Quantification of Order in the Lennard-Jones System

TL;DR

This study investigates the structural order in Lennard-Jones systems across different phases and configurations, revealing relationships between order metrics and showing that Lennard-Jones and hard sphere systems share configuration space at high densities.

Contribution

It introduces a comprehensive analysis of order in Lennard-Jones systems using an ordering map, linking equilibrium and non-equilibrium states, and compares these with hard sphere systems.

Findings

Bond-orientational and translational order are not independent in simple systems.

Lennard-Jones and hard sphere systems sample the same configuration space at supercritical densities.

Structural order relates to inherent structures in quenched and minimized configurations.

Abstract

We conduct a numerical investigation of structural order in the shifted-force Lennard-Jones system by calculating metrics of translational and bond-orientational order along various paths in the phase diagram covering equilibrium solid, liquid, and vapor states. A series of non-equilibrium configurations generated through isochoric quenches, isothermal compressions, and energy minimizations are also considered. Simulation results are analyzed using an ordering map representation [Torquato et al., Phys. Rev. Lett. 84, 2064 (2000); Truskett et al., Phys. Rev. E 62, 993 (2000)] that assigns to both equilibrium and non-equilibrium states coordinates in an order metric plane. Our results show that bond-orientational order and translational order are not independent for simple spherically symmetric systems at equilibrium. We also demonstrate quantitatively that the Lennard-Jones and hard sphere systems sample the same configuration space at supercritical densities. Finally, we relate the structural order found in fast-quenched and minimum-energy configurations (inherent structures).