Valency

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

X-ray absorption spectra and the local structure of nickel in some oxycompounds and fluorides

Abstract: X-ray absorption spectra were measured for a number of nickel oxycompounds and fluorides which contain nickel with valencies in the range of 2 to 4. Information on the local structure and nature of bonding of nickel were derived using theoretical standards generated with the FEFF code. The energies of the main Ni K-edge and the pre-edge peak were found to shift to higher values by about 1.5 and 0.6 eV, respectively, per unit increase in the valency of nickel. The average Ni-O and Ni-F bond length within the octahedron decreased linearly with increase in nickel valency from 2 to 4. The local structure parameters for the higher valency nickel oxycompounds are consistent with a multi-phase model in which up to three phases corresponding to Ni 2+ , Ni 3+ , and Ni 4+ could be present in different proportions depending on preparation procedures.

The crystal structure of tetrachlorocyclohexane, M. P. 174° C

Abstract: Following electron diffraction measurements of the vapour of tetrachlorocyclohexane of m.p. 174°C., a crystal-structure determination of the substance was carried out. The crystals are orthorhombic pseudotetragonal with two molecules in the unit cell. The space group is D23–P21212. Fourier projections of the structure in the planes (001) and (010) are given. The configuration of the molecule is 1∊, 2∊, 4κ, 5κ. Some deviations from an `ideal' structure with tetrahedral valency angles are observed.

Extending the coverage of a valency dictionary

Abstract: Information on subcategorization and selectional restrictions is very important for natural language processing in tasks such as monolingual parsing, accurate rule-based machine translation and automatic summarization. However, adding this detailed information to a valency dictionary is both time consuming and costly.In this paper we present a method of assigning valency information and selectional restrictions to entries in a bilingual dictionary, based on information in an existing valency dictionary. The method is based on two assumptions: words with similar meaning have similar subcategorization frames and selectional restrictions; and words with the same translations have similar meanings. Based on these assumptions, new valency entries are constructed for words in a plain bilingual dictionary, using entries with similar source-language meaning and the same target-language translations. We evaluate the effects of various measures of similarity.

A modern version of Lewis’s theory of valency

Abstract: A modern version of Lewis’s theory of valency is presented. This takes account of the results of quantum–mechanical calculations on molecules. Topics covered are polar covalent bonds, hypervalency, coordinate bonds, nonintegral bonds, oxo-anions, variable valency among transition elements, and nonclassical compounds. A distinction is drawn between the valence shell of an atom and the Lewis shell. The concept of a fractional bond pair is presented.

EngVallex - English Valency Lexicon

Abstract: EngVallex is the English counterpart of the PDT-Vallex valency lexicon, using the same view of valency, valency frames and the description of a surface form of verbal arguments. EngVallex contains links also to PropBank and Verbnet, two existing English predicate-argument lexicons used, i.a., for the PropBank project. The EngVallex lexicon is fully linked to the English side of the PCEDT parallel treebank, which is in fact the PTB re-annotated using the Prague Dependency Treebank style of annotation. The EngVallex is available in an XML format in our repository, and also in a searchable form with examples from the PCEDT.