Pressure and temperature effects on NaCl-type transition metal carbide from first-principles calculations

The structural and thermal properties of titanium carbide at high temperatures and high pressures are investigated using the ultrasoft pseudopotentials within the generalized gradient approximation in the framework of first-principles. The bulk ground-state characters such as lattice constants, Poisson’s ratios, elastic constants, shear moduli and Young’s moduli are calculated. It shows that the elastic constants of the titanium carbide crystal are well consistent with the experimental data under ambient conditions. The bulk modulus of titanium carbide as a function of applied temperature is presented. Besides, the phonon dispersion curves of TiC are obtained along the main symmetry directions. The calculated phonon density of states suggests that the motion of C atoms is confined to optic branches while the vibrations of Ti atoms belong to acoustic branches. To complete the fundamental characteristics of this crystal we have investigated the coefficients of thermal expansion, isochoric heat capacities and elastic moduli of titanium carbide in the whole temperature range from 0 to 2000 K and pressure range from 0 to 45 GPa. These results are in favourable agreement with previous theoretical works and the existing experimental data.