Structure and bonding of III/V compounds X 2Y 2, with X=B, Al, Ga, and Y=N, P, As

Abstract

The geometries and electronic states of group III/V (13/15) X 2Y 2 compounds were investigated by B3LYP and MP2 calculations, using a 6-311+G(3df) basis set. Twelve different starting geometries for B 2N 2, B 2P 2, B 2As 2, Al 2N 2, Al 2P 2, Al 2As 2, Ga 2N 2, Ga 2P 2, and Ga 2As 2 were chosen for both singlet and triplet states. For aluminum and gallium compounds, the lowest energy structure was a rhombus in a 1A g ground state, having the group V atoms on the short diagonal. Al 2N 2 and Ga 2N 2 have a linear X–N–N–X Σ g − 3 state that lies only 0.05 and 0.08 eV, respectively, higher than the 1A g rhombus. B 2N 2 prefers a linear B–N–B–N arrangement in a triplet state ( 3Π), but a 3B 2 g rhombus, having the B atoms on the short diagonal, lies 0.14 eV (B3LYP) or 0.07 eV (MP2) higher. B 2P 2 and B 2As 2 were found to be most stable in a rhombus ( 3B 2 g) structure, with B on the short diagonal. Bonding in the rhombus and in linear symmetric structures is described.