Statistical mechanics of vicinal surface : Thermodynamical interplay between adsorption and surface steps

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We have presented a restricted-solid-on-solid (RSOS) model ceupled with Ising (RSOS-IC) system in order to study thermodynamical interplay between surface and adsorbate. We have made statistical mechanical calculation on the vicinal surfacu of the RSOS-IC model. by a transfer matrix method with the product wave-function renormalization group (PWFRG) algorithm, which is an extended method of the density matrix renormalization group(DMRG) algorithm.Results1.The case of the attractive interaction among adsorbates in the lateral direction.We have studied the slope, temperature, and chemical potential dependence of the surface free energy, adsorption coverage, step tension, and step stiffness. Then, we have established the thermal step bunching (or the macro step formation) in the equilibrium, where the thermal step bunching we call is the thermodynamical step condensation. We find that two mechanisms cause the thermal step bunching : the external field induced bunching, and the adsorption … More density fluctuation induced bunching.2.The case of the repulsive interaction among adsorbates in the lateral direction.In this case, the field induced thermal step bunching disappears as is expected. On the other hand, the fluctuation induced thermal step bunching appears. In low temperature, the planar surface with adsorption has adsorption induced ordered structure with √2x√2R45. In high temperature, the order is destroyed to lxldisrodered structure. Around the order-disorder transition temperature, the fluctuation of the adsorption induced ordered structure causes short-range attractive interaction between steps. Then, steps condense due to the adsorption induced inter-step attraction. By the detailed calculation, we have obtained the phase diagram.3.The case of the strong microscopic interaction between step and adsorption.The surface model with the non-monotonic temperature dependence of step stiffness has not known, so far. We find that the RSOS-IC model shown the non-monotonic temperature dependence of the step stiffness in case of the strong microscopic interaction between a step and adsorbates. Less