  In this paper we investigate theoretically the ground state NiAs-type
structure of MnAs and we compare the magnetic and structural properties with an
hypothetical zincblende structure. A zincblende structure can be obtained, in
principle, from the diluted magnetic semiconductor Ga$_{1-x}$Mn$_x$As in the
limit $x=1$. Using density functional calculations within the local
spin-density approximation (LSDA), we show that the zincblende structure,
although showing half metallic behavior which is very attractive for
spintronics, can not be stabilized at equilibrium. We perform a tight-binding
analysis of the Mn-As bond in the tetrahedral coordination to investigate the
nature of the bonding in diluted magnetic semiconductors.
