Motivated by the negative thermal expansion observed for silicon between 20 K and 120 K, we present an ab initio study of the volume dependence of interatomic force constants, phonon frequencies of transverse-acoustic TA(X) and TA(L) modes, and of the associated mode Grüneisen parameters. The influence of successive nearest-neighbor shells is analyzed. Analytical formulas, taking into account interactions up to second-nearest neighbors, are developed for phonon frequencies of TA(X) and TA(L) modes and the corresponding mode Grüneisen parameters. We also analyze the volume and pressure dependence of various thermodynamic properties (specific heat, bulk modulus, and thermal expansion), and point out the effect of the negative mode Grüneisen parameters of the acoustic branches on these properties. Finally, we present the evolution of the mean-square atomic displacement and of the atomic temperature factor with the temperature for different volumes, for which the anomalous effects are even greater.
|Number of pages||10|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1996|