A biased grand canonical Monte Carlo method for simulating adsorption using all-atom and branched united atom models

Configurational-bias Monte Carlo sampling techniques have been developed wh ich overcome the difficulties of sampling configuration space efficiently f or all-atom molecular models and for branched species represented with unit ed atom models. Implementation details of this sampling scheme are discusse d. The accuracy of a united atom forcefield with non-bond parameters optimi zed for zeolite adsorption and a widely used all-atom forcefield are evalua ted by comparison with experimental sorption isotherms of linear and branch ed hydrocarbons.