The structural properties and stability of zinc-blende Gax Mn1-x As over the whole Mn composition range are studied by means of the highly precise full-potential linearized augmented plane-wave method and the Connolly-Williams cluster expansion method, within the local-density approximation (LDA), generalized gradient approximation (GGA), and LDA+U. In contrast to LDA and GGA predictions, the calculated LDA+U lattice constant is found to increase when the Mn composition increases, even in the case that the Mn atoms substitutionally occupy cation sites, due to the correlation correction of the pd hybridization strength between the Mn 3d bands and the As 4p valence bands, which agrees with recent experimental findings. In addition, we confirm that the system has a tendency to segregate into GaAs and MnAs, and so inherently favors clustering. A temperature-composition phase diagram is obtained with the mean-field approximation for the entropy, in which the Mn solubility into GaAs is found to be very low at low temperatures (∼300°C).
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - May 21 2007|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics