The electron structure of hydroxyapatite was investigated by using the tight-binding recursion method. The local density of states, partial density of states, structural energy and charge transfer were calculated, as well as the interatomic energy. The calculations showed that both the OH group and the PO4 group could be regarded as being individual structural units, due to the strong interactions between the atoms. The atomic structure of a grain boundary was also determined on the basis of the near-coincidence site lattice model, while taking account of the bond lengths in the crystal, and of the lattice distortion. The electron structure and energy of a Σ = 7 grain boundary were calculated, and the results showed that a grain boundary with a slight lattice misfit had a lower energy.

Q.Song, C.Wang, S.Wen: Philosophical Magazine A, 1998, 77[5], 1309-21