First principles calculations on the novel high pressure phase of HfC

Abstract

A new high-pressure structure of hafnium monocarbide (HfC) has been predicted by particle swarm optimization (PSO) algorithm based on first principles calculations. The newly found phase AuCu (L1[Formula: see text] belongs to the tetragonal P4/mmm space group. The transition pressure of NaCl (B1)[Formula: see text]L10 is predicted to be 387.6 GPa, which is much lower than that of B1[Formula: see text]CsCl (B2). L10 phase is found to transform to B2 structure at [Formula: see text]896.7 GPa. The structural stability criterion for tetragonal crystal was successfully deduced, which confirms the mechanical stability of L10 phase according to the calculated elastic constants. Thus, the equilibrium structure of HfC under high pressure was predicted to be L10 phase instead of B2. Furthermore, the bulk modulus, shear modulus, Young’s modulus and the compressional and shear wave velocities of HfC in B1 and L10 phases are found to increase monotonically as the pressure increases.