Bulk and nanoscale GaN:: Role of Ga d states

We have studied the role of Ga 3d states in determining the properties of bulk as well as nano-GaN using projected augmented wave potentials. A significant contribution of the Ga d states in the valence band is found to arise from interaction of Ga 4d states with the dominantly N p states making up the valence band. The errors in the calculated lattice constant arising from not treating the Ga 3d states as a part of the valence are found to be similar, similar to 1%, for bulk as well as for nanoclusters of GaN.