Nucleation rate isotherms of argon from molecular dynamics simulations

We report six nucleation rate isotherms of vapor-liquid nucleation of Lennard-Jones argon from molecular dynamics simulations. The isotherms span three orders of magnitude in nucleation rates, 10(23) < J/cm(-3) s(-1) < 10(26) , in a temperature range of 45-70 K below the triple point. The rates are very accurately determined using the concept of mean first-passage times, which also allows a determination of the critical cluster size directly from the kinetics. The results deviate from classical nucleation theory (CNT) by two to seven orders of magnitude, which nevertheless is much smaller than the more than 20 orders of magnitude encountered in recent experiments in a similar temperature range. The extended modified liquid drop-dynamical nucleation theory (EMLD-DNT) shows excellent agreement with the simulation results with deviations of less than one order of magnitude over the entire studied temperature range. Both simulation and experiment confirm the same incorrect temperature trend of CNT, which seems to be corrected in the EMLD-DNT model. However, the predictions of CNT for the critical cluster sizes agree well with the results obtained from the simulations using the nucleation theorem, supporting the notion that CNT successfully estimates the location of the transition state but severely fails to predict its height. (C) 2007 American Institute of Physics.