New Approaches for Describing Non-Ideal Adsorption and Reaction at Transition Metal Surfaces

Computational modeling of heterogeneous catalysis relies on our ability to efficiently model the free energies of adsorption. These free energies depend on a number of factors, including the nature of adsorbate/surface composition, system temperature, gas phase reactant and product partial pressures, and adsorbate coverage. Under a given set of conditions, the system attempts to minimize its free energy. The minimization of free energy is driven by two competing factors: energetic driving force for creating adsorbate-surface bonds and the entropic cost of reducing the degrees of freedom of an adsorbate as it moves from a fluid phase to the surface. Standard density functional theory (DFT) approaches begin with the optimization of the location of an adsorbate on a surface and computation of the associated binding energy, followed by approximation of internal, translational, and configurational contributions to the free energy. In this work, we explored both the aspects of free energy, the contribution from creation of adsorbate-surface bonds and the estimation of entropic contribution to the free energy.