Mathematical models of water nucleation process for the Direct Simulation Monte Carlo method

Two models of the nucleation process are developed on the basis of (a) size corrected classical nucleation theory and (b) kinetic approach within the Direct Simulation Monte Carlo method. Expressions for probabilities of cluster formation/decomposition reactions are proposed using the models for corresponding rate constants. Both models are employed for the direct simulation of stationary nucleation process in a spatially homogeneous water vapor, where the monomer parameters are kept constant. The relaxation of size distribution function of water clusters is computed for moderate supersaturation values and temperature of 320 K. Numerical analysis shows sufficient difference in results obtained within above mentioned models. The difference arises due to the incorrect description of the internal cluster temperatures caused by the limitation of the classical nucleation theory consisting in one-temperature approximation, which does not describe the details of the energy relaxation. The impact of the dimer formation mechanism (by triple and binary collisions) on cluster size distribution is also analyzed.