Structural properties, elastic anisotropies and thermal conductivities of tetragonal LnB2C2 (Ln = Rare Earth) compounds from first-principles calculations

Abstract

In this work, we used the first-principles calculations to study structural properties, elastic constants and moduli, polycrystalline elastic moduli, anisotropic properties and thermal conductivities of tetragonal LnB2C2 (Ln = Rare Earth) compounds. The polycrystalline elastic modulus, Poisson's ratio, hardness and Debye temperature were calculated based on the single crystal elastic constant. Estimation of elastic anisotropy was carried out by elastic anisotropy index and surface projection. The elastic anisotropy for these compounds is a sequence of LuB2C2 > TmB2C2 > ErB2C2 > LaB2C2 > HoB2C2 > TbB2C2 > DyB2C2 > NdB2C2 > PrB2C2 > CeB2C2. The calculated minimum thermal conductivity and Debye temperature are in the same order of LaB2C2 > TmB2C2 > LuB2C2 > ErB2C2 > HoB2C2 > CeB2C2 > DyB2C2 > NdB2C2 > PrB2C2 > TbB2C2. The obtained sound velocities and minimum thermal conductivity of LnB2C2 compounds are also anisotropic.