Communication: Generalizing Rosenfeld's excess-entropy scaling to predict long-time diffusivity in dense fluids of Brownian particles: From hard to ultrasoft interactions

Abstract

Computer simulations are used to test whether a recently introduced generalization of Rosenfeld's excess-entropy scaling method for estimating transport coefficients in systems obeying molecular dynamics can be extended to predict long-time diffusivities in fluids of particles undergoing Brownian dynamics in the absence of interparticle hydrodynamic forces. Model fluids with inverse-power-law, Gaussian-core, and Hertzian pair interactions are considered. Within the generalized Rosenfeld scaling method, long-time diffusivities of ultrasoft Gaussian-core and Hertzian particle fluids, which display anomalous trends with increasing density, are predicted (to within 20%) based on knowledge of interparticle interactions, excess entropy, and scaling behavior of simpler inverse-power-law fluids.

Thermodynamic and structural properties of the high density Gaussian core model

“…When ρ * is sufficiently large, we can neglect the third term on the left-hand side, leading to the asymptotic expression of T th of Eq. (16). Figure 10 shows that this asymptotic expression is very accurate down to ρ * ∼ 1.…”

“…Recently, thermodynamic and transport anomalies of the fluid phase in the vicinity of the reentrant peaks are investigated. 10,[12][13][14][15][16] Microscopic and structural properties such as the static structure factor in the fluid phase are also reported and documented. 6,7,9,11 These studies revealed that, as the density increases beyond the reentrant peak but at a fixed temperature, thermodynamic and structural properties of GCM becomes more ideal-gas-like, signaled by the lowering of the peak of the structure factors and the better agreement with simple approximations such as the random phase approximation (RPA).…”

“…GCM was first introduced by Stillinger 4 and has been studied by many groups. [5][6][7][8][9][10][11][12][13][14][15][16] Despite of its simple form of the pair potential, GCM exhibits many typical thermodynamic behaviors of the ultra-soft particles. According to thermodynamic phase diagram obtained by numerical simulations, 4,8 GCM basically behaves such as hard spheres at very low densities and temperatures; the crystalline structure in the solid phase is fcc and the freezing/melting temperatures sharply increase with density.…”

Isomorphs, hidden scale invariance, and quasiuniversality

“…• Excess entropy scaling, stating that the reduced-unit diffusion constants of different liquids have an approximately universal dependence on the excess entropy per particle [66][67][68][69].…”

Communication: Local structure-mobility relationships of confined fluids reverse upon supercooling

“…[17][18][19][20][21][22][23][24][25][26][27] To wit, it has been shown that single-particle diffusivities, relaxation times, and viscosities along structurally invariant (i.e., isotropic) dimensions of simple confined fluids can be predicted based on knowledge of how dynamic properties of the bulk fluid relate to static quantities including excess entropy s ex (relative to the ideal gas) and fractional available space exp{c (1) } (or insertion probability p 0 ), which characterize short-range static correlations and particle packings, respectively.…”