; Taulelle, Pascal; Bebon, Christine; Colson, Didier; Klein, Jean-Paul; Veesler, Stéphane
2008-01-01
In this contribution, we present an experimental investigation of the growth of four different organic molecules produced at industrial scale with a view to understand the crystallization mechanism of acicular or needle-like crystals. For all organic crystals studied in this article, layer-by-layer growth of the lateral faces is very slow and clear, as soon as the supersaturation is high enough, there is competition between growth and surface-activated secondary nucleation. This gives rise to pseudo-twinned crystals composed of several needle individuals aligned along a crystallographic axis; this is explained by regular over- and inter-growths as in the case of twinning. And when supersaturation is even higher, nucleation is fast and random. In an industrial continuous crystallization, the rapid growth of needle-like crystals is to be avoided as it leads to fragile crystals or needles, which can be partly broken or totally detached from the parent crystals especially along structural anisotropic axis corresponding to weaker chemical bonds, thus leading to slower growing faces. When an activated mechanism is involved such as a secondary surface nucleation, it is no longer possible to obtain a steady state. Therefore, the crystal number, size and habit vary significantly with time, leading to troubles in the downstream processing operations and to modifications of the final solid-specific properties. These results provide valuable information on the unique crystallization mechanisms of acicular crystals, and show that it is important to know these threshold and critical values when running a crystallizer in order to obtain easy-to-handle crystals.
Sacha, Krzysztof; Zakrzewski, Jakub
2018-01-01
Time crystals are time-periodic self-organized structures postulated by Frank Wilczek in 2012. While the original concept was strongly criticized, it stimulated at the same time an intensive research leading to propositions and experimental verifications of discrete (or Floquet) time crystals—the structures that appear in the time domain due to spontaneous breaking of discrete time translation symmetry. The struggle to observe discrete time crystals is reviewed here together with propositions that generalize this concept introducing condensed matter like physics in the time domain. We shall also revisit the original Wilczek’s idea and review strategies aimed at spontaneous breaking of continuous time translation symmetry.
Abortion: Strong's counterexamples fail
DEFF Research Database (Denmark)
Di Nucci, Ezio
2009-01-01
This paper shows that the counterexamples proposed by Strong in 2008 in the Journal of Medical Ethics to Marquis's argument against abortion fail. Strong's basic idea is that there are cases--for example, terminally ill patients--where killing an adult human being is prima facie seriously morally...
International Nuclear Information System (INIS)
Goldman, M.V.
1984-01-01
After a brief discussion of beam-excited Langmuir turbulence in the solar wind, we explain the criteria for wave-particle, three-wave and strong turbulence interactions. We then present the results of a numerical integration of the Zakharov equations, which describe the strong turbulence saturation of a weak (low-density) high energy, bump-on-tail beam instability. (author)
Two-phonon bound states in imperfect crystals
International Nuclear Information System (INIS)
Behera, S.N.; Samsur, Sk.
1980-01-01
The question of the occurrence of two-phonon bound states in imperfect crystals is investigated. It is shown that the anharmonicity mediated two-phonon bound state which is present in perfect crystals gets modified due to the presence of impurities. Moreover, the possibility of the occurrence of a purely impurity mediated two-phonon bound state is demonstrated. The bound state frequencies are calculated using the simple Einstein oscillator model for the host phonons. The two-phonon density of states for the imperfect crystal thus obtained has peaks at the combination and difference frequencies of two host phonons besides the peaks at the bound state frequencies. For a perfect crystal the theory predicts a single peak at the two-phonon bound state frequency in conformity with experimental observations and other theoretical calculations. Experimental data on the two-phonon infrared absorption and Raman scattering from mixed crystals of Gasub(1-c)Alsub(c)P and Gesub(1-c)Sisub(c) are analysed to provide evidence in support of impurity-mediated two-phonon bound states. The relevance of the zero frequency (difference spectrum) peak to the central peak, observed in structural phase transitions, is conjectured. (author)
Photonics of liquid-crystal structures: A review
Energy Technology Data Exchange (ETDEWEB)
Palto, S. P., E-mail: palto@online.ru; Blinov, L M; Barnik, M I; Lazarev, V V; Umanskii, B A; Shtykov, N M [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
2011-07-15
The original results of studies of the electro-optical and laser effects which have been performed at the Laboratory of Liquid Crystals of the Institute of Crystallography, Russian Academy of Sciences, over the last few years are reviewed. Cholesteric liquid crystals as vivid representatives of photonic structures and their behavior in an electric field are considered in detail. The formation of higher harmonics in the periodic distribution of the director field in a helical liquid crystal structure and, correspondingly, the new (anharmonic) mode of electro-optical effects are discussed. Another group of studies is devoted to bistable light switching by an electric field in chiral nematics. Polarization diffraction gratings controlled by an electric field are also considered. The results of studies devoted to microlasers on various photonic structures with cholesteric and nematic liquid crystals are considered in detail. Particular attention is given to the new regime: leaky-mode lasing. Designs of liquid crystal light amplifiers and their polarization, field, and spectral characteristics are considered in the last section.
Nonlinear phononics and structural control of strongly correlated materials
Energy Technology Data Exchange (ETDEWEB)
Mankowsky, Roman
2016-01-20
Mid-infrared light pulses can be used to resonantly excite infrared-active vibrational modes for the phase control of strongly correlated materials on subpicosecond timescales. As the energy is transferred directly into atomic motions, dissipation into the electronic system is reduced, allowing for the emergence of unusual low energy collective properties. Light-induced superconductivity, insulator-metal transitions and melting of magnetic order demonstrate the potential of this method. An understanding of the mechanism, by which these transitions are driven, is however missing. The aim of this work is to uncover this process by investigating the nonlinear lattice dynamics induced by the excitation and to elucidate their contribution to the modulation of collective properties of strongly correlated materials. The first signature of nonlinear lattice dynamics was reported in the observation of coherent phonon oscillations, resonant with the excitation of an infrared-active phonon mode in a manganite. This nonlinear phononic coupling can be described within a model, which predicts not only oscillatory coherent phonons dynamics but also directional atomic displacements along the coupled modes on average, which could cause the previously observed transitions. We verified this directional response and quantified the anharmonic coupling constant by tracing the atomic motions in a time-resolved hard X-ray diffraction experiment with sub-picometer spatial and femtosecond temporal resolution. In a subsequent study, we investigated the role of nonlinear lattice dynamics in the emergence of superconductivity far above the equilibrium transition temperature, an intriguing effect found to follow lattice excitation of YBa{sub 2}Cu{sub 3}O{sub 6+x}. By combining density functional theory (DFT) calculations of the anharmonic coupling constants with time-resolved X-ray diffraction experiments, we identified a structural rearrangement, which appears and decays with the same temporal
Energy Technology Data Exchange (ETDEWEB)
Matsunaga, Toshiyuki [Materials Science and Analysis Technology Centre, Panasonic Corporation, Osaka (Japan); Japan Synchrotron Radiation Research Institute Hyogo (Japan); Yamada, Noboru [Digital and Network Technology Development Centre, Panasonic Corporation, Osaka (Japan); Japan Synchrotron Radiation Research Institute Hyogo (Japan); Kojima, Rie [Digital and Network Technology Development Centre, Panasonic Corporation, Osaka (Japan); Shamoto, Shinichi [Neutron Science Research Centre, Japan Atomic Energy Research Institute, Ibaraki (Japan); Sato, Masugu; Tanida, Hajime; Uruga, Tomoya; Kohara, Shinji [Japan Synchrotron Radiation Research Institute, Hyogo (Japan); Takata, Masaki [SPring-8/RIKEN, Hyogo, Japan, Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo, Chiba (Japan); Zalden, Peter; Bruns, Gunnar; Wuttig, Matthias [I. Physikalisches Institut und JARA-FIT, RWTH Aachen Univ. (Germany); Sergueev, Ilya [European Synchrotron Radiation Facility, Grenoble (France); Wille, Hans Christian [Deutsches Elektronen-Synchrotron, Hamburg (Germany); Hermann, Raphael Pierre [Juelich Centre for Neutron Science JCNS and Peter Gruenberg, Institut PGI, JARA-FIT, Forschungszentrum Juelich GmbH (Germany); Faculte des Sciences, Universite de Liege (Belgium)
2011-06-21
Crystallization of an amorphous solid is usually accompanied by a significant change of transport properties, such as an increase in thermal and electrical conductivity. This fact underlines the importance of crystalline order for the transport of charge and heat. Phase-change materials, however, reveal a remarkably low thermal conductivity in the crystalline state. The small change in this conductivity upon crystallization points to unique lattice properties. The present investigation reveals that the thermal properties of the amorphous and crystalline state of phase-change materials show remarkable differences such as higher thermal displacements and a more pronounced anharmonic behavior in the crystalline phase. These findings are related to the change of bonding upon crystallization, which leads to an increase of the sound velocity and a softening of the optical phonon modes at the same time. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Excitation of different chromium centres by synchrotron radiation in MgO:Cr single crystals
Energy Technology Data Exchange (ETDEWEB)
Shablonin, E. [Institute of Physics, University of Tartu, Ravila Str. 14c, 50411 Tartu (Estonia); Popov, A.I., E-mail: popov@latnet.lv [Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV-1063 (Latvia); Lushchik, A., E-mail: aleksandr.lushchik@ut.ee [Institute of Physics, University of Tartu, Ravila Str. 14c, 50411 Tartu (Estonia); Kotlov, A. [Photon Science at DESY, Notkestrasse 85, 22607 Hamburg (Germany); Dolgov, S. [Institute of Physics, University of Tartu, Ravila Str. 14c, 50411 Tartu (Estonia)
2015-11-15
The excitation spectra for the emissions of chromium-containing centres have been measured at 10 K using synchrotron radiation of 4–32 eV in MgO single crystals with different content of Cr{sup 3+} (5–850 ppm) and Ca{sup 2+} impurity ions. Both virgin crystals and the samples preliminarily irradiated with x-rays at 295 K have been studied. The role of complex chromium centres containing two Cr{sup 3+} and a cation vacancy (sometimes nearby a Ca{sup 2+} ion) on the luminescence processes and the transformation/creation of structural defects has been analysed. Such anharmonic complex centres could serve as the seeds for the creation of 3D defects that facilitate the cracking and brittle destruction of MgO crystals under their irradiation with ∼GeV heavy ions providing extremely high excitation density within cylindrical ion tracks.
Salna, Bridget; Benabbas, Abdelkrim; Russo, Douglas; Champion, Paul M
2017-07-20
A proper description of proton donor-acceptor (D-A) distance fluctuations is crucial for understanding tunneling in proton-coupled electron transport (PCET). The typical harmonic approximation for the D-A potential results in a Gaussian probability distribution, which does not appropriately reflect the electronic repulsion forces that increase the energetic cost of sampling shorter D-A distances. Because these shorter distances are the primary channel for thermally activated tunneling, the analysis of tunneling kinetics depends sensitively on the inherently anharmonic nature of the D-A interaction. Thus, we have used quantum chemical calculations to account for the D-A interaction and developed an improved model for the analysis of experimental tunneling kinetics. Strong internal electric fields are also considered and found to contribute significantly to the compressive forces when the D-A distance distribution is positioned below the van der Waals contact distance. This model is applied to recent experiments on the wild type (WT) and a double mutant (DM) of soybean lipoxygenase-1 (SLO). The compressive force necessary to prepare the tunneling-active distribution in WT SLO is found to fall in the ∼ nN range, which greatly exceeds the measured values of molecular motor and protein unfolding forces. This indicates that ∼60-100 MV/cm electric fields, aligned along the D-A bond axis, must be generated by an enzyme conformational interconversion that facilitates the PCET tunneling reaction. Based on the absolute value of the measured tunneling rate, and using previously calculated values of the electronic matrix element, the population of this tunneling-active conformation is found to lie in the range 10 -5 -10 -7 , indicating this is a rare structural fluctuation that falls well below the detection threshold of recent ENDOR experiments. Additional analysis of the DM tunneling kinetics leads to a proposal that a disordered (high entropy) conformation could be
Dessi, Roberta; Rustichini, Aldo
2015-01-01
A large literature in psychology, and more recently in economics, has argued that monetary rewards can reduce intrinsic motivation. We investigate whether the negative impact persists when intrinsic motivation is strong, and test this hypothesis experimentally focusing on the motivation to undertake interesting and challenging tasks, informative about individual ability. We find that this type of task can generate strong intrinsic motivation, that is impervious to the effect of monetary incen...
Bitcoin Meets Strong Consistency
Decker, Christian; Seidel, Jochen; Wattenhofer, Roger
2014-01-01
The Bitcoin system only provides eventual consistency. For everyday life, the time to confirm a Bitcoin transaction is prohibitively slow. In this paper we propose a new system, built on the Bitcoin blockchain, which enables strong consistency. Our system, PeerCensus, acts as a certification authority, manages peer identities in a peer-to-peer network, and ultimately enhances Bitcoin and similar systems with strong consistency. Our extensive analysis shows that PeerCensus is in a secure state...
Strong gravity and supersymmetry
International Nuclear Information System (INIS)
Chamseddine, Ali H.; Salam, A.; Strathdee, J.
1977-11-01
A supersymmetric theory is constructed for a strong f plus a weak g graviton, together with their accompanying massive gravitinos, by gaugin the gradel 0Sp(2,2,1)x 0Sp(2,2,1) structure. The mixing term between f and g fields, which makes the strong graviton massive, can be introduced through a spontaneous symmetry-breaking mechanism implemented in this note by constructing a non-linear realization of the symmetry group
Bidimensional distortion in ferroelectric liquid crystals with strong ...
Indian Academy of Sciences (India)
characterized by bistability and optical memory in the surface-stabilized bookshelf [2,3] ... tic layers, which lies in a plane parallel to the cell walls (see figure 1). Up to now ... Theory. We consider a liquid crystalline material exhibiting ferroelectric phase organized in book- ... By applying an external electric field Eext along.
International Nuclear Information System (INIS)
Joshi, A.; Lawande, S.V.
1990-01-01
A systematic study of squeezing obtained from k-photon anharmonic oscillator (with interaction hamiltonian of the form (a † ) k , k ≥ 2) interacting with light whose statistics can be varied from sub-Poissonian to poissonian via binomial state of field and super-Poissonian to poissonian via negative binomial state of field is presented. The authors predict that for all values of k there is a tendency increase in squeezing with increased sub-Poissonian character of the field while the reverse is true with super-Poissonian field. They also present non-classical behavior of the first order coherence function explicitly for k = 2 case (i.e., for two-photon anharmonic oscillator model used for a Kerr-like medium) with variation in the statistics of the input light
Phonon Anharmonicity of Germanium in the Temperature Range 80-880 K
Energy Technology Data Exchange (ETDEWEB)
Nelin, G; Nilsson, G
1974-06-15
Phonon frequency shifts and line widths in germanium have been studied in the temperature range 80 - 880 K by means of thermal neutron spectrometry. The results cannot be described in terms of the quasiharmonic approximation in which phonon frequencies are solely volume dependent. Theoretical calculations are found to be more satisfactory for the Raman frequency than for most other modes. A good account of the observed shifts is given by a proposal due to Barron according to which the relative frequency renormalization of a crystal is proportional to the total harmonic vibrational energy. An analysis of the gradients of measured dispersion relations in the principal symmetry directions at 80 K is presented. It is shown that accidental degeneracies may influence the dispersion
Effect of anharmonicity and Debye-Waller factor on the superconductivity of PdHsub(x) and PdDsub(x)
International Nuclear Information System (INIS)
Griessen, R.; Groot, D.G. de
1983-01-01
On the basis of existing superconducting tunnelling, neutron scattering, electrical resistivity and Raman scattering data and new thermal expansion, elastic moduli and point-contact spectroscopy data it is concluded that the anharmonicity of the proton (deuteron)-palladium potential is such that Msub(H)#betta#sub(H) 2 /(Msub(D)#betta#sub(D) 2 ) = 1.12 +- 0.05 Msub(H(D)) is the mass and #betta#sub(H(D)) the frequency of the vibration of hydrogen (deuterium). This anharmonicity is approximately 2 times too weak to reproduce the observed inverse isotope effect in the superconducting transition temperature of concentrated PdHsub(x) and PdDsub(x) alloys. Within a pseudopotential formalism it is shown that the Debye-Waller factor arising from the large zero-point amplitude of the interstitial hydrogen (deuterium) leads to a contribution to the inverse isotope effect in Tsub(c) which is as large as that of anharmonicity alone. (Auth.)
International Nuclear Information System (INIS)
Ginsburg, C.A.
1977-01-01
A new method for approximating the eigenfunctions and eigenvalues of anharmonic oscillators. An attempt was made to develop an analytic method which provides simple formulae for all values of the parameters as the W.K.B. approximation and perturbation theory do for certain limiting case, and which has the convergence properties associated with the computer methods. The procedure is based upon combining knowledge of the asymptotic behavior of the wave function for large and small values of the coordinate(s) to obtain approximations valid for all values of coordinate(s) and all strengths of the anharmonicity. A systematic procedure for improving these approximations is developed. Finally the groundstate of a lattice model of the phi 4 field theory which consists of an infinite number of coupled anharmonic oscillators. A first order calculation yields a covariant expression for the groundstate eigenvalue with the physical mass, m, given by a characteristic polynomial which involves the bare mass, μ, the lattice spacing, l, and the coupling constant, lambda. For l > 0, μ can be adjusted (a mass renormalization) 0 < m < infinity. As l → 0 lambda (l) (a charge renormalization) is adjusted so that lambda/sup 1/3//l → eta, a constant, as l → 0. Then eta can be chosen so that m can take any experimental value
Kosevich, Yu. A.; Potyomina, L. G.; Darinskii, A. N.; Strelnikov, I. A.
2018-03-01
crystal plane almost completely filled with heavy-isotope defects. We show that the phonon-interference-induced transparency can be produced by the defect nanolayer with the non-nearest-neighbor interactions, filled with two types of isotopes with relatively small difference in masses or binding force constants. In this case, relatively broad transmission antiresonance is accompanied by the narrow transmission peak close to the antiresonance frequency. We describe the softening of the flexural surface acoustic wave, localized at the embedded defect nanolayer, caused by negative surface stress in the layer. The surface wave softening results in spatially periodic static bending deformation of the embedded nanolayer with the definite wave number. The latter effect is estimated for graphene monolayer embedded in a strained matrix of polyethylene. We analyze the effect of nonlinearity in the dynamics of defect atoms on the one- and two-path phonon interference and show that the interference transmission resonances and antiresonances are shifted in frequencies but not completely suppressed by rather strong anharmonicity of interatomic bonds. The reduction of the Kapitza thermal interface conductance caused by the destructive phonon interference in a defect monolayer is described. We show that the additional relatively weak non-nearest-neighbor interactions through the defect crystal plane filled with heavy isotopes substantially reduces the interface thermal conductance, and this effect is stronger in the three-dimensional system than in the quasi-one-dimensional systems studied previously.
Mode instability in one-dimensional anharmonic lattices: Variational equation approach
Yoshimura, K.
1999-03-01
The stability of normal mode oscillations has been studied in detail under the single-mode excitation condition for the Fermi-Pasta-Ulam-β lattice. Numerical experiments indicate that the mode stability depends strongly on k/N, where k is the wave number of the initially excited mode and N is the number of degrees of freedom in the system. It has been found that this feature does not change when N increases. We propose an average variational equation - approximate version of the variational equation - as a theoretical tool to facilitate a linear stability analysis. It is shown that this strong k/N dependence of the mode stability can be explained from the view point of the linear stability of the relevant orbits. We introduce a low-dimensional approximation of the average variational equation, which approximately describes the time evolution of variations in four normal mode amplitudes. The linear stability analysis based on this four-mode approximation demonstrates that the parametric instability mechanism plays a crucial role in the strong k/N dependence of the mode stability.
Strongly interacting Fermi gases
Directory of Open Access Journals (Sweden)
Bakr W.
2013-08-01
Full Text Available Strongly interacting gases of ultracold fermions have become an amazingly rich test-bed for many-body theories of fermionic matter. Here we present our recent experiments on these systems. Firstly, we discuss high-precision measurements on the thermodynamics of a strongly interacting Fermi gas across the superfluid transition. The onset of superfluidity is directly observed in the compressibility, the chemical potential, the entropy, and the heat capacity. Our measurements provide benchmarks for current many-body theories on strongly interacting fermions. Secondly, we have studied the evolution of fermion pairing from three to two dimensions in these gases, relating to the physics of layered superconductors. In the presence of p-wave interactions, Fermi gases are predicted to display toplogical superfluidity carrying Majorana edge states. Two possible avenues in this direction are discussed, our creation and direct observation of spin-orbit coupling in Fermi gases and the creation of fermionic molecules of 23Na 40K that will feature strong dipolar interactions in their absolute ground state.
International Nuclear Information System (INIS)
Marier, D.
1992-01-01
This article presents the results of a financial rankings survey which show a strong economic activity in the independent energy industry. The topics of the article include advisor turnover, overseas banks, and the increase in public offerings. The article identifies the top project finance investors for new projects and restructurings and rankings for lenders
Late, Dattatray J; Shirodkar, Sharmila N; Waghmare, Umesh V; Dravid, Vinayak P; Rao, C N R
2014-06-06
We report the temperature-dependent Raman spectra of single- and few-layer MoSe2 and WSe2 in the range 77-700 K. We observed linear variation in the peak positions and widths of the bands arising from contributions of anharmonicity and thermal expansion. After characterization using atomic force microscopy and high-resolution transmission electron microscopy, the temperature coefficients of the Raman modes were determined. Interestingly, the temperature coefficient of the A(2)(2u) mode is larger than that of the A(1g) mode, the latter being much smaller than the corresponding temperature coefficients of the same mode in single-layer MoS2 and of the G band of graphene. The temperature coefficients of the two modes in single-layer MoSe2 are larger than those of the same modes in single-layer WSe2. We have estimated thermal expansion coefficients and temperature dependence of the vibrational frequencies of MoS2 and MoSe2 within a quasi-harmonic approximation, with inputs from first-principles calculations based on density functional theory. We show that the contrasting temperature dependence of the Raman-active mode A(1g) in MoS2 and MoSe2 arises essentially from the difference in their strain-phonon coupling. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Liu, Wei; Chen, Shu-Ming; Zhang, Jian; Wu, Chun-Wang; Wu, Wei; Chen, Ping-Xing
2015-03-01
It is widely believed that Shor’s factoring algorithm provides a driving force to boost the quantum computing research. However, a serious obstacle to its binary implementation is the large number of quantum gates. Non-binary quantum computing is an efficient way to reduce the required number of elemental gates. Here, we propose optimization schemes for Shor’s algorithm implementation and take a ternary version for factorizing 21 as an example. The optimized factorization is achieved by a two-qutrit quantum circuit, which consists of only two single qutrit gates and one ternary controlled-NOT gate. This two-qutrit quantum circuit is then encoded into the nine lower vibrational states of an ion trapped in a weakly anharmonic potential. Optimal control theory (OCT) is employed to derive the manipulation electric field for transferring the encoded states. The ternary Shor’s algorithm can be implemented in one single step. Numerical simulation results show that the accuracy of the state transformations is about 0.9919. Project supported by the National Natural Science Foundation of China (Grant No. 61205108) and the High Performance Computing (HPC) Foundation of National University of Defense Technology, China.
