Structural, electronic, elastic and thermal properties for curium monopnictides: A first-principles study

An investigation on structural, electronic, elastic and thermal properties of curium monopnictides (CmX; X = N, P, As, Sb and Bi) under ambient and high pressure is conducted using first-principles calculations based on density functional theory (DFT) within generalized gradient approximation (GGA) and local spin density approximation (LSDA) along with Hubbard-U corrections and spin–orbit coupling. Our results demonstrate that there exist a structural phase transition from their ambient NaCl (B1) type structure to CsCl (B2) type structure at 111.80, 36.81, 22.08, 7.52 and 7.14 GPa for CmN, CmP, CmAs, CmSb and CmBi respectively using LSDA. The structural parameters like lattice constant (a0), bulk modulus (B) and pressure derivative of bulk modulus (B′) are reported in B1 and B2 phases and also compared with available results. The calculated band structures indicate that B1 phase of all the CmX compounds are metallic for majority spin and semi metallic for minority spin. The LSDA + U strategy shows significant impact on the energy levels of the occupied and unoccupied ‘f’ states in the electronic structure and provides better description of all the compounds. The thermal and mechanical properties are predicted from the calculated values of elastic constants. The ductility of these compounds is determined by calculating the bulk to shear ratio B/GH. Our calculated results are consistent with experimental and other theoretical data. Elastic constants of these compounds are determined for the first time.