The structure of CaSiO3 glass and the modified random network model

This work presents a computational modelling study of CaSiO3 glass, with the aims of examining the local atomic environment of Ca, the interpretation of the Ca-Ca distribution, and the influence of network topology. One model was constructed using the molecular dynamics method and has a broad Q(n) distribution, whereas another model was constructed using the reverse Monte Carlo method to control network topology and has a narrow Qn distribution. Both models have average Ca-O coordination with N = 6.3 and modal distance R = 2.40 angstrom, which are in fair agreement with previous experimental results. In both models the majority of bridging oxygens are also coordinated to Ca. Hence nonbridging oxygens by themselves are not sufficient to define the interface between network former and network modifier regions. Despite having different Q(n) distributions, both models have similar x-ray diffraction structure factor and Ca-Ca distribution, and these are in fair agreement with experimental results. Hence strong effects due to network topology are not exhibited. The Ca-Ca distribution is not similar to that in wollastonite and there is no evidence of layer like ordering of CaON polyhedra, in contradiction to a previous interpretation