Directory of Open Access Journals (Sweden)
A. Glensk
2014-02-01
Full Text Available We study the temperature dependence of the Gibbs energy of vacancy formation in Al and Cu from T=0 K up to the melting temperature, fully taking into account anharmonic contributions. Our results show that the formation entropy of vacancies is not constant as often assumed but increases almost linearly with temperature. The resulting highly nonlinear temperature dependence in the Gibbs formation energy naturally explains the differences between positron annihilation spectroscopy and differential dilatometry data and shows that nonlinear thermal corrections are crucial to extrapolate high-temperature experimental data to T=0 K. Employing these corrections—rather than the linear Arrhenius extrapolation that is commonly assumed in analyzing experimental data—revised formation enthalpies are obtained that differ up to 20% from the previously accepted ones. Using the revised experimental formation enthalpies, we show that a large part of the discrepancies between DFT-GGA and unrevised experimental vacancy formation energies disappears. The substantial shift between previously accepted and the newly revised T=0 K formation enthalpies also has severe consequences in benchmarking ab initio methods against experiments, e.g., in deriving corrections that go beyond commonly used LDA and GGA exchange-correlation functionals such as the AM05 functional.
Hybrid colloidal plasmonic-photonic crystals.
Romanov, Sergei G; Korovin, Alexander V; Regensburger, Alois; Peschel, Ulf
2011-06-17
We review the recently emerged class of hybrid metal-dielectric colloidal photonic crystals. The hybrid approach is understood as the combination of a dielectric photonic crystal with a continuous metal film. It allows to achieve a strong modification of the optical properties of photonic crystals by involving the light scattering at electronic excitations in the metal component into moulding of the light flow in series to the diffraction resonances occurring in the body of the photonic crystal. We consider different realizations of hybrid plasmonic-photonic crystals based on two- and three-dimensional colloidal photonic crystals in association with flat and corrugated metal films. In agreement with model calculations, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tuneable functionality of these crystals. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Strong Electroweak Symmetry Breaking
Grinstein, Benjamin
2011-01-01
Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...
Plasmons in strong superconductors
International Nuclear Information System (INIS)
Baldo, M.; Ducoin, C.
2011-01-01
We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.
International Nuclear Information System (INIS)
Lipson, S.G.
1987-01-01
Hexagonal close-packed helium crystals in equilibrium with superfluid have been found to be one of the few systems in which an anisotropic solid comes into true thermodynamic equilibrium with its melt. The discovery of roughening transitions at the liquid-solid interface have shown this system to be ideal for the study of the statistical mechanics of interface structures. We describe the effect of roughening on the shape and growth of macroscopic crystals from both the theoretical and experimental points of view. (author)
International Nuclear Information System (INIS)
Gorenstein, M. I.; Gazdzicki, M.
2011-01-01
Analysis of fluctuations of hadron production properties in collisions of relativistic particles profits from use of measurable intensive quantities which are independent of system size variations. The first family of such quantities was proposed in 1992; another is introduced in this paper. Furthermore we present a proof of independence of volume fluctuations for quantities from both families within the framework of the grand canonical ensemble. These quantities are referred to as strongly intensive ones. Influence of conservation laws and resonance decays is also discussed.
Strong-coupling approximations
International Nuclear Information System (INIS)
Abbott, R.B.
1984-03-01
Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive phi 4 field theory in 1 + 1 dimensions. 9 references, 6 figures
Strongly disordered superconductors
International Nuclear Information System (INIS)
Muttalib, K.A.
1982-01-01
We examine some universal effects of strong non-magnetic disorder on the electron-phonon and electron-electron interactions in a superconductor. In particular we explicitly take into account the effect of slow diffusion of electrons in a disordered medium by working in an exact impurity eigenstate representation. We find that the normal diffusion of electrons characterized by a constant diffusion coefficient does not lead to any significant correction to the electron-phonon or the effective electron-electron interactions in a superconductor. We then consider sufficiently strong disorder where Anderson localization of electrons becomes important and determine the effect of localization on the electron-electron interactions. We find that due to localization, the diffusion of electrons becomes anomalous in the sense that the diffusion coefficient becomes scale dependent. This results in an increase in the effective electron-electron interaction with increasing disorder. We propose that this provides a natural explanation for the unusual sensitivity of the transition temperature T/sub c/ of the high T/sub c/ superconductors (T/sub c/ > 10 0 K) to damage effects
Dvali, Gia
2009-01-01
We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the ...
International Nuclear Information System (INIS)
Ozolins, V.; Wolverton, C.; Zunger, A.
1998-01-01
Epitaxial strain energies of epitaxial films and bulk superlattices are studied via first-principles total-energy calculations using the local-density approximation. Anharmonic effects due to large lattice mismatch, beyond the reach of the harmonic elasticity theory, are found to be very important in Cu/Au (lattice mismatch 12%), Cu/Ag (12%), and Ni/Au (15%). We find that left-angle 001 right-angle is the elastically soft direction for biaxial expansion of Cu and Ni, but it is left-angle 201 right-angle for large biaxial compression of Cu, Ag, and Au. The stability of superlattices is discussed in terms of the coherency strain and interfacial energies. We find that in phase separating systems such as Cu-Ag the superlattice formation energies decrease with superlattice period, and the interfacial energy is positive. Superlattices are formed easiest on (001) and hardest on (111) substrates. For ordering systems, such as Cu-Au and Ag-Au, the formation energy of superlattices increases with period, and interfacial energies are negative. These superlattices are formed easiest on (001) or (110) and hardest on (111) substrates. For Ni-Au we find a hybrid behavior: superlattices along left-angle 111 right-angle and left-angle 001 right-angle behave like phase separating systems, while for left-angle 110 right-angle they behave like ordering systems. Finally, recent experimental results on epitaxial stabilization of disordered Ni-Au and Cu-Ag alloys, immiscible in the bulk form, are explained in terms of destabilization of the phase separated state due to lattice mismatch between the substrate and constituents. copyright 1998 The American Physical Society
Marronnier, Arthur; Roma, Guido; Boyer-Richard, Soline; Pedesseau, Laurent; Jancu, Jean-Marc; Bonnassieux, Yvan; Katan, Claudine; Stoumpos, Constantinos C; Kanatzidis, Mercouri G; Even, Jacky
2018-04-24
Hybrid organic-inorganic perovskites emerged as a new generation of absorber materials for high-efficiency low-cost solar cells in 2009. Very recently, fully inorganic perovskite quantum dots also led to promising efficiencies, making them a potentially stable and efficient alternative to their hybrid cousins. Currently, the record efficiency is obtained with CsPbI 3 , whose crystallographical characterization is still limited. Here, we show through high-resolution in situ synchrotron XRD measurements that CsPbI 3 can be undercooled below its transition temperature and temporarily maintained in its perovskite structure down to room temperature, stabilizing a metastable perovskite polytype (black γ-phase) crucial for photovoltaic applications. Our analysis of the structural phase transitions reveals a highly anisotropic evolution of the individual lattice parameters versus temperature. Structural, vibrational, and electronic properties of all the experimentally observed black phases are further inspected based on several theoretical approaches. Whereas the black γ-phase is shown to behave harmonically around equilibrium, for the tetragonal phase, density functional theory reveals the same anharmonic behavior, with a Brillouin zone-centered double-well instability, as for the cubic phase. Using total energy and vibrational entropy calculations, we highlight the competition between all the low-temperature phases of CsPbI 3 (γ, δ, β) and show that avoiding the order-disorder entropy term arising from double-well instabilities is key to preventing the formation of the yellow perovskitoid phase. A symmetry-based tight-binding model, validated by self-consistent GW calculations including spin-orbit coupling, affords further insight into their electronic properties, with evidence of Rashba effect for both cubic and tetragonal phases when using the symmetry-breaking structures obtained through frozen phonon calculations.
Energy Technology Data Exchange (ETDEWEB)
Santos, Ludovic; Vaeck, Nathalie [Laboratoire de Chimie Quantique et Photophysique, CP 160/09 Université Libre de Bruxelles, B-1050 Brussels (Belgium); Justum, Yves [Laboratoire de Chimie Physique, UMR 8000 and CNRS, Université Paris-Sud, F-91405 Orsay (France); Desouter-Lecomte, M. [Laboratoire de Chimie Physique, UMR 8000 and CNRS, Université Paris-Sud, F-91405 Orsay (France); Département de Chimie, Université de Liège, Bât B6c, Sart Tilman B-4000, Liège (Belgium)
2015-04-07
Following a recent proposal of L. Wang and D. Babikov [J. Chem. Phys. 137, 064301 (2012)], we theoretically illustrate the possibility of using the motional states of a Cd{sup +} ion trapped in a slightly anharmonic potential to simulate the single-particle time-dependent Schrödinger equation. The simulated wave packet is discretized on a spatial grid and the grid points are mapped on the ion motional states which define the qubit network. The localization probability at each grid point is obtained from the population in the corresponding motional state. The quantum gate is the elementary evolution operator corresponding to the time-dependent Schrödinger equation of the simulated system. The corresponding matrix can be estimated by any numerical algorithm. The radio-frequency field which is able to drive this unitary transformation among the qubit states of the ion is obtained by multi-target optimal control theory. The ion is assumed to be cooled in the ground motional state, and the preliminary step consists in initializing the qubits with the amplitudes of the initial simulated wave packet. The time evolution of the localization probability at the grids points is then obtained by successive applications of the gate and reading out the motional state population. The gate field is always identical for a given simulated potential, only the field preparing the initial wave packet has to be optimized for different simulations. We check the stability of the simulation against decoherence due to fluctuating electric fields in the trap electrodes by applying dissipative Lindblad dynamics.
Determination of the Young modulus relaxation of high orders from dynamic experiments on crystals
International Nuclear Information System (INIS)
Topchyan, I.I.; Dokhner, R.D.
1977-01-01
A theoretical investigation into the inelastic behaviour of a crystal under the effect of a periodic load was carried out. Both the dimentional and module effects in the interaction of anisotropic point effects with the applied-stress fields and also the anharmonism of the interatomic interaction forces were taken into account. In this case the crystal deformation can be presented as a superposition of higher-order harmonics with a frequency multiple of that of the field applied. It is shown that the phase shift in the first harmonic determines the usually measured internal friction and depends exclusively on the dimentional effect in the interaction of defects with elastic-stress fields. The phase shift in the higher-order harmonics is due both to dimentional and module effects and it is possible, by measuring shift, to determine the ratios between the elastic modules of a defect
Ideal gas behavior of a strongly coupled complex (dusty) plasma.
Oxtoby, Neil P; Griffith, Elias J; Durniak, Céline; Ralph, Jason F; Samsonov, Dmitry
2013-07-05
In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.
Antonella Del Rosso
2016-01-01
Twenty years of designing, building and testing a number of innovative technologies, with the strong belief that the endeavour would lead to a historic breakthrough. The Bulletin publishes an abstract of the Courier’s interview with Barry Barish, one of the founding fathers of LIGO. The plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. (Image: Caltech/MIT/LIGO Lab) On 11 February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations published a historic paper in which they showed a gravitational signal emitted by the merger of two black holes. These results come after 20 years of hard work by a large collaboration of scientists operating the two LIGO observatories in the US. Barry Barish, Linde Professor of Physics, Emeritus at the California Institute of Technology and former Director of the Global Design Effort for the Internat...
Strongly interacting Higgs bosons
International Nuclear Information System (INIS)
Appelquist, T.; Bernard, C.
1980-01-01
The sensitivity of present-energy weak interactions to a strongly interacting heavy-Higgs-boson sector is discussed. The gauged nonlinear sigma model, which is the limit of the linear model as the Higgs-boson mass goes to infinity, is used to organize and catalogue all possible heavy-Higgs-boson effects. As long as the SU(2)/sub L/ x SU(2)/sub R/ symmetry of the Higgs sector is preserved, these effects are found to be small, of the order of the square of the gauge coupling times logarithms (but not powers) of the Higgs-boson mass divided by the W mass. We work in the context of a simplified model with gauge group SU(2)/sub L/; the extension to SU(2)/sub L/ x U(1) is briefly discussed
Kumar Pal, Santanu
2017-01-01
This book covers in-depth discussion of design principles, synthesis and thermal behavior of all types of liquid crystal (LC) dimers. The text presents recent advances in the field of LC dimers consisting of different mesogenic units such as calamitic, discotic and bent-core molecules. It starts with a chapter on the introduction of liquid crystal dimers, including their odd-even behavior, basic classification of dimers and common mesophases in dimers. The text shows how the molecular architectures are being used to develop new materials to study a range of interesting phenomena such as the biaxial nematic phase containing rod-like and disc-like mesogenic units. Finally, the text presents perspectives related to technological relevance of these dimers such as dopants in LC display mixtures exhibiting faster relaxation time, strong flexoelectric coupling and others to effect control over the properties of these materials.
Energy Technology Data Exchange (ETDEWEB)
Volpe, M.C. [Caen Univ., 14 (France)
1997-12-31
Double Giant Resonances, vibrational states in which a Giant Resonance is excited on top of another Giant Resonance, have been in the last years the object of many theories and studies. Whereas the measured energies and widths of these states agree with a theoretical predictions, the measured excitation cross sections on the other hand are almost always larger than the calculated ones. The standard theoretical approaches are based both on a harmonic approximation for the collective motion on the nucleus and on its linear response to an external field. In this work the influence of anharmonicities and non-linearities in the external field on the excitation of Double Giant Resonances are studied. First, an oscillator model and an extension of the Lipkin-Meshkow-Glick model are used to study the effects of anharmonicities and non-linearities on the excitation probabilities. The results show that these terms can influence the excitation probability of the second excited state in a significant way. Secondly, these exactly soluble schematic models are used to study some of the approximations made in microscopic calculations based on boson expansion methods and also some aspects on the time-dependent mean field approach. Finally, a microscopic calculation of the Coulomb excitation cross sections of Double Giant Resonances is presented for several nuclei. It is found that, for {sup 208} Pb, the inclusion of anharmonicities and non-linearities and the consideration of many states that play a role in the excitation process give a satisfactory agreement between calculated and observed cross sections. (author). 113 refs.
Crystal structure of the high temperature phase of oxidised Pr2NiO4+δ
International Nuclear Information System (INIS)
Allancon, C.; Odier, P.; Bassat, J.M.; Loup, J.P.; Fernandez-Diaz, M.T.; Martinez, J.L.
1996-01-01
Powder neutron diffraction measurements have been carried out on oxidised Pr 2 NiO 4+δ at high temperature under O 2 atmosphere. A structural transition takes place at about 720 K from an orthorhombic symmetry to a tetragonal one. The high temperature structure has been refined in the P4 2 /ncm space group using a split-atom model for apical oxygens simulating their strong anharmonic motion. The interstitial oxygens occupy the sites (4e) and (8f) following a uniform distribution. The refined occupancy is in good agreement with the value measured by TGA, corresponding to an oxygen excess as high as δ=0.18. (orig.)
Photonic crystal fiber based antibody detection
DEFF Research Database (Denmark)
Duval, A; Lhoutellier, M; Jensen, J B
2004-01-01
An original approach for detecting labeled antibodies based on strong penetration photonic crystal fibers is introduced. The target antibody is immobilized inside the air-holes of a photonic crystal fiber and the detection is realized by the means of evanescent-wave fluorescence spectroscopy...
Dispersion properties of photonic crystal fibres
DEFF Research Database (Denmark)
Bjarklev, Anders Overgaard; Broeng, Jes; Dridi, Kim
1998-01-01
Approximate dispersion and bending properties of all-silica two-dimensional photonic crystal fibres are characterised by the combination of an effective-index model and classical analysis tools for optical fibres. We believe for the first time to have predicted the dispersion properties of photonic...... crystal fibres. The results strongly indicate that these fibres have potential applications as dispersion managing components...
Channeling crystals for positron production
International Nuclear Information System (INIS)
Decker, F.J.
1991-05-01
Particles traversing at small angles along a single crystal axis experience a collective scattering force of many crystal atoms. The enormous fields can trap the particles along an axis or plane, called channeling. High energy electrons are attracted by the positive nuclei and therefore produce strongly enhanced so called coherent bremsstrahlung and pair production. These effects could be used in a positron production target: A single tungsten crystal is oriented to the incident electron beam within 1 mrad. At 28 GeV/c the effective radiation length is with 0.9 mm about one quarter of the amorphous material. So the target length can be shorter, which yields a higher conversion coefficient and a lower emittance of the positron beam. This makes single crystals very interesting for positron production targets. 18 refs., 2 figs
Molecular mechanisms of crystal growth
International Nuclear Information System (INIS)
Pina, C. M.
2000-01-01
In this paper I present an example of the research that the Mineral Surface Group of the Munster University is conducting in the field of Crystal Growth. Atomic Force Microscopy (Am) in situ observations of different barite (BaSO4) faces growing from aqueous solutions, in combination with computer simulations of the surface attachment of growth units allows us to test crystal growth models. Our results demonstrate the strong structural control that a crystal can exert on its own growth, revealing also the limitation of the classical crystal growth theories (two dimensional nucleation and spiral growth models) in providing a complete explanation for the growth behaviour at a molecular scale. (Author) 6 refs
de Toledo, T. A.; da Costa, R. C.; Bento, R. R. F.; Pizani, P. S.
2018-03-01
The structural, thermal and vibrational properties of the molecular crystal 2-amine-1,3,4-thiadiazole (ATD) were investigated combining X-ray diffraction, infrared spectroscopy, Raman scattering (in solid and in solution) and thermal analysis as experimental techniques and first principle calculations based on density functional theory using PZ, BLYP in condensed-phase and B3LYP/cc-pVTZ in isolated molecule methods. The structural stability and phonon anharmonicity were also studied using Raman spectroscopy at different temperatures and hydrostatic pressures. A reasonable agreement was obtained between calculated and experimental results. The main difference between experimental and computed structural and vibrational spectra occurred in the intermolecular bond distance Nsbnd H⋯N and stretching modes of NH2. The vibrational spectra were interpreted and assigned based on group theory and functional group analysis assisted by theoretical results, which led to a more comprehensive knowledge about external and internal modes at different thermodynamic conditions. As temperature increases, it was observed the line-width increases and red-shifts, indicating a phonon anharmonicity without a temperature-induced phase transition in the range 10-413 K. However, ATD crystal undergoes a phase transition in the temperature range 413-475 K, as indicated by thermal analysis curve and Raman spectra. Furthermore, increasing pressure from ambient to 3.1 GPa, it was observed the splitting of the external Raman bands centered at 122 cm-1 (at 0.2 GPa), 112 cm-1 (1.1 GPa), 93 cm-1 (2.4 GPa) in two components as well as the appearance of new band near 50 cm-1 at 1.1 GPa, indicating a possible phase-transition. The blue-shift of the Raman bands was associated to anharmonicity of the interatomic potential caused by unit cell contraction.
Strong-interaction nonuniversality
International Nuclear Information System (INIS)
Volkas, R.R.; Foot, R.; He, X.; Joshi, G.C.
1989-01-01
The universal QCD color theory is extended to an SU(3) 1 direct product SU(3) 2 direct product SU(3) 3 gauge theory, where quarks of the ith generation transform as triplets under SU(3)/sub i/ and singlets under the other two factors. The usual color group is then identified with the diagonal subgroup, which remains exact after symmetry breaking. The gauge bosons associated with the 16 broken generators then form two massive octets under ordinary color. The interactions between quarks and these heavy gluonlike particles are explicitly nonuniversal and thus an exploration of their physical implications allows us to shed light on the fundamental issue of strong-interaction universality. Nonuniversality and weak flavor mixing are shown to generate heavy-gluon-induced flavor-changing neutral currents. The phenomenology of these processes is studied, as they provide the major experimental constraint on the extended theory. Three symmetry-breaking scenarios are presented. The first has color breaking occurring at the weak scale, while the second and third divorce the two scales. The third model has the interesting feature of radiatively induced off-diagonal Kobayashi-Maskawa matrix elements
Wickens, F
Our friend and colleague John Strong was cruelly taken from us by a brain tumour on Monday 31st July, a few days before his 65th birthday John started his career working with a group from Westfield College, under the leadership of Ted Bellamy. He obtained his PhD and spent the early part of his career on experiments at Rutherford Appleton Laboratory (RAL), but after the early 1970s his research was focussed on experiments in CERN. Over the years he made a number of notable contributions to experiments in CERN: The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras to record the sparks in the spark chambers; He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems; He was responsible for the second level trigger system for the ALEPH detector and spent five years leading a team that designed and built the system, which ran for twelve years with only minor interventions. Following ALEPH he tur...
Stirring Strongly Coupled Plasma
Fadafan, Kazem Bitaghsir; Rajagopal, Krishna; Wiedemann, Urs Achim
2009-01-01
We determine the energy it takes to move a test quark along a circle of radius L with angular frequency w through the strongly coupled plasma of N=4 supersymmetric Yang-Mills (SYM) theory. We find that for most values of L and w the energy deposited by stirring the plasma in this way is governed either by the drag force acting on a test quark moving through the plasma in a straight line with speed v=Lw or by the energy radiated by a quark in circular motion in the absence of any plasma, whichever is larger. There is a continuous crossover from the drag-dominated regime to the radiation-dominated regime. In the crossover regime we find evidence for significant destructive interference between energy loss due to drag and that due to radiation as if in vacuum. The rotating quark thus serves as a model system in which the relative strength of, and interplay between, two different mechanisms of parton energy loss is accessible via a controlled classical gravity calculation. We close by speculating on the implicati...
Cavity QED experiments with ion Coulomb crystals
DEFF Research Database (Denmark)
Herskind, Peter Fønss; Dantan, Aurélien; Marler, Joan
2009-01-01
Cavity QED experimental results demonstrating collective strong coupling between ensembles of atomic ions cooled into Coulomb crystals and optical cavity fields have been achieved. Collective Zeeman coherence times of milliseconds have furthermore been obtained.......Cavity QED experimental results demonstrating collective strong coupling between ensembles of atomic ions cooled into Coulomb crystals and optical cavity fields have been achieved. Collective Zeeman coherence times of milliseconds have furthermore been obtained....
Crystallized Schroedinger cat states
International Nuclear Information System (INIS)
Castanos, O.; Lopez-Pena, R.; Man'ko, V.I.
1995-01-01
Crystallized Schroedinger cat states (male and female) are introduced on the base of extension of group construction for the even and odd coherent states of the electromagnetic field oscillator. The Wigner and Q functions are calculated and some are plotted for C 2 , C 3 , C 4 , C 5 , C 3v Schroedinger cat states. Quadrature means and dispersions for these states are calculated and squeezing and correlation phenomena are studied. Photon distribution functions for these states are given explicitly and are plotted for several examples. A strong oscillatory behavior of the photon distribution function for some field amplitudes is found in the new type of states
Crystal Deflectors for High Energy Ion Beams
Scandale, W
2013-01-01
The motion of charged particles entering a crystal at small angles with respect to a crystalline plane is strongly influenced by the average electric field of the ordered nuclei. For sufficiently small angles the particles can be captured in channeling states, thus performing quasi-harmonic oscillations in the potential well between the crystal planes. Channeled particles in a bent crystal are deflected along the bent planes of the crystal. This provides a powerful method to steer and control particle trajectories that has been investigated and occasionally exploited for some decades already.
