DOF phase separation of the Lennard-Jones fcc(111) surface

TL;DR

This study uses extensive molecular dynamics simulations to investigate phase separation on the Lennard-Jones fcc(111) surface, providing evidence for preroughening-driven phenomena in a realistic continuous system.

Contribution

It demonstrates that phase separation and preroughening predicted by lattice models also occur in a continuous Lennard-Jones system through detailed MD simulations.

Findings

Anomaly at ~0.83Tm indicating phase separation

Distinct roughening transition at ~0.94Tm

Evidence supports preroughening-driven phase separation scenario

Abstract

Recent lattice model calculations have suggested that a full-layered crystal surface may undergo, under canonical (particle-conserving) conditions, a preroughening-driven two-dimensional phase separation into two disordered flat (DOF) regions, of opposite order parameter. We have carried out extensive classical molecular dynamics (MD) simulations of the Lennard-Jones fcc(111) surface, to check whether these predictions are relevant or not for a realistic continuous system. Very long simulation times, a grid of temperatures from (2/3)Tm to Tm, and unusually large system sizes are employed to ensure full equilibrium and good statistics. By examining layer-by-layer occupancies, height fluctuations, sublattice order parameter and X-ray structure factors, we find a clear anomaly at ~0.83Tm. The anomaly is distinct from roughening (whose incipiency is also detected at ~0.94Tm), and is seen to be consistent with the preroughening plus phase separation scenario.