Structure and electronic properties of oxyanionic crystal surfaces

The atomic and electronic structures of the surfaces of alkali-metal nitrates, chlorates, and perchlorates are determined in the gradient approximation of density functional theory via the linear combination of atomic orbitals using the CRYSTAL09 program package. The geometric parameters, surface energies, densities of states, overlap populations, and atomic charges are calculated. It is established that the upper layer is formed by oxygen atoms for the most stable surfaces. For oxygen atoms of the upper layer, the intra-anionic bond length decreases with respect to that in the bulk, the overlap populations increase, and the charges decrease. Changes in the atomic and electronic structures of the surface decrease with respect to those of the bulk as the cation atomic number increases.