Pressure-induced structural phase transition in iron phosphide

Abstract

The high-pressure structural stability of FeP is systematically explored up to 150GPa by using first-principles calculations combined with crystal structure prediction techniques. We firstly predicted that FeP undergoes a structural phase transition from the low-pressure MnP-type phase to a simple cubic FeSi-type phase at high pressure of 87.5GPa with a volume drop of 4.3%. The occurrence of this high-pressure FeSi-type phase follows the increased distortions of FeP6 polyhedron in MnP-type phase and the coordination of Fe atoms increased from 6 to 7. Phonon calculations indicated that this FeSi-type structure is dynamically stable under high pressure as well as ambient pressure. The variations of elastic parameters (including elastic constants, elastic moduli, and sound velocities) of these two structures for FeP under pressure are also investigated for the first time. Further electronic structure calculations showed that FeSi-type structure exhibits a much weaker metallic character compared to the low-pressure MnP-type phase, originating from the increased Fe-d–P-p orbital hybridization under high pressure.