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Lattice Dynamics (lattice + dynamics)
Selected AbstractsCrystal Structure and Lattice Dynamics of Superionic Copper Selenide Cu2-,Se.CHEMINFORM, Issue 1 2004S. A. Danilkin Abstract For Abstract see ChemInform Abstract in Full Text. [source] Lattice dynamics of tetragonal Nd2BaZnO5JOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2007H. C. Gupta Abstract A short-range force constant model (SRFCM) has been applied to investigate the Raman and the infrared wavenumbers in Nd2BaZnO5 in its tetragonal phase of space group I4/mcm. Calculations of zone-center phonons are made with five stretching and five bending force constants. All the Raman and infrared values are then assigned to their corresponding modes. Two Raman modes are reassigned on the basis of group theoretical calculations. The calculated Raman wavenumbers exhibit good agreement with the observed values. Copyright © 2007 John Wiley & Sons, Ltd. [source] Lattice dynamics of Ca4GdO(BO3)3JOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2004M. Ma, czka Abstract Polarized Raman and IR spectra were obtained for Ca4GdO(BO3)3 crystal at ambient temperature. The assignment of the observed bands to the respective internal and external phonons is proposed on the basis of lattice dynamics calculations. This study also shows that significant LO,TO splitting exists for some internal modes. Copyright © 2004 John Wiley & Sons, Ltd. [source] Lattice dynamics of chalcopyrite semiconductors LiAlTe2, LiGaTe2 and LiInTe2PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2009A. V. Kosobutsky Abstract Within density functional perturbation theory using norm-conserving pseudopotentials and a plane-wave basis set calculations of phonon dispersion relations and densities of states of LiAlTe2, LiGaTe2 and LiInTe2 compounds being crystallized into the tetragonal chalcopyrite structure have been performed. Theoretical values of phonon mode frequencies in LiGaTe2 and LiInTe2 are in good agreement with the experimental data available for these crystals obtained by the methods of Raman and infrared spectroscopies. The similarity of the physical and chemical properties of the crystals concerned manifests itself in the similarity of their phonon spectra that are especially close to each other in low- and high-frequency ranges. Phonon modes of the upper phonon band are predominantly caused by the lithium sublattice vibrations and have an upper bound of 350,370 cm,1. In a mid-frequency range a significant downshift of the vibrational frequencies is observed on going from LiAlTe2 to LiGaTe2 and LiInTe2 that is a consequence of the third group cation mass reduction. From calculated electron density maps it follows that Li-containing chalcopyrites are characterized by a less pronounced bond between the first group cation and anion as compared with the Cu- and Ag-based analogs due to the absence of pd-hybridization. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Lattice dynamics of CuAlO2 under high pressure from ab initio calculationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007P. Rodríguez-Hernández Abstract The density functional perturbation theory is employed to study the vibrational properties of CuAlO2 under pressure. The calculations are preformed using the pseudopotential wave method and the local density approximation for the exchange-correlation (XC) potential. The d electrons of Cu are treated as valence states. We present the phonon dispersion curves. Our results are in good agreement with the available experimental Raman scattering experiments. Ab initio calculations show the presence of a dynamical instability, possibly related with the experimentally observed phase transition. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Lattice dynamics and the electromechanical properties of BaTiO3 in tetragonal phasePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006Ali Khalal Abstract A lattice dynamical formalism using the shell model (R. A. Cowley, Phys. Rev. 134, A981 (1964) [1]) is applied to ferroelectric crystal BaTiO3, in the tetragonal phase. This microscopic model includes the short-range interactions of axially symmetric type and the long-range Coulomb interactions takes into account the electronic polarizability of constituent ions. The stability conditions of crystal are used to determine several first-derivatives potential for the crystals. Zone center phonons are used for fitting. In general, we obtained the best agreement between the calculated and observed frequencies. A calculation of the oblique phonons and electromechanical coupling are presented and compared with the available experimental data. It can be seen that, the electromechanical coupling is at a maximum when the acoustic wave is polarized parallel to the polar c -axis, and there is zero coupling when the polarization is perpendicular to this axis. