Island Formation and Condensation of a Chemisorbed Overlayer.
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The condensation of a chemisorbed overlayer from a lattice gas into a particular ordered structure is discussed in terms of the lattice-gas theory of Lee and Yang. The formation of islands of ordered structure is identified with the condensation phenomenon predicted by the theory. The phase diagram transition temperature vs. coverage based on the theory of a two-dimensional Ising ferromagnet in zero magnetic field is constructed for the condensation of a lattice gas system with net attractive interactions between the particles. It is demonstrated that critical points at coverages other than theta 0.5 are achieved for overlayer systems with unit meshes larger than 1 x 1. Low-energy electron diffraction results of the thermal disordering island dissolution for oxygen chemisorbed on W110 are compared with the theory, and the effect of substrate surface heterogeneity on the phase diagram is discussed. Author
- Physical Chemistry