Al and Si coordination in SiO2-Al2O3 glasses and liquids: A study by NMR and IR spectroscopy and MD simulations

摘要: Abstract Structural properties of a series SiO2-Al2O3 glasses with up to 59 mole% Al2O3 were investigated by magic angle spinning NMR and infrared absorption spectroscopies. The results showed that Al is present in IV- VI-coordinated sites. relative proportions these species depends on composition quench rate. 27Al have been used “calibrate” the IR spectra, features spectra assigned Al-O stretching vibrations different AlOx polyhedral species. This will be useful for future situ studies melts at high pressures or temperature, when experiments are difficult perform, do not give information structural For comparison results, molecular dynamics simulations liquids carried out several compositions along join. pair distribution functions analyzed Si coordination liquids. At silica content, both predominantly occupy IV-coordinated sites, though presence some III-coordinated indicated. With increasing proportion AlV AlVI increased, average number liquid approaches 5.0. Concomitant increases SiV sites observed, ∼ 4.7 near pure Al2O3.