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Adiabatic bond charge model for lattice dynamics of ternary chalcopyrite semiconductorsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2006T. Gürel Abstract The adiabatic bond charge model of Rustagi and Weber is extended to study lattice dynamical properties of ternary chalcopyrite semiconductors AgGaS2, AgGaSe2, CuInS2, CuInSe2, CuGaS2, CuGaSe2, CuAlS2 and CuAlSe2. The new model calculations agree well with the results of Raman/IR and neutron measurements of Brillouin zone center phonon frequencies for both low and high frequency modes which was difficult for other phenomenological lattice dynamical models. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Raman spectroscopy on carbon nanotubes at high pressureJOURNAL OF RAMAN SPECTROSCOPY, Issue 7-8 2003I. Loa Abstract Raman spectroscopy has been the most extensively employed method to study carbon nanotubes at high pressures. This review covers reversible pressure-induced changes of the lattice dynamics and structure of single- and multi-wall carbon nanotubes and irreversible transformations induced by high pressures. The interplay of covalent and van der Waals bonding in single-wall nanotube bundles and a structural distortion near 2 GPa are discussed in detail. Attempts to transform carbon nanotubes into diamond and other ,superhard' phases are reviewed critically. Copyright © 2003 John Wiley & Sons, Ltd. [source] Raman Spectroscopy of Ferroelectric Thin Films and SuperlatticesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Dmitri A. Tenne Recent results of Raman spectroscopy studies of lattice dynamics and phase transitions in ferroelectric thin films and superlattices are reviewed. Raman studies of SrTiO3, BaTiO3, and BaxSr1,xTiO3 thin films in comparison with corresponding single crystals are presented; essential differences in the lattice dynamics behavior of thin films and single crystals are discussed. Application of ultraviolet Raman spectroscopy for studies of nanoscale ferroelectric heterostructures, such as BaTiO3/SrTiO3 superlattices, is demonstrated. [source] Symmetry-based analysis of the electron,phonon interaction in graphenePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009I. Milo Abstract Symmetry-based analysis of the electron,phonon interaction in graphene is performed. Some nontrivial physical properties of graphene are shown to be direct consequence of symmetry, independent on the applied dynamical model. Namely, it is found that there are vibronically uncoupled non symmetric modes which thus might be responsible for the stability of the honeycomb lattice. Symmetry also predicts vanishing of the electron,phonon interaction for quite a number of the normal displacements. Consequently, lattice dynamics along these degrees of freedom is governed by the ion repulsion which leads to the anharmonic terms, being linear in absolute elongation. In particular, this effect is attributed to the K and , points of the Brillouin zone, giving insight into origin of the Kohn anomaly. The results are further numerically confirmed within full and tight-binding density functional calculations and force constants model. [source] Optical phonons in hexagonal GaN/AlN and GaN/AlGaN superlatticesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005V. Yu. Abstract In this work, by using numerical simulation of the lattice dynamics of hexagonal GaN/AlN superlattices, the microscopic nature of the vibrational states corresponding to the most intense lines in Raman spectra has been established and the interpretation of experimental spectra has been suggested. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Proceedings of the 11th International Conference on Phonon Scattering in Condensed Matter (Phonons2004)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004Alexander Kaplyanskii The 11th International Conference on Phonon Scattering (Phonons2004) was held in St. Petersburg, Russia, 25,30 July 2004. Both theoretical and experimental results on studies in phonon physics and related phenomena were presented and discussed. Main topical areas were: Phonons in nanostructures, coherent phonons, phononic crystals and superlattices, ultrafast acoustics, solitons and nonlinear phenomena, electron,phonon interaction, phonons in glasses and disordered materials, phonon transport and imaging, quantum fluids, lattice dynamics, and Raman and neutron scattering. [source] EXAFS studies of lattice dynamics and thermal expansionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004P. Fornasini Abstract Accurate temperature-dependent EXAFS measurements can give original information on the correlation of thermal motion in crystals, not only along the bond direction (parallel Mean Square Relative Displacement, MSRD), but also within the perpendicular plane (perpendicular MSRD). This potential is demonstrated by the results obtained for copper and germanium, taken as model systems. Possible applications for investigating on the local origin of Negative Thermal Expansion are being supported by measurements on crystals with the cuprite structure. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||