Chemical approach to medium range order in glass

Abstract

The question on medium range order in glass is approached from three different angles. Voltammetric determinations indicate that below 30 mol% alkali oxide, binary lithium silicate melts contain silica clusters, while sodium and potassium silicate melts form discrete ions about 2 nm in size. Regardless of the alkali ion, silica forms complexes with acidic cations. By applying the Lux-Flood acid-base concept, it can be shown that the lithium silicate as well as the acidic sodium silicate melts contain bidentate ligands, while potassium as well as alkaline sodium silicate melts contain monodentate ligands. The complexation of acidic cations is in accordance with expectations from basic concepts of chemical bonding.