Application of an improved point-charge model to study the crystal Hg2F2

An improved point-charge model has been applied to study the relatively clo se-packing crystal Hg2F2 compound. For this model, the point-charge values used for defining the Madelung potential are based on Mulliken population a nalysis, and then spherical expansions are made for the point charges. Bond lengths, bond energies, force constants, and vibrational frequencies have been determined. The calculated various properties are in reasonable agreem ent with the experimental crystalline data, which indicates the success of the model. We have also shown that this model is applicable to the Hg2Cl2 c rystal as well. (C) 1999 Academic Press.