An ab initio parameterized interatomic force field for hydroxyapatite

A classical interatomic force field for hydroxyapatite has been parameterized from periodicab initio calculations carried out on the hexagonal structure (space group P63). The GULPprogram has been used for fitting geometry and phonon frequencies computed with theCRYSTAL06 program using the B3LYP hybrid functional and Gaussian-type basis set ofpolarized double zeta quality. Polarization effects and covalent bonding have been includedthrough the shell-ion model potential. Excellent agreement has been found in reproducingstructural features, lattice dynamics, the OH stretching vibrations and relative phase stabilitiesbetween the monoclinic structure (space group P21/b) and the hexagonal one. Transferability fromhydroxyapatite to other calcium phosphates has also been demonstrated.