Kesharwani, Manoj K; Brauer, Brina; Martin, Jan M L
2015-03-05
We have obtained uniform frequency scaling factors λ(harm) (for harmonic frequencies), λ(fund) (for fundamentals), and λ(ZPVE) (for zero-point vibrational energies (ZPVEs)) for the Weigend-Ahlrichs and other selected basis sets for MP2, SCS-MP2, and a variety of DFT functionals including double hybrids. For selected levels of theory, we have also obtained scaling factors for true anharmonic fundamentals and ZPVEs obtained from quartic force fields. For harmonic frequencies, the double hybrids B2PLYP, B2GP-PLYP, and DSD-PBEP86 clearly yield the best performance at RMSD = 10-12 cm(-1) for def2-TZVP and larger basis sets, compared to 5 cm(-1) at the CCSD(T) basis set limit. For ZPVEs, again, the double hybrids are the best performers, reaching root-mean-square deviations (RMSDs) as low as 0.05 kcal/mol, but even mainstream functionals like B3LYP can get down to 0.10 kcal/mol. Explicitly anharmonic ZPVEs only are marginally more accurate. For fundamentals, however, simple uniform scaling is clearly inadequate.
Energy Technology Data Exchange (ETDEWEB)
Al Sdran, N. [King Khalid University, Faculty of Science, Physics Department P.O. Box 9004 Abha (Saudi Arabia); Najran University, Faculty of Sciences and Arts, Najran (Saudi Arabia); Maiz, F., E-mail: fethimaiz@gmail.com [King Khalid University, Faculty of Science, Physics Department P.O. Box 9004 Abha (Saudi Arabia); Thermal Process Laboratory Research and Technologies Centre of Energy, BP 95, 2050 Hammam-lif (Tunisia)
2016-06-15
The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x) = Ax{sup 2α} + Bx{sup 2}, (A>0, B<0), with (α = 2) for quadratic, (α =3) for sextic and (α =4) for octic anharmonic oscillators. The Airy function approach is based on the replacement of the real potential V(x) by a piecewise-linear potential v(x), while, the Numerov method is based on the discretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It’s found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.
Local Polar Fluctuations in Lead Halide Perovskite Crystals
Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.
2017-03-01
Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3 NH3 PbBr3 ) and all-inorganic (CsPbBr3 ) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3 .
Local Polar Fluctuations in Lead Halide Perovskite Crystals
Energy Technology Data Exchange (ETDEWEB)
Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.
2017-03-01
Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) leadhalide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-tohead Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.
Zeng, Lunwu; Xu, Jin; Wang, Chengen; Zhang, Jianhua; Zhao, Yuting; Zeng, Jing; Song, Runxia
2017-12-07
When space (time) translation symmetry is spontaneously broken, the space crystal (time crystal) forms; when permittivity and permeability periodically vary with space (time), the photonic crystal (photonic time crystal) forms. We proposed the concept of photonic time crystal and rewritten the Maxwell's equations. Utilizing Finite Difference Time Domain (FDTD) method, we simulated electromagnetic wave propagation in photonic time crystal and photonic space-time crystal, the simulation results show that more intensive scatter fields can obtained in photonic time crystal and photonic space-time crystal.
Effect of strong coupling on interfacial electron transfer dynamics in ...
Indian Academy of Sciences (India)
Unknown
regarded as the best sensitizing dyes for solar energy conversion for their strong visible absorption bands, long-lived ... solar cells based on dye-sensitized nanocrystalline. TiO2. High affinity for the TiO2 surface, which is ... pump pulses at 400 nm, one part of 800 nm with. 200 µJ/pulse, is frequency doubled in BBO crystals.
National Research Council Canada - National Science Library
Kristiansen, Rene E
2005-01-01
This report results from a contract tasking Crystal Fibre A/S as follows: Crystal Fibre will conduct research and development of large mode area, dual clad multi-core Yb-doped photonic crystal fiber...
Colloquium: Strong-field phenomena in periodic systems
Kruchinin, Stanislav Yu.; Krausz, Ferenc; Yakovlev, Vladislav S.
2018-04-01
The advent of visible-infrared laser pulses carrying a substantial fraction of their energy in a single field oscillation cycle has opened a new era in the experimental investigation of ultrafast processes in semiconductors and dielectrics (bulk as well as nanostructured), motivated by the quest for the ultimate frontiers of electron-based signal metrology and processing. Exploring ways to approach those frontiers requires insight into the physics underlying the interaction of strong high-frequency (optical) fields with electrons moving in periodic potentials. This Colloquium aims at providing this insight. Introduction to the foundations of strong-field phenomena defines and compares regimes of field-matter interaction in periodic systems, including (perfect) crystals as well as optical and semiconductor superlattices, followed by a review of recent experimental advances in the study of strong-field dynamics in crystals and nanostructures. Avenues toward measuring and controlling electronic processes up to petahertz frequencies are discussed.
Najbauer, Eszter E.; Bazsó, Gábor; Apóstolo, Rui; Fausto, Rui; Biczysko, Malgorzata; Barone, Vincenzo; Tarczay, György
2018-01-01
The conformers of α-serine were investigated by matrix-isolation IR spectroscopy combined with NIR laser irradiation. This method, aided by 2D correlation analysis, enabled unambiguously grouping the spectral lines to individual conformers. On the basis of comparison of at least nine experimentally observed vibrational transitions of each conformer with empirically scaled (SQM) and anharmonic (GVPT2) computed IR spectra, 6 conformers were identified. In addition, the presence of at least one more conformer in Ar matrix was proved, and a short-lived conformer with a half-live of (3.7±0.5)·103 s in N2 matrix was generated by NIR irradiation. The analysis of the NIR laser induced conversions revealed that the excitation of the stretching overtone of both the side-chain and the carboxylic OH groups can effectively promote conformational changes, but remarkably different paths were observed for the two kinds of excitations. PMID:26201050
Energy Technology Data Exchange (ETDEWEB)
Alvarez-Bajo, O. [Dpto. Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva (Spain); Carvajal, M., E-mail: miguel.carvajal@dfa.uhu.es [Dpto. Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva (Spain); Perez-Bernal, F. [Dpto. Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva (Spain)
2012-01-02
Graphical abstract: Schematic diagram of a bent triatomic molecule, depicting the atom numbering, and molecular axis system. An algebraic approach to perform global rovibrational analysis is presented. Highlights: Black-Right-Pointing-Pointer Novel approach for a global rovibrational analysis of polyatomic molecules spectra. Black-Right-Pointing-Pointer One-dimensional vibron model limit combined with rotational degrees of freedom. Black-Right-Pointing-Pointer Phase space Hamiltonian written in terms of anharmonic ladder operators. Black-Right-Pointing-Pointer Algebraic calculations performed with a symmetry-adapted rovibrational basis. Black-Right-Pointing-Pointer Description of the rovibrational spectrum of H{sub 2}Se in the ground electronic state. - Abstract: An algebraic approach to perform global rovibrational analysis of molecular spectra is presented. The approach combines the one-dimensional limit of the vibron model with rotational degrees of freedom. The model is based on the expression of the phase space Hamiltonian in terms of anharmonic ladder operators and the use of a symmetry-adapted basis set given by the linear combination of products of local vibrational and rotational wavefunctions. As an example we model the rovibrational spectra of a bent triatomic molecule, providing a global analysis for vibrational bands up to polyad 12 and J{sub max} = 5 of Hydrogen Selenide (H{sub 2}Se). Satisfactory fits of vibrational and rovibrational energies are obtained. A prediction of 2579 rovibrational energies up to J Less-Than-Or-Slanted-Equal-To 5 and polyad 12 for the 140 lowest vibrational bands is also obtained. A possible extension of the model to reach spectroscopic quality results in larger molecular systems is also given.
Grabska, Justyna; Beć, Krzysztof B; Ishigaki, Mika; Wójcik, Marek J; Ozaki, Yukihiro
2017-10-05
Quantum chemical reproduction of entire NIR spectra is a new trend, enabled by contemporary advances in the anharmonic approaches. At the same time, recent increase of the importance of NIR spectroscopy of biological samples raises high demand for gaining deeper understanding of NIR spectra of biomolecules, i.e. fatty acids. In this work we investigate saturated and unsaturated medium-chain fatty acids, hexanoic acid and sorbic acid, in the near-infrared region. By employing fully anharmonic density functional theory (DFT) calculations we reproduce the experimental NIR spectra of these systems, including the highly specific spectral features corresponding to the dimerization of fatty acids. Broad range of concentration levels from 5·10 -4 M in CCl 4 to pure samples are investigated. The major role of cyclic dimers can be evidenced for the vast majority of these samples. A highly specific NIR feature of fatty acids, the elevation of spectral baseline around 6500-4000cm -1 , is being explained by the contributions of combination bands resulting from the vibrations of hydrogen-bonded OH groups in the cyclic dimers. Based on the high agreement between the calculated and experimental NIR spectra, a detailed NIR band assignments are proposed for hexanoic acid and sorbic acid. Subsequently, the correlations between the structure and NIR spectra are elucidated, emphasizing the regions in which clear and universal traces of specific bands corresponding to saturated and unsaturated alkyl chains can be established, thus demonstrating the wavenumber regions highly valuable for structural identifications. Copyright © 2017 Elsevier B.V. All rights reserved.
Phase diagram of power law and Lennard-Jones systems: Crystal phases
International Nuclear Information System (INIS)
Travesset, Alex
2014-01-01
An extensive characterization of the low temperature phase diagram of particles interacting with power law or Lennard-Jones potentials is provided from Lattice Dynamical Theory. For power law systems, only two lattice structures are stable for certain values of the exponent (or softness) (A15, body centered cube (bcc)) and two more (face centered cubic (fcc), hexagonal close packed (hcp)) are always stable. Among them, only the fcc and bcc are equilibrium states. For Lennard-Jones systems, the equilibrium states are either hcp or fcc, with a coexistence curve in pressure and temperature that shows reentrant behavior. The hcp solid never coexists with the liquid. In all cases analyzed, for both power law and Lennard-Jones potentials, the fcc crystal has higher entropy than the hcp. The role of anharmonic terms is thoroughly analyzed and a general thermodynamic integration to account for them is proposed
Isotope effects in lithium hydride and lithium deuteride crystals by molecular dynamics simulations.
Dammak, Hichem; Antoshchenkova, Ekaterina; Hayoun, Marc; Finocchi, Fabio
2012-10-31
Molecular dynamics (MD) simulations have been carried out to study isotope effects in lithium hydride and lithium deuteride crystals. Quantum effects on nuclear motion have been included through a quantum thermal bath (QTB). The interatomic forces were described either within the density functional theory (DFT) in the generalized gradient approximation (GGA) or by the phenomenological approach using the shell model. For both models, the isotopic shift in the lattice parameter can be successfully predicted by QTB-MD simulations. The slope of the experimental isotopic shift in pressure is satisfactorily reproduced by QTB-MD within DFT-GGA, in contrast to both density functional perturbation theory and QTB-MD with the shell model. We have analyzed the reasons for these discrepancies through the vibrational densities of states and the isotopic shifts in bulk modulus. The results illustrate the importance of anharmonic contributions to vibrations and to the isotopic pressure shift between LiH and LiD.
Thermodynamic properties of bcc crystals at high temperatures: The transition metals
International Nuclear Information System (INIS)
MacDonald, R.A.; Shukla, R.C.
1985-01-01
The second-neighbor central-force model of a bcc crystal, previously used in lowest-order anharmonic perturbation theory to calculate the thermodynamic properties of the alkali metals, is here applied to the transition metals V, Nb, Ta, Mo, and W. The limitations of the model are apparent in the thermal-expansion results, which fall away from the experimental trend above about 1800 K. The specific heat similarly fails to exhibit the sharp rise that is observed at higher temperatures. A static treatment of vacancies cannot account for the difference between theory and experiment. The electrons have been taken into account by using a model that specifically includes d-band effects in the electron ground-state energy. The results thus obtained for the bulk moduli are quite satisfactory. In the light of these results, we discuss the prerequisites for a better treatment of metals when the electrons play an important role in determining the thermodynamic properties
Quantum electrodynamics of strong fields
International Nuclear Information System (INIS)
Greiner, W.
1983-01-01
Quantum Electrodynamics of Strong Fields provides a broad survey of the theoretical and experimental work accomplished, presenting papers by a group of international researchers who have made significant contributions to this developing area. Exploring the quantum theory of strong fields, the volume focuses on the phase transition to a charged vacuum in strong electric fields. The contributors also discuss such related topics as QED at short distances, precision tests of QED, nonperturbative QCD and confinement, pion condensation, and strong gravitational fields In addition, the volume features a historical paper on the roots of quantum field theory in the history of quantum physics by noted researcher Friedrich Hund
Instabilities in strongly coupled plasmas
Kalman, G J
2003-01-01
The conventional Vlasov treatment of beam-plasma instabilities is inappropriate when the plasma is strongly coupled. In the strongly coupled liquid state, the strong correlations between the dust grains fundamentally affect the conditions for instability. In the crystalline state, the inherent anisotropy couples the longitudinal and transverse polarizations, and results in unstable excitations in both polarizations. We summarize analyses of resonant and non-resonant, as well as resistive instabilities. We consider both ion-dust streaming and dust beam-plasma instabilities. Strong coupling, in general, leads to an enhancement of the growth rates. In the crystalline phase, a resonant transverse instability can be excited.
Energy Technology Data Exchange (ETDEWEB)
Vigneron, Jean Pol, E-mail: jean-pol.vigneron@fundp.ac.be [Research Center in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), rue de Bruxelles, 61, B-5000 Namur (Belgium); Simonis, Priscilla [Research Center in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), rue de Bruxelles, 61, B-5000 Namur (Belgium)
2012-10-15
Photonic structures appeared in nature several hundred millions years ago. In the living world, color is used for communication and this important function strongly impacts the individual chances of survival as well as the chances to reproduce. This has a statistical influence on species populations. Therefore, because they are involved in evolution, natural color-generating structures are - from some point of view - highly optimized. In this short review, a survey is presented of the development of natural photonic crystal-type structures occurring in insects, spiders, birds, fishes and other marine animals, in plants and more, from the standpoint of light-waves propagation. One-, two-, and three-dimensional structures will be reviewed with selected examples.
International Nuclear Information System (INIS)
Vigneron, Jean Pol; Simonis, Priscilla
2012-01-01
Photonic structures appeared in nature several hundred millions years ago. In the living world, color is used for communication and this important function strongly impacts the individual chances of survival as well as the chances to reproduce. This has a statistical influence on species populations. Therefore, because they are involved in evolution, natural color-generating structures are - from some point of view - highly optimized. In this short review, a survey is presented of the development of natural photonic crystal-type structures occurring in insects, spiders, birds, fishes and other marine animals, in plants and more, from the standpoint of light-waves propagation. One-, two-, and three-dimensional structures will be reviewed with selected examples.
Crystal structure of Earth's inner core: A first-principles study
Moustafa, S. G.; Schultz, A. J.; Zurek, E.; Kofke, D. A.
2017-12-01
Since the detection of the Earth's solid inner core (IC) by Lehmann in 1936, its composition and crystal structure (which are essential to understand Earth's evolution) have been controversial. While seismological measurements (e.g. PREM) can give a robust estimation of the density, pressure, and elasticity of the IC, they cannot be directly used to determine its composition and/or crystal structure. Experimentally, reaching the extreme IC conditions ( 330 GPa and 6000 K) and getting reliable measurements is very challenging. First-principles calculations provide a viable alternative that can work as a powerful investigative tool. Although several attempts have been made to assess phase stability at IC conditions computationally, they often use a low level of theory for electronic structure (e.g., classical force-field), adopt approximate methods (e.g., quasiharmonic approximation, fixed hcp-c/a), or do not consider finite-size effects. The study of phase stability using accurate first-principles methods is hampered in part by the difficulty of computing the free energy (FE), the central thermodynamic quantity that determines stability, while including anharmonic and finite-size effects. Additional difficulty related to the IC in particular is introduced by the dynamical instability of one of the IC candidate structures (bcc) at low temperature. Recently [1-3], we introduced a novel method (denoted as "harmonically mapped averaging", or HMA) to efficiently measure anharmonic properties (e.g. FE, pressure, elastic modulus) by molecular simulation, yielding orders of magnitude CPU speedup compared to conventional methods. We have applied this method to the hcp candidate phase of iron at the IC conditions, obtaining first-principles anharmonic FE values with unprecedented accuracy and precision [4]. We have now completed and report HMA calculations to assess the phase stability of all IC candidate phases (fcc/hcp/bcc). This knowledge is the prerequisite for
Crystallization of Ulex europaeus lectin I.
Vandonselaar, M; Delbaere, L T
1994-10-21
The lectin I from Ulex europaeus (UEAI) has a strong affinity for the H-type 2 human blood group determinant. Single crystals of UEAI have been grown in the monoclinic crystal system. Initial crystals were obtained after 11 months from a solution of 10 mg/ml protein, 40% 2,4-methylpentanediol and 0.1 N acetate buffer at pH 5.2. The technique of washing and reseeding was used to generate large suitable crystals. The space group is C2 with a = 78.84 A, b = 69.85 A, c = 120.62 A, beta = 108.74 degrees and Z = 4; there is one molecular dimer per asymmetric unit and the solvent content is estimated to be 58%. The crystals diffract to at least 2.8 A d spacings and are stable in the X-ray beam for more than three days.
Deleer, B. G. M.
1981-11-01
Based on population balance, CSD behavior as a function of geometrical and operating variables was studied, using a crystallizer. A potash alum-water system, involving a separation technique which uses surface active agents and an apolar, organic liquid to separate potash alum crystals from mother liquid under the influence of gravity was used to check experimental findings against literature data. Results show action of annular settling spaces is strongly influenced by fluid velocities perpendicular to those directed upwards. The well-mixed volume decreases with increasing crystallizer size until a minimum effective volume is reached. As supersaturation is constant throughout the crystallizer volume under stationary operating conditions, the annular settling space behaves like a growth chamber for crystals in its volume. Swirl in the lower part of the annular volume introduces significant back mixing. Crystals within this space either grow and return to the well-mixed part, or withdraw from the annular volume permanently.
Short proofs of strong normalization
Wojdyga, Aleksander
2008-01-01
This paper presents simple, syntactic strong normalization proofs for the simply-typed lambda-calculus and the polymorphic lambda-calculus (system F) with the full set of logical connectives, and all the permutative reductions. The normalization proofs use translations of terms and types to systems, for which strong normalization property is known.
International Nuclear Information System (INIS)
DeSantis, G.N.
1995-01-01
The calculation decides the integrity of the safety latch that will hold the strong-back to the pump during lifting. The safety latch will be welded to the strong-back and will latch to a 1.5-in. dia cantilever rod welded to the pump baseplate. The static and dynamic analysis shows that the safety latch will hold the strong-back to the pump if the friction clamps fail and the pump become free from the strong-back. Thus, the safety latch will meet the requirements of the Lifting and Rigging Manual for under the hook lifting for static loading; it can withstand shock loads from the strong-back falling 0.25 inch
Energy Technology Data Exchange (ETDEWEB)
Zuo, Biao, E-mail: chemizuo@zstu.edu.cn, E-mail: wxinping@yahoo.com; Xu, Jianquan; Sun, Shuzheng; Liu, Yue; Yang, Juping; Zhang, Li; Wang, Xinping, E-mail: chemizuo@zstu.edu.cn, E-mail: wxinping@yahoo.com [Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of the Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018 (China)
2016-06-21
Crystallization is an important property of polymeric materials. In conventional viewpoint, the transformation of disordered chains into crystals is usually a spatially homogeneous process (i.e., it occurs simultaneously throughout the sample), that is, the crystallization rate at each local position within the sample is almost the same. Here, we show that crystallization of ultra-thin poly(ethylene terephthalate) (PET) films can occur in the heterogeneous way, exhibiting a stepwise crystallization process. We found that the layered distribution of glass transition dynamics of thin film modifies the corresponding crystallization behavior, giving rise to the layered distribution of the crystallization kinetics of PET films, with an 11-nm-thick surface layer having faster crystallization rate and the underlying layer showing bulk-like behavior. The layered distribution in crystallization kinetics results in a particular stepwise crystallization behavior during heating the sample, with the two cold-crystallization temperatures separated by up to 20 K. Meanwhile, interfacial interaction is crucial for the occurrence of the heterogeneous crystallization, as the thin film crystallizes simultaneously if the interfacial interaction is relatively strong. We anticipate that this mechanism of stepwise crystallization of thin polymeric films will allow new insight into the chain organization in confined environments and permit independent manipulation of localized properties of nanomaterials.
Pressure cryocooling protein crystals
Kim, Chae Un [Ithaca, NY; Gruner, Sol M [Ithaca, NY
2011-10-04
Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.
Channeling and related crystal effects
International Nuclear Information System (INIS)
Uggerhoj, Erik
1995-01-01
Channeling, the interaction of particles with oriented crystals, has been applied in a wide variety of scientific and technological areas. A workshop at Aarhus, Denmark, this summer highlighted progress and future directions. Radiation emission has been explored and linked to coherent bremsstrahlung and other oriented crystal radiations. Dramatic effects have been found for ultra-relativistic electrons with Lorentz factors of 105 6. Single crystals are unique for investigations of quantum electrodynamics in strong external fields because probabilities for processes in axial/ planar fields are determined by the magnitude of these fields in the particle rest frame. Erik Uggerhoj of Aarhus reported on an extensive series of experiments concerning radiation emission, pair production, and shower formation carried out at CERN by the NA43 collaboration. As Vladimir Baier of Novosibirsk and Yuri Kononets of Kurchatov noted, theoretical treatment of these interconnected radiation distributions is challenging and much work needs to be done. In general, the agreement with the CERN experiments is good, but many areas like polarization phenomena and particle production need investigation. Prominent among high energy applications is extraction from accelerators. At the workshop, Alexei Asseev reported on beam extraction using a bent crystal at Serpukhov. Konrad Elsener and Jukka Klem reviewed recent CERN SPS studies driven by the possibility of using crystals for extraction of LHC beams. Thornton Murphy of Fermilab announced a step in that direction, with a demonstration this summer of extraction from the Tevatron at 900 GeV. Bent crystal channeling is also used for handling extracted high energy beams. Niels Doble presented a beautiful example of a beam for the CERN NA48 CP-violation experiment. Yuri Chesnokov reported that beams had been deflected through angles up to 150 milliradians at Serpukhov
Dynamics of Spontaneous Emission Controlled by Local Density of States in Photonic Crystals
DEFF Research Database (Denmark)
Lodahl, Peter; Nikolaev, Ivan S.; van Driel, A. Floris
2006-01-01
We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter.......We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter....
