Stability, chemical bonding behavior, elastic properties and lattice thermal conductivity of molybdenum and tungsten borides under hydrostatic pressure

The thermodynamic stability and mechanical properties of Mo–B and W–B binary compounds are investigated by first principles calculations and compared with other theoretical and experimental results. In order to determine the stability, compressive behavior and mechanical properties of Mo2B5 and W2B5 phases, hydrostatic pressure up to 10 GPa is applied to the crystal. The formation enthalpy, phonon spectrum, electronic structure and mechanical modulus at different pressure are obtained and variety of chemical bonding behavior has close relationship with the change of elastic properties. Temperature-dependent thermodynamics parameters of Mo2B5 and W2B5 are analyzed under different pressure. Moreover, the whole profile of temperature dependent lattice thermal conductivity of Mo2B5 and W2B5 from Debye temperature up to high temperature limit at different pressure is predicted by combining the Slack׳s, Clarke׳s and Cahill׳s model. The difference between the variation of lattice thermal conductivity of Mo2B5 along [001] and [100] directions is attributed to the anisotropic chemical bonding behavior of B–B bonds and M–B bonds under pressure effect.