Extending reverse nonequilibrium molecular dynamics to the calculation of mutual diffusion coefficients in molecular fluid mixtures

In a recent publication, a reverse nonequilibrium molecular dynamics method was introduced to calculate the mutual diffusion (binary diffusion, interdiffusion) coefficient of binary Lennard-Jones mixture directly. In this work, modification is made to this method for calculation the mutual diffusion coefficient of complicated binary mixture of molecules containing the same number of particle in calculation. As test, this method is applied to calculate the mutual diffusion coefficient of water/deuterium oxide (H2O/D2O) and benzene/cyclohexane (C6H6/C6H12) systems. Steady mass flows are induced by suitably exchanging molecule positions and velocities in different regions. The analysis of the resulting steady state concentration profiles allows the calculation of mutual diffusion coefficient. The obtained results are qualitative agreement with the references. The excess energy introduced by swapping molecules becomes strong when the studied mixture contains large and/or complicated molecules. For the systems studied, however, a standard thermostat is still able to remove the excess energy efficiently.