An ab initio parameterized interatomic force field for hydroxyapatite

Abstract

A classical interatomic force field for hydroxyapatite has been parameterized from periodic ab initio calculations carried out on the hexagonal structure (space group P6₃). The GULP program has been used for fitting geometry and phonon frequencies computed with the CRYSTAL06 program using the B3LYP hybrid functional and Gaussian-type basis set of polarized double zeta quality. Polarization effects and covalent bonding have been included through the shell-ion model potential. Excellent agreement has been found in reproducing structural features, lattice dynamics, the OH stretching vibrations and relative phase stabilities between the monoclinic structure (space group P2₁/b) and the hexagonal one. Transferability from hydroxyapatite to other calcium phosphates has also been demonstrated.