LATTICE DYNAMICS OF α-LiIO3

1991 ◽  
Vol 05 (17) ◽  
pp. 1167-1173
Author(s):  
YIMIN JIANG ◽  
HONG LIN ◽  
CHENG GOU ◽  
SHIWEN NIU
Keyword(s):  
Lattice Dynamics ◽  
Molecular Crystal ◽  
Field Model ◽  
Phonon Dispersion ◽  
Normal Modes ◽  
Coulomb Force ◽  
Strong Mixing ◽  
Phonon Dispersion Curves ◽  
Good Agreement ◽  
Rigid Ion Model

The phonon dispersion curves of α- LiIO 3, which exhibit a characteristic molecular crystal behaviour, are calculated on the basis of a modified rigid-ion model in which a Born-Mayer potential is used for short-range repulsive interactions between Li ions and [Formula: see text] groups and a central force constant model is used for internal interactions in the [Formula: see text] group. The computed phonon frequencies are in good agreement with those of Raman, infrared and neutron measurements. The calculations show a strong mixing of the pre-normal modes given by Crettez et al.,4 therefore indicating that the long-range Coulomb force may change greatly the assignments previously obtained from a force-field model.

scholarly journals Lattice dynamics in CePd2Al2 and LaPd2Al2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Petr Doležal ◽  
Petr Cejpek ◽  
Satoshi Tsutsui ◽  
Koji Kaneko ◽  
Dominik Legut ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Elastic Interaction ◽  
Bound State ◽  
Dispersion Curves ◽  
Phonon Modes ◽  
Phonon Dispersion Curves ◽  
X Ray Scattering ◽  
Oppenheimer Approximation ◽  
Good Agreement

AbstractThe interaction between phonons and 4f electrons, which is forming a new quantum state (quasi-bound state) beyond Born-Oppenheimer approximation, is very prominent and lattice dynamics plays here a key role. There is only a small number of compounds in which the experimental observation suggest such a scenario. One of these compounds is CePd2Al2. Here the study of phonon dispersion curves of (Ce,La)Pd2Al2 at 1.5, 7.5, 80 and 300 K is presented. The inelastic X-ray scattering technique was used for mapping the phonon modes at X and Z points as well as in Λ and Δ directions, where the symmetry analysis of phonon modes was performed. The measured spectra are compared with the theoretical calculation, showing very good agreement. The measurements were performed in several Brillouin zones allowing the reconstruction of phonon dispersion curves. The results are discussed with respect to the magneto-elastic interaction and are compared with other cerium compounds. The phonon mode symmetry A1g was found to be unaffected by the interaction, which is in contrast to previous assumptions.

Lattice dynamics of ZnTe, CdTe, GaP, and InP

1980 ◽  
Vol 58 (3) ◽  
pp. 351-358 ◽  
Author(s):  
M. S. Kushwaha ◽  
S. S. Kushwaha
Keyword(s):  
Lattice Dynamics ◽  
Present Model ◽  
Phonon Dispersion ◽  
Model Parameters ◽  
Force Model ◽  
Phonon Dispersion Curves ◽  
Bending Force ◽  
Zinc Blende ◽  
Bond Bending ◽  
Good Agreement

An eight-parameter bond-bending force model (BBFM), recently developed by us for zinc-blende (ZB) structure, has been used to study the lattice dynamics of other compounds of the II–VI and III–V groups. The model parameters were calculated using six critical point phonon frequencies, two elastic constants, and the lattice equilibrium condition. Phonon dispersion curves, phonon density of states, and Debye-characteristic temperatures have been calculated. The comparison of theoretical and the available experimental results reveals a fairly good agreement. The merits and demerits of the present model have been discussed in full.

scholarly journals Phonon Dispersion Relations for Chromium and Tantalum

1975 ◽  
Vol 28 (1) ◽  
pp. 57 ◽  
Author(s):  
Jyoti Prakash ◽  
LP Pathak ◽  
MP Hemkar
Keyword(s):  
Force Constant ◽  
Phonon Dispersion ◽  
Normal Modes ◽  
Inelastic Neutron ◽  
Neutron Spectroscopy ◽  
Phonon Dispersion Curves ◽  
Modes Of Vibration ◽  
Experimental Values ◽  
Good Agreement ◽  
Phonon Dispersion Relations

Phonon dispersion curves for the normal modes of vibration in chromium and tantalum are calculated along the symmetry directions [100], [110] and [111] using the five force-constant model of Behari and Tripathi (1970a). The results are compared with experimental values obtained from inelastic neutron spectroscopy and reasonably good agreement is found.

scholarly journals Study of lattice dynamics of silicon

BIBECHANA ◽  
2012 ◽  
Vol 9 ◽  
pp. 13-17
Author(s):  
SRB Thapa
Keyword(s):  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Characteristic Temperature ◽  
Central Force ◽  
Phonon Dispersion Curves ◽  
Valence Force Field ◽  
Model Following ◽  
Bond Stretching ◽  
Bond Bending ◽  
Good Agreement

Lattice dynamics of Si has been investigated by using a Urey-Bradley Valence Force Field (UVFF) model which is a phenomenological model. In this model following interactions are taken into account: (i) the central force due to bond-stretching (ii) the angular force due to bond bending (iii) central force between non-bonded atoms (iv) the force due to interaction of one internal co-ordinate to adjacent internal coordinate. Calculated results of phonon dispersion curves, Debye Characteristic temperature, microscopic elastic constants and Bulk modulus of Si are compared with experimental results giving fairly good agreement. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7145BIBECHANA 9 (2013) 13-17

scholarly journals Lattice Dynamics of YBa2Cu3O6+x (x = 0·25, 0·5, 0.75)

