Phase transition and mechanical, vibrational, and electronic properties of NbC under pressure

Abstract

The crystal structure, phase transition, mechanical, vibrational, and electronic properties of NbC under high-pressure were studied within the framework of density functional theory. The results show that a lattice parameter at zero GPa is in good agreement with the available experimental and theoretical data. Enthalpy calculations show pressure-induced phase transition B1 (NaCl) to B2 (CsCl) at 345 GPa. According to Born's structural stability criterion, the B1 and B2 phases are stable for all the pressures range studied. The Pugh's and Poisson's criteria suggest a brittle behavior at zero GPa and a ductile behavior for pressures above zero GPa. Furthermore, the phonon dispersion curves show that the B1 phase is stable in all pressure range studied, while the B2 phase is stable only under pressure. The density of states at the Fermi energy in both phases decreases due to Nb 4d states.