Low-Frequency Light Scattering and Superstructural Groupings in Alkali Borate Glasses

this paper, we try to establish the structural base for the behavior of the correlational length, lc (the parameter characterizing the linear size of structural inhomogeneities) as a function of the modifier oxide content in lithium and sodium borate glasses. With the content of the modifying oxide up to -30 mol %, the considered glasses are characterized by a significant similarity of the structure in the near-order region (the distribution of basic structural units) with a significant difference in their chemical structure and, as a consequence, the structure in the intermediate-order region. Based on thermodynamic modeling data (distribution of superstructural groups) and geometric analysis of structural groups in the intermediate-order region present in Na2O-B2O3 and Li2O-B2O3 glasses, the average size of the region of the ordered arrangement of atoms, R, is calculated. Matching the correlational length lc and average size R showed the presence of a simple linear and universal relationship between these two parameters characterizing the structural features of glasses in different spatial scales. The existence of such a relationship means that the change in the correlational length is closely related to the features of the distribution of superstructural groups and not to the modification of the glass structure at the level of basic structural units.