Thermodynamics and kinetics of homogeneous crystal nucleation studied by computer simulation

Crystal nucleation is numerically simulated in the Lennard-Jones model. By isobaric cooling and isothermal compression of a liquid, we succeeded in fu lly crystallizing a large number of systems up to 10000 atoms. We assessed thermodynamic data (density, enthalpy, and chemical potential) of the cryst alline as well as the (metastable) liquid phase for considerably larger ran ges of pressure and temperature than published so far. Using these data, we were able to confront our simulation results with classical nucleation the ories without the need to recognize a critical cluster during the simulatio ns. One of the findings is that in our experiments the steady-state nucleat ion regime was almost never reached. Careful analysis resulted in an estima te of the time-dependent effects in the nucleation rate, during which the n ucleation rate grows from zero to its steadystate value. This way we were a ble to determine the values of the steady-state nucleation rate, which are consistent with independent estimates for both the preexponential factor an d the nucleation barrier. In most previous experimental and simulation stud ies by other research groups, preexponential factors have been found that a re orders of magnitude too large or too small. Our investigations show that an important factor in this discrepancy could be due to an underestimation of time-dependent nucleation effects.