High-frequency dielectric constant of AIIB2IIIC4VI ordered-vacancy compounds

The mean high-frequency dielectric constant of ZnIn₂Se₄, CdIn₂Se₄, ZnIn₂Te₄ and CdIn₂ Te₄ was determined from unpolarized infrared reflectivity spectra measured in the wavenumber range v̄ = 600 – 4000 cm⁻¹. A simple relation based on the quantum dielectric theory for multibond crystals is proposed to estimate the mean high-frequency dielectric constant of the A^IIB₂^IIIC₄^VI compounds from individual bond susceptibilities. The results of the calculations are compared with existing experimental data, and susceptibilities of the Hg C^VI bonds are estimated.