(139g) Pair Correlations, Excess Entropy, And The Single-Particle Dynamics Of Complex Fluids Within The Gaussian-Core Model

The Gaussian-core model is a so-called ?core-softened? pair potential that is bounded. It allows overlap of interacting particles, but it energetically penalizes such configurations with a term that decays in a Gaussian manner with interparticle center-of-mass separation. This model can be used to simulate the effective pair interactions between polymer chains, star copolymers, or dendrimers in solution. The ability of such systems to display a number of unusual properties (e.g., density anomalies and enhanced mobility upon compression) has generated broad interest in recent years. The focus of this study is the use of molecular dynamics simulations to probe the molecular origins of these properties. In particular, the global behaviors of the self-diffusivity, the thermal expansion coefficient, the excess entropy, and the two-body contribution to the excess entropy [calculable from the pair correlation function] are investigated. We use this data to test whether quasi-universal scaling laws (1, 2) that successfully relate self-diffusivity to excess entropy [or its two-body approximation] in simpler model systems also hold for the Gaussian-core fluid. The results, which we report in this talk, provide new insights into whether pair correlations alone can predict dynamic behavior.

(1) Y. Rosenfeld, J. Phys.: Condens. Matter 11, 5415 (1999)

(2) M. Dzugutov, Nature (London) 381, 137 (1996)