Adsorption chemical potential (${\mu }_{\mathrm{ads}}=k_{\mathrm{B}}T\ln [\theta /(1-\theta )]-k_{\mathrm{B}}T\ln z$)

The chemical potential of an ideal single-occupancy lattice gas with occupied-site internal partition function $z$ and surface coverage $\theta$. The ratio $\theta /(1-\theta )$ accounts for the entropy of distributing particles among occupied and vacant adsorption sites.