Strong Coupling of Microwave Photons to Antiferromagnetic Fluctuations in an Organic Magnet
Mergenthaler, Matthias; Liu, Junjie; Le Roy, Jennifer J.; Ares, Natalia; Thompson, Amber L.; Bogani, Lapo; Luis, Fernando; Blundell, Stephen J.; Lancaster, Tom; Ardavan, Arzhang; Briggs, G. Andrew D.; Leek, Peter J.; Laird, Edward A.
2017-10-01
Coupling between a crystal of di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium radicals and a superconducting microwave resonator is investigated in a circuit quantum electrodynamics (circuit QED) architecture. The crystal exhibits paramagnetic behavior above 4 K, with antiferromagnetic correlations appearing below this temperature, and we demonstrate strong coupling at base temperature. The magnetic resonance acquires a field angle dependence as the crystal is cooled down, indicating anisotropy of the exchange interactions. These results show that multispin modes in organic crystals are suitable for circuit QED, offering a platform for their coherent manipulation. They also utilize the circuit QED architecture as a way to probe spin correlations at low temperature.
Abbate, Sergio; Longhi, Giovanna; Gangemi, Fabrizio; Gangemi, Roberto; Superchi, Stefano; Caporusso, Anna Maria; Ruzziconi, Renzo
2011-10-01
The IR and Near infrared (NIR) vibrational circular dichroism (VCD) spectra of molecules endowed with noncentral chirality have been investigated. Data for fundamental, first, and second overtone regions of (S)-2,3-pentadiene, exhibiting axial chirality, and methyl-d(3) (R)- and (S)-[2.2]paracyclophane-4-carboxylate, exhibiting planar chirality have been measured and analyzed. The analysis of NIR and IR VCD spectra was based on the local-mode model and the use of density functional theory (DFT), providing mechanical and electrical anharmonic terms for all CH-bonds. The comparison of experimental and calculated spectra is satisfactory and allows one to monitor fine details in the asymmetric charge distribution in the molecules: these details consist in the harmonic frequencies, in the principal anharmonicity constants, in both the atomic polar and axial tensors and in their first and second derivatives with respect to the CH-stretching coordinates. Copyright © 2011 Wiley-Liss, Inc.
Energy Technology Data Exchange (ETDEWEB)
Clabo, D.A. Jr.
1987-04-01
Inclusion of the anharmonicity normal mode vibrations (i.e., the third and fourth (and higher) derivatives of a molecular Born-Oppenheimer potential energy surface) is necessary in order to theoretically reproduce experimental fundamental vibrational frequencies of a molecule. Although ab initio determinations of harmonic vibrational frequencies may give errors of only a few percent by the inclusion of electron correlation within a large basis set for small molecules, in general, molecular fundamental vibrational frequencies are more often available from high resolution vibration-rotation spectra. Recently developed analytic third derivatives methods for self-consistent-field (SCF) wavefunctions have made it possible to examine with previously unavailable accuracy and computational efficiency the anharmonic force fields of small molecules.
International Nuclear Information System (INIS)
Clabo, D.A. Jr.
1987-04-01
Inclusion of the anharmonicity normal mode vibrations [i.e., the third and fourth (and higher) derivatives of a molecular Born-Oppenheimer potential energy surface] is necessary in order to theoretically reproduce experimental fundamental vibrational frequencies of a molecule. Although ab initio determinations of harmonic vibrational frequencies may give errors of only a few percent by the inclusion of electron correlation within a large basis set for small molecules, in general, molecular fundamental vibrational frequencies are more often available from high resolution vibration-rotation spectra. Recently developed analytic third derivatives methods for self-consistent-field (SCF) wavefunctions have made it possible to examine with previously unavailable accuracy and computational efficiency the anharmonic force fields of small molecules
CRYSTALLIZATION IN MULTICOMPONENT GLASSES
Energy Technology Data Exchange (ETDEWEB)
KRUGER AA; HRMA PR
2009-10-08
In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.
Crystallization In Multicomponent Glasses
International Nuclear Information System (INIS)
Kruger, A.A.; Hrma, P.R.
2009-01-01
In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.
Photoemission in case of a strongly asymmetric X-ray dinamic diffraction
International Nuclear Information System (INIS)
Kruglov, M.V.; Sazontov, E.A.; Solomin, I.K.
1985-01-01
Possibility has been studied of utilizing strongly asymmet-- ric reflections, in particular in case when the reflected wave slips at a small angle along the surface, for investigating the structural violations of the surface crystal layers. Angular dependence extrinsic photoeffect (ADEP) in the region of X-ray incedence angles close to the Bragg diffraction angle was studied in this paper conformably to crystals with a distorted surface layer. Measurements were conducted with ideal germanium crystals using CuKsub(α) radiation reflections (220) and silicon crystals using CrKsub(α) radiation reflections (22O). It is shown that, in investigating deformed surface layers with low thichkness and large variation of interplanar space, as compared to the basic crystal matric, application of strongly asymmetric reflections anables to increase the sensitivity and information content of the method of abnormal ADEP
New results on strong-interaction effects in antiprotonic hydrogen
Gotta, D; Augsburger, M A; Borchert, G L; Castelli, C M; Chatellard, D; El-Khoury, P; Egger, J P; Gorke, H; Hauser, P R; Indelicato, P J; Kirch, K; Lenz, S; Nelms, N; Rashid, K; Schult, O W B; Siems, T; Simons, L M
1999-01-01
Lyman and Balmer transitions of antiprotonic hydrogen and deuterium have been measured at the low-energy antiproton ring LEAR at CERN in order to determine the strong interaction effects. The X-rays were detected using charge-coupled devices (CCDs) and a reflection type crystal spectrometer. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction. (33 refs).
New results on strong-interaction effects in antiprotonic hydrogen
International Nuclear Information System (INIS)
Anagnostopoulos, D. F.; Augsburger, M.; Borchert, G.; Castelli, C.; Chatellard, D.; El-Khoury, P.; Egger, J.-P.; Gorke, H.; Gotta, D.; Hauser, P.; Indelicato, P.; Kirch, K.; Lenz, S.; Nelms, N.; Rashid, K.; Schult, O. W. B.; Siems, Th.; Simons, L. M.
1999-01-01
Lyman and Balmer transitions of antiprotonic hydrogen and deuterium have been measured at the Low-Energy Antiproton Ring LEAR at CERN in order to determine the strong interaction effects. The X-rays were detected using Charge-Coupled Devices (CCDs) and a reflection type crystal spectrometer. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction
International Nuclear Information System (INIS)
Aoki, Ken-ichi
1988-01-01
Existence of a strong coupling phase in QED has been suggested in solutions of the Schwinger-Dyson equation and in Monte Carlo simulation of lattice QED. In this article we recapitulate the previous arguments, and formulate the problem in the modern framework of the renormalization theory, Wilsonian renormalization. This scheme of renormalization gives the best understanding of the basic structure of a field theory especially when it has a multi-phase structure. We resolve some misleading arguments in the previous literature. Then we set up a strategy to attack the strong phase, if any. We describe a trial; a coupled Schwinger-Dyson equation. Possible picture of the strong coupling phase QED is presented. (author)
Anscombe, Nadya
2011-08-01
Over the past ten years, Crystal Fiber, now part of NKT Photonics, has been busy commercializing photonic crystal fibre. Nadya Anscombe finds out about the evolution of the technology and its applications.
Crystallization Pathways in Biomineralization
Weiner, Steve; Addadi, Lia
2011-08-01
A crystallization pathway describes the movement of ions from their source to the final product. Cells are intimately involved in biological crystallization pathways. In many pathways the cells utilize a unique strategy: They temporarily concentrate ions in intracellular membrane-bound vesicles in the form of a highly disordered solid phase. This phase is then transported to the final mineralization site, where it is destabilized and crystallizes. We present four case studies, each of which demonstrates specific aspects of biological crystallization pathways: seawater uptake by foraminifera, calcite spicule formation by sea urchin larvae, goethite formation in the teeth of limpets, and guanine crystal formation in fish skin and spider cuticles. Three representative crystallization pathways are described, and aspects of the different stages of crystallization are discussed. An in-depth understanding of these complex processes can lead to new ideas for synthetic crystallization processes of interest to materials science.
Photonic Crystal Nanocavity Arrays
National Research Council Canada - National Science Library
Altug, Hatice; Vuckovic, Jelena
2006-01-01
We recently proposed two-dimensional coupled photonic crystal nanocavity arrays as a route to achieve a slow-group velocity of light in all crystal directions, thereby enabling numerous applications...
Energy Technology Data Exchange (ETDEWEB)
Patil, Vidya, E-mail: vidya.patil@ruparel.edu; Patki, Mugdha, E-mail: mugdha.patki@ruparel.edu [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)
2016-05-06
Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.
Strong interactions at high energy
International Nuclear Information System (INIS)
Anselmino, M.
1995-01-01
Spin effects in strong interaction high energy processes are subtle phenomena which involve both short and long distance physics and test perturbative and non perturbative aspects of QCD. Moreover, depending on quantities like interferences between different amplitudes and relative phases, spin observables always test a theory at a fundamental quantum mechanical level; it is then no surprise that spin data are often difficult to accommodate within the existing models. A report is made on the main issues and contributions discussed in the parallel Session on the open-quote open-quote Strong interactions at high energy close-quote close-quote in this Conference. copyright 1995 American Institute of Physics
Strong-field dissociation dynamics
International Nuclear Information System (INIS)
DiMauro, L.F.; Yang, Baorui.
1993-01-01
The strong-field dissociation behavior of diatomic molecules is examined under two distinctive physical scenarios. In the first scenario, the dissociation of the isolated hydrogen and deuterium molecular ions is discussed. The dynamics of above-threshold dissociation (ATD) are investigated over a wide range of green and infrared intensities and compared to a dressed-state model. The second situation arises when strong-field neutral dissociation is followed by ionization of the atomic fragments. The study results in a direct measure of the atomic fragment's ac-Stark shift by observing the intensity-dependent shifts in the electron or nuclear fragment kinetic energy. 8 figs., 14 refs
Apparatus for mounting crystal
Longeway, Paul A.
1985-01-01
A thickness monitor useful in deposition or etching reactor systems comprising a crystal-controlled oscillator in which the crystal is deposited or etched to change the frequency of the oscillator. The crystal rests within a thermally conductive metallic housing and arranged to be temperature controlled. Electrode contacts are made to the surface primarily by gravity force such that the crystal is substantially free of stress otherwise induced by high temperature.
ALICE photon spectrometer crystals
Maximilien Brice
2006-01-01
Members of the mechanical assembly team insert the last few crystals into the first module of ALICE's photon spectrometer. These crystals are made from lead-tungstate, a crystal as clear as glass but with nearly four times the density. When a high-energy particle passes through one of these crystals it will scintillate, emitting a flash of light allowing the energy of photons, electrons and positrons to be measured.
Scheel, Hans J.; Fukuda, Tsuguo
2004-06-01
This volume deals with the technologies of crystal fabrication, of crystal machining, and of epilayer production and is the first book on industrial and scientific aspects of crystal and layer production. The major industrial crystals are treated: Si, GaAs, GaP, InP, CdTe, sapphire, oxide and halide scintillator crystals, crystals for optical, piezoelectric and microwave applications and more. Contains 29 contributions from leading crystal technologists covering the following topics: General aspects of crystal growth technology Silicon Compound semiconductors Oxides and halides Crystal machining Epitaxy and layer deposition Scientific and technological problems of production and machining of industrial crystals are discussed by top experts, most of them from the major growth industries and crystal growth centers. In addition, it will be useful for the users of crystals, for teachers and graduate students in materials sciences, in electronic and other functional materials, chemical and metallurgical engineering, micro-and optoelectronics including nanotechnology, mechanical engineering and precision-machining, microtechnology, and in solid-state sciences.
Food crystallization and eggs.
Egg products can be utilized to control crystallization in a diverse realm of food products. Albumen and egg yolk can aid in the control of sugar crystal formation in candies. Egg yolk can enhance the textural properties and aid in the control of large ice crystal formation in frozen desserts. In...
Directory of Open Access Journals (Sweden)
A Nokhodchi
2010-06-01
Full Text Available "n "n Background and the purpose of the study: The success of any direct-tableting procedure is strongly affected by the quality of the crystals used in the process. Ibuprofen is a poorly compactible drug with a high tendency for capping. In order to use ibuprofen in direct compression formulations, physico-mechanical properties of ibuprofen should be improved considerably. The aim of the present investigation was to employ crystallization techniques in order to improve the physico-mechanical properties of ibuprofen for direct compression. "nMethods:The experimental methods involved the preparation of ibuprofen crystals by solvent change technique. Ibuprofen was dissolved in ethanol and crystallized out with water in the absence or presence of various hydrophilic additives (PEG 6000, 8000, Brij 98P and polyvinyl alcohol 22000, PVA 22000 with different concentrations. The physico-mechanical properties of the ibuprofen crystals were studied in terms of flow, density, tensile strength and dissolution behaviour. Morphology of ibuprofen crystals was studied by scanning electron microscopic (SEM. Solid state of the recrystallized particles was also investigated using differential scanning calorimeter (DSC and FT-IR. "nResults:Ibuprofen samples crystallized in the presence of PEG 6000 and 8000 and PVA showed remarkable increase in the tensile strengths of the directly compressed tablets, while some other additives, i.e. Brij 98P did not produce improved ibuprofen crystals. Ibuprofen powders made from particles obtained in the presence of PVA and Brij 98P showed similar dissolution profiles to the commercial ibuprofen particles. DSC and FT-IR results ruled out any significant interaction between ibuprofen and additives except for the samples crystallized in the presence of PEG 8000. Conclusion:The crystal habit of ibuprofen can be altered successfully by the crystallization technique which was developed in this study. The crystals developed in the
Strong Decomposition of Random Variables
DEFF Research Database (Denmark)
Hoffmann-Jørgensen, Jørgen; Kagan, Abram M.; Pitt, Loren D.
2007-01-01
A random variable X is stongly decomposable if X=Y+Z where Y=Φ(X) and Z=X-Φ(X) are independent non-degenerated random variables (called the components). It is shown that at least one of the components is singular, and we derive a necessary and sufficient condition for strong decomposability...... of a discrete random variable....
Strong coupling electroweak symmetry breaking
International Nuclear Information System (INIS)
Barklow, T.L.; Burdman, G.; Chivukula, R.S.
1997-04-01
The authors review models of electroweak symmetry breaking due to new strong interactions at the TeV energy scale and discuss the prospects for their experimental tests. They emphasize the direct observation of the new interactions through high-energy scattering of vector bosons. They also discuss indirect probes of the new interactions and exotic particles predicted by specific theoretical models
Strong coupling electroweak symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Barklow, T.L. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Burdman, G. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics; Chivukula, R.S. [Boston Univ., MA (United States). Dept. of Physics
1997-04-01
The authors review models of electroweak symmetry breaking due to new strong interactions at the TeV energy scale and discuss the prospects for their experimental tests. They emphasize the direct observation of the new interactions through high-energy scattering of vector bosons. They also discuss indirect probes of the new interactions and exotic particles predicted by specific theoretical models.
The colours of strong interaction
International Nuclear Information System (INIS)
1995-01-01
The aim of this session is to draw a consistent framework about the different ways to consider strong interaction. A large part is dedicated to theoretical work and the latest experimental results obtained at the first electron collider HERA are discussed. (A.C.)
Strong cosmic censorship and the strong curvature singularities
International Nuclear Information System (INIS)
Krolak, A.
1987-01-01
Conditions are given under which any asymptotically simple and empty space-time that has a partial Cauchy surface with an asymptotically simple past is globally hyperbolic. It is shown that this result suggests that the Cauchy horizons of the type occurring in Reissner--Nordstroem and Kerr space-times are unstable. This in turn gives support for the validity of the strong cosmic censorship hypothesis
Quantum dynamics of crystals of molecular magnets inside microwave resonators
Energy Technology Data Exchange (ETDEWEB)
Amigo, R.; Tejada, J.; Chudnovsky, E.M.; Hernandez, J.M.; Garcia-Santiago, A. E-mail: antonio@ubxlab.comtoni@ubxlab.com
2004-05-01
It is shown that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. Strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing evidence of the coherent microwave radiation by the crystals. These observations open the possibility of building a nanomagnetic microwave laser pumped by the magnetic field.
Quantum dynamics of crystals of molecular magnets inside microwave resonators
International Nuclear Information System (INIS)
Amigo, R.; Tejada, J.; Chudnovsky, E.M.; Hernandez, J.M.; Garcia-Santiago, A.
2004-01-01
It is shown that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. Strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing evidence of the coherent microwave radiation by the crystals. These observations open the possibility of building a nanomagnetic microwave laser pumped by the magnetic field
Predicting Crystallization of Amorphous Drugs with Terahertz Spectroscopy
DEFF Research Database (Denmark)
Sibik, Juraj; Löbmann, Korbinian; Rades, Thomas
2015-01-01
of the crystallization. We determine the onset temperature Tβ above which the JG relaxation contributes to the fast molecular dynamics and analytically quantify the level of this contribution. We then show there is a strong correlation between the increase in the fast molecular dynamics and onset of crystallization...
International Nuclear Information System (INIS)
Li, C.T.; Klein, A.
1979-01-01
The theory of anharmonic nuclear vibrational motion (nonlinear equations-of-motion method) developed in the preceding paper is applied to atsup 60,62,64atNi, which exhibit one and two phonon quadrupole collective states. A model Hamiltonian consisting of a modified pairing plus quadrupole interaction is studied first by comparing the results of the nonlinear equations-of-motion method with those of an exact diagonalization. Contrary to popular opinion, the model chosen fails to produce a vibrational spectrum, except in the case of 60 Ni, and as a consequence, the nonlinear equations-of-motion method, designed specifically to describe vibrational spectra, accords well with the exact calculations only for this case. A simple method is then described, within the framework of the nonlinear equations-of-motion method, for refining the model Hamiltonian so as to bring it into accord with experiment. In practice, it is found that a simple additional parameter in the Hamiltonian suffices to yield descriptions of the quadrupole states in Ni isotopes comparable in precision to the most up-to-date versions (modified, adjusted, etc.) of the surface delta interaction model
Study of the anharmonic effects on low-lying states of odd-mass nuclei in 1g sub(9/2)+ shell region
International Nuclear Information System (INIS)
Nakano, Masahiro
1980-01-01
Anharmonic effects on the low-lying states of the odd-mass nuclei in 1g sub(9/2)sup(+) shell region are investigated by introduction of 1, 3, 5 and 7 quasiparticle modes. Special attention is paid to the energy-lowering of anomalous coupling states in N = 41 nuclei and to the spin sequence of so-called ''one-quasiparticle-two-phonon multiplet''. It is shown that one cannot attribute the special-lowering of the energies of the anomalous coupling (j - 2) states to the dynamical effects due to the coupling between the 3-quasiparticle mode and the 5-quasiparticle mode, and is also shown that not only the kinematical effect but also the dynamical effect plays an important role in the energy-lowering of the anomalous coupling (j - 1) states in N = 41 nuclei. The second (j - 2) state is predicted to be the lowest member of one-quasiparticle-two-phonon multiplet by taking account of the kinematical effect for the 5-quasiparticle mode, which corresponds to the experimental fact. (author)
Anharmonic Oxygen Displacements in La2-x (Sr, Ba)xCuO4 Planes and in YBa2Cu3O7 Chains
International Nuclear Information System (INIS)
Pickett, W. E.
1995-01-01
An earlier calculation of the energy surface for X-point tilts if the CuO6 octahedra in La 2-x (Sr, Ba) x CuO 4 revealed an eight well potential surface. This surface indicated an extremely anharmonic situation and seemed to provide an explanation of a number of observed phenomena in this system, especially the coincidence of a drop in Tc with the occurrence of the low temperature tetragonal phase. We review experimental developments since that time, which indicate new complications. We also reconsider the zone boundary chain-buckling mode of the chain oxygen atoms in YBa 2 Cu 3 O 7 , for which our earlier calculation indicated a very flat (slightly double well) energy surface that would provide very little restoring force to this motion. We have studied the coupling of the chain buckling motion to the carriers by evaluating the shifts of bands near the Fermi energy. These deformation potentials themselves are not large (∼ 0.1-0.2 eV/A) and non-linear coupling is minor out to displacements of 0.25 A. (author)
Growth and Characterization of Tetraphenylphosphonium Bromide Crystal
Directory of Open Access Journals (Sweden)
Guangqiang Wang
2017-05-01
Full Text Available Multiple-phenyl phosphorous compounds are a group of chemical materials that have been used as reactants, pharmaceutical intermediates, extractants, and catalysts in organic synthetic reactions. However, the crystal growth of bulk crystals of multiple-phenyl phosphorous compounds, which may expand their applications in photonics technology, have been largely overlooked. In this article, the crystal growth of tetraphenylphosphonium bromide (TPPB has been studied in organic solvents and water. The crystal structures and crystallization features are analyzed by X-ray diffraction data. By a slow temperature-lowering method, a single-crystal of TPPB (2H2O with the size of 27 × 20 × 20 mm3 has been obtained in water. The basic thermal and optical properties were characterized. We find that the TPPB (2H2O crystal shows excellent transparent property in the near-IR region. Large Raman shifts and strong Raman scattering intensity indicate that TPPB is a potential candidate in Raman-scattering-based nonlinearity applications.
Ab initio molecular crystal structures, spectra, and phase diagrams.
Hirata, So; Gilliard, Kandis; He, Xiao; Li, Jinjin; Sode, Olaseni
2014-09-16
Conspectus Molecular crystals are chemists' solids in the sense that their structures and properties can be understood in terms of those of the constituent molecules merely perturbed by a crystalline environment. They form a large and important class of solids including ices of atmospheric species, drugs, explosives, and even some organic optoelectronic materials and supramolecular assemblies. Recently, surprisingly simple yet extremely efficient, versatile, easily implemented, and systematically accurate electronic structure methods for molecular crystals have been developed. The methods, collectively referred to as the embedded-fragment scheme, divide a crystal into monomers and overlapping dimers and apply modern molecular electronic structure methods and software to these fragments of the crystal that are embedded in a self-consistently determined crystalline electrostatic field. They enable facile applications of accurate but otherwise prohibitively expensive ab initio molecular orbital theories such as Møller-Plesset perturbation and coupled-cluster theories to a broad range of properties of solids such as internal energies, enthalpies, structures, equation of state, phonon dispersion curves and density of states, infrared and Raman spectra (including band intensities and sometimes anharmonic effects), inelastic neutron scattering spectra, heat capacities, Gibbs energies, and phase diagrams, while accounting for many-body electrostatic (namely, induction or polarization) effects as well as two-body exchange and dispersion interactions from first principles. They can fundamentally alter the role of computing in the studies of molecular crystals in the same way ab initio molecular orbital theories have transformed research practices in gas-phase physical chemistry and synthetic chemistry in the last half century. In this Account, after a brief summary of formalisms and algorithms, we discuss applications of these methods performed in our group as compelling
Nonlinear dynamical phenomena in liquid crystals
International Nuclear Information System (INIS)
Wang, X.Y.; Sun, Z.M.
