Nonequilibrium molecular-dynamics simulation of net evaporation and net condensation, and evaluation of the gas-kinetic boundary condition at the interphase

Algorithms for simulating steady net evaporation and net condensation with molecular dynamics are presented. The evaporation and condensation coefficients are calculated, showing that they are not equal outside equilibrium. The distribution function at the interphase boundary is evaluated. There is a drift away from the interphase in the distribution function for the evaporated molecules and a drift velocity towards the interphase for the reflected molecules, both for net evaporation and for net condensation.