Determination of nucleation rates of FeCl2 in supercritical water by molecular dynamics simulations

Nucleation and growth of FeCl2 in supercritical water at different state points in the temperature range from 798 to 873 K and system densities between 0.18 and 0.13 g/cm3 have been studied by molecular dynamics simulations. For the determination of nucleation rates we employed and compared the method of Yasuoka and Matsumoto [J. Chem. Phys. 109 (1998) 8451–8462] and the mean first passage time method by Wedekind et al. [J. Chem. Phys. 126 (2007) 134103]. While the method of Yasuoka and Matsumoto could be applied straightforward, the method of Wedekind et al. needed additional assumptions to be applied successfully on the studied systems which show very fast nucleation and growth due to a very low-nucleation barrier. Depending on the applied method, the obtained nucleation rates vary between 1035 and 1037 m−3 s−1. The critical cluster sizes as estimated by the mean first passage time method vary between 12 and 15 ions for the thermodynamic conditions used in this study.