1988-09-01
Because of the existence of the orientational order and anisotropy in liquid crystals, strong nonlinear phenomena and singular behaviors, such as solitary wave, transient periodic structure, chaos, fractal and viscous fingering, can be excited by a very small disturbance. These phenomena and behaviors are in connection with physics, biology and mathematics. 12 refs, 6 figs
2003-01-01
In order to rapidly and efficiently grow crystals, tools were needed to automatically identify and analyze the growing process of protein crystals. To meet this need, Diversified Scientific, Inc. (DSI), with the support of a Small Business Innovation Research (SBIR) contract from NASA s Marshall Space Flight Center, developed CrystalScore(trademark), the first automated image acquisition, analysis, and archiving system designed specifically for the macromolecular crystal growing community. It offers automated hardware control, image and data archiving, image processing, a searchable database, and surface plotting of experimental data. CrystalScore is currently being used by numerous pharmaceutical companies and academic and nonprofit research centers. DSI, located in Birmingham, Alabama, was awarded the patent Method for acquiring, storing, and analyzing crystal images on March 4, 2003. Another DSI product made possible by Marshall SBIR funding is VaporPro(trademark), a unique, comprehensive system that allows for the automated control of vapor diffusion for crystallization experiments.
Fleming, James G [Albuquerque, NM; Lin, Shawn-Yu [Albuquerque, NM; Bur, James A [Corrales, NM
2004-07-27
A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.
Strongly Correlated Systems Theoretical Methods
Avella, Adolfo
2012-01-01
The volume presents, for the very first time, an exhaustive collection of those modern theoretical methods specifically tailored for the analysis of Strongly Correlated Systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognized main contributors. The exposition has a clear pedagogical cut and fully reports on the most relevant case study where the specific technique showed to be very successful in describing and enlightening the puzzling physics of a particular strongly correlated system. The book is intended for advanced graduate students and post-docs in the field as textbook and/or main reference, but also for other researchers in the field who appreciates consulting a single, but comprehensive, source or wishes to get acquainted, in a as painless as po...
Strongly correlated systems numerical methods
Mancini, Ferdinando
2013-01-01
This volume presents, for the very first time, an exhaustive collection of those modern numerical methods specifically tailored for the analysis of Strongly Correlated Systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and material science, belong to this class of systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognized main contributors. The exposition has a clear pedagogical cut and fully reports on the most relevant case study where the specific technique showed to be very successful in describing and enlightening the puzzling physics of a particular strongly correlated system. The book is intended for advanced graduate students and post-docs in the field as textbook and/or main reference, but also for other researchers in the field who appreciate consulting a single, but comprehensive, source or wishes to get acquainted, in a as painless as possi...
Strongly correlated systems experimental techniques
Mancini, Ferdinando
2015-01-01
The continuous evolution and development of experimental techniques is at the basis of any fundamental achievement in modern physics. Strongly correlated systems (SCS), more than any other, need to be investigated through the greatest variety of experimental techniques in order to unveil and crosscheck the numerous and puzzling anomalous behaviors characterizing them. The study of SCS fostered the improvement of many old experimental techniques, but also the advent of many new ones just invented in order to analyze the complex behaviors of these systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. The volume presents a representative collection of the modern experimental techniques specifically tailored for the analysis of strongly correlated systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognize...
Flavour Democracy in Strong Unification
Abel, S A; Abel, Steven; King, Steven
1998-01-01
We show that the fermion mass spectrum may naturally be understood in terms of flavour democratic fixed points in supersymmetric theories which have a large domain of attraction in the presence of "strong unification". Our approach provides an alternative to the approximate Yukawa texture zeroes of the Froggatt-Nielsen mechanism. We discuss a particular model based on a broken gauged $SU(3)_L\\times SU(3)_R$ family symmetry which illustrates our approach.
String dynamics at strong coupling
International Nuclear Information System (INIS)
Hull, C.M.
1996-01-01
The dynamics of superstring, supergravity and M-theories and their compactifications are probed by studying the various perturbation theories that emerge in the strong and weak-coupling limits for various directions in coupling constant space. The results support the picture of an underlying non-perturbative theory that, when expanded perturbatively in different coupling constants, gives different perturbation theories, which can be perturbative superstring theories or superparticle theories. The p-brane spectrum is considered in detail and a criterion found to establish which p-branes govern the strong-coupling dynamics. In many cases there are competing conjectures in the literature, and this analysis decides between them. In other cases, new results are found. The chiral 6-dimensional theory resulting from compactifying the type IIB string on K 3 is studied in detail and it is found that certain strong-coupling limits appear to give new theories, some of which hint at the possibility of a 12-dimensional origin. (orig.)
PREFACE: Strongly correlated electron systems Strongly correlated electron systems
Saxena, Siddharth S.; Littlewood, P. B.
2012-07-01
This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which
Macromolecular crystallization in microgravity generated by a superconducting magnet.
Wakayama, N I; Yin, D C; Harata, K; Kiyoshi, T; Fujiwara, M; Tanimoto, Y
2006-09-01
About 30% of the protein crystals grown in space yield better X-ray diffraction data than the best crystals grown on the earth. The microgravity environments provided by the application of an upward magnetic force constitute excellent candidates for simulating the microgravity conditions in space. Here, we describe a method to control effective gravity and formation of protein crystals in various levels of effective gravity. Since 2002, the stable and long-time durable microgravity generated by a convenient type of superconducting magnet has been available for protein crystal growth. For the first time, protein crystals, orthorhombic lysozyme, were grown at microgravity on the earth, and it was proved that this microgravity improved the crystal quality effectively and reproducibly. The present method always accompanies a strong magnetic field, and the magnetic field itself seems to improve crystal quality. Microgravity is not always effective for improving crystal quality. When we applied this microgravity to the formation of cubic porcine insulin and tetragonal lysozyme crystals, we observed no dependence of effective gravity on crystal quality. Thus, this kind of test will be useful for selecting promising proteins prior to the space experiments. Finally, the microgravity generated by the magnet is compared with that in space, considering the cost, the quality of microgravity, experimental convenience, etc., and the future use of this microgravity for macromolecular crystal growth is discussed.
International Nuclear Information System (INIS)
L'Huillier, A.
2002-01-01
When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)
Rydberg atoms in strong fields
International Nuclear Information System (INIS)
Kleppner, D.; Tsimmerman, M.
1985-01-01
Experimental and theoretical achievements in studying Rydberg atoms in external fields are considered. Only static (or quasistatic) fields and ''one-electron'' atoms, i.e. atoms that are well described by one-electron states, are discussed. Mainly behaviour of alkali metal atoms in electric field is considered. The state of theoretical investigations for hydrogen atom in magnetic field is described, but experimental data for atoms of alkali metals are presented as an illustration. Results of the latest experimental and theoretical investigations into the structure of Rydberg atoms in strong fields are presented
Strong versions of Bell's theorem
International Nuclear Information System (INIS)
Stapp, H.P.
1994-01-01
Technical aspects of a recently constructed strong version of Bell's theorem are discussed. The theorem assumes neither hidden variables nor factorization, and neither determinism nor counterfactual definiteness. It deals directly with logical connections. Hence its relationship with modal logic needs to be described. It is shown that the proof can be embedded in an orthodox modal logic, and hence its compatibility with modal logic assured, but that this embedding weakens the theorem by introducing as added assumptions the conventionalities of the particular modal logic that is adopted. This weakening is avoided in the recent proof by using directly the set-theoretic conditions entailed by the locality assumption
Strongly interacting light dark matter
International Nuclear Information System (INIS)
Bruggisser, Sebastian; Riva, Francesco; Urbano, Alfredo
2016-07-01
In the presence of approximate global symmetries that forbid relevant interactions, strongly coupled light Dark Matter (DM) can appear weakly coupled at small-energy and generate a sizable relic abundance. Fundamental principles like unitarity restrict these symmetries to a small class, where the leading interactions are captured by effective operators up to dimension-8. Chiral symmetry, spontaneously broken global symmetries and non-linearly realized supersymmetry are examples of this. Their DM candidates (composite fermions, pseudo-Nambu-Goldstone Bosons and Goldstini) are interesting targets for LHC missing-energy searches.
Weak consistency and strong paraconsistency
Directory of Open Access Journals (Sweden)
Gemma Robles
2009-11-01
Full Text Available In a standard sense, consistency and paraconsistency are understood as, respectively, the absence of any contradiction and as the absence of the ECQ (“E contradictione quodlibet” rule that allows us to conclude any well formed formula from any contradiction. The aim of this paper is to explain the concepts of weak consistency alternative to the standard one, the concepts of paraconsistency related to them and the concept of strong paraconsistency, all of which have been defined by the author together with José M. Méndez.
Energy Technology Data Exchange (ETDEWEB)
Dowrick, N.J. (Dept. of Physics, Oxford (United Kingdom)); McDougall, N.A. (National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan))
1992-07-09
We show that two well-known solutions to the strong CP problem, the axion and a massless quark, may be understood in terms of the mechanism recently proposed by Samuel where long-range interactions between topological charges may be responsible for the removal of CP violation. We explain how the axion and a QCD meson (identified as the {eta}' if all quarks are massless) suppress fluctuations in global topological charge by almost identical dynamical although the masses, couplings and relevant length scales are very different. Furthermore, we elucidate the precise origin of the {eta}' mass. (orig.).
Scalar strong interaction hadron theory
Hoh, Fang Chao
2015-01-01
The scalar strong interaction hadron theory, SSI, is a first principles' and nonlocal theory at quantum mechanical level that provides an alternative to low energy QCD and Higgs related part of the standard model. The quark-quark interaction is scalar rather than color-vectorial. A set of equations of motion for mesons and another set for baryons have been constructed. This book provides an account of the present state of a theory supposedly still at its early stage of development. This work will facilitate researchers interested in entering into this field and serve as a basis for possible future development of this theory.
Estimation of strong ground motion
International Nuclear Information System (INIS)
Watabe, Makoto
1993-01-01
Fault model has been developed to estimate a strong ground motion in consideration of characteristics of seismic source and propagation path of seismic waves. There are two different approaches in the model. The first one is a theoretical approach, while the second approach is a semi-empirical approach. Though the latter is more practical than the former to be applied to the estimation of input motions, it needs at least the small-event records, the value of the seismic moment of the small event and the fault model of the large event
Crystal growth of various ruthenates
Energy Technology Data Exchange (ETDEWEB)
Kunkemoeller, Stefan; Braden, Markus [II. Physikalisches Institut, Universitaet zu Koeln (Germany); Nugroho, Agung [Institut Teknologi Bandung (Indonesia)
2013-07-01
Ruthenates of the Ruddlesdon-Popper series exhibit a variety of interesting phenomena ranging from unconventional superconductivity to orbitally polarized Mott insulators. Unfortunately the crystal growth of most of these ruthenates is extremely difficult partially due to the high evaporation of ruthenium; this strongly limits the research on these fascinating materials. We have started to grow single crystals of layered and perovskite ruthenates by the travelling floating-zone method using a Canon SC1-MDH mirror furnace. For the layered Ca{sub 2-x}Sr{sub x}RuO{sub 4} series we focused first on the range of concentration where recent My-SR experiments reveal spin-density wave ordering to occur at relatively high temperature and with a sizeable ordered moment. Good quality crystals of Ca{sub 1.5}Sr{sub 0.5}RuO{sub 4} can be obtained, when an excess of 15 percent of ruthenium is added to the initial preparation of the rod and when a high growth speed up to 40mm/h is used. Even slight modifications of the growing conditions result in large amounts of (Sr/Ca)RuO{sub 3} and (Sr/Ca){sub 3}Ru{sub 2}O{sub 7} intergrowth phases. First attempts to grow perovskite and double-layered ruthenates are discussed as well.
Effective lagrangian for strong interactions
International Nuclear Information System (INIS)
Jain, P.
1988-01-01
We attempt to construct a realistic phenomenological Lagrangian in order to describe strong interactions. This is in general a very complicated problem and we shall explore its various aspects. We first include the vector mesons by writing down the most general chiral invariant terms proportional to the Levi-Civita symbol ε μναβ . These terms involve three unknown coefficients, which are calculated by using the experimental results of strong interaction processes. We then calculate the static nucleon properties by finding the solitonic excitations of this model. The results turn out to be, as is also the case for most other vector-pseudoscalar Lagrangians, better than the Skyrme model but are still somewhat different from the experiments. Another aspect that we shall study is the incorporation of scale anomaly of QCD into the Skyrme model. We thus introduce a scalar glueball in our Lagrangian. Here we find an interesting result that the effective glue field dynamically forms a bag for the soliton. Depending on the values of the parameters, we get either a deep bag or a shallow bag. However by including the scalar meson, we find that to get realistic scalar sector we must have the shallow bag. Finally we show some intriguing connections between the chiral quark model, in which the nucleon is described as a solitonic excitation, and the ordinary potential binding quark model
EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems
Ronning, Filip; Batista, Cristian
2011-03-01
Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context. The 2010 International Conference on Strongly Correlated Electron Systems was held in Santa Fe, New Mexico, a reunion of sorts from the 1989 International Conference on the Physics of Highly Correlated Electron Systems that also convened in Santa Fe. SCES 2010—co-chaired by John Sarrao and Joe Thompson—followed the tradition of earlier conferences, in this century, hosted by Buzios (2008), Houston (2007), Vienna (2005), Karlsruhe (2004), Krakow (2002) and Ann Arbor (2001). Every three years since 1997, SCES has joined the International Conference on Magnetism (ICM), held in Recife (2000), Rome (2003), Kyoto (2006) and Karlsruhe (2009). Like its predecessors, SCES 2010 topics included strongly correlated f- and d-electron systems, heavy-fermion behaviors, quantum-phase transitions, non-Fermi liquid phenomena, unconventional superconductivity, and emergent states that arise from electronic correlations. Recent developments from studies of quantum magnetism and cold atoms complemented the traditional subjects and were included in SCES 2010. 2010 celebrated the 400th anniversary of Santa Fe as well as the birth of astronomy. So what's the connection to SCES? The Dutch invention of the first practical telescope and its use by Galileo in 1610 and subsequent years overturned dogma that the sun revolved about the earth. This revolutionary, and at the time heretical, conclusion required innovative combinations of new instrumentation, observation and mathematics. These same combinations are just as important 400 years later and are the foundation of scientific discoveries that were discussed
Strong Selective Adsorption of Polymers.
Ge, Ting; Rubinstein, Michael
2015-06-09
A scaling theory is developed for selective adsorption of polymers induced by the strong binding between specific monomers and complementary surface adsorption sites. By "selective" we mean specific attraction between a subset of all monomers, called "sticky", and a subset of surface sites, called "adsorption sites". We demonstrate that, in addition to the expected dependence on the polymer volume fraction ϕ bulk in the bulk solution, selective adsorption strongly depends on the ratio between two characteristic length scales, the root-mean-square distance l between neighboring sticky monomers along the polymer, and the average distance d between neighboring surface adsorption sites. The role of the ratio l / d arises from the fact that a polymer needs to deform to enable the spatial commensurability between its sticky monomers and the surface adsorption sites for selective adsorption. We study strong selective adsorption of both telechelic polymers with two end monomers being sticky and multisticker polymers with many sticky monomers between sticky ends. For telechelic polymers, we identify four adsorption regimes at l / d 1, we expect that the adsorption layer at exponentially low ϕ bulk consists of separated unstretched loops, while as ϕ bulk increases the layer crosses over to a brush of extended loops with a second layer of weakly overlapping tails. For multisticker chains, in the limit of exponentially low ϕ bulk , adsorbed polymers are well separated from each other. As l / d increases, the conformation of an individual polymer changes from a single-end-adsorbed "mushroom" to a random walk of loops. For high ϕ bulk , adsorbed polymers at small l / d are mushrooms that cover all the adsorption sites. At sufficiently large l / d , adsorbed multisticker polymers strongly overlap. We anticipate the formation of a self-similar carpet and with increasing l / d a two-layer structure with a brush of loops covered by a self-similar carpet. As l / d exceeds the
Strongly nonlinear electronic transport in Cr-Si composite films
International Nuclear Information System (INIS)
Burkov, A.T.; Vinzelberg, H.; Schumann, J.; Nakama, T.; Yagasaki, K.
2004-01-01
The phase formation, the resistivity and the thermopower of amorphous Cr 0.15 Si 0.85 , and nanocrystalline CrSi 2 -Si thin film composites have been studied. The films were produced by a magnetron sputtering of a composite target onto unheated substrates with subsequent crystallization of the film at high temperatures. As the film composite develops under the heat treatment from the initial amorphous state into the final polycrystalline material, two percolation thresholds were found. At first, the percolating cluster of nanocrystalline CrSi 2 is formed. However, this cluster is destroyed with further annealing due to crystallization and redistribution of Si. The composite films which are close to this insulating threshold reveal a strongly nonlinear conductivity. The conductivity increases with the current by two orders of magnitude
Scintillation crystal mounting apparatus
International Nuclear Information System (INIS)
Engdahl, L.W.; Deans, A.J.
1982-01-01
An improved detector head for a gamma camera is disclosed. The detector head includes a housing and a detector assembly mounted within the housing. Components of the detector assembly include a crystal sub-assembly, a phototube array, and a light pipe between the phototube array and crystal sub-assembly. The invention provides a unique structure for maintaining the phototubes in optical relationship with the light pipe and preventing the application of forces that would cause the camera's crystal to crack
Laurent Guiraud
2000-01-01
These crystals are made from lead tungstate, a crystal that is as clear as glass yet with nearly four times the density. They have been produced in Russia to be used as scintillators in the electromagnetic calorimeter on the CMS experiment, part of the LHC project at CERN. When an electron, positron or photon passes through the calorimeter it will cause a cascade of particles that will then be absorbed by these scintillating crystals, allowing the particle's energy to be measured.
Macromolecular crystallization in microgravity
International Nuclear Information System (INIS)
Snell, Edward H; Helliwell, John R
2005-01-01
Density difference fluid flows and sedimentation of growing crystals are greatly reduced when crystallization takes place in a reduced gravity environment. In the case of macromolecular crystallography a crystal of a biological macromolecule is used for diffraction experiments (x-ray or neutron) so as to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal then the greater the molecular structure detail that can be extracted. It is this structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences, with major potential in understanding disease pathologies. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyse the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural advances. Finally, limitations and alternatives to microgravity and future directions for this research are covered. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry and mathematics meet to enable insight to the fundamentals of life. As the reader will see, there is a great deal of physics involved when the microgravity environment is applied to crystallization, some of it known, and undoubtedly much yet to
Active Photonic Crystal Waveguides
DEFF Research Database (Denmark)
Ek, Sara
This thesis deals with the fabrication and characterization of active photonic crystal waveguides, realized in III-V semiconductor material with embedded active layers. The platform offering active photonic crystal waveguides has many potential applications. One of these is a compact photonic...... due to photonic crystal dispersion. The observations are explained by the enhancement of net gain by light slow down. Another application based on active photonic crystal waveguides is micro lasers. Measurements on quantum dot micro laser cavities with different mirror configurations and photonic...
2007-01-01
The production of crystals for the barrel of the CMS electromagnetic calorimeter has been completed. This is an important milestone for the experiment, which received the last of its 62,960 crystals on 9 March. The members of the team responsible for the crystal acceptance testing at CERN display the last crystal for the CMS electromagnetic calorimeter barrel. From left to right: Igor Tarasov, Etiennette Auffray and Hervé Cornet.One of the six machines specially developed to measure 67 different parameters on each crystal. Igor Tarasov is seen inserting the last batch of crystals into the machine. The last of the 62,960 CMS barrel crystals arrived at CERN on 9 March. Once removed from its polystyrene protection, this delicate crystal, like thousands of its predecessors, will be inserted into the last of the 36 supermodules of the barrel electromagnetic calorimeter in a few days' time. This marks the end of an important chapter in an almost 15-year-long journey by the CMS crystals team, some of whose member...
Automation in biological crystallization.
Stewart, Patrick Shaw; Mueller-Dieckmann, Jochen
2014-06-01
Crystallization remains the bottleneck in the crystallographic process leading from a gene to a three-dimensional model of the encoded protein or RNA. Automation of the individual steps of a crystallization experiment, from the preparation of crystallization cocktails for initial or optimization screens to the imaging of the experiments, has been the response to address this issue. Today, large high-throughput crystallization facilities, many of them open to the general user community, are capable of setting up thousands of crystallization trials per day. It is thus possible to test multiple constructs of each target for their ability to form crystals on a production-line basis. This has improved success rates and made crystallization much more convenient. High-throughput crystallization, however, cannot relieve users of the task of producing samples of high quality. Moreover, the time gained from eliminating manual preparations must now be invested in the careful evaluation of the increased number of experiments. The latter requires a sophisticated data and laboratory information-management system. A review of the current state of automation at the individual steps of crystallization with specific attention to the automation of optimization is given.
Crystallization Formulation Lab
Federal Laboratory Consortium — The Crystallization Formulation Lab fills a critical need in the process development and optimization of current and new explosives and energetic formulations. The...
Ideal gas behavior of a strongly-coupled complex (dusty) plasma
Oxtoby, Neil P.; Griffith, Elias J.; Durniak, Céline; Ralph, Jason F.; Samsonov, Dmitry
2012-01-01
In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly-coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.
Strong growth for Queensland mining
Energy Technology Data Exchange (ETDEWEB)
1990-10-01
The Queensland mining industry experienced strong growth during 1989-90 as shown in the latest statistics released by the Department of Resource Industries. The total value of Queensland mineral and energy production rose to a new record of $5.1 billion, an increase of 16.5% on 1988-89 production. A major contributing factor was a 20.9 percent increase in the value of coal production. While the quantity of coal produced rose only 1.1 percent, the substantial increase in the value of coal production is attributable to higher coal prices negotiated for export contracts. In Australian dollar terms coal, gold, lead, zinc and crude oil on average experienced higher international prices than in the previous year. Only copper and silver prices declined. 3 tabs.
Strong moduli stabilization and phenomenology
Dudas, Emilian; Mambrini, Yann; Mustafayev, Azar; Olive, Keith A
2013-01-01
We describe the resulting phenomenology of string theory/supergravity models with strong moduli stabilization. The KL model with F-term uplifting, is one such example. Models of this type predict universal scalar masses equal to the gravitino mass. In contrast, A-terms receive highly suppressed gravity mediated contributions. Under certain conditions, the same conclusion is valid for gaugino masses, which like A-terms, are then determined by anomalies. In such models, we are forced to relatively large gravitino masses (30-1000 TeV). We compute the low energy spectrum as a function of m_{3/2}. We see that the Higgs masses naturally takes values between 125-130 GeV. The lower limit is obtained from the requirement of chargino masses greater than 104 GeV, while the upper limit is determined by the relic density of dark matter (wino-like).
Strongly interacting W's and Z's
International Nuclear Information System (INIS)
Gaillard, M.K.
