Valency

About: Valency is a research topic. Over the lifetime, 1632 publications have been published within this topic receiving 26141 citations.

Metal Ions in Unusual Valency States.

Abstract: This paper is concerned with the formation of novel valency states, their characterization and chemical behavior.

Compressibility and Polymorphism of Solids

Abstract: : The compressibility of solids is expressed in terms of fundamental physical quantities in relation to the energy of an electron in the L-shell orbital. When the concept of 'apparent valency' z sub a = (rho)z, the product of classical valency (z) and the ratio (rho) of the atomic coordinations of two successive polymorphs is used, the formula becomes generally applicable. As a result, the structure of each substance under ambient conditions can be classified as being either in the 'reduced,' 'basic' or 'elevated' state. This allows the prediction of volumetric compressibility data from pertinent atomic data and physical constants as well as a qualitative prediction of possible structural modifications. The relationship between the damping parameter of a solid and the radius ratio is shown to be useful in differentiating between the various possible structural modifications under a given set of pressure and temperature conditions. (Author)

Ternary ion exchange. Part 4.—Activity corrections for the solution phase

Abstract: A previously developed model for the evaluation of activity coefficient ratios in mixed dilute solution is employed with particular respect to ternary cation exchange in zeolites in the presence of up to three different coanions in solution. Potential errors arising from ignoring either completely or partially the non-ideality correction for the solution phase are evaluated and discussed. Exchanges involving counter-ions of the same valency, or involving ions of different valencies, are both considered. It is shown that when all the counter-ions have the same valency, the magnitude of the non-ideality correction is independent of the selectivity of the exchanger. When the valencies of the counter-ions are different it is essential to apply the mixed-salt activity correction for any accurate studies of ternary ion-exchange equilibria.

Exploring Structure-Sensitive Relations for Small Species Adsorption Using Machine Learning

Abstract: Accurate prediction of adsorption energies on heterogeneous catalyst surfaces is crucial to predicting reactivity and screening materials. Adsorption linear scaling relations have been developed extensively but often lack accuracy and apply to one adsorbate and a single binding site type at a time. These facts undermine their ability to predict structure sensitivity and optimal catalyst structure. Using machine learning on nearly 300 density functional theory calculations, we demonstrate that generalized coordination number scaling relations hold well for oxygen- and high-valency carbon-binding species but fail for others. We reveal that the valency and the electronic coupling of a species with the surface, along with the site type and its coordination environment, are critical for small species adsorption. The model simultaneously predicts the adsorption energy and preferred site and significantly outperforms linear scalings in accuracy. It can expose the structure sensitivity of chemical reactions and enable enhanced catalyst activity via engineering particle shape and facet defects. The generality of our methodology is validated by training the model with transition metal data and transferring it to predict adsorption energies on single-atom alloys.

Identifying valency and occupation sites of Ir dopants in antiferromagnetic α-Fe2O3 thin films with X-ray absorption fine structure and Mössbauer spectroscopy

Abstract: A combined analysis of Ir-doped α-Fe2O3 (001) films, which show a drastic enhancement in the Morin transition temperature as a result of Ir doping, was performed by employing X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Mossbauer spectroscopy analyses at room temperature. The Mossbauer spectra reveal that the valency of Fe remains 3+ after Ir doping. The XANES spectra indicate that the valency of the Ir ion in Ir-doped α-Fe2O3 varies from 3+ to 4+. The EXAFS analysis results clarified that the Ir ions occupy the Fe-sites of α-Fe2O3. These findings help elucidate the mechanism for controlling the Morin transition temperature in α-Fe2O3 films toward antiferromagnetic spintronic applications.