Semi-empirical methods as a tool in solid-state chemistry

A new method for performing periodic calculations using the MNDO, AMI and PM3 semi-empirical methods, with treatment of the long range interactions by lattice summation techniques, has been devised and implemented. The performance of the existing parametrisations are examined for the bulk and surface properties of alumina, the prediction of the relative stability of silica polymorphs, and for the modelling of ice crystals. While the results for the more ionic materials suggest that some reparametrisation will be needed for solid-state problems, the method shows promise for molecular crystals, particularly those where hydrogen bonding is the dominant interaction.