Van der Waals effect in weak adsorption affecting trends in adsorption, reactivity, and the view of substrate nobility

The ubiquitous van der Waals (vdW) force, particularly discernible in weak adsorption, is studied on noble and transition metals. In calculations with the vdW density functional (DF) [ M. Dion et al., Phys. Rev. Lett. 92, 246401 (2004)], the atomic structure near the adsorption site is systematically varied, including dense fcc(111) surface, adatom, pyramid, and step defects. In weak adsorption the vdW force (i) is shown necessary to account for, (ii) is sizable, (iii) has a strong spatial variation, relevant for adsorption on surface defects, (iv) changes reaction rules, and (v) changes adsorption trends in agreement with experimental data. Traditional physisorption theory is also given support and interpretation

The effect of surface relaxation on the N-2 dissociation rate on stepped Ru: A Transition State Theory Study

van Harrevelt R, Honkala K, Norskov JK, Manthe U. The effect of surface relaxation on the N2 dissociation rate on stepped Ru: A Transition State Theory Study. Journal of Chemical Physics. 2006;124(2):026102: 026102

The reaction rate for dissociative adsorption of N-2 on stepped Ru(0001): Six-dimensional quantum calculations

van Harrevelt R, Honkala K, Norskov JK, Manthe U. The reaction rate for dissociative adsorption of N2 on stepped Ru(0001): Six-dimensional quantum calculations. Journal of Chemical Physics. 2005;122(23): 234702.Quantum-mechanical calculations of the reaction rate for dissociative adsorption of N-2 on stepped Ru(0001) are presented. Converged six-dimensional quantum calculations for this heavy-atom reaction have been performed using the multiconfiguration time-dependent Hartree method. A potential-energy surface for the transition-state region is constructed from density-functional theory calculations using Shepard interpolation. The quantum results are in very good agreement with the results of the harmonic transition-state theory. In contrast to the findings of previous model calculations on similar systems, the tunneling effect is found to be small. (C) 2005 American Institute of Physics

Density functional study of the adsorption and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2

Accurate calculations of adsorption energies of cyclic molecules are of key importance in investigations of, e.g., hydrodesulfurization (HDS) catalysis. The present density functional theory (DFT) study of a set of important reactants, products, and inhibitors in HDS catalysis demonstrates that van der Waals interactions are essential for binding energies on MoS2 surfaces and that DFT with a recently developed exchange-correlation functional (vdW-DF) accurately calculates the van der Waals energy. Values are calculated for the adsorption energies of butadiene, thiophene, benzothiophene, pyridine, quinoline, benzene, and naphthalene on the basal plane of MoS2, showing good agreement with available experimental data, and the equilibrium geometry is found as flat at a separation of about 3.5 \uc5 for all studied molecules. This adsorption is found to be due to mainly van der Waals interactions. Furthermore, the manifold of adsorption-energy values allows trend analyses to be made, and they are found to have a linear correlation with the number of main atoms. \ua9 2009 American Institute of Physics

Functional Independent Scaling Relation for ORR/OER Catalysts

A widely used adsorption energy scaling relation between OH* and OOH* intermediates in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), has previously been determined using density functional theory and shown to dictate a minimum thermodynamic overpotential for both reactions. Here, we show that the oxygen–oxygen bond in the OOH* intermediate is, however, not well described with the previously used class of exchange-correlation functionals. By quantifying and correcting the systematic error, an improved description of gaseous peroxide species versus experimental data and a reduction in calculational uncertainty is obtained. For adsorbates, we find that the systematic error largely cancels the vdW interaction missing in the original determination of the scaling relation. An improved scaling relation, which is fully independent of the applied exchange–correlation functional, is obtained and found to differ by 0.1 eV from the original. This largely confirms that, although obtained with a method suffering from systematic errors, the previously obtained scaling relation is applicable for predictions of catalytic activity