Localization model description of diffusion and structural relaxation in glass-forming Cu-Zr alloys

We test the localization model (LM) prediction of a parameter-free relationship between the a-structural relaxation time tau(alpha) and the Debye-Waller factor < u(2)> for a series of simulated glass-forming Cu-Zr metallic liquids having a range of alloy compositions. After validating this relationship between the picosecond ('fast') and long-time relaxation dynamics over the full range of temperatures and alloy compositions investigated in our simulations, we show that it is also possible to estimate the self-diffusion coefficients of the individual atomic species (D-Cu, D-Zr) and the average diffusion coefficient D using the LM, in conjunction with the empirical fractional Stokes-Einstein (FSE) relation linking these diffusion coefficients to tau(alpha). We further observe that the fragility and extent of decoupling between D and tau(alpha) strongly correlate with < u(2)> at the onset temperature of glass-formation T-A where particle caging and the breakdown of Arrhenius relaxation first emerge.