SUPPLEMENT IV: Results Associated with a Canyon 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 III: Hexagonal Surface Feature

For this work, the surface consists of 100 x 100 atoms and is initially free of argon gas. The surface has two opposite edges filled with ten rows of fixed calcium atoms. One edge has the fixed calcium atoms on B sites, while the other has the fixed calcium atoms on C sites. A perfect surface, 80 atoms wide, exists between these two regions. We have termed this surface topography as the canyon. Movies M-P illustrate the evolution of the surface when exposed to 8% argon flux at different temperatures (each movie frame represents 200 time steps). Figures M-P depict surface evolution at various time steps and temperatures.

As in all 90 K, 100 K, and 120 K simulations, during the first 1,000 time steps, a mixed-site microstructure is observed, which evolves to form larger domains. By approximately 1,000 time steps, the gas atoms immediately adjacent to the canyon walls are predominantly of the same site type as the walls; over the remaining 99% of the simulation time, the microstructure evolves toward a stable dual-domain configuration with a linear interface. At 140 K, the surface is dynamic, and no stable structure evolves between the canyon walls. The change from stable evolution to a dynamic configuration occurs at a critical temperature, and above the critical temperature there is a reduction in coverage.

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 M (~920 kb) T = 90 K	Figure Ma t = 100; T = 90 K	Figure Mb t = 1,000; T = 90 K	Figure Mc t = 10,000; T = 90 K	Figure Md t = 100,000; T = 90 K
Movie N (~1 Mb) T = 100 K	Figure Na t = 100; T = 100 K	Figure Nb t = 1,000; T = 100 K	Figure Nc t = 10,000; T = 100 K	Figure Nd t = 100,000; T = 100 K
Movie O (~2.4 Mb) T = 120 K	Figure Oa t = 100; T = 120 K	Figure Ob t = 1,000; T = 120 K	Figure Oc t = 10,000; T = 120 K	Figure Od t = 100,000; T = 120 K
Movie P (~3.4 Mb) T = 140 K	Figure Pa t = 100; T = 140 K	Figure Pb t = 1,000; T = 140 K	Figure Pc t = 10,000; T = 140 K	Figure Pd t = 100,000; T = 140 K