Vicinal surface with Langmuir adsorption: A decorated restricted solid-on-solid model

We study the vicinal surface of the restricted solid-on-solid model coupled with the Langmuir adsorbates that we regard as two-dimensional lattice gas without lateral interaction. The effect of the vapor pressure of the adsorbates in the environmental phase is taken into consideration through the chemical potential. We calculate the surface free energy f, the adsorption coverage Theta, the step tension gamma, and the step stiffness <(<gamma>)over tilde> by the transfer matrix method combined with the density-matrix algorithm. Detailed step-density dependence of (c)(j) and Theta is obtained. We draw the roughening transition curve in the plane of the temperature and the chemical potential of adsorbates. We find the multireentrant roughening transition accompanying the inverse roughening phenomena. We also find quasireentrant behavior in the step tension.