Elastic, mechanical and thermodynamic properties at high pressures and temperatures of transition metal monocarbides

Abstract

The elastic and thermodynamic properties of transition metal monocarbides XC (X = Ti, Zr, Nb, Hf, and Ta) for high pressures and temperatures are presented. For cubic XC (X = Ti, Zr, Nb, Hf, and Ta), effective interatomic interaction potential incorporating long-range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions is formulated. Both charge transfer interactions and covalency effect apart from long-range Coulomb are important in revealing high-pressure induced volume collapse, elastic and thermodynamic properties. The elastic constants, Debye temperature, and thermal expansion coefficient obtained are consistent with the available results. The XC compounds are mechanically stiffened, thermally softened, and brittle in nature. To our knowledge this is the first quantitative theoretical prediction on XC of pressure and temperature dependence of elastic, thermal and thermodynamic properties and still awaits experimental confirmation.