Our calculations with spin-polarized density functional theory were carried out to characterize the adsorption and dissociation of the NH3 molecule on the Fe(111) surface. The molecular structures and adsorbate/substrate interaction energies of NH3/Fe(111), NH2/Fe(111), NH/Fe(111), N/Fe(111), and H/Fe(111) configurations were predicted. In these calculations, four adsorption sites, such as top (T), bridge (B), 3-fold-shallow (S), and 3-fold-deep (D) sites, of the Fe(111) surface, were considered. It was shown that the barriers for the stepwise NH3 dissociation reaction, NH3(g) -> N-(a) + 3H((a)), are 28.32 kcal/mol (for H2N-H bond activation), 28.49 kcal/mol (for HN-H bond activation), and 25.34 kcal/mol (for N-H bond activation), and the entire process is 20.08 kcal/mol exothermic. To gain insight into the catalytic activity of the Fe(111) surface for the dehydrogenation of NH3, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis

We have studied the mechanism of the waterÀgas shift reaction (WGS, CO + H 2 O f CO 2 + H 2 ) catalyzed by nanosized gold particles by using density functional theory calculations. The molecular structures and adsorbate/ substrate interaction energies of H 2 O/Au 38 , CO/Au 38 , HO/Au 38 , and H/Au 38 configurations were predicted. Several adsorption sites on the Au 38 nanoparticle were considered in this study and characterized as top, bridge, hollow, and hcp sites. A potential energy surface for WGS reaction on the Au 38 nanoparticle has been constructed using the nudged elastic band method. It was found that water dissociation (H 2 O f H + OH) is the rate-limiting step, with an energy barrier of 31.41 kcal/mol. The overall reaction CO + H 2 O + Au 38 f CO 2 + H 2 + Au 38 is exothermic by 16.18 kcal/mol. To gain insights into the high catalytic activity of the gold nanoparticles, the nature of the interaction between adsorbate and substrate is also analyzed by the detailed electronic local density of states.

In this work, we identified a large number of structurally distinct isomers of midsized deprotonated water clusters, OH(-)(H2O)n=4-7, using first-principles methods. The temperature dependence of the structural variation in the solvation shell of OH(-) for these clusters was examined under the harmonic superposition approximation. We simulated the vibrational and photoelectron spectra based on these thermodynamic calculations. We found that the isomers with 3-coordinated hydroxide dominate the population in these midsized clusters. Furthermore, an increase in temperature causes a topological change from compact isomers with many intermolecular hydrogen bonds to open isomers with fewer but more directional intermolecular hydrogen bonds. We showed that this evolution in structure can be observed through the change in the vibrational spectra at 3200-3400 cm(-1). In addition, the increase in directional hydrogen bonded isomers, which have outer hydration shell with OH bonds pointing to the hydroxide, causes the vertical detachment energy to increase at higher temperatures. Lastly, we also performed studies to understand the variation in the aforementioned spectral quantities with the variation in the coordination number of the hydroxide.