(281a) Ideas Old and New Applied to Non-Ideal Surface Adsorption and Reaction

Free energies of adsorption are arguably the most elementary quantities in heterogeneous catalysis. These free energies depend on the surface and adsorbate (reactant, intermediate, or product) of interest, system temperature and adsorbate coverage. The free energy represents a balance between the energetic driving force for creating bonds between an adsorbate and a surface and the entropic cost of moving an adsorbate from a fluid phase to a surface. Standard density functional theory (DFT) approaches generally begin by optimizing the location of an adsorbate on a surface, computing a binding energy, and approximating the internal, translational, and configurational contributions to the free energy. In this work we examine the reliability of standard approximations and describe easily applied improvements that give reliable free energy estimates. We describe applications to adsorption at metal surfaces and in the pores of zeolites.