Computer simulation of nucleation and crystal growth

Abstract

The computer simulations of four crystallization phenomena: three- and two-dimensional nucleation, expansion of a monomolecular layer and crystal growth, are described in detail. They are based on the same molecular model as used in the classical theory of Volmer and others. The dependence of nucleation frequencies and rates of growth on supercooling is of the same order as in the classical theory. Their dependence on the interfacial free energy parameter is significantly different, large deviations being observed at low values of this parameter. Nuclei as defined in the classical theory do not show up in the simulations. Crystal growth appears to be controlled by successive initiations of monomolecular layers (the degree of supercooling not being small) if an initiation frequency is taken into account that follows from the simulation of secondary nucleation. Deviations arise at low values of the interfacial free energy parameter, where the growth face appears to be rough, whereas it is smooth at high values of this parameter. Induction times in the systems studied are negligible. Potential induction times for secondary nucleation are too small to influence rates of crystal growth. The simulation model allows many alterations and the building-in of various constraints. The method, therefore, seems appropriate for the study of various kinds of growth and adsorption phenomena.