1984-01-01
The study focussed primarily on the dynamics of a strongly interacting W, Z(SIW) sector, with the aim of sharpening predictions for total W, Z yield and W, Z multiplicities expected from WW fusion for various scenarios. Specific issues raised in the context of the general problem of modeling SIW included the specificity of the technicolor (or, equivalently, QCD) model, whether or not a composite scalar model can be evaded, and whether the standard model necessarily implies an I = J = O state (≅ Higgs particle) that is relatively ''light'' (M ≤ hundreds of TeV). The consensus on the last issue was that existing arguments are inconclusive. While the author shall briefly address compositeness and alternatives to the technicolor model, quantitative estimates will be of necessity based on technicolor or an extrapolation of pion data
Uniquely Strongly Clean Group Rings
Institute of Scientific and Technical Information of China (English)
WANG XIU-LAN
2012-01-01
A ring R is called clean if every element is the sum of an idempotent and a unit,and R is called uniquely strongly clean (USC for short) if every element is uniquely the sum of an idempotent and a unit that commute.In this article,some conditions on a ring R and a group G such that RG is clean are given.It is also shown that if G is a locally finite group,then the group ring RG is USC if and only if R is USC,and G is a 2-group.The left uniquely exchange group ring,as a middle ring of the uniquely clean ring and the USC ring,does not possess this property,and so does the uniquely exchange group ring.
Electrophoresis in strong electric fields.
Barany, Sandor
2009-01-01
Two kinds of non-linear electrophoresis (ef) that can be detected in strong electric fields (several hundred V/cm) are considered. The first ("classical" non-linear ef) is due to the interaction of the outer field with field-induced ionic charges in the electric double layer (EDL) under conditions, when field-induced variations of electrolyte concentration remain to be small comparatively to its equilibrium value. According to the Shilov theory, the non-linear component of the electrophoretic velocity for dielectric particles is proportional to the cubic power of the applied field strength (cubic electrophoresis) and to the second power of the particles radius; it is independent of the zeta-potential but is determined by the surface conductivity of particles. The second one, the so-called "superfast electrophoresis" is connected with the interaction of a strong outer field with a secondary diffuse layer of counterions (space charge) that is induced outside the primary (classical) diffuse EDL by the external field itself because of concentration polarization. The Dukhin-Mishchuk theory of "superfast electrophoresis" predicts quadratic dependence of the electrophoretic velocity of unipolar (ionically or electronically) conducting particles on the external field gradient and linear dependence on the particle's size in strong electric fields. These are in sharp contrast to the laws of classical electrophoresis (no dependence of V(ef) on the particle's size and linear dependence on the electric field gradient). A new method to measure the ef velocity of particles in strong electric fields is developed that is based on separation of the effects of sedimentation and electrophoresis using videoimaging and a new flowcell and use of short electric pulses. To test the "classical" non-linear electrophoresis, we have measured the ef velocity of non-conducting polystyrene, aluminium-oxide and (semiconductor) graphite particles as well as Saccharomice cerevisiae yeast cells as a
Transient Plasma Photonic Crystals for High-Power Lasers.
Lehmann, G; Spatschek, K H
2016-06-03
A new type of transient photonic crystals for high-power lasers is presented. The crystal is produced by counterpropagating laser beams in plasma. Trapped electrons and electrically forced ions generate a strong density grating. The lifetime of the transient photonic crystal is determined by the ballistic motion of ions. The robustness of the photonic crystal allows one to manipulate high-intensity laser pulses. The scheme of the crystal is analyzed here by 1D Vlasov simulations. Reflection or transmission of high-power laser pulses are predicted by particle-in-cell simulations. It is shown that a transient plasma photonic crystal may act as a tunable mirror for intense laser pulses. Generalizations to 2D and 3D configurations are possible.
Modified dynamical equation for dye doped nematic liquid crystals
Energy Technology Data Exchange (ETDEWEB)
Manohar, Rajiv, E-mail: rajlu1@rediffmail.co [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow 226007 (India); Misra, Abhishek Kumar; Srivastava, Abhishek Kumar [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow 226007 (India)
2010-04-15
Dye doped liquid crystals show changed dielectric properties in comparison to pure liquid crystals. These changes are strongly dependent on the concentration of dye. In the present work we have measured dielectric properties of standard nematic liquid crystals E-24 and its two guest host mixtures of different concentrations with Anthraquinone dye D5. The experimental results are fitted using linear response and in the light of this we have proposed some modifications in the dynamical equation for the nematic liquid crystals by introducing two new variables as dye concentration coefficients. The limitations of the proposed equation in high temperature range have also been discussed. With the help of the proposed dynamical equation for the guest-host liquid crystals (GHLCs) it is possible to predict the various parameters like rotational viscosity, dielectric anisotropy and relaxation time for GHLCs at other concentrations of dye in liquid crystals theoretically.
Hydrodynamic interactions in active colloidal crystal microrheology.
Weeber, R; Harting, J
2012-11-01
In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme significantly improves our results and allows to show that hydrodynamics strongly impacts the development of defects, the crystal regeneration, as well as the jamming behavior.
Strong Ideal Convergence in Probabilistic Metric Spaces
Indian Academy of Sciences (India)
In the present paper we introduce the concepts of strongly ideal convergent sequence and strong ideal Cauchy sequence in a probabilistic metric (PM) space endowed with the strong topology, and establish some basic facts. Next, we define the strong ideal limit points and the strong ideal cluster points of a sequence in this ...
Strong Statistical Convergence in Probabilistic Metric Spaces
Şençimen, Celaleddin; Pehlivan, Serpil
2008-01-01
In this article, we introduce the concepts of strongly statistically convergent sequence and strong statistically Cauchy sequence in a probabilistic metric (PM) space endowed with the strong topology, and establish some basic facts. Next, we define the strong statistical limit points and the strong statistical cluster points of a sequence in this space and investigate the relations between these concepts.
Directory of Open Access Journals (Sweden)
Lei Pan
2016-07-01
Full Text Available Three-dimensional photonic crystals of zirconia were prepared by electrodeposition in a colloidal crystals template following calcination at 500 °C. Scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and reflectance spectroscopy were employed to characterize the photonic crystals of zirconia. It was found that hydrated zirconium ions could penetrate the colloidal crystals template and reach the substrate easily by electrodeposition, which resulted in stronger bonding between the substrate and the as-deposited membrane. Moreover, the electrodeposited membrane had low water content, leading to a low amount of shrinkage during calcination. Both these properties could suppress detachment from the substrate upon removal of the colloidal crystals template. Therefore, the three-dimensional photonic crystals of zirconia synthesized in this study exhibited very good preservation of the ordered structures of the colloidal crystals template with a high density. A peak of reflection higher than 70% was formed in the reflectance spectrum because of the strong diffraction of the ordered structures.
A strong-topological-metal material with multiple Dirac cones
Ji, Huiwen; Pletikosić, I; Gibson, Q. D.; Sahasrabudhe, Girija; Valla, T.; Cava, R. J.
2015-01-01
We report a new, cleavable, strong-topological-metal, Zr2Te2P, which has the same tetradymite-type crystal structure as the topological insulator Bi2Te2Se. Instead of being a semiconductor, however, Zr2Te2P is metallic with a pseudogap between 0.2 and 0.7 eV above the fermi energy (EF). Inside this pseudogap, two Dirac dispersions are predicted: one is a surface-originated Dirac cone protected by time-reversal symmetry (TRS), while the other is a bulk-originated and slightly gapped Dirac cone...
Strongly modified plasmon-matter interaction with mesoscopic quantum emitters
DEFF Research Database (Denmark)
Andersen, Mads Lykke; Stobbe, Søren; Søndberg Sørensen, Anders
2011-01-01
Semiconductor quantum dots (QDs) provide useful means to couple light and matter in applications such as light-harvesting1, 2 and all-solid-state quantum information processing3, 4. This coupling can be increased by placing QDs in nanostructured optical environments such as photonic crystals...... or metallic nanostructures that enable strong confinement of light and thereby enhance the light–matter interaction. It has thus far been assumed that QDs can be described in the same way as atomic photon emitters—as point sources with wavefunctions whose spatial extent can be disregarded. Here we demonstrate...
Canonical Transform Method for Treating Strongly Anisotropy Magnets
DEFF Research Database (Denmark)
Cooke, J. F.; Lindgård, Per-Anker
1977-01-01
An infinite-order perturbation approach to the theory of magnetism in magnets with strong single-ion anisotropy is given. This approach is based on a canonical transformation of the system into one with a diagonal crystal field, an effective two-ion anisotropy, and reduced ground-state corrections....... A matrix-element matching procedure is used to obtain an explicit expression for the spin-wave energy to second order. The consequences of this theory are illustrated by an application to a simple example with planar anisotropy and an external magnetic field. A detailed comparison between the results...
2006-01-01
Our friend and colleague John Strong was cruelly taken from us by a brain tumour on 31 July, a few days before his 65th birthday. John started his career and obtained his PhD in a group from Westfield College, initially working on experiments at Rutherford Appleton Laboratory (RAL). From the early 1970s onwards, however, his research was focused on experiments in CERN, with several particularly notable contributions. The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras (a type of television camera) to record the sparks in the spark chambers. This highly automated system allowed Omega to be used in a similar way to bubble chambers. He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems. In these experiments the Westfield group joined forces with Italian colleagues to measure the form factors of the pion and the kaon, and the lifetime of some of the newly discovered charm particles. Such h...
Remnants of strong tidal interactions
International Nuclear Information System (INIS)
Mcglynn, T.A.
1990-01-01
This paper examines the properties of stellar systems that have recently undergone a strong tidal shock, i.e., a shock which removes a significant fraction of the particles in the system, and where the shocked system has a much smaller mass than the producer of the tidal field. N-body calculations of King models shocked in a variety of ways are performed, and the consequences of the shocks are investigated. The results confirm the prediction of Jaffe for shocked systems. Several models are also run where the tidal forces on the system are constant, simulating a circular orbit around a primary, and the development of tidal radii under these static conditions appears to be a mild process which does not dramatically affect material that is not stripped. The tidal radii are about twice as large as classical formulas would predict. Remnant density profiles are compared with a sample of elliptical galaxies, and the implications of the results for the development of stellar populations and galaxies are considered. 38 refs
Strongly correlated perovskite fuel cells
Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram
2016-06-01
Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.
Strong seismic ground motion propagation
International Nuclear Information System (INIS)
Seale, S.; Archuleta, R.; Pecker, A.; Bouchon, M.; Mohammadioun, G.; Murphy, A.; Mohammadioun, B.
1988-10-01
At the McGee Creek, California, site, 3-component strong-motion accelerometers are located at depths of 166 m, 35 m and 0 m. The surface material is glacial moraine, to a depth of 30.5 m, overlying homfels. Accelerations were recorded from two California earthquakes: Round Valley, M L 5.8, November 23, 1984, 18:08 UTC and Chalfant Valley, M L 6.4, July 21, 1986, 14:42 UTC. By separating out the SH components of acceleration, we were able to determine the orientations of the downhole instruments. By separating out the SV component of acceleration, we were able to determine the approximate angle of incidence of the signal at 166 m. A constant phase velocity Haskell-Thomson model was applied to generate synthetic SH seismograms at the surface using the accelerations recorded at 166 m. In the frequency band 0.0 - 10.0 Hz, we compared the filtered synthetic records to the filtered surface data. The onset of the SH pulse is clearly seen, as are the reflections from the interface at 30.5 m. The synthetic record closely matches the data in amplitude and phase. The fit between the synthetic accelerogram and the data shows that the seismic amplification at the surface is a result of the contrast of the impedances (shear stiffnesses) of the near surface materials
Thermotropic Ionic Liquid Crystals
Axenov, Kirill V.; Laschat, Sabine
2011-01-01
The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed. PMID:28879986
Thermotropic Ionic Liquid Crystals.
Axenov, Kirill V; Laschat, Sabine
2011-01-14
The last five years' achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.
Thermotropic Ionic Liquid Crystals
Axenov, Kirill V.; Laschat, Sabine
2011-01-01
The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.
DEFF Research Database (Denmark)
Lægsgaard, Jesper; Hansen, K P; Nielsen, M D
2003-01-01
Photonic crystal fibers having a complex microstructure in the transverse plane constitute a new and promising class of optical fibers. Such fibers can either guide light through total internal reflection or the photonic bandgap effect, In this paper, we review the different types and applications...... of photonic crystal fibers with particular emphasis on recent advances in the field....
Tactical Miniature Crystal Oscillator.
1980-08-01
manufactured by this process are expected to require 30 days to achieve minimum aging rates. (4) FUNDEMENTAL CRYSTAL RETRACE MEASUREMENT. An important crystal...considerable measurement time to detect differences and characterize components. Before investing considerable time in a candidate reactive element, a
Antonella Del Rosso
2012-01-01
Bent crystals can be used to deflect charged particle beams. Their use in high-energy accelerators has been investigated for almost 40 years. Recently, a bent crystal was irradiated for the first time in the HiRadMat facility with an extreme particle flux, which crystals would have to withstand in the LHC. The results were very encouraging and confirmed that this technology could play a major role in increasing the beam collimation performance in future upgrades of the machine. UA9 bent crystal tested with a laser. Charged particles interacting with a bent crystal can be trapped in channelling states and deflected by the atomic planes of the crystal lattice (see box). The use of bent crystals for beam manipulation in particle accelerators is a concept that has been well-assessed. Over the last three decades, a large number of experimental findings have contributed to furthering our knowledge and improving our ability to control crystal-particle interactions. In modern hadron colliders, su...
Shtukenberg, Alexander; Kahr, Bart
2007-01-01
Optical anomalies in crystals are puzzles that collectively constituted the greatest unsolved problems in crystallography in the 19th Century. The most common anomaly is a discrepancy between a crystal’s symmetry as determined by its shape or by X-ray analysis, and that determined by monitoring the polarization state of traversing light. These discrepancies were perceived as a great impediment to the development of the sciences of crystals on the basis of Curie’s Symmetry Principle, the grand organizing idea in the physical sciences to emerge in the latter half of the 19th Century. Optically Anomalous Crystals begins with an historical introduction covering the contributions of Brewster, Biot, Mallard, Brauns, Tamman, and many other distinguished crystallographers. From this follows a tutorial in crystal optics. Further chapters discuss the two main mechanisms of optical dissymmetry: 1. the piezo-optic effect, and 2. the kinetic ordering of atoms. The text then tackles complex, inhomogeneous crystals, and...
Lecoq, P; Gundacker, S; Hillemanns, H; Jarron, P; Knapitsch, A; Leclercq, J L; Letartre, X; Meyer, T; Pauwels, K; Powolny, F; Seassal, C
2010-01-01
The renewal of interest for Time of Flight Positron Emission Tomography (TOF PET) has highlighted the need for increasing the light output of scintillating crystals and in particular for improving the light extraction from materials with a high index of refraction. One possible solution to overcome the problem of total internal reflection and light losses resulting from multiple bouncing within the crystal is to improve the light extraction efficiency at the crystal/photodetector interface by means of photonic crystals, i.e. media with a periodic modulation of the dielectric constant at the wavelength scale. After a short reminder of the underlying principles this contribution proposes to present the very encouraging results we have recently obtained on LYSO pixels and the perspectives on other crystals such as BGO, LuYAP and LuAG. These results confirm the impressive predictions from our previously published Monte Carlo simulations. A detailed description of the sample preparation procedure is given as well ...
Organic semiconductor crystals.
Wang, Chengliang; Dong, Huanli; Jiang, Lang; Hu, Wenping
2018-01-22
Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure-property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.
Strongly interacting photons and atoms
International Nuclear Information System (INIS)
Alge, W.
1999-05-01
This thesis contains the main results of the research topics I have pursued during the my PhD studies at the University of Innsbruck and partly in collaboration with the Institut d' Optique in Orsay, France. It is divided into three parts. The first and largest part discusses the possibility of using strong standing waves as a tool to cool and trap neutral atoms in optical cavities. This is very important in the field of nonlinear optics where several successful experiments with cold atoms in cavities have been performed recently. A discussion of the optical parametric oscillator in a regime where the nonlinearity dominates the evolution is the topic of the second part. We investigated mainly the statistical properties of the cavity output of the three interactive cavity modes. Very recently a system has been proposed which promises fantastic properties. It should exhibit a giant Kerr nonlinearity with negligible absorption thus leading to a photonic turnstile device based on cold atoms in cavity. We have shown that this model suffers from overly simplistic assumptions and developed several more comprehensive approaches to study the behavior of this system. Apart from the division into three parts of different contents the thesis is divided into publications, supplements and invisible stuff. The intention of the supplements is to reach researchers which work in related areas and provide them with more detailed information about the concepts and the numerical tools we used. It is written especially for diploma and PhD students to give them a chance to use the third part of our work which is actually the largest one. They consist of a large number of computer programs we wrote to investigate the behavior of the systems in parameter regions where no hope exists to solve the equations analytically. (author)
Topics in strong Langmuir turbulence
International Nuclear Information System (INIS)
Skoric, M.M.
1981-01-01
This thesis discusses certain aspects of the turbulence of a fully ionised non-isothermal plasma dominated by the Langmuir mode. Some of the basic properties of strongly turbulent plasmas are reviewed. In particular, interest is focused on the state of Langmuir turbulence, that is the turbulence of a simple externally unmagnetized plasma. The problem of the existence and dynamics of Langmuir collapse is discussed, often met as a non-linear stage of the modulational instability in the framework of the Zakharov equations (i.e. simple time-averaged dynamical equations). Possible macroscopic consequences of such dynamical turbulent models are investigated. In order to study highly non-linear collapse dynamics in its advanced stage, a set of generalized Zakharov equations are derived. Going beyond the original approximation, the author includes the effects of higher electron non-linearities and a breakdown of slow-timescale quasi-neutrality. He investigates how these corrections may influence the collapse stabilisation. Recently, it has been realised that the modulational instability in a Langmuir plasma will be accompanied by the collisionless-generation of a slow-timescale magnetic field. Accordingly, a novel physical situation has emerged which is investigated in detail. The stability of monochromatic Langmuir waves in a self-magnetized Langmuir plasma, is discussed, and the existence of a novel magneto-modulational instability shown. The wave collapse dynamics is investigated and a physical interpretation of the basic results is given. A problem of the transient analysis of an interaction of time-dependent electromagnetic pulses with linear cold plasma media is investigated. (Auth.)
Promoting Strong Written Communication Skills
Narayanan, M.
2015-12-01
The reason that an improvement in the quality of technical writing is still needed in the classroom is due to the fact that universities are facing challenging problems not only on the technological front but also on the socio-economic front. The universities are actively responding to the changes that are taking place in the global consumer marketplace. Obviously, there are numerous benefits of promoting strong written communication skills. They can be summarized into the following six categories. First, and perhaps the most important: The University achieves learner satisfaction. The learner has documented verbally, that the necessary knowledge has been successfully acquired. This results in learner loyalty that in turn will attract more qualified learners.Second, quality communication lowers the cost per pupil, consequently resulting in increased productivity backed by a stronger economic structure and forecast. Third, quality communications help to improve the cash flow and cash reserves of the university. Fourth, having high quality communication enables the university to justify the need for high costs of tuition and fees. Fifth, better quality in written communication skills result in attracting top-quality learners. This will lead to happier and satisfied learners, not to mention greater prosperity for the university as a whole. Sixth, quality written communication skills result in reduced complaints, thus meaning fewer hours spent on answering or correcting the situation. The University faculty and staff are thus able to devote more time on scholarly activities, meaningful research and productive community service. References Boyer, Ernest L. (1990). Scholarship reconsidered: Priorities of the Professorate.Princeton, NJ: Carnegie Foundation for the Advancement of Teaching. Hawkins, P., & Winter, J. (1997). Mastering change: Learning the lessons of the enterprise.London: Department for Education and Employment. Buzzel, Robert D., and Bradley T. Gale. (1987
One-Dimensional Photonic Crystal Superprisms
Ting, David
2005-01-01
Theoretical calculations indicate that it should be possible for one-dimensional (1D) photonic crystals (see figure) to exhibit giant dispersions known as the superprism effect. Previously, three-dimensional (3D) photonic crystal superprisms have demonstrated strong wavelength dispersion - about 500 times that of conventional prisms and diffraction gratings. Unlike diffraction gratings, superprisms do not exhibit zero-order transmission or higher-order diffraction, thereby eliminating cross-talk problems. However, the fabrication of these 3D photonic crystals requires complex electron-beam substrate patterning and multilayer thin-film sputtering processes. The proposed 1D superprism is much simpler in structural complexity and, therefore, easier to design and fabricate. Like their 3D counterparts, the 1D superprisms can exhibit giant dispersions over small spectral bands that can be tailored by judicious structure design and tuned by varying incident beam direction. Potential applications include miniature gas-sensing devices.
Russia needs a strong counterpart
International Nuclear Information System (INIS)
Slovak, K.; Marcan, P.
2008-01-01
In this paper an interview with the head of OMV, Wolfgang Ruttenstorfer is published. There is extract from this interview: Q: There have been attempts to take over MOL for a quite long time. Do you think you can still succeed? Since the beginning we kept saying that this would not happen from one day to another. But it may take two to three years. But we are positive that it is justified. Q: Resistance from MOL and the Hungarian government is strong. We have tried to persuade the Hungarian government. We offered them a split company management. A part of the management would be in Budapest. We would locate the management of the largest division - the refinery, there. And of course only the best could be part of the management. We would not nominate people according to their nationality, it would not matter whether the person was Austrian, Hungarian or Slovak. We want a Central European company, not Hungarian, Romanian or Slovak company. Q: Would the transaction still be attractive if, because of pressure exercised by Brussels, you had to sell Slovnaft or your refinery in Szazhalobatta? We do not intend to sell any refineries. Q: Rumours are spreading that the Commission may ask you to sell a refinery? We do not want to speculate. Let us wait and see what happens. We do not want to sell refineries. Q: It is said that OMV is coordinating or at least consulting its attempts to acquire MOL with Gazprom. There are many rumours in Central Europe. But I can tell you this is not true. We are interested in this merger because we feel the increasing pressure exercised by Kazakhstan and Russia. We, of course, have a good relationship with Gazprom which we have had enjoyed for over forty years. As indeed Slovakia has. Q: A few weeks ago Austrian daily Wirtschaftsblatt published an article about Gazprom's interest in OMV shares. That is gossip that is more than ten years' old. Similarly to the rumours that Gazprom is a shareholder of MOL. There are no negotiations with Gazprom
Clarage, James Braun, II
1990-01-01
Methods have been developed for analyzing the diffuse x-ray scattering in the halos about a crystal's Bragg reflections as a means of determining correlations in atomic displacements in protein crystals. The diffuse intensity distribution for rhombohedral insulin, tetragonal lysozyme, and triclinic lysozyme crystals was best simulated in terms of exponential displacement correlation functions. About 90% of the disorder can be accounted for by internal movements correlated with a decay distance of about 6A; the remaining 10% corresponds to intermolecular movements that decay in a distance the order of size of the protein molecule. The results demonstrate that protein crystals fit into neither the Einstein nor the Debye paradigms for thermally fluctuating crystalline solids. Unlike the Einstein model, there are correlations in the atomic displacements, but these correlations decay more steeply with distance than predicted by the Debye-Waller model for an elastic solid. The observed displacement correlations are liquid -like in the sense that they decay exponentially with the distance between atoms, just as positional correlations in a liquid. This liquid-like disorder is similar to the disorder observed in 2-D crystals of polystyrene latex spheres, and similar systems where repulsive interactions dominate; hence, these colloidal crystals appear to provide a better analogy for the dynamics of protein crystals than perfectly elastic lattices.
