AN IMPROVED REPRESENTATION FOR THE HIGH-DENSITY STRUCTURE OF LENNARD-JONES SYSTEMS - FROM LIQUID TOWARD GLASS

We show that a modified hypernetted-chain (MHNC) integral equation wit h a properly chosen hard sphere bridge function can yield an excellent representation for the high-density structure and thermodynamics of m onatomic Lennard-Jones (LJ) systems, continuously from fluid to superc ooled liquid and glassy states. In particular, the theory is able to r eproduce the gradual development of the second peak splitting in the r adial distribution function. The LJ bridge function is approximated wi th a hard sphere bridge function calculated through a slight modificat ion of a formula due to Malijevsky and Labik (ML). To select the equiv alent hard sphere diameter d, several methods are tested. First, a cri terion proposed by Rosenfeld and Blum and, second, a best fit of struc tural and thermodynamic simulation data; finally, an empirical paramet rization for d as a function of density and temperature. For stable fl uid states the predictions of the MHNC-ML theory are successfully comp ared with a wide set of simulation results from the literature. For su percooled liquid and glassy states the comparison is made with a molec ular dynamics simulation of an isochoric quench, which we have perform ed.