Studying the phase transition, thermal expansion, and heat capacity of technetium mononitride by first-principles calculations

Abstract

The pressure-induced B3⿿B1 phase transition and some interesting thermodynamic properties for B3 structure of ideal stoichiometric technetium mononitride (TcN) have been studied systematically by first-principles calculations. It is found that TcN has a B3 ground-state phase at zero pressure and the transition pressure from B3 to B1 structure determined by the energy vs volume curves is about 35GPa. Through the quasi-harmonic Debye model, the dependences of thermal expansion coefficient, constant-volume heat capacity, and constant-pressure heat capacity of TcN with B3 phase on temperature up to 1600K are successfully predicted at 0, 10, 20 and 35GPa pressures, respectively.