Kahr, Bart; Freudenthal, John; Gunn, Erica
2010-05-18
We have made images of crystals illuminated with polarized light for almost two decades. Early on, we abandoned photosensitive chemicals in favor of digital electrophotometry with all of the attendant advantages of quantitative intensity data. Accurate intensities are a boon because they can be used to analytically discriminate small effects in the presence of larger ones. The change in the form of our data followed camera technology that transformed picture taking the world over. Ironically, exposures in early photographs were presumed to correlate simply with light intensity, raising the hope that photography would replace sensorial interpretation with mechanical objectivity and supplant the art of visual photometry. This was only true in part. Quantitative imaging accurate enough to render the separation of crystalloptical quantities had to await the invention of the solid-state camera. Many pioneers in crystal optics were also major figures in the early history of photography. We draw out the union of optical crystallography and photography because the tree that connects the inventors of photography is a structure unmatched for organizing our work during the past 20 years, not to mention that silver halide crystallites used in chemical photography are among the most consequential "crystals in light", underscoring our title. We emphasize crystals that have acquired optical properties such as linear birefringence, linear dichroism, circular birefringence, and circular dichroism, during growth from solution. Other crystalloptical effects were discovered that are unique to curiously dissymmetric crystals containing embedded oscillators. In the aggregate, dyed crystals constitute a generalization of single crystal matrix isolation. Simple crystals provided kinetic stability to include guests such as proteins or molecules in excited states. Molecular lifetimes were extended for the preparation of laser gain media and for the study of the photodynamics of single
Stevens, K W
2014-01-01
There have been many demonstrations, particularly for magnetic impurity ions in crystals, that spin-Hamiltonians are able to account for a wide range of experimental results in terms of much smaller numbers of parameters. Yet they were originally derived from crystal field theory, which contains a logical flaw; electrons on the magnetic ions are distinguished from those on the ligands. Thus there is a challenge: to replace crystal field theory with one of equal or greater predictive power that is based on a surer footing. The theory developed in this book begins with a generic Hamiltonian, on
Silumins alloy crystallization
Directory of Open Access Journals (Sweden)
S. Pietrowski
2009-07-01
Full Text Available This paper presents the results of research, by ATD method, of hypo-, near- and hyperutectic silumins crystallization containing the following alloying additives: Mg, Ni, Cu, Cr, Mo, W, V. It has been shown that, depending on their concentration may crystallize pre-eutectic or eutectic multicomponent phases containing these alloy additives. It has been revealed that any subsequent crystallizable phase nucleate and grows near the liquid/former crystallized phase interface. In multiphases compound also falls the silicon, resulting in a reduction in its quantity and the fragmentation in the eutectic mixture. As a result, it gets a high hardness of silumins in terms of 110-220HB.
Gorishnyy, T; Ullal, C K; Maldovan, M; Fytas, G; Thomas, E L
2005-03-25
In this Letter we propose the use of hypersonic phononic crystals to control the emission and propagation of high frequency phonons. We report the fabrication of high quality, single crystalline hypersonic crystals using interference lithography and show that direct measurement of their phononic band structure is possible with Brillouin light scattering. Numerical calculations are employed to explain the nature of the observed propagation modes. This work lays the foundation for experimental studies of hypersonic crystals and, more generally, phonon-dependent processes in nanostructures.
Energy flow in photonic crystal waveguides
DEFF Research Database (Denmark)
Søndergaard, Thomas; Dridi, Kim
2000-01-01
Theoretical and numerical investigations of energy flow in photonic crystal waveguides made of line defects and branching points are presented. It is shown that vortices of energy flow may occur, and the net energy flow along: the line defect is described via the effective propagation velocity....... Single-mode and multimode operations are studied, and dispersion relations are computed for different waveguide widths. Both strong positive, strong negative, and zero dispersion an possible. It is shown that geometric parameters such as the nature of the lattice, the line defect orientation, the defect...... width, and the branching-point geometry have a significant influence on the electrodynamics. These are important issues for the fabrication of photonic crystal structures....
Adaptive Liquid Crystal Windows
Energy Technology Data Exchange (ETDEWEB)
Taheri, Bahman; Bodnar, Volodymyr
2011-12-31
Energy consumption by private and commercial sectors in the U.S. has steadily grown over the last decade. The uncertainty in future availability of imported oil, on which the energy consumption relies strongly, resulted in a dramatic increase in the cost of energy. About 20% of this consumption are used to heat and cool houses and commercial buildings. To reduce dependence on the foreign oil and cut down emission of greenhouse gases, it is necessary to eliminate losses and reduce total energy consumption by buildings. To achieve this goal it is necessary to redefine the role of the conventional windows. At a minimum, windows should stop being a source for energy loss. Ideally, windows should become a source of energy, providing net gain to reduce energy used to heat and cool homes. It is possible to have a net energy gain from a window if its light transmission can be dynamically altered, ideally electronically without the need of operator assistance, providing optimal control of the solar gain that varies with season and climate in the U.S. In addition, the window must not require power from the building for operation. Resolution of this problem is a societal challenge and of national interest and will have a broad global impact. For this purpose, the year-round, allclimate window solution to provide an electronically variable solar heat gain coefficient (SHGC) with a wide dynamic range is needed. AlphaMicron, Inc. (AMI) developed and manufactured 1ft × 1ft prototype panels for the world’s first auto-adjusting Adaptive Liquid Crystal Windows (ALCWs) that can operate from sunlight without the need for external power source and demonstrate an electronically adjustable SHGC. This novel windows are based on AlphaMicron’s patented e-Tint® technology, a guesthost liquid crystal system implemented on flexible, optically clear plastic films. This technology is suitable both for OEM and aftermarket (retro-fitting) lamination to new and existing windows. Low level of
Brela, Mateusz Z.; Boczar, Marek; Malec, Leszek M.; Wójcik, Marek J.; Nakajima, Takahito
2018-05-01
Hydrogen bond networks in uracil, 1-methyluracil and 1-methyl-4-thiouracil were studied by ab initio molecular dynamics as well as analysis of the orbital interactions. The power spectra calculated by ab initio molecular dynamics for atoms involved in hydrogen bonds were analyzed. We calculated spectra by using anharmonic approximation based on the autocorrelation function of the atom positions obtained from the Born-Oppenheimer simulations. Our results show the differences between hydrogen bond networks in uracil and its methylated derivatives. The studied methylated derivatives, 1-methyluracil as well as 1-methyl-4-thiouracil, form dimeric structures in the crystal phase, while uracil does not form that kind of structures. The presence of sulfur atom instead oxygen atom reflects weakness of the hydrogen bonds that build dimers.
Non-isothermal crystallization of PET/PLA blends
International Nuclear Information System (INIS)
Chen, Huipeng; Pyda, Marek; Cebe, Peggy
2009-01-01
Binary blends of poly(ethylene terephthalate) with poly(lactic acid), PET/PLA, were studied by differential scanning calorimetry and X-ray scattering. The PET/PLA blends, prepared by solution casting, were found to be miscible in the melt over the entire composition range. Both quenched amorphous and semicrystalline blends exhibit a single, composition dependent glass transition temperature. We report the non-isothermal crystallization of (a) PET, with and without the presence of PLA crystals and (b) PLA, with and without the presence of PET crystals. PET can crystallize in all blends, regardless of whether PLA is amorphous or crystalline, and degree of crystallinity of PET decreases as PLA content increases. In contrast, PLA crystallization is strongly affected by the mobility of the PET fraction. When PET is wholly amorphous, PLA can crystallize even in 70/30 blends, albeit weakly. But when PET is crystalline, PLA cannot crystallize when its own content drops below 0.90. These different behaviors may possibly be related to the tendency of each polymer to form constrained chains, i.e., to form the rigid amorphous fraction, or RAF. PET is capable of forming a large amount of RAF, whereas relatively smaller amount of RAF forms in PLA. Like the crystals, the rigid amorphous fraction of one polymer component may inhibit the growth of crystals of the other blend partner.
Enhanced Gain in Photonic Crystal Amplifiers
DEFF Research Database (Denmark)
Ek, Sara; Semenova, Elizaveta; Hansen, Per Lunnemann
2012-01-01
We experimentally demonstrate enhanced gain in the slow-light regime of quantum well photonic crystal amplifiers. A strong gain enhancement is observed with the increase of the group refractive index, due to light slow-down. The slow light enhancement is shown in a amplified spontaneous emission....... These results are promising for short and efficient semiconductor optical amplifiers. This effect will also benefit other devices, such as mode locked lasers....
Ultrabroadband terahertz spectroscopy of a liquid crystal
DEFF Research Database (Denmark)
Vieweg, N.; Fischer, B. M.; Reuter, M.
2012-01-01
Liquid crystals (LCs) are becoming increasingly important for applications in the terahertz frequency range. A detailed understanding of the spectroscopic parameters of these materials over a broad frequency range is crucial in order to design customized LC mixtures for improved performance. We p...... show that the spectra are dominated by multiple strong spectral features mainly at frequencies above 4 THz, originating from intramolecular vibrational modes of the weakly LC molecules....
Photonic crystal fibres in the market
DEFF Research Database (Denmark)
Broeng, Jes; Laurila, Marko; Noordegraaf, Danny
2011-01-01
Photonic crystal fibres (PCFs) emerged as a research topic in the mid 1990'ies [1]. Today, 15 years later, these fibres are increasing deployed in various commercial markets. Here, we will address three of these markets; medical imaging, materials processing and sensors. We will describe how...... the PCFs provide radical improvements and illustrate the strong diversity in the evolution of PCFs to serve these different markets....
Smalyukh, Ivan I.
2018-03-01
Colloids are abundant in nature, science, and technology, with examples ranging from milk to quantum dots and the colloidal atom paradigm. Similarly, liquid crystal ordering is important in contexts ranging from biological membranes to laboratory models of cosmic strings and liquid crystal displays in consumer devices. Some of the most exciting recent developments in both of these soft matter fields emerge at their interface, in the fast-growing research arena of liquid crystal colloids. Mesoscale self-assembly in such systems may lead to artificial materials and to structures with emergent physical behavior arising from patterning of molecular order and nano- or microparticles into precisely controlled configurations. Liquid crystal colloids show exceptional promise for new discovery that may impinge on composite material fabrication, low-dimensional topology, photonics, and so on. Starting from physical underpinnings, I review the state of the art in this fast-growing field, with a focus on its scientific and technological potential.
International Nuclear Information System (INIS)
Poirier, J.-P.
1988-01-01
Creep mechanisms for metals, ceramics and rocks, effect of pressure and temperature on deformation processes are considered. The role of crystal defects is analysed, different models of creep are described. Deformation mechanisms maps for different materials are presented
International Nuclear Information System (INIS)
Schweke, D.; Brauer, B.; Gerber, R.B.; Haas, Y.
2007-01-01
The infrared spectrum of N-phenylpyrrole (PP) was measured in the gas phase and in an argon matrix, and the Raman spectrum was obtained in a single crystal. The measured matrix shifts are found to be small: many bands are not split, and the shifts from the gas phase values are less than 1%. Splitting to two sub-bands is observed for some bands, indicating the presence of two major trapping sites, in agreement with previous predictions. The spectra are analyzed with the help of harmonic calculations on the free molecule and on its adduct with one or two argon atoms, and anharmonic frequency calculations on the free molecule. Harmonic frequencies were obtained at the MP2/cc-pVDZ and DFT-B3LYP/cc-pVDZ levels. Anharmonic frequencies were obtained by the correlation-corrected vibrational self-consistent field (CC-VSCF) method with a variant of the PM3 semiempirical electronic structure method, calibrated for much improved spectroscopic accuracy. The potential surfaces used in the CC-VSCF calculation obtained by adjusting standard PM3 surfaces so that they provide harmonic frequencies that are comparable to those obtained at the DFT-B3LYP/cc-pVDZ level. Agreement between the experimental and theoretical results is in general very good, allowing the assignments of most bands. The harmonic frequency calculations of PP-Ar clusters, at the MP2/cc-pVDZ level show that the environment can greatly affect the intensities of some of the transitions, which is in accord with experiment
Thermotropic Ionic Liquid Crystals
Directory of Open Access Journals (Sweden)
Sabine Laschat
2011-01-01
Full Text Available The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.
Optical switching in nonlinear photonic crystals lightly doped with nanostructures
Energy Technology Data Exchange (ETDEWEB)
Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Lipson, R H [Department of Chemistry, University of Western Ontario, London, ON N6A 5B7 (Canada)
2008-01-14
A possible switching mechanism has been investigated for nonlinear photonic crystals doped with an ensemble of non-interacting three-level nanoparticles. In this scheme, an intense pump laser field is used to change the refractive index of the nonlinear photonic crystal while a weaker probe field monitors an absorption transition in the nanoparticles. In the absence of the strong laser field the system transmits the probe field when the resonance energy of the nanoparticles lies near the edge of the photonic band gap due to strong coupling between the photonic crystal and the nanoparticles. However, upon application of an intense pump laser field the system becomes absorbing due to a band edge frequency shift that arises due to a nonlinear Kerr effect which changes the refractive index of the crystal. It is anticipated that the optical switching mechanism described in this work can be used to make new types of photonic devices.
Single Crystal Diffuse Neutron Scattering
Directory of Open Access Journals (Sweden)
Richard Welberry
2018-01-01
Full Text Available Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.
Theory of Vortex Crystal Formation in Two-Dimensional Turbulence
Jin, D. Z.
1999-11-01
The free relaxation of inviscid, incompressible 2D turbulence is often dominated by strong vortices (coherent patches of intense vorticity) that move chaotically and merge. However, recent experiments(K.S. Fine et al., Phys. Rev. Lett. 75), 3277 (1995). with pure electron plasmas have found that freely relaxing turbulent flows with a single sign of vorticity can spontaneously form ``vortex crystals'' -- symmetric, stable arrays of strong vortices that are immersed in a low vorticity background. In this talk we discuss how these complex equilibria can form from 2D turbulence. First, we formulate a statistical theory of the vortex crystals. We show that vortex crystals are well described as ``regional'' maximum fluid entropy (RMFE) states, which are equilibrium states reached through ergodic mixing of the background by the strong vortices.(D.Z. Jin and D.H.E. Dubin, Phys. Rev. Lett. 80), 4434 (1998). Given the dynamically conserved quantities as well as the number and the vorticity distributions of the strong vortices, the theory predicts the positions of the strong vortices and the coarse-grained vorticity distribution of the background. These predictions agree well with the observed vortex crystals. Second, we examine the formation process of the vortex crystals in more detail. In the RMFE theory, the vortex crystal equilibrium can only be predicted if the number Nc of the strong vortices in the final state is given. Here, we estimate Nc from the characteristics of the early turbulent flow. The estimate relies on the idea that vortex crystals form because the chaotic motions of the strong vortices are ``cooled'' due to mixing of the background by the vortices. When the rate of cooling is faster than the rate of pairwise mergers, the vortices fall into a crystal pattern before they can merge. We estimate the merger rate from the observed power law decay of the number of strong vortices in the early stages of the flow, and the cooling rate from the rate of mixing of
2007-01-01
The end-caps of the CMS electromagnetic calorimeter (ECAL) take shape as the first quadrant was completed on Wednesday 3 October. 1831 crystals, organised into five by five blocks named ‘supercrystals’, make up the first quadrant of Dee 1.With the 61,200-crystal barrel of its electromagnetic calorimeter (ECAL) complete, CMS is now building the endcaps, on the tenth anniversary of their initial design. Crystals for the endcaps were the last to be made, so the race is now on to have them all in place and ready for the turn-on of the LHC next year. Assembly of the first of eight quadrants began in June and crystal mounting was completed on Wednesday 3 October. Each crystal is transparent, has a volume just larger than a CERN coffee cup yet weighs a huge 1.5kg. 1831 of these lead tungstate crystals went into the first quadrant from a total 14,648 in the endcaps. The lead and tungsten account for 86% of each crystal’s weight, but as project leader Dave Cockerill expl...
An unusually strong resonant phonon scattering by 3-d impurities in II-VI semiconductors
Energy Technology Data Exchange (ETDEWEB)
Lonchakov, A.T.; Sokolov, V.I.; Gruzdev, N.B. [Institute of Metal Physics, Russian Academy of Sciences, Ural Branch, S. Kovalevskaya Str. 18, 620219 Ekaterinburg (Russian Federation)
2004-11-01
Low temperature phonon heat conductivity was measured for ZnSe and ZnS crystals, doped with 3-d impurities. A strong resonance-like phonon scattering by 3-d ions with orbitally degenerate ground state was observed. The Jahn-Teller effect is proposed as the reason of the strong resonance-like behaviour of heat conductivity. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Khine, Y. Y.; Walker, J. S.
1996-08-01
Centrifugal pumping flows are produced in the melt by the rotations of crystal and crucible during the Czochralski growth of silicon crystals. This paper treats the centrifugal pumping effects with a steady, strong, non-uniform axisymmetric magnetic field. We consider a family of magnetic fields ranging from a uniform axial field to a "cusp" field, which has a purely radial field at the crystal-melt interface and free surface. We present the numerical solutions for the centrifugal pumping flows as the magnetic field is changed continuously from a uniform axial field to a cusp one, and for arbitrary Hartmann number. Since the perfect alignment between the local magnetic field vector and the crystal-melt interface or free surface is not likely, we also investigate the effects of a slight misalignment.
Energy Technology Data Exchange (ETDEWEB)
Albert, S.; Pradel, A.; Ribes, M. [CNRS Montpellier Univ., 34 (France). Inst. Charles Gerhardt Montpellier; Pillet, S.; Lecomte, C. [CNRS Nancy Univ., 54 - Vandoeuvre-les-Nancy (France). Lab. de Cristallographie et de Modelisation des Materiaux Mineraux et Biologiques
2008-02-15
A temperature-dependent structural investigation of the substituted argyrodite Ag{sub 7}GeSe{sub 5}I has been carried out on a single crystal from 15 to 475 K, in steps of 50 K, and correlated to its conductivity properties. The argyrodite crystallizes in a cubic cell with the F anti 43m space group. The crystal structure exhibits high static and dynamic disorder which has been efficiently accounted for using a combination of (i) Gram- Charlier development of the Debye-Waller factors for iodine and silver, and (ii) a split-atom model for Ag{sup +} ions. An increased delocalization of the mobile d{sup 10} Ag{sup +} cations with temperature has been clearly shown by the inspection of the joint probability-density functions; the corresponding diffusion pathways have been determined. (orig.)
Screening and Crystallization Plates for Manual and High-throughput Protein Crystal Growth
Thorne, Robert E. (Inventor); Berejnov, Viatcheslav (Inventor); Kalinin, Yevgeniy (Inventor)
2010-01-01
In one embodiment, a crystallization and screening plate comprises a plurality of cells open at a top and a bottom, a frame that defines the cells in the plate, and at least two films. The first film seals a top of the plate and the second film seals a bottom of the plate. At least one of the films is patterned to strongly pin the contact lines of drops dispensed onto it, fixing their position and shape. The present invention also includes methods and other devices for manual and high-throughput protein crystal growth.
Direct detection of antihydrogen atoms using a BGO crystal
Energy Technology Data Exchange (ETDEWEB)
Nagata, Y. [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, 184-8588 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Kuroda, N., E-mail: kuroda@phys.c.u-tokyo.ac.jp [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Ohtsuka, M. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Leali, M.; Lodi-Rizzini, E.; Mascagna, V. [Dipartimento di Ingegneria dell' Informazione, Universitá di Brescia, Brescia 25133 (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, Brescia 25133 (Italy); Tajima, M.; Torii, H.A. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Zurlo, N. [Dipartimento di Ingegneria dell' Informazione, Universitá di Brescia, Brescia 25133 (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, Brescia 25133 (Italy); Matsuda, Y. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Venturelli, L. [Dipartimento di Ingegneria dell' Informazione, Universitá di Brescia, Brescia 25133 (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, Brescia 25133 (Italy); Yamazaki, Y. [Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan)
2016-12-21
The ASACUSA collaboration has developed a detector consisting of a large size BGO crystal to detect an atomic antihydrogen beam, and performed the direct detection of antihydrogen atoms. Energy spectra from antihydrogen annihilation on the BGO crystal are discussed in comparison to simulation results from the GEANT4 toolkit. Background mainly originating from cosmic rays were strongly suppressed by analyzing the energy deposited in the BGO and requiring a multiplicity of charged pions. Thus antihydrogen events were identified.
New developments in flexible cholesteric liquid crystal displays
Schneider, Tod; Davis, Donald J.; Franklin, Sean; Venkataraman, Nithya; McDaniel, Diaz; Nicholson, Forrest; Montbach, Erica; Khan, Asad; Doane, J. William
2007-02-01
Flexible Cholesteric liquid crystal displays have been rapidly maturing into a strong contender in the flexible display market. Encapsulation of the Cholesteric liquid crystal permits the use of flexible plastic substrates and roll-to-roll production. Recent advances include ultra-thin displays, laser-cut segmented displays of variable geometry, and smart card applications. Exciting technologies such as simultaneous laser-edge sealing and singulation enable high volume production, excellent quality control and non-traditional display geometries and formats.
A strongly coupled open system with a non-linear bath: fluctuation-dissipation and Langevin dynamics
Bhadra, Chitrak
2018-03-01
The study of Langevin dynamics and fluctuation-dissipation relation (FDR) for a generic probe system (represented by a mass M ), bilinearly coupled to a bath of harmonic oscillators, has been a standard paradigm for the microscopic theory of stochastic processes for several decades. The question that we probe in this paper is, how robust the structure of the classical FDR is, when one replaces the harmonic bath by an anharmonic one in the limit of strong system-bath coupling? Such a picture carries the signature of the probe system in the zeroth order through a nonlocal time kernel. We observe that the two-time noise correlations hold a rich structure from which the usual FDR emerges only in the leading order of perturbation. Beyond this order, multiple time scales and nontrivial dependence on the temperature starts to manifest. These new aspects conspire to break the time-translational invariance of the noise-correlations. Several other interesting features show up and we discuss them methodically through rigorous calculations order-by-order in perturbation. This formalistic derivation along with a specific example of non-linearity can be easily applied to a huge range of processes and statistical observables that fall under the purview of a system-reservoir theory.
Hoekstra, Hugo; Yudistira, D.; Stoffer, Remco
2005-01-01
Structures in channel or slab waveguides, applied deliberately or due to imperfections, may lead to strong modal losses, corresponding to the excitation of radiation modes. As an example, losses are generally very large in slab photonic crystal (PhC) impurity waveguides (WGs) due to the combined
DEFF Research Database (Denmark)
Lundeman, Jesper Holm; Jensen, Ole Bjarlin; Andersen, Peter E.
2009-01-01
We present a measurement series of the efficiency of periodically poled KTP used for second-harmonic generation in an external phase-locked cavity. Due to the high absorption (0.01 cm^−1) in the PPKTP crystal at the pump wavelength a strong thermal dephasing of the periodically poled grating...
