Molecular Dynamics Method for Simulating Diffusivities

A new two-parameters, namely temperature and pressure relaxation times, model was proposed based on the basis of the isothermal-isobaric MD methods and both the parameters optimized by using the orthogonal test are 2 fs. The maximal deviation of system volume simulated under the optimal conditions was within the limit of 10%. The new model was used to simulate the selfdiffusion coefficients of argon and supercritical carbon dioxide at different temperatures, and the influence of temperature and pressure on selfdiffusion coefficients was analyzed qualitatively by the use of the kinetics theory. Good agreement is obtained between the simulated results and the experimentally measured data.