| Research Abstract |
1. Anomalous Dynamics neax Liquid-Glass Transition : On approaching n a liquid-glass transition, the relaxation time of density fluctuations in a supercooled liquid becomes extremely long. With this dynamical slowing down, various anomalous properties are observed in highly supercooled liquids. Then, we have studied atomic-level mechanisms as well as dynamical structures of highly supercooled liquids, using a simple binary alloy model, for which molecular dynamics(MD)simulations have been carried out. Main results obtained axe(1)the density autocorrelation functions in highly supercooled liquids are well fitted by a stretched exponential function, (2)the atomic diffusion takes place mainly through jump motions correlated with several nearby atoms, (3)non-Gaussian parameter(NGP)becomes unusually large compared with that of normal liquid states, (4)the maximum of the NGP times the corresponding time makes it possible to estimate the liquid-glass transition ; one of the most advantage of this method is that the glass transition can be determined by an intermediate time behavior rather than long time behavior Eke self-diffusion, and(5)the exponent of the stretched exponential function stated in(1)depends on the temperature(density), so that this result disagrees with that of the simplest version of mode coupling models.
2. Theory of Slow Dynamics near the Glass Transition : With a trapping diffusion model, we have studied dynamical properties of supercooled liquids, which turns out to be consistent with the present MD results.
3. Theory of Pair Distribution Functions for Supercooled Liquids : With an improved integral equation(MHNCS), we have obtained an interesting result on the effect of a short range repulsive interaction on the phase separation of binary mixtures.
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