Pressure Induced Structural Phase Transition in Actinide Monophospides: Ab Initio Calculations

The structural and electronic properties of monophospides of Thorium, Uranium and Neptunium have been investigated using tight binding linear muffin-in-orbital (TB-LMTO) method within the local density approximation (LDA). From present study with the help of total energy calculations it is found that ThP, UP and NpP are stable in NaCl - type structure under ambient pressure. The structure stability of ThP, UP and NpP changes under the application of pressure. We predict a structural phase transition from NaCl-type (B-1-phase) structure to CsCl-type (B-2-phase) structure for these phospides in the pressure range of 37.0 - 24.0 GPa (ThP to NpP). The calculated equilibrium lattice parameters and bulk modulus are in good agreement with experimental and theoretical work.