Gas adsorption at a crystal surface changes the interfacial free energy and, therefore, modifies the corresponding equilibrium crystal shape (ECS). A simple lattice-gas model of the adsorption process, including both adatom-adatom and adatom–crystal-atom interactions, allows this shape change to be computed explicitly at zero temperature. The dependence of the ECS on the adsorbed-gas chemical potential is calculated for cubic crystals (sc, bcc, fcc) with a variety of crystal-atom–crystal-atom interactions. Adsorption changes the ECS both by causing the appearance of new facets and by altering the relative areas of existing facets. The shape-change systematics is given in terms of ECS phase diagrams.

• Received 15 June 1987

DOI:https://doi.org/10.1103/PhysRevB.36.9068