SUPPLEMENT III: Results Associated with a Hexagonal Surface Feature The following is a supplement to the article "Predicting Microstructure from Atomistic Rule Set Cellular Automata" by K.J.W. Atkinson et al., which is as part of JOM-e, 51 (8) (1999).
Main Text Supplement I: Perfect Surface Supplement II: Distributed Surface Roughness Supplement IV: Canyon Surface Feature

For this work, the starting surface consists of 100 x 100 atoms and is initially free of argon gas. A hexagonal feature of calcium atoms on B sites covers approximately 10% of the surface. Movies I-L illustrate the evolution of the surface when exposed to 8% argon flux at different temperatures (each movie frame represents 200 time steps). Figures I-L depict surface evolution at various time steps and temperatures.

For simulations carried out at 90 K, 100 K, and 120 K, the surface tends toward a microstructure that is dominated by all B-site gas atoms (i.e., the same site as the hexagon). The growth of the B-site gas atom coverage seems to spread from the hexagonal feature, but this is not the only point from which B-site growth proceeds. At 140 K, the surface is again dynamic and no longer able to proceed toward a single-site configuration. There is also some evidence at this temperature of B-site stability at the perimeter of the hexagonal feature, but this does not extend far into the remaining surface. The change from stable evolution to a dynamic configuration occurs at a critical temperature, and reduced coverage is evident above the critical temperature.

Color Key		Initial Surface
Argon Gas Atom on B Site	Argon Gas Atom on C Site
Fixed Calcium Atom on B Site	Fixed Calcium Atom on C Site

Movie I (~1.1 Mb) T = 90 K	Figure Ia t = 100; T = 90 K	Figure Ib t = 1,000; T = 90 K	Figure Ic t = 10,000; T = 90 K	Figure Id t = 100,000; T = 90 K
Movie J (~1.4 Mb) T = 100 K	Figure Ja t = 100; T = 100 K	Figure Jb t = 1,000; T = 100 K	Figure Jc t = 10,000; T = 100 K	Figure Jd t = 100,000; T = 100 K
Movie K (~2.8 Mb) T = 120 K	Figure Ka t = 100; T = 120 K	Figure Kb t = 1,000; T = 120 K	Figure Kc t = 10,000; T = 120 K	Figure Kd t = 100,000; T = 120 K
Movie L (~3.8 Mb) T = 140 K	Figure La t = 100; T = 140 K	Figure Lb t = 1,000; T = 140 K	Figure Lc t = 10,000; T = 140 K	Figure Ld t = 100,000; T = 140 K