Molecular dynamics study of a two-dimensional system with screened Coulomb interactions

We have used molecular dynamics to study a two-dimensional system of point particles with screened Coulomb interactions, in a "box" whose size is allowed to vary. In addition to determining the familiar energy-temperature relations at both constant area and constant pressure, we have obtained pressure-area isotherms, diffusion constants, and pair-correlation functions. The results of our simulation are expected to be relevant to such systems as polar monolayers on the surface of water (Langmuir films) and thin colloidal suspensions. By monitoring the energy-temperature relation and the diffusion constant, we have observed first order solid-liquid transitions with hysteresis under both constant area and constant pressure conditions. However, the discontinuities in the pressure-area isotherms at the transition are almost imperceptible. Other thermodynamic relations such as area vs temperature at constant pressure, and the derivative of pressure vs area, are presented to support the analysis.