Correlation between effective activation energy and pre-exponential factor for diffusion in bulk metallic glasses

The values of effective activation energy (Q) and pre-exponential factor (D₀) reported in the literature for diffusion in the novel bulk metallic glasses, both in the glassy and the deeply supercooled liquid regions, are found to follow the same correlation as reported earlier in conventional metallic glasses, namely D₀ = A exp(Q/B), where A and B are fitting parameters with values A = 4.8 × 10⁻¹⁹ m² s⁻¹ and B = 0.056 eV atom⁻¹. A possible explanation for the observed values of A and B is given by combining an activation energy and a free volume term. The interpretation favors a cooperative mechanism for diffusion in the glassy and deeply supercooled liquid states.