RESUMO
We study calcium silicate glass of composition (CaO)X(SiO2)(1-X), where X = 40-70 mol%, by means of molecular dynamics for different cooling rates between 1011-1013 K s-1. The thermodynamic and kinetic properties of calcium silicate materials are determined, discussed, and correlated to local structures at short and intermediate range orders and to the potential energies of the oxygen atoms. We show that the amount of non-bridging oxygens and the appearance of free oxygens are related to the increase of the glass transition temperature for an increasing CaO content. Our results are analyzed and discussed in connection with the available experimental data.
RESUMO
Non-Arrhenius behavior is observed for a number of virgin potassium silicate glasses (1-x)SiO2-xK2O with a potassium oxide concentration larger than a certain value x = x(c). Recovering of Arrhenius behavior is provided by the annealing that enhances densification. These various results are the manifestation of the floppy or rigid nature of the network. Compositional effects and saturation with temperature can be analyzed with a combination of constraint theory and a point defect model. They underscore the key role played by network rigidity for the understanding of conduction and saturation effects in glassy electrolytes.
