Pressure-induced structural phase transition and electronic properties of actinide nitrides: Ab initio calculations

Abstract

We report ab initio calculations of pressure-induced structural phase transition and electronic properties of the NaCl-type actinide nitrides namely AnN (An=Np and Cm). The total energy as a function of volume is obtained using the self-consistent tight-binding linear muffin tin orbital (TB-LMTO) method by performing spin and non-spin-polarized calculations. Magnetically the AnN compounds are stable in ferromagnetic (FM) state at ambient condition. From the present study, we predict a structural phase transition from ferromagnetic (FM) NaCl-type (B 1 phase) structure to ferromagnetic CsCl-type (B 2 phase) structure for these in the pressure range of 80.0–50.0 GPa. The pressure-induced transition is found to be first order. The band structure and density of states (DOS) are reported in both FM-B 1 phase and FM-B 2 phase. The ground-state properties such as magnetic moment, lattice parameter and bulk modulus are calculated and compared with the available theoretical and experimental results.