Topic
Valence (chemistry)
About: Valence (chemistry) is a research topic. Over the lifetime, 24937 publications have been published within this topic receiving 645252 citations. The topic is also known as: valency.
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TL;DR: The catalytic mechanisms of transition-metal compounds during the hydrogen sorption reaction of magnesium-based hydrides were investigated through relevant experiments and found to be influenced by four distinct physico-thermodynamic properties.
Abstract: The catalytic mechanisms of transition-metal compounds during the hydrogen sorption reaction of magnesium-based hydrides were investigated through relevant experiments. Catalytic activity was found to be influenced by four distinct physico-thermodynamic properties of the transition-metal compound: a high number of structural defects, a low stability of the compound, which however has to be high enough to avoid complete reduction of the transition metal under operating conditions, a high valence state of the transition-metal ion within the compound, and a high affinity of the transition-metal ion to hydrogen. On the basis of these results, further optimization of the selection of catalysts for improving sorption properties of magnesium-based hydrides is possible. In addition, utilization of transition-metal compounds as catalysts for other hydrogen storage materials is considered.
233 citations
TL;DR: In this paper, the authors derived the asymmetry parameters necessary for determining the differential cross-sections of randomly-oriented atoms within the one-electron, central-potential model and the dipole approximation for all subshells of C, O, Al, Si, S, Ni, Cu, Ga, Ge, As, Se, In, Sb, Cs, Ba, Ce, Ta, W, Pt, Au, and Pb.
233 citations
TL;DR: In this paper, the authors investigated the methane oxidation activity and structure of a number of complex metal oxides with the objective of determining the relationship between catalytic and such solid-state parameters as the type of transition metal cation incorporated in the oxide crystal structure, the metalcation valence state, oxygen stoichiometry, and defect structure.
232 citations
TL;DR: The spectra are found to be dominated by iron np to 1s electric dipole allowed transitions, with pronounced sensitivity to spin state, ligand identity, lig and ionization state, hybridization state and metal-ligand bond lengths.
Abstract: A systematic study of 12 ferric and ferrous Kβ X-ray emission spectra (XES) is presented. The factors contributing to the Kβ main line and the valence to core region of the spectra are experimentally assessed and quantitatively evaluated. While the Kβ main line spectra are dominated by spin state contributions, the valence to core region is shown to have greater sensitivity to changes in the chemical environment. A density functional theory (DFT) based approach is used to calculate the experimental valence spectra and to evaluate the contributions to experimental intensities and energies. The spectra are found to be dominated by iron np to 1s electric dipole allowed transitions, with pronounced sensitivity to spin state, ligand identity, ligand ionization state, hybridization state, and metal−ligand bond lengths. These findings serve as an important calibration for future applications to iron active sites in biological and chemical catalysis. Potential applications to Compound II heme derivatives are high...
231 citations
TL;DR: A study of the structural and electronic properties of selected transition metals and their carbides and nitrides is presented in this article, focusing on assessing trends of possible importance for understanding their hardness.
Abstract: A study of the structural and electronic properties of selected transition metals and their carbides and nitrides is presented We focus on assessing trends of possible importance for understanding their hardness Lattice constants, bulk moduli (B[sub o]), and charge densities are calculated using the local density approximation with a pseudopotential plane wave approach An fcc lattice is employed for the transition metal elements in order to make comparisons and study trends relateable to their carbides and nitrides Our results show that both increasing the number of valence d electrons and the presence of f electrons in the core lead to larger (B[sub o]) Charge density plots and histograms enable us to explain the nature of the charge distribution in the interstitial region for the different compounds considered In addition, we include the heavier elements seaborgium, bohrium, and hasnium in order to test further trends Surprisingly, the calculated B[sub o] for Hs is comparable to that of diamond [copyright] [ital 1999] [ital The American Physical Society]
231 citations