EFFECTIVE CHARGE AT HIGH-PRESSURE IN FLUORITE STRUCTURED IONIC-CRYSTALS

In high pressure studies of ionic crystals it is important to have the value of the effective charge and its variation with pressure. This m agnitude may be obtained directly from Sziget's generalized equation, with the restriction that experimental data of various magnitudes at h igh pressure are required and are not always available. In the present work values are proposed of the variation of the effective charge wit h volume, calculated with an alterantive formalism (Hardy's Model), fo r ionic crystals of the fluorite structure. These results are compared with partial derivative lns/partial derivative lnv values obtained fr om a Shell Model with a formalism developed here.