Effect of polarizability on the vibrational and thermal properties of rare gas solids

1978 ◽  
Vol 56 (7) ◽  
pp. 849-858 ◽  
Author(s):  
S. K. Jain ◽  
G. P. Srivastava
Keyword(s):  
Lattice Dynamics ◽  
Interatomic Potential ◽  
Phonon Dispersion ◽  
Zero Point ◽  
Rare Gas ◽  
Model Parameters ◽  
Point Energy ◽  
Phonon Dispersion Curves ◽  
Boundary Frequency ◽  
Experimental Values

A simple shell model theory has been developed for the study of lattice dynamics of monatomic crystals. The phonon dispersion curves and variations of heat capacities with temperature are reported for solidified krypton and argon. The model parameters have been evaluated using the recent experimental values of elastic constants, polarizability of atoms, and a zone boundary frequency in each case. The zero point effects are also included by expressing the zero point energy in terms of the interatomic potential. The agreement between the theoretical and experimental results is found to improve appreciably by incorporating polarizability of atoms.

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.

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 Dispersion of Phonons in Ideal Crystals

1969 ◽  
Vol 22 (4) ◽  
pp. 471 ◽  
Author(s):  
NP Gupta
Keyword(s):  
Experimental Data ◽  
Phonon Dispersion ◽  
Zero Point ◽  
Lattice Vibrations ◽  
Rare Gases ◽  
Point Energy ◽  
Phonon Dispersion Curves ◽  
Debye Theory ◽  
Specific Heats ◽  
Theoretical Frequency

A quasiharmonic central force rigid-atom model has been used to study the lattice vibrations of frozen rare gases. The model takes care of interactions up to fourth neighbour and estimates zero-point energy and its volume derivatives by the Debye theory of specific heats. The theoretical frequency distribution and phonon dispersion curves are found to compare reasonably well with the available experimental data. Various causes of the discrepancies and possibilities of improvement of the results are discussed.

scholarly journals Lattice Dynamics of YBa2Cu3O6+x (x = 0,1)

1992 ◽  
Vol 45 (2) ◽  
pp. 221 ◽  
Author(s):  
KK Yim ◽  
J Oitmaa ◽  
MM Elcombe
Keyword(s):  
Shell Model ◽  
Density Of States ◽  
Normal State ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Model Parameters ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves ◽  
Least Squares Fit

We report shell model based calculations of the lattice dynamics of YBa2Cu306 and YBa2Cu307. Two models are proposed for YBa2Cu306, the model parameters being obtained by a least squares fit to recent neutron scattering results. The parameters obtained are then used, with modification, to model the lattice dynamics of YBa2Cu307. Since this material has significant carrier concentration, even in the normal state we have used both screened and unscreened versions of the shell model. The screened model gives a better overall description of the lattice dynamics of YBa2Cu307. The phonon dispersion curves along the symmetry directions and the weighted phonon density of states for both YBa2Cu306 and YBa2Cu307 are presented.

On a Non-Linear Differential Equation for the Zero-point Energies of the Rare Gas Solids

1961 ◽  
Vol 57 (1) ◽  
pp. 107-114 ◽  
Author(s):  
Michael E. Fisher ◽  
I. J. Zucker
Keyword(s):  
Interatomic Potential ◽  
Characteristic Temperature ◽  
Additional Term ◽  
Zero Point ◽  
Dominant Factor ◽  
Rare Gas ◽  
Theoretical Argument ◽  
Point Energy ◽  
Linear Differential ◽  
Image Position

Domb and Salter (3) have postulated that the Debye characteristic temperature for the rare gas solids should be given by where C involves atomic constants and the atomic mass of the rare gas, r is the mean interatomic distance and Φ(r) is the interatomic potential. This formula provides a good approximation for the heavier rare gas solids but breaks down for the lighter inert elements. On the basis of Born's argument (1) that the dynamic rather than the static equilibrium positions should be considered, Domb (2) suggested that (1) might be replaced by , where the additional term is effectively the zero-point energy contribution to the lattice equilibrium. (R is the gas constant.) From experimental measurements of the Gruneisen parameter γ Domb obtained numerical values which, when substituted in the right-hand side of (2), yielded values of vD that appeared to compare favourably with direct experiments. More recently Hooton (6) considered the problem of lattice dynamics with anharmonic forces (which are the dominant factor in the lighter rare gas solids) and developed a theoretical argument which also led to Domb's equation (2).

scholarly journals Modulation of optical absorption in m-Fe1−xRuxS2 and exploring stability in new m-RuS2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
H. Joshi ◽  
M. Ram ◽  
N. Limbu ◽  
D. P. Rai ◽  
B. Thapa ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Phonon Dispersion ◽  
Applied Pressure ◽  
Orthorhombic Phase ◽  
Zero Point ◽  
Computational Method ◽  
Crystal Field Theory ◽  
Point Energy ◽  
Practical Applications ◽  
New Phase

AbstractA first-principle computational method has been used to investigate the effects of Ru dopants on the electronic and optical absorption properties of marcasite FeS2. In addition, we have also revealed a new marcasite phase in RuS2, unlike most studied pyrite structures. The new phase has fulfilled all the necessary criteria of structural stability and its practical existence. The transition pressure of 8 GPa drives the structural change from pyrite to orthorhombic phase in RuS2. From the thermodynamical calculation, we have reported the stability of new-phase under various ranges of applied pressure and temperature. Further, from the results of phonon dispersion calculated at Zero Point Energy, pyrite structure exhibits ground state stability and the marcasite phase has all modes of frequencies positive. The newly proposed phase is a semiconductor with a band gap comparable to its pyrite counterpart but vary in optical absorption by around 106 cm−1. The various Ru doped structures have also shown similar optical absorption spectra in the same order of magnitude. We have used crystal field theory to explain high optical absorption which is due to the involvement of different electronic states in formation of electronic and optical band gaps. Lӧwdin charge analysis is used over the customarily Mulliken charges to predict 89% of covalence in the compound. Our results indicate the importance of new phase to enhance the efficiency of photovoltaic materials for practical applications.

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

Zero-Point Energy of Rare-Gas Crystals to Orderη4

1973 ◽  
Vol 8 (12) ◽  
pp. 5967-5971 ◽  
Author(s):  
K. G. Aggarwal
Keyword(s):  
Zero Point ◽  
Rare Gas ◽  
Zero Point Energy ◽  
Point Energy
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