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 alumin ophosphates, 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 str ucture, elastic and dielectric properties. This model is comparable to previous partial-charge models for the reproduction of the elastic, d ielectric, piezoelectric and phonon properties of berlinite, while bei ng superior for the crystal structure. The thermal expansion of berlin ite within the quasi-harmonic approximation has also been determined. Calculations on MAPO-36 demonstrate the transferability of the potenti al model to other aluminophosphates.