Molecular dynamics calculations of near-critical liquid oxygen droplet surface tension

Surface tension is an important concept when considering any aspect of droplet behavior. Surface tension causes the spherical geometry that droplets form and determines the liquid pressure within the droplet as a function of droplet size. As the critical point for the liquid is approached, the surface tension goes to zero and droplets no longer form, a defining aspect for supercritical conditions. The surface tension of liquid oxygen droplets in gaseous oxygen and helium environments at a variety of pressures was calculated in the course of a molecular dynamics simulation. The surface tension was calculated by averaging the net interatomic attractive force experienced by atoms in the simulation. The calculated values of surface tension as a function of pressure compared well with experimentally measured values. The effect of the helium environment in raising the critical point of the oxygen was reproduced by the simulations.