The Structure of Glasses

A theory of the structure of glasses is presented. It is assumed that the volume and various other properties can be computed additively from contributions characteristic of the types of “structon” present, a structon being defined as an atom surrounded by close neighbors in a specific way. If the possible types of structon differ enough in stability, the number of such types present in appreciable quantities in a sample at equilibrium is small. If it is the minimum number required to give the correct over‐all composition, the sets of structon types present change suddenly as the composition changes. This explains the observed fact that certain property‐composition curves consist of straight‐line segments, with sharp breaks between them. Detailed consideration is given to the volumes (and densities) of well‐annealed sodium silicate glasses. Reasonable sets of structon types account quantitatively for the locations of the observed breaks. Certain definite conclusions are drawn regarding the types of structon present in the different composition ranges, their relative numbers, and their contributions to the total volume.