Abstract
The force fields controlling the structures of MgF2, ZnF2 and FeF2 have been subjected to inspection in comparison with that in rutile previously dealt with. The force constants have been determined by the normal coordinate treatment on the basis of the modified Urey-Bradley force field, with the result that the calculated frequencies have been found well in accordance with the observed frequencies. It has been clarified that the ionic characters are to a certain extent reflected on the data obtained as to the interatomic force constants for the crystals in question. On the one hand, the nature of the bonds in, and the characteristics of, the rutile-type structures have been examined mainly with respect to the force field, and on the other, the elastic constants considered microscopically have been deduced from the force constants.
