Diffusivity, excess entropy, and the potential-energy landscape of monatomic liquids

Abstract

The connection between thermodynamic, transport, and potential-energy landscape features is studied for liquids with Lennard-Jones-type pair interactions using both microcanonical molecular-dynamics and isothermal-isobaric ensemble Monte Carlo simulations. Instantaneous normal-mode and saddle-point analyses of two variants of the monatomic Lennard-Jones liquid have been performed. The diffusivity is shown to depend linearly on several key properties of instantaneous and saddle configurations-the energy, the fraction of negative curvature directions, and the mean, maximum, and minimum eigenvalues of the Hessian. Since the Dzugutov scaling relationship also holds for such systems [Nature (London) 381, 137 (1996)], the exponential of the excess entropy, within the two-particle approximation, displays the same linear dependence on energy landscape properties as the diffusivity.

Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface

“…24 This feature is encoded, in an effective way, in a number of models of energy landscapes developed in the last years, 25,26,27,28 and has sometimes been addressed in numerical simulations. 29 Statistical properties of high-order stationary points of the PES have been investigated recently for a variety of monoatomic and binary systems, both in the liquid 30,31 and supercooled regime. 17,32 The existence of some universal features in the energy landscape of different model liquids 17,32 has been highlighted.…”

Structural predictor for nonlinear sheared dynamics in simple glass-forming liquids

“…For simple spherical particle fluids, the two-body excess entropy is found to account for more than 90% of the total excess entropy (31,32). The two-body excess entropy scaling has found widespread use in predicting the dynamics of, for example, metallic and hydrogen-bonding liquids such as water (23,(33)(34)(35)(36)(37). From a practical point of view, it is easier to calculate the twobody excess entropy requiring only knowledge of g(r) rather than calculating the full excess entropy that may require sophisticated free-energy methods (24).…”

Determining landscape-based criteria for freezing of liquids

“…20 Here we extend the earlier study by considering the correlation of a wider range of landscape properties which could potentially be correlated with the available configurational volume as well as by examining the liquid at several state points in the neighborhood of the freezing transition, both in the stable and supercooled regimes. 1 Our recent work on pair-additive Lennard-Jones liquids in the stable liquid regime where the Dzugutov scaling relationship holds showed that diffusivity, and therefore also the exponential of the excess entropy, depends linearly on several landscape properties, such as mean curvature and the fraction of negative curvature directions associated with the instantaneous configurations sampled from a suitable ensemble probability distribution.…”

“…10,20 No spherical potential cutoff was required for the densities and simulation cell sizes used here. Parameter a fixes the length of the interaction, so that the attraction is smoothly truncated to zero at r = a. Parameters A and a are chosen to reproduce the location and depth of the minimum in the 12-6 Lennard-Jones potential and are set to A = 6.767 441 and a = 2.464 918 32.…”