Second-Order Raman Spectra and Phonon Dispersion in GaP

1973 ◽  
Vol 51 (1) ◽  
pp. 63-76 ◽  
Author(s):  
R. M. Hoff ◽  
J. C. Irwin
Keyword(s):  
Specific Heat ◽  
Phonon Dispersion ◽  
Second Order ◽  
Phonon Density ◽  
Specific Heat Data ◽  
Phonon Dispersion Curves ◽  
Point Analysis ◽  
The One ◽  
Critical Point Analysis ◽  
Heat Data

The second-order Raman spectrum of GaP has been investigated experimentally. The experiments were performed on oriented single crystals at both 300 and 77 °K. A critical point analysis of the data has been carried out with the aid of the polarization selection rules. The resulting frequencies are also consistent with a theoretical model which in turn is used to calculate the phonon dispersion throughout the Brillouin zone. The one- and two-phonon density of states and the specific heat have also been calculated and compared to our spectra and available specific heat data. The calculated quantities have also been compared to similar quantities obtained from neutron scattering experiments. This comparison provides information on the accuracy and reliability of phonon dispersion curves obtained from Raman scattering experiments.

THEORETICAL STUDY OF LATTICE DYNAMICAL PROPERTIES IN FERROELECTRIC LiTaO3

1992 ◽  
Vol 06 (20) ◽  
pp. 3279-3293 ◽  
Author(s):  
YIMIN JIANG ◽  
CHENG GOU
Keyword(s):  
Specific Heat ◽  
Theoretical Study ◽  
Phonon Dispersion ◽  
Dispersion Curves ◽  
Optical Data ◽  
General Function ◽  
Zero Temperature ◽  
Phonon Dispersion Curves ◽  
Maximum Value ◽  
The One

We present the phonon-dispersion curves, the one-phonon density of states, the lattice specific heat cv(T) and the Debye temperature Θ(T) of the ferroelectric LiTaO 3, based on full lattice dynamical model whose parametèrs are fitted to the optical data and neutron measured dispersion curves. A model theory is developed to describe the transition from Debye to non-Debye behaviors observed in the low temperature part of the cv/T3 curve. The cv/T3 function, when is properly scaled, can be fitted by a general function derived from the model. It can be characterized by the temperature T max at which it has maximum, its maximum value (cv/T3)T=T max and its value at zero temperature (cv/T3)T=0. These results are considered useful in searching possibly anomalous phonon behavior from the specific heat cv(T).

Specific heat data of high-Tc superconductors: Lattice and electronic contributions

1989 ◽  
Vol 69 (6) ◽  
pp. 625-629 ◽  
Author(s):  
J.E. Gordon ◽  
M.L. Tan ◽  
R.A. Fisher ◽  
N.E. Phillips
Keyword(s):  
Specific Heat ◽  
High Tc Superconductors ◽  
Specific Heat Data ◽  
High Tc ◽  
Heat Data

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.

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