Dimensionless Density: Packing and Structure in Oxide Glass Systems
Physics Department, Coe College, 1220 First Ave NE, Cedar Rapids, IA 52402 USA
Density is an essential comparative measure for all structural models of glasses. Molar volume and packing efficiency seek to normalize density for both the masses and volumes
of ions before comparison to atomic-level order. In this talk, packing fractions from five oxide glass systems were determined and compared to each other and to atomic-level structural
models. Both short-range and intermediate-range order may be discerned in the resulting trends of packing fraction as a function of glass composition. Furthermore, in several specific
glass systems, generalizations have been found in the packing trends that are independent of alkali type. In glasses with small modifier ions the packing is strongly influenced by the
atomic structure of the glass forming network while in the case of larger modifiers random packing of these large ions controls the overall packing and is independent of modifier itself.
This work was supported by the National Science Foundation under grant number DMR-1407404. Hundreds of Coe College students are thanked for their large efforts in making the glass
samples and determining the density.