Theoretical LEED parameters for the zinc-blende GaN (110) surface

We present a theoretical study of the equilibrium atomic structure of the GaN (110) surface based on accurate, parameter-free, self-consistent total energy and force calculations using the density functional theory, the local-density approximation for the exchange–correlation term and the full potential linear augmented plane wave approach associated to the slab supercell model. We are concerned with the LEED parameters Δ1⊥, Δ1x, Δ2⊥, d12⊥, d12x and ω for the (110) surface. We analyze the changes in the bond-lengths and in the bond-angles at the anion and cation sites. We conclude that similarly to the III-Arsenides (110) and III-Phosphides (110) surfaces the GaN (110) surface relax such that the Ga-surface atom moves inward and the N-surface atom moves outward. The driving mechanism for this atomic rearrangement is that the Ga atom tends to a planar sp2-like bonding situation with its three N neighbours and the N atom tends to a p-bonding with its three Ga neighbors.