Influence of impurities on the surface morphology of the TIBr crystal semiconductor
International Nuclear Information System (INIS)
Santos, Robinson A. dos; Silva, Julio B. Rodrigues da; Martins, Joao F.T.; Ferraz, Caue de M.; Costa, Fabio E. da; Mesquita, Carlos H. de; Hamada, Margarida M.; Gennari, Roseli F.
2013-01-01
The impurity effect in the surface morphology quality of TlBr crystals was evaluated, aiming a future application of these crystals as room temperature radiation semiconductor detectors. The crystals were purified and grown by the Repeated Bridgman technique. Systematic measurements were carried out for determining the stoichiometry, structure orientation, surface morphology and impurity of the crystal. A significant difference in the crystals impurity concentration was observed for almost all impurities, compared to those found in the raw material. The crystals wafer grown twice showed a surface roughness and grains which may be due to the presence of impurities on the surface, while those obtained with crystals grown three times presented a more uniform surface: even though, a smaller roughness was still observed. It was demonstrated that the impurities affect strongly the surface morphology quality of crystals. (author)
Two-dimensionally confined topological edge states in photonic crystals
International Nuclear Information System (INIS)
Barik, Sabyasachi; Miyake, Hirokazu; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad
2016-01-01
We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three-dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters. (paper)
Hydrothermal crystallization of zirconia and zirconia solid solutions
International Nuclear Information System (INIS)
Pyda, W.; Haberko, K.; Bucko, M.M.
1991-01-01
Zirconia as well as yttria-zirconia and calcia-zirconia solid-solution powders were crystallized under hydrothermal conditions from (co)precipitated hydroxides. The morphology of the power particles is strongly dependent on the crystallization conditions. The powders crystallized in a water solution of Na, K, and Li hydroxides show elongated particles of much larger sizes than those which result from the process carried out in pure water or a water solution of Na, K, or Li chlorides. The shapes of the latter particles are isometric. In this paper the growth mechanism of the elongated particles is suggested
Inkjet printing of single-crystal films.
Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo
2011-07-13
The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. 'Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm(2) V(-1) s(-1). This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.
Production and several properties of single crystal austenitic stainless steels
International Nuclear Information System (INIS)
Okamoto, Kazutaka; Yoshinari, Akira; Kaneda, Junya; Aono, Yasuhisa; Kato, Takahiko
1998-01-01
The single crystal austenitic stainless steels Type 316L and 304L were grown in order to improve the resistance to stress corrosion cracking (SCC) using a unidirectional solidification method which can provide the large size single crystals. The mechanical properties and the chemical properties were examined. The orientation and temperature dependence of tensile properties of the single crystals were measured. The yield stress of the single crystal steels are lower than those of the conventional polycrystal steels because of the grain boundary strength cannot be expected in the single crystal steels. The tensile properties of the single crystal austenitic stainless steel Type 316L depend strongly on the orientation. The tensile strength in orientation are about 200 MPa higher than those in the and orientations. The microstructure of the single crystal consists of a mixture of the continuous γ-austenitic single crystal matrix and the δ-ferrite phase so that the effects of the γ/δ boundaries on the chemical properties were studied. The effects of the δ-ferrite phases and the γ/δ boundaries on the resistance to SCC were examined by the creviced bent beam test (CBB test). No crack is observed in all the CBB test specimens of the single crystals, even at the γ/δ boundaries. The behavior of the radiation induced segregation (RIS) at the γ/δ boundaries in the single crystal austenitic stainless steel Type 316L was evaluated by the electron irradiation test in the high voltage electron microscope (HVEM). The depletion of oversized solute chromium at the γ/δ boundary in the single crystal austenitic stainless steel Type 316L is remarkably lower than that at the grain boundary in the polycrystalline-type 316L. (author)
Strong Bisimilarity of Simple Process Algebras
DEFF Research Database (Denmark)
Srba, Jirí
2003-01-01
We study bisimilarity and regularity problems of simple process algebras. In particular, we show PSPACE-hardness of the following problems: (i) strong bisimilarity of Basic Parallel Processes (BPP), (ii) strong bisimilarity of Basic Process Algebra (BPA), (iii) strong regularity of BPP, and (iv......) strong regularity of BPA. We also demonstrate NL-hardness of strong regularity problems for the normed subclasses of BPP and BPA. Bisimilarity problems of simple process algebras are introduced in a general framework of process rewrite systems, and a uniform description of the new techniques used...
DEFF Research Database (Denmark)
Petersen, Sidsel Rübner; Alkeskjold, Thomas Tanggaard; Olausson, Christina Bjarnal Thulin
2014-01-01
The parametric gain range of a degenerate four-wave mixing process is determined in the undepleted pump regime. The gain range is considered with and without taking the mode field distributions of the four-wave mixing components into account. It is found that the mode field distributions have...
Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper
2014-08-15
The parametric gain range of a degenerate four-wave mixing process is determined in the undepleted pump regime. The gain range is considered with and without taking the mode field distributions of the four-wave mixing components into account. It is found that the mode field distributions have to be included to evaluate the parametric gain correctly in dispersion-tailored speciality fibers and that mode profile engineering can provide a way to increase the parametric gain range.
Downstream Processability of Crystal Habit-Modified Active Pharmaceutical Ingredient
DEFF Research Database (Denmark)
Pudasaini, Nawin; Upadhyay, Pratik Pankaj; Parker, Christian Richard
2017-01-01
Efficient downstream processing of active pharmaceutical ingredients (APIs) can depend strongly on their particulate properties, such as size and shape distributions. Especially in drug products with high API content, needle-like crystal habit of an API may show compromised flowability and tablet......Efficient downstream processing of active pharmaceutical ingredients (APIs) can depend strongly on their particulate properties, such as size and shape distributions. Especially in drug products with high API content, needle-like crystal habit of an API may show compromised flowability...
Application of strong phosphoric acid to radiochemistry
International Nuclear Information System (INIS)
Terada, Kikuo
1977-01-01
Not only inorganic and organic compounds but also natural substrances, such as accumulations in soil, are completely decomposed and distilled by heating with strong phosphoric acid for 30 to 50 minutes. As applications of strong phosphoric acid to radiochemistry, determination of uranium and boron by use of solubilization effect of this substance, titration of uranyl ion by use of sulfuric iron (II) contained in this substance, application to tracer experiment, and determination of radioactive ruthenium in environmental samples are reviewed. Strong phosphoric acid is also applied to activation analysis, for example, determination of N in pyrographite with iodate potassium-strong phosphoric acid method, separation of Os and Ru with sulfuric cerium (IV) - strong phosphoric acid method or potassium dechromate-strong phosphoric acid method, analysis of Se, As and Sb rocks and accumulations with ammonium bromide, sodium chloride and sodium bromide-strong phosphoric acid method. (Kanao, N.)
Navrotsky, Alexandra
Thermodynamics of Crystals is a gold mine of a references bargain with more derivations of useful equations per dollar, or per page, than almost any other book I know. Useful to whom? To the solid state physicist, the solid state chemist working the geophysicist, the rock mechanic, the mineral physicist. Useful for what? For lattice dynamics, crystal potentials, band structure. For elegant, rigorous, and concise derivations of fundamental equations. For comparison of levels of approximation. For some data and physical insights, especially for metals and simple halides. This book is a reissue, with some changes and additions, of a 1970 treatise. It ages well, since the fundamentals do not change.
DEFF Research Database (Denmark)
Bjarklev, Anders Overgaard; Broeng, Jes; Sanchez Bjarklev, Araceli
Photonic crystal fibres represent one of the most active research areas today in the field of optics. The diversity of applications that may be addressed by these fibres and their fundamental appeal, by opening up the possibility of guiding light in a radically new way compared to conventional...... optical fibres, have spun an interest from almost all areas of optics and photonics. The aim of this book is to provide an understanding of the different types of photonic crystal fibres and to outline some of the many new and exciting applications that these fibres offer. The book is intended for both...
Palacios, Jordana K.; Zhao, Junpeng; Hadjichristidis, Nikolaos; Mü ller, Alejandro J.
2017-01-01
PEO-b-PCL-b-PLLA triblock terpolymers are fascinating triple-crystalline materials. In this work, the isothermal crystallization kinetics of these terpolymers evaluated by differential scanning calorimetry (DSC) is presented for the first time and compared to analogous PCL-b-PLLA diblock copolymers and to PLLA, PCL, and PEO homopolymers. The results are complemented by in situ SAXS/WAXS synchrotron experiments. One-, two-, and three-step crystallization protocols were employed to study the crystallization kinetics of the blocks. At PLLA block crystallization temperatures, both PCL and PEO molten chains caused a strong plasticizing effect on the PLLA block crystallization, and the overall crystallization rate of the PLLA block in the terpolymers was higher than that in the PLLA-b-PCL diblock copolymers. In the case of the PCL block, the crystallization was followed after PLLA was fully crystallized (two-step crystallization). A nucleating effect induced by the previously formed PLLA crystals was observed. However, an antiplasticizing effect on PCL crystallization was detected if the sample is quenched directly from the melt to the PCL crystallization temperature (one-step crystallization). Finally, the crystallization of the PEO block was followed after PLLA and PCL had fully crystallized (three-step crystallization). The PEO crystallization rate highly decreased due to the confinement imposed by the previously formed PLLA and PCL crystals. Complex competitive effects such as plasticization, nucleation, antiplasticization, and confinement occurred during the isothermal crystallization of tricrystalline PEO-b-PCL-b-PLLA triblock terpolymers.
Palacios, Jordana K.
2017-12-05
PEO-b-PCL-b-PLLA triblock terpolymers are fascinating triple-crystalline materials. In this work, the isothermal crystallization kinetics of these terpolymers evaluated by differential scanning calorimetry (DSC) is presented for the first time and compared to analogous PCL-b-PLLA diblock copolymers and to PLLA, PCL, and PEO homopolymers. The results are complemented by in situ SAXS/WAXS synchrotron experiments. One-, two-, and three-step crystallization protocols were employed to study the crystallization kinetics of the blocks. At PLLA block crystallization temperatures, both PCL and PEO molten chains caused a strong plasticizing effect on the PLLA block crystallization, and the overall crystallization rate of the PLLA block in the terpolymers was higher than that in the PLLA-b-PCL diblock copolymers. In the case of the PCL block, the crystallization was followed after PLLA was fully crystallized (two-step crystallization). A nucleating effect induced by the previously formed PLLA crystals was observed. However, an antiplasticizing effect on PCL crystallization was detected if the sample is quenched directly from the melt to the PCL crystallization temperature (one-step crystallization). Finally, the crystallization of the PEO block was followed after PLLA and PCL had fully crystallized (three-step crystallization). The PEO crystallization rate highly decreased due to the confinement imposed by the previously formed PLLA and PCL crystals. Complex competitive effects such as plasticization, nucleation, antiplasticization, and confinement occurred during the isothermal crystallization of tricrystalline PEO-b-PCL-b-PLLA triblock terpolymers.
Protein Crystals as Novel Catalytic Materials.
Margolin, Alexey L.; Navia, Manuel A.
2001-06-18
In this era of molecular biology, protein crystallization is often considered to be a necessary first step in obtaining structural information through X-ray diffraction analysis. In a different light, protein crystals can also be thought of as materials, whose chemical and physical properties make them broadly attractive and useful across a larger spectrum of disciplines. The full potential of these protein crystalline materials has been severely restricted in practice, however, both by their inherent fragility, and by strongly held skepticism concerning their routine and predictable growth, formulation, and practical application. Fortunately, these problems have turned out to be solvable. A systematic exploration of the biophysics and biochemistry of protein crystallization has shown that one can dependably create new protein crystalline materials more or less at will. In turn, these crystals can be readily strengthened, both chemically and mechanically, to make them suitable for practical commercialization. Today, these novel materials are used as industrial catalysts on a commercial scale, in bioremediation and "green chemistry" applications, and in enantioselective chromatography of pharmaceuticals and fine chemicals. In the near future, their utility will expand, to include the purification of protein drugs, formulation of direct protein therapeutics, and development of adjuvant-less vaccines.
A study of RHIC crystal collimation
International Nuclear Information System (INIS)
Trbojevic, D.; Harrison, M.; Parker, B.; Thompson, P.; Stevens, A.; Biryukov, V.; Mokhov, N.; Drozhdin, A.
1998-01-01
The Relativistic Heavy Ion Collider (RHIC) will experience increasing longitudinal and transverse heavy ion emittances, mostly due to intra-beam scattering (IBS). The experiments in RHIC are expected to not only have reduced luminosities due to IBS but also background caused by beam halo. Primary betatron collimators will be used to remove the large amplitude particles. The efficiency of the primary collimator in RHIC strongly depends on the alignment of the jaws which needs to be within about ten micro-radians for the optimum conditions. As proposed by V. biryukov bent crystals could be used to improve the efficiency of an existing collimation system by installing them upstream of the collimator jaws. Bent crystals have been successfully used in SPS, Protvino and Fermilab for extraction of the beam particles channeled through them. This study examines possible improvements of the primary collimator system for heavy ions at RHIC by use of bent crystals. Bent crystals will reduce the collimator jaws alignment requirement and will increase collimator efficiency thereby reducing detector background
Spall response of single-crystal copper
Turley, W. D.; Fensin, S. J.; Hixson, R. S.; Jones, D. R.; La Lone, B. M.; Stevens, G. D.; Thomas, S. A.; Veeser, L. R.
2018-02-01
We performed a series of systematic spall experiments on single-crystal copper in an effort to determine and isolate the effects of crystal orientation, peak stress, and unloading strain rate on the tensile spall strength. Strain rates ranging from 0.62 to 2.2 × 106 s-1 and peak shock stresses in the 5-14 GPa range, with one additional experiment near 50 GPa, were explored as part of this work. Gun-driven impactors, called flyer plates, generated flat top shocks followed by spall. This work highlights the effect of crystal anisotropy on the spall strength by showing that the spall strength decreases in the following order: [100], [110], and [111]. Over the range of stresses and strain rates explored, the spall strength of [100] copper depends strongly on both the strain rate and shock stress. Except at the very highest shock stress, the results for the [100] orientation show linear relationships between the spall strength and both the applied compressive stress and the strain rate. In addition, hydrodynamic computer code simulations of the spall experiments were performed to calculate the relationship between the strain rate near the spall plane in the target and the rate of free surface velocity release during the pullback. As expected, strain rates at the spall plane are much higher than the strain rates estimated from the free surface velocity release rate. We have begun soft recovery experiments and molecular dynamics calculations to understand the unusual recompression observed in the spall signature for [100] crystals.
Najbauer, Eszter E; Bazsó, Gábor; Apóstolo, Rui; Fausto, Rui; Biczysko, Malgorzata; Barone, Vincenzo; Tarczay, György
2015-08-20
The conformers of α-serine were investigated by matrix-isolation IR spectroscopy combined with NIR laser irradiation. This method, aided by 2D correlation analysis, enabled unambiguously grouping the spectral lines to individual conformers. On the basis of comparison of at least nine experimentally observed vibrational transitions of each conformer with empirically scaled (SQM) and anharmonic (GVPT2) computed IR spectra, six conformers were identified. In addition, the presence of at least one more conformer in Ar matrix was proved, and a short-lived conformer with a half-life of (3.7 ± 0.5) × 10(3) s in N2 matrix was generated by NIR irradiation. The analysis of the NIR laser-induced conversions revealed that the excitation of the stretching overtone of both the side chain and the carboxylic OH groups can effectively promote conformational changes, but remarkably different paths were observed for the two kinds of excitations.
Wang Li; Sun, L L; Wang, W H; Wang, W K
2003-01-01
The pressure dependence of the acoustic velocities of a Pd sub 3 sub 9 Ni sub 1 sub 0 Cu sub 3 sub 0 P sub 2 sub 1 bulk metallic glass have been investigated up to 0.5 GPa at room temperature with the pulse echo overlap method. Two independent second-order elastic coefficients C sub 1 sub 1 and C sub 4 sub 4 and their pressure derivatives are yielded. The vibrational anharmonicity is shown by calculating both the acoustic mode Grueneisen parameters in the long-wavelength limit and the thermal Grueneisen parameter, and this result is compared with that for the Pd sub 4 sub 0 Ni sub 4 sub 0 P sub 2 sub 0 bulk glass.
The Crystal Hotel: A Microfluidic Approach to Biomimetic Crystallization.
Gong, Xiuqing; Wang, Yun-Wei; Ihli, Johannes; Kim, Yi-Yeoun; Li, Shunbo; Walshaw, Richard; Chen, Li; Meldrum, Fiona C
2015-12-02
A "crystal hotel" microfluidic device that allows crystal growth in confined volumes to be studied in situ is used to produce large calcite single crystals with predefined crystallographic orientation, microstructure, and shape by control of the detailed physical environment, flow, and surface chemistry. This general approach can be extended to form technologically important, nanopatterned single crystals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Liquid crystal boojum-colloids
International Nuclear Information System (INIS)
Tasinkevych, M; Silvestre, N M; Telo da Gama, M M
2012-01-01
Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D
Strong blue emission from zinc hydroxide carbonate nanosheets
International Nuclear Information System (INIS)
Mao, Jing; Chen, Xuemin; Ling, Tao; Du, Xiwen
2016-01-01
Zinc hydroxide carbonate (ZHC) is a typical layered salt composed of zinc hydroxide layers separated with carbonate ions and water molecules. Studies of morphology control and the constitution of functional ZHC material with intercalated ions has been widely developed. Also, ZnO can be easily obtained by anneal treatment of ZHC, and the porous structure as synthesized had great potential in gas sensors, photocatalysts and dye-sensitized solar cells. However, the optical of ZHC have rarely been investigated. In our research, a strong blue emission of ZHC is reported. The effect of growth time, annealing treatment and modification of surfactants on blue emission have been systematically studied. Combined with information of interior effect of OH groups, crystal structure and electronegativity of surfactants, a possible emission mechanism of ZHC has been proposed.
Electromagnetic processes in strong crystalline fields - NA63 Status Report
Ugerhoj, Ulrik
2009-01-01
Results obtained in the framework of the NA63 experiment cite{Ande05} at CERN are reported. Analysis of the trident production in the strong crystalline fields of single Ge crystals is completed. Yields in the random ('amorphous') orientation are in good agreement with calculations, and in the aligned case the production is enhanced by about a factor 3 compared to a Ge amorphous material. Results on the formation lengths of several microns for the production of GeV photons from ultrarelativistic electrons have been published. In 2008 we performed a measurement of resonance phenomena in structured targets and studied a possible change in restricted energy loss in thin solid state detectors, for sufficiently high values of the Lorentz factor. The plans for 2009 are to study the 'semi-bare electron' from radiation emission in thin targets and to study the spin-flip mechanisms in radiation emission, relevant for beamstrahlung phenomena in future linear colliders such as CLIC.
Directory of Open Access Journals (Sweden)
J. Piątkowski
2009-07-01
Full Text Available Adding high-melting point elements (Mo, Nb, Ni, Ti, W to complex silumins results in hardening of the latter ones, owing to the formation of new intermetallic phases of the AlxMey type, with refinement of dendrites in α solution and crystals in β phase. The hardening is also due to the effect of various inoculants. An addition of the inoculant is expected to form substrates, the crystal lattice of which, or some (privileged lattice planes and interatomic spaces should bear a strong resemblance to the crystal nucleus. To verify this statement, using binary phase equilibria systems, the coefficient of crystal lattice matching, being one of the measures of the crystallographic similarity, was calculated. A compatibility of this parameter (up to 20% may decide about the structure compatibility between the substrate and crystal which, in turn, is responsible for the effectiveness of alloy modification. Investigations have proved that, given the temperature range of their formation, the density, the lattice type, and the lattice parameter, some intermetallic phases of the AlxMey type can act as substrates for the crystallisation of aluminium and silicon, and some of the silumin hardening phases.
Laser-induced optical effects in triglycine-zinc chloride single crystals
International Nuclear Information System (INIS)
Wojciechowski, A.; Kityk, I.V.; Lakshminarayana, G.; Fuks-Janczarek, I.; Berdowski, J.; Berdowska, E.; Tylczynski, Z.
2010-01-01
The influence of irradiation by a cw 532 nm laser on the behavior of the absorption and optical second harmonic generation of triglicyne-zinc chloride crystal has been studied. Additional absorption bands correlate well with the time of the cw laser exposure. These lines occur at 260 nm, 305 nm, and, with small intensity, at 355 nm. The remaining part of the spectra shows substantially less changes. According to the performed quantum chemical simulations, one may expect that the observed dependences and the stability of the observed photoinduced changes are caused by formation of polarized electron-phonon states and the principal role should belong here to the electron-phonon anharmonicities, which cause the effects described by the non-polar third rank polar tensor like optical second harmonic generation. The increasing optical SHG signal shows a clear correlation with the behavior of the green laser-532 nm. It is important principal that for the blue laser-405 nm, the SHG effect is substantially less. This may reflect that the additional absorption maxima may be responsible for the non-linear optical effects. The effect demonstrates a slow time decay.
Hydrothermally grown zeolite crystals
International Nuclear Information System (INIS)
Durrani, S.K.; Qureshi, A.H.; Hussain, M.A.; Qazi, N.K.
2009-01-01
The aluminium-deficient and ferrosilicate zeolite-type materials were synthesized by hydrothermal process at 150-170 degree C for various periods of time from the mixtures containing colloidal reactive silica, sodium aluminate, sodium hydroxide, iron nitrate and organic templates. Organic polycation templates were used as zeolite crystal shape modifiers to enhance relative growth rates. The template was almost completely removed from the zeolite specimens by calcination at 550 degree C for 8h in air. Simultaneous thermogravimetric (TG) and differential thermal analysis (DTA) was performed to study the removal of water molecules and the amount of organic template cations occluded inside the crystal pore of zeolite framework. The 12-13% weight loss in the range of (140-560 degree C) was associated with removal of the (C/sub 3/H/sub 7/)/sub 4/ N+ cation and water molecules. X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) techniques were employed to study the structure, morphology and surface features of hydrothermally grown aluminium-deficient and ferrosilicate zeolite-type crystals. In order to elucidate the mode of zeolite crystallization the crystallinity and unit cell parameters of the materials were determined by XRD, which are the function of Al and Fe contents of zeolites. (author)
This September 19, 2016 letter from EPA approves the petition from Poet Biorefining-Lake Crystal, regarding non-grandfathered ethanol produced through a dry mill process, qualifying under the Clean Air Act for renewable fuel (D-code 6) RINs under the RFS
International Nuclear Information System (INIS)
Takami, K.
1981-01-01
An improved liquid crystal display device is described which can display letters, numerals and other necessary patterns in the night time using a minimized amount of radioactive material. To achieve this a self-luminous light source is placed in a limited region corresponding to a specific display area. (U.K.)
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 6. Soap Bubbles and Crystals. Jean E Taylor. General Article Volume 11 Issue 6 June 2006 pp 26-30. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/011/06/0026-0030. Keywords. Soap bubble ...
2011-01-03
75, pp. 3253-3256, Oct. 1995. [24] F. Benabid, J. C. Knight, and P. S. J. Russell, “Particle levitation and guidance in hollow-core photonic crystal...B. Mizaikoff, “Midinfrared sensors meet nanotechnology: Trace gas sensing with quantum cascade lasers inside photonic band-gap hollow waveguides