An ab initio study of the elastic behavior of single crystal group (IV) diborides at elevated temperatures

We report on an ab initio molecular dynamics study of the lattice parameters, thermal expansion coefficients, and elastic constants of $ZrB2$⁠, $TiB2$⁠, and $HfB2$ ceramics at ultrahigh temperatures (up to 2200 K). Equilibrium lattice parameters of the ceramics are determined at finite temperatures. A finite strain method is used to extract the stiffness tensor of the ceramics. The results obtained for $ZrB2$ and $TiB2$ agree well with experimental results reported in the literature. Our work demonstrate that accurate properties may be obtained from a statistical averaging of the lattice parameters alone neglecting phonon interactions.