Ab initio characterization of -MnAs

In this work is studied the electronic structure and phase stability of orthorhombic (B31) β -MnAs, which is compared with hexagonal (B82) α -MnAs. In both phases the magnetic moment on the Mn atom decreases monotonically under lattice compression. The electronic effect which arises from the α → β  geometrical distortion with increasing temperature is reminiscent of a second-order static Jahn–Teller effect. From the characteristics of the calculated Fermi surfaces is found evidence for the larger resistivity experimentally observed in the β -phase, which exhibits unfavorable conditions for the formation of open orbits. The results indicate that the structural transition (318 K) is driven by nesting of the Fermi surfaces.