  We describe a numerical model of faceted crystal growth using a cellular
automata method that incorporates admolecule diffusion on faceted surfaces in
addition to bulk diffusion in the medium surrounding the crystal. The model was
developed for investigating the diffusion-limited growth of ice crystals in air
from water vapor, where the combination of bulk diffusion and strongly
anisotropic molecular attachment kinetics yields complex faceted structures. We
restricted the present model to cylindrically symmetric crystal growth with
relatively simple growth morphologies, as this was sufficient for making
quantitative comparisons between theoretical models and ice growth experiments.
Overall this numerical model reproduces ice growth behavior with reasonable
fidelity over a wide range of conditions, albeit with some limitations. The
model could easily be adapted for other material systems, and the cellular
automata technique appears well suited for investigating crystal growth
dynamics when strongly anisotropic surface attachment kinetics cause faceted
growth morphologies.
