Pressure-induced silicon coordination and tetrahedral structural changes in alkali oxide-silica melts up to 12 GPa: NMR, Raman, and infrared spectroscopy

Abstract

The 29Si and 23Na NMR, Raman, and infrared spectra of glasses quenched from liquids at pressures up to 12 GPa for three alkali silicate compositions (Na2Si2O5, Na2Si4O9, K2Si4 O9) and silica (SiO2) reveal systematic changes in the melt structure with pressure. The most novel change is the occurrence of [5]Si and [6]Si species at high pressures identified by peaks in the 29Si MAS NMR spectra of the alkali silicate glasses. -from Authors