Empirical relationship between effective ionic charges and optical dielectric constants in binary and ternary cubic compounds

The effective ionic charge Z*e of each ion is determined within a narrow variable range for cubic and near-cubic ternary compounds. The Szigeti effective charge eₛ*[=3√ε_∝Z*e(ε_∝+2)] is also evaluated for the anion from the value Z*e by using the observed optical dielectric constant ε_∞. The correlation between eₛ* and the dielectric constant ε_∞ is empirically found for many kinds of binary and ternary compounds as ε_∞-1=2.0[(eₛ*Zeffe)+(eₛ*Zeffe)²]. The value Zeff indicates the effective chemical valency. In the correlation, the relatively large scatter for some compounds is explained by the d- or f-electron effect on the dielectric constant ε_∞, and by the screening and the anisotropic effects on the effective charge. From these results, the applicable ranges of the equation used and of the localized effective charge are discussed.