Cation polarization and the crystal structure of SnO

Tin(II) oxide has an unusual crystal structure (litharge) which exhibits numerous 'non-ionic' features, such as nearest neighbour ions of like charge and a large lattice energy compared with other oxides of similar cation radius. It is shown that a generic ionic interaction model for oxides, with an ab initio based representation of such many-body effects as ionic polarization and the compression of the oxide ion by its environment, predicts litharge as the lowest energy structure. Cation polarization is found to play the dominant role