A computational study of structural transitions in NpAs and NpTe induced by pressure

Spin-polarized electronic structure calculations, by the tight binding linear muffin tin orbital (TBLMTO) method within the atomic sphere approximation (ASA), for neptunium compounds NpAs and NpTe at ambient pressure and high pressure are reported. The self-consistently calculated total energies at various cell volumes were fitted to Birch equation of state (EOS) in order to obtain the transition pressure from the B1 to the B2 phase and the volume collapse for each compound. The results indicate good agreement with high pressure X-ray diffraction (HPXRD) experiments. The role of interatomic distances in the transition is also examined. (orig.)