disilicate

Disilicate is a term used in silicate chemistry to describe a structural unit consisting of two silicon-centered tetrahedra (SiO4) that share a single oxygen atom. The resulting anion is Si2O7^6−, containing seven oxygens in total and a 6− charge. The two silicon atoms remain tetrahedral, linked by the bridging oxygen to form a disilicate linkage. This motif is commonly referred to as the pyrosilicate unit in minerals and synthetic materials.

In mineralogy, compounds containing Si2O7 units are called disilicates or pyrosilicates and typically have the general formula M2Si2O7, where M represents a metal cation such as Mg, Fe, Ca, or Na. These units exist in solid silicate phases and can also be encountered in silicate solutions under certain conditions, contributing to the diversity of silicate polymerization patterns alongside metasilicate (SiO3) and orthosilicate (SiO4) units.

The presence of disilicate groups influences the properties of minerals and glasses by altering network connectivity; disilicate units are less polymerized than higher-order silicate structures, which can affect melting behavior, hardness, and thermal stability. In materials science, disilicate motifs are discussed in the context of silicate glass networks and related compounds, where they help describe the arrangement of silicon-oxygen frameworks.

See also: silicate, metasilicate, orthosilicate, pyrosilicate.