Roughening and preroughening in nonreconstructed fcc(110) surfaces: A Monte Carlo study

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Abstract
An anisotropic body-centered solid-on-solid (BCSOS) model Hamiltonian of the fcc(110) surface is reexamined and studied for the description of phase transitions on nonreconstructed noble- and near-noble-metal surfaces. The limit case corresponding to the isotropic BCSOS model is examined and some results are obtained for the staggered order-parameter susceptibility. With parameters roughly appropriate for a nonreconstructed surface such as Ag(110), a preroughening-type phase transition associated with the in-plane degrees of freedom is detected. It takes place somewhat below the roughening transition temperature and presents critical exponents which differ significantly from the two-dimensional Ising values. The analysis of the model is carried out through standard Monte Carlo simulation techniques. Scattering intensities are also evaluated, both to give a deeper insight into the disordered flat phase lying between the two transitions and to suggest a possible experimental verification of the proposed phase structure for the nonreconstructed two-sublattice surfaces.