Transitions between NiAs and MnP Type Phases: An Electronically Driven Distortion of Triangular (36) Nets

Abstract

An interesting sequence of deformations from the NiAs structure type occurs in simple 3d transition-metal phosphides. Whereas for d1and d2 electron counts the NiAs structure type is preferred, for d3 to d6 electron counts a distortion to the MnP type structure occurs, breaking the triangular (36) nets of atoms and involving the formation of metal-metal and phosphorus-phosphorus zigzag chains. Going to a d7 electron count we find a double pairing distortion in the NiP structure with metal and phosphorus pairs. The first deformation is driven by a second-order Jahn-Teller-like distortion, splitting a strong peak in the density of states of the NiAs structure. The distortion from the MnP to the NiP structure type is traced to bond formation between pairs of metal and phosphorus atoms, the driving force being the introduction of an energy gap close to the Fermi level. © 1986, American Chemical Society. All rights reserved.