Valency

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

Acid–Base Control of Valency within Carboranedithiol Self-Assembled Monolayers: Molecules Do the Can-Can

Abstract: We use simple acid–base chemistry to control the valency in self-assembled monolayers of two different carboranedithiol isomers on Au{111}. Monolayer formation proceeds via Au–S bonding, where manipulation of pH prior to or during deposition enables the assembly of dithiolate species, monothiol/monothiolate species, or combination. Scanning tunneling microscopy (STM) images identify two distinct binding modes in each unmodified monolayer, where simultaneous spectroscopic imaging confirms different dipole offsets for each binding mode. Density functional theory calculations and STM image simulations yield detailed understanding of molecular chemisorption modes and their relation with the STM images, including inverted contrast with respect to the geometric differences found for one isomer. Deposition conditions are modified with controlled equivalents of either acid or base, where the coordination of the molecules in the monolayers is controlled by protonating or deprotonating the second thiol/thiolate on ...

Experiments on the choice of features for learning verb classes

Abstract: The choice of verb features is crucial for the learning of verb classes. This paper presents clustering experiments on 168 German verbs, which explore the relevance of features on three levels of verb description, purely syntactic frame types, prepositional phrase information and selectional preferences. In contrast to previous approaches concentrating on the sparse data problem, we present evidence for a linguistically defined limit on the usefulness of features which is driven by the idiosyncratic properties of the verbs and the specific attributes of the desired verb classification.

A computational exploration of CO2 reduction via CO dimerization on mixed-valence copper oxide surface

Abstract: The catalytic role of Cu ions in CO2 reduction on oxide-derived Cu has been elusive. In the presence of oxygen vacancy, CO⋯CO dimerization is predicted to be thermodynamically favorable with an accessible barrier on Cu4O3(202). The material's mixed valency is responsible for stabilizing the charge-separated (OC)δ+(CO)δ− intermediate.

Mixed valency transition metal perovskites as cathodic reduction catalysts

Abstract: Ionic crystals having a perovskite structure and comprising a solid solution of oxides of the formulas ABO3 and A''BO3 where A and A'' are nontransition metals and B is a transition metal present in two different valency states are effective cathodic electrocatalysts for use in electrochemical cells such as fuel cells.