Ab initio Calculation of Thermal Expansion Coefficients for MeB₂ (Me-Ti, Zr) and LaB₆ Borides and LaB₆–MeB₂ Eutectic Composites

Abstract

Thermal expansion coefficients of transition metal borides, lanthanum hexaboride, and associated eutectic composites are calculated with the aprioristic pseudopotential method. To determine the relationship between the energy of the electron–ion system and the crystal lattice parameters at temperatures other than zero, a model based on a comparison of the energy scale of the system at absolute zero temperature and at a temperature different from zero is proposed. There is an abrupt increase in the thermal expansion coefficient of the composites in the temperature range from 750 to 1000 K.