Stokes-Einstein violation and fragility in calcium aluminosilicate glass formers: a molecular dynamics study

International audienceA series of classical molecular dynamics simulations of calcium aluminosilicate (CAS) (CaO-Al2O3)(1-x)(SiO2)(x) melts with varying silica content x, along the CaO/Al2O3 concentration ratio R=1, have been performed for the purpose of studying (i) the evolution of fragility with silica content and (ii) the temperature and composition evolution of self-diffusion coefficients, viscosity and -relaxation times. Our results indicate a decrease in the fragility of the CAS systems along R=1 from calcium aluminate to pure silica. It is found that upon cooling, the Stokes-Einstein relation breaks down at a temperature significantly higher than the critical temperature of the mode-coupling theory T-C for all compositions and also above the melting point