The diffusivity of tagged particles is demonstrated to be heterogeneous on time scales comparable to or less than the structural relaxation time in a highly supercooled liquid via 3D molecular dynamics simulation. The particle motions in the relatively active regions dominantly contribute to the mean square displacement, giving rise to a diffusion constant systematically larger than the Stokes-Einstein value. The van Hove self-correlation function Gs(r,t) is shown to have a large r tail which can be scaled in terms of r/t1/2 for t≲3τα, where τα≅ the stress relaxation time. Its presence indicates heterogeneous diffusion in the active regions. However, the diffusion process eventually becomes homogeneous on time scales longer than the life time of the heterogeneity structure (∼3τα).
The 8th Tohwa University International Symposium on Slow Dynamics in Complex Xystems
- Pub Date:
- April 1999
- Diffusion and thermal diffusion;
- Glass transitions;
- Condensed Matter - Soft Condensed Matter
- 8pages, 6 figures (Proceeding of the 8th Tohwa University International Symposium on "Slow Dynamics in Complex Systems" Nov. 9-14, 1998, Fukuoka)