Electronic Structure and Pressure Dependence for Some Ternary Calcium Nitrides

In this paper we present pseudopotential LDA calculations using a plane wave basis set. We investigate the structure of Ca3AsN and Ca3PN and consider its pressure dependence. Between the structures considered no phase transitions were found for positive pressures. Experimentally Ca3AsN and Ca3PN were found to have an orthorhombic structure which corresponds to a distorted cubic structure. Also theoretically this orthorhombic structure was found to be energetically the most favourable. Its corresponding lattice constants are in good agreement with the experimental data. Besides the lattice constants, the bulk moduli and its pressure derivatives we also calculate the electronic bandstructure.