Vibrational Spectra, Force Constants, and Si-O Bond Character in Calcium Silicate Crystal Structure

Abstract

Vibrational spectroscopic methods were used to study the Si-O bond character in silicates with different complex anions and crystal structures. The following calcium silicates were examined: Ca,(SiO5), γ-Ca2(SiO4), β-Ca2(SiO4), Ca3(Si2O7), Ca(SiO3), and Ca(Si3O3). The band assignments in IR and Raman spectra of these compounds have been deduced mainly from 28Si−30Si and 40Ca−44Ca isotopic shifts. The GF matrix method and molecular approximation for force constant calculations in silicate anions were used. The Si-O bond parameters (bond order, charge distribution, and bond ionicity, etc.) were obtained from calculated force constants. The nature of Si-O bonds with respect to complex anion and crystal structure will be discussed.