A molecular dynamics simulation study of octopoles in the field of a planar surface

Abstract

The molecular dynamics simulation method is used to investigate a model of tetrahedral molecules, such as methane, adsorbed in a monolayer at a flat surface, such as graphite. The model consists of 64 octopoles arranged in a planar triangular lattice, with nearest neighbour interactions, and with an external (surface) field applied. The equations of motion are framed entirely in terms of quaternion parameters. Orientational order parameters, and thermodynamic properties, are monitored, and a single phase transition, from a rotationally ordered to a disordered state, with a broad anomaly in the heat capacity, is observed.