Ab initio lattice dynamics and thermodynamics of rare-earth hexaborides LaB6 and CeB6

Abstract

We have performed an ab initio study of structural, elastic, lattice-dynamical, and thermodynamical properties of rare-earth hexaborides LaB6 and CeB6. The calculations have been carried out within the density-functional theory and linear-response formalism using pseudopotentials and a plane-wave basis. Thermodynamical properties of LaB6 and CeB6 obtained from quasiharmonic approximation are in a good agreement with the available experimental data. We also present the complete phonon-dispersion curves, phonon density of states, and mode-Gruneisen parameters and compared with the experimental measurements. A sizable difference between the vibrational contribution to entropy of LaB6 and CeB6 is found. The thermal electronic contribution to entropy and specific heat is found to be important for CeB6.