Monomer adsorption on bcc (110) surfaces with first- and second-neighbor interactions

Abstract

The low-temperature phases of monomer adsorption on body-centered-cubic (110) surfaces, infinite in one direction and of finite width, M, with non-periodic boundaries, are obtained with first- and second-neighbor interactions. These ordered phases, far below the critical temperature, are observed at values of the external gas pressure within specific ranges, and are characterized by M and the values of the interaction energies. One finds two distinct sets of phases, depending on whether first-neighbor interactions are repulsive or attractive. As in the case of the square lattice, most of the numerical results fit exact closed-form expressions in M, allowing analytic extrapolations to the infinite two-dimensional surface ( M=∞). The conditions under which a transition from one ordered phase to another ordered phase are also determined, depending on M and the first- and second-neighbor interaction energies. To the extent to which these interactions are predominant, the model shows that it is possible to obtain them from an experimental observation of the phases and the external gas pressure at which transitions between phases occur. The finite width results are of particular interest when considering adsorption on terraces.