1993 ◽  
Vol 46 (4) ◽  
pp. 535 ◽  
Author(s):  
KK Yim ◽  
J Oitmaa ◽  
MM Elcombe
Keyword(s):  
Oxygen Concentration ◽  
Density Of States ◽  
Coulomb Potential ◽  
Lattice Dynamics ◽  
Short Range ◽  
Phonon Dispersion ◽  
Normal Modes ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves

The lattice dynamics of YBa2Cu306+x with partially filled 0(4) sites is investigated using a supercell method. The model used is the lattice-dynamical shell model, which incorporates the short-range interactions and the long-range Coulomb potential as well as the polarisabilities of ions. Varying the oxygen content produces small changes throughout the spectrum of normal modes, as well as major changes in those modes with large 0(4) amplitudes. Selected phonon dispersion curves are presented, with emphasis on the variation of frequency with oxygen concentration. The nature of new modes, which appear with an increase in oxygen concentration, is investigated. The overall phonon density of states is also presented.

Influence of the static electron gas screening function on the lattice dynamics of sodium

1970 ◽  
Vol 48 (2) ◽  
pp. 183-192 ◽  
Author(s):  
D. J. W. Geldart ◽  
Roger Taylor ◽  
Y. P. Varshni
Keyword(s):  
Distribution Function ◽  
Lattice Dynamics ◽  
Phonon Frequency ◽  
Phonon Dispersion ◽  
Electron Gas ◽  
Phonon Dispersion Curves ◽  
X Ray ◽  
Debye Temperatures ◽  
Static Electron ◽  
Good Agreement

The static electron gas screening function calculated by Geldart and Taylor has been used in conjunction with the theory of Vosko, Taylor, and Keech to calculate the phonon dispersion curves, the effective calorimetric and X-ray Debye temperatures, and moments of the phonon frequency distribution function of sodium. The results which compare very favorably with those obtained using other screening functions give good agreement with experiment, indicating that the new screening function is reasonably adequate for calculations in sodium.

The crystal dynamics of cuprous halides

1982 ◽  
Vol 60 (11) ◽  
pp. 1589-1594 ◽  
Author(s):  
Manvir S. Kushwaha
Keyword(s):  
Phonon Dispersion ◽  
Characteristic Temperature ◽  
Force Model ◽  
Phonon Dispersion Curves ◽  
Debye Characteristic Temperature ◽  
Zinc Blende ◽  
Crystal Dynamics ◽  
Bond Bending ◽  
Dynamical Description ◽  
Good Agreement

The lattice dynamics of cuprous halides have been thoroughly investigated by means of an 8-parameter bond-bending force model (BBFM), recently developed and applied successfully to study phonons in various II–VI and III–V compound semiconductors having zinc-blende (ZB) structure. The application of BBFM is made to calculate the phonon dispersion relations, phonon density of states, and temperature variation of the Debye characteristic temperature [Formula: see text] of CuCl, CuBr, and CuI. The room-temperature neutron scattering measurements for phonon dispersion curves along three principal symmetry directions and calorimetric experimental data for the Debye characteristic temperature have been used to check the validity of BBFM for the three crystals. The overall good agreement between theoretical and experimental results supports its use as an appropriate model for the dynamical description of ZB crystals.

Electron Correlation Effects on the Lattice Dynamics of Sodium and Potassium

1975 ◽  
Vol 53 (16) ◽  
pp. 1507-1512 ◽  
Author(s):  
V. K. Jindal
Keyword(s):  
Dielectric Function ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Matrix Elements ◽  
Correlation Effects ◽  
Phonon Dispersion Curves ◽  
Electron Correlation Effects ◽  
Experimental Values ◽  
The One ◽  
Sodium And Potassium

The phonon dispersion curves for sodium and potassium have been calculated using the one OPW (orthogonalized plane wave) bare electron matrix elements and the dielectric function of Vashishta and Singwi. Results are compared with experimental results as well as with similar calculations using the dielectric function of Geldart and Taylor. It is found that the screening function of Vashishta and Singwi gives at least as good an agreement with experimental values as obtained from the screening function of Geldart and Taylor. The interionic potentials for these metals have also been calculated and compared with similar calculations done previously. The reason for the appreciable difference between the potentials is discussed.

Article

1998 ◽  
Vol 76 (2) ◽  
pp. 143-151
Author(s):  
J S Ononiwu
Keyword(s):  
Lattice Dynamics ◽  
Alkaline Earth ◽  
Phonon Dispersion ◽  
Earth Metal ◽  
Model Potential ◽  
Dispersion Curves ◽  
The Body ◽  
Symmetry Direction ◽  
Normal Ordering ◽  
Phonon Dispersion Curves

A phenomenological one-parameter model potential that includes sp-d hybridization and core--core exchange contributions is used to calculate the phonon dispersion curves in the lattice dynamics of the body-centered cubic alkaline-earth metal, barium. There is good overall agreement between theory and experiment, and in particular, in the [xi00] direction we obtained frequencies of the transverse dispersion curves that are lower than those of the longitudinal dispersion curves along the [100] symmetry direction thereby restoring the normal ordering of the branches.PACS Nos.: 63.20D

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