Anisotropy in elasticity and thermodynamic properties of zirconium tetraboride under high pressure
The recently predicted ZrB4 with an Amm2 orthorhombic structure has great scientific and technical significance owing to its novel B–Zr–B “sandwich” layer bonding and evaluated high hardness. To better understand the performance of Amm2-ZrB4, its elastic and thermodynamic properties under pressure and temperature are studied here by taking advantage of first principles calculations in combination with the quasi-harmonic Debye model. It is found that ZrB4 keeps brittleness and mechanical stability up to 100 GPa, possessing pronounced elastic anisotropy demonstrated by the elastic anisotropy factors, the direction-dependent Young's modulus, shear modulus and Poisson's ratio. The pressure and temperature dependences of the thermodynamics parameters including normalized volume V/V0, bulk modulus, specific heat, Debye temperature, thermal expansion coefficient and Grüneisen parameter in wide temperature (0–1000 K) and pressure (0–50 GPa) ranges are obtained and discussed in detail.