Mixing effects in glass-forming Lennard-Jones mixtures

Mixing effects have been investigated from molecular dynamics simulations at constant number of particles, volume, and temperature on the Kob-Andersen glass-forming Lennard-Jones atomic mixture A(x)B(1-x) for 0 < or = x < or = 1 compositions. Upon cooling, crystallization is observed for x < or = 0.5 and x > or = 0.9 compositions. The crystalline states can be described by a quite complex coexistence of voids (x < or = 0.5), point defects, and one or two crystal structures which were characterized and found identical to those reported by Fernandez and Harrowell [Phys. Rev. E 67, 011403 (2003)] from energy minimization. Amorphization is also seen at 0.6 < or = x < or = 0.8 compositions and it is suggested that both crystal structures, CsCl and fcc-hcp, do not compete at these compositions since only one type of crystalline seed is found in the liquid, either fcc/hcp or CsCl. A significant decrease in the diffusion constants for both A and B particles is also seen above x(A) approximately = 0.5. The problem of the extraordinary stability of the model against crystallization is discussed.