Interrelationship between polarisability and polarising power of cations: application to glasses containing zinc oxide

An examination is made of the quantitative, but empirical, connection between optical basicity and the electronic polarisability of oxide(-II) in oxidic systems. It reveals that for metal ions there is an intimate relationship between their polarisability and their polarising power (expressed as the basicity moderating parameter, gamma). The relationship is applied to silicate and borosilicate glasses containing ZnO as a major component. The refractivity data of these glasses are consistent with an optical basicity of 0(.)91 for ZnO (gamma(Zn)=1(.)10) and a polarisability for the Zn2+ ion of 0-55 angstrom(3). Further consideration of cation polarising power shows that it is not dependent on cationic charge (oxidation number), but upon cation radius. The relationship between cation radius and polarisability is explored and used to understand how the polarisability of metal ions is influence by their basicity moderating parameters.