Cation-Oxygen Ion Interaction Parameter in Glassy PbO–SiO₂ System

Abstract

The classification of Raman bands observed for the glassy silica to ν₁, ν₃, ν₄ modes of the T_d symmetry is attempted and the force constants are estimated by Wilson’s method. In order to consider the dependence of the observed wave numbers ν₃(n) corresponding to the above ν₃ mode on the mole fraction n of PbO, the parameters, I(n)=(1−n)I_Si–O⁄{(1−n)I_Si–O+nI_Pb–O}, and P(n)=(1−n)P_Si⁄{(1−n)P_Si+nP_Pb}, are introduced in the composition ranges of 45∼62.5 and 62.5∼70 mol% of PbO respectively, where I_X−O=2Z⁄a² and P_X=Ze⁄r² (Z: ionic valence, a: X−O bond length, r: ionic radius, e: elementary charge). The interesting results which may give some insight of the structure of this glassy system are found, that is, the relations, ν₃²(n)=ν₃²(0)I(n)+b and ν₃²(n)=ν₃²(0)P(n)+b′, hold in each composition range.