Ab initio characterization of ββ-MnAs

In this work is studied the electronic structure and phase stability of orthorhombic (B31) ββ-MnAs, which is compared with hexagonal (B82) αα-MnAs. In both phases the magnetic moment on the Mn atom decreases monotonically under lattice compression. The electronic effect which arises from the αα→→ββ 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 ββ-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.