Test of the master curve for self-diffusion in strong glass-forming liquids

The master curve for self-diffusion coefficient D in strong glass-forming liquids recently proposed by Tokuyama is tested by performing the extensive molecular-dynamics simulations on SiO2 under the NVT ensemble. Two types of potentials, the BKS potential with long-range interactions and the Nakano-Vashishta potential with two- and three-body short-range interactions, are employed. Then, the a-relaxation time tau(alpha) and the beta-relaxation time tau(beta) are shown to obey the power laws recently proposed by Tokuyama as tau(alpha) similar to D-13/11 and tau(beta) similar to D-9/11. Thus, all the simulation results are shown to be described by the strong master curve. The simulations on Al2O3 with the Born-Mayer type potential are also performed. The simulation results are shown to support the fragile properties for tau(alpha), tau(beta), and D, although this potential has the same two-body long-range interactions as BKS. The difference between fragile liquids and strong liquids is thus discussed from a unified point of view.