Derivation of interatomic potentials for microporous aluminophosphates from the structure and properties of berlinite

A Born model using formal oxidation states has been derived for aluminophosphates, based on the mineral berlinite, which is compatible with existing potentials for ionic materials. Empirical fitting was used to determine the phosphorus–oxygen potential, based upon the crystal structure, elastic and dielectric properties. This model is comparable to previous partial-charge models for the reproduction of the elastic, dielectric, piezoelectric and phonon properties of berlinite, while being superior for the crystal structure. The thermal expansion of berlinite within the quasi-harmonic approximation has also been determined. Calculations on MAPO-36 demonstrate the transferability of the potential model to other aluminophosphates.