Refractive index–structure correlations in silicate glasses

A model has been presented to correlate the refractive index with the structure of CaO–SiO2, SrO–SiO2, BaO–SiO2 and related ternary glasses. A quantitative analysis of the property-composition dependence has been carried out. Any of the structural units present in these glasses has a specific ability (the differential refraction) to refract the light. The differential refraction depends only on the type of the modifier oxide, but not on its concentration. It increases linearly with the increase in the number of non-bridging oxygen ions in the structural unit. The differential refraction for a structural unit in ternary silicate glasses remains the same found for the corresponding binary glasses. On the basis of the structural units distribution, relations are given to calculate the refractive index as a function in composition for the binary- or the mixed-modifier silicate glasses. The results indicate that the refraction of light is the result of interaction between the waves and the structural unit as a whole rather than with the ions separately.