Zinc-blende (α-) and NiAs-type (β-) MnAs are investigated with a combined first-principles linearized argumented plane wave and DMol3 study within both the local density approximation (LDA) and the generalized gradient approximation (GGA). First-principles calculations within the GGA predict the lattice volume for β-MnAs much better than LDA (which underestimates it by 15%) compared with experiment. The LDA calculated equilibrium lattice volume of α-MnAs is 10% smaller than that of GaAs, which is in contradiction to the well-accepted fact that the lattice volume of Ga1-xMnxAs increases with x. In contrast, the GGA predicts a reasonable lattice volume for α-MnAs. The ferromagnetic α-MnAs is shown to be a metal at a= 5.7 Å, and to undergo a transition to a half-metallic phase when it expands to a>5.8 Å due to the decreased bandwidth. Further, the calculated cohesive energy of β-MnAs is nearly 0.87 eV greater than that of α-MnAs, which provides theoretical support for the instability of α-MnAs.
|Original language||English (US)|
|Number of pages||4|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Mar 15 2002|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics