An improved representation for the high-density structure of Lennard-Jones systems: From liquid toward glass

Abstract

We show that a modified hypernetted-chain (MHNC) integral equation with a properly chosen hard sphere bridge function can yield an excellent representation for the high-density structure and thermodynamics of monatomic Lennard-Jones (LJ) systems, continuously from fluid to supercooled liquid and glassy states. In particular, the theory is able to reproduce the gradual development of the second peak splitting in the radial distribution function. The LJ bridge function is approximated with a hard sphere bridge function calculated through a slight modification of a formula due to Malijevsky and Labik (ML). To select the equivalent hard sphere diameter d, several methods are tested. First, a criterion proposed by Rosenfeld and Blum and, second, a best fit of structural and thermodynamic simulation data; finally, an empirical parametrization for d as a function of density and temperature. For stable fluid states the predictions of the MHNC-ML theory are successfully compared with a wide set of simulation results from the literature. For supercooled liquid and glassy states the comparison is made with a molecular dynamics simulation of an isochoric quench, which we have performed.