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Bond length
About: Bond length is a research topic. Over the lifetime, 19966 publications have been published within this topic receiving 498004 citations.
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TL;DR: In this paper, a general approximate formula for covalent resonance energies is obtained in terms of partial overlap populations and Ī's, including one or two empirical coefficients, which indicates that forced hybridization due to inner shells should make important negative contributions to bond energies.
Abstract: LCAO molecular orbital overlap populations give in general much more flexible and widely useful measures of the non‐Coulombic parts of covalent bond energies than do LCAO bond orders. They are immediately applicable to both π and σ bonds, including bonds involving hybrid AOs of all kinds, and they take account directly of the effects of variations in bond length on bond strength. In the last section of this paper, a number of ways of defining LCAO bond orders are reviewed, and their advantages and disadvantages discussed.If all LCAO parameters β are assumed proportional to corresponding overlap integrals S times suitable mean atomic ionization energies Ī, a simple general approximate formula for covalent resonance energies is obtained in terms of partial overlap populations and Ī's, including one or two empirical coefficients. This formula indicates that forced hybridization (see III of this series) due to inner shells should make important negative contributions to bond energies. The application of the f...
1,844 citations
TL;DR: In this article, a medium basis set based upon contractions of Gaussian primitives was developed for the third-row elements K through Zn. The basis functions generalize the 6-31G and 631G* sets commonly used for atoms up to Ar.
Abstract: Medium basis sets based upon contractions of Gaussian primitives are developed for the third-row elements K through Zn. The basis functions generalize the 6-31G and 6-31G* sets commonly used for atoms up to Ar. They use six primitive Gaussians for 1s, 2s, 2p, 3s, and 3p orbitals, and a split-valence pair of three and one primitives for valence orbitals, which are 4s and 5p for atoms K and Ca, and 4s, 4p, and 3d for atoms Sc through Zn. A 6-31G* set is formed by adding a single set of Gaussian polarization functions to the 6-31G set. They are Cartesian d-functions for atoms K and Ca, and Cartesian f-functions for atoms Sc through Zn. Comparison with experimental data shows relatively good agreement with bond lengths and angles for representative vapor-phase metal complexes.
1,709 citations
TL;DR: The quadratic elongation is dimensionless, giving a quantitative measure of polyhedral disortion which is independent of the effective size of the polyhedron.
Abstract: Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrachedral corrdination complexes, both of which show variations in bond length and bond angle. The quadratic elongation is dimensionless, giving a quantitative measure of polyhedral disortion which is independent of the effective size of the polyhedron.
1,671 citations
TL;DR: A self-consistent system of additive covalent radii, R(AB)=r(A) + r(B), is set up for the entire periodic table, Groups 1-18, Z=1-118, and is close to the methyl-based one of Suresh and Koga and its predecessors.
Abstract: A self-consistent system of additive covalent radii, R(AB)=r(A) + r(B), is set up for the entire periodic table, Groups 1-18, Z=1-118. The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same fit. Both E-E, E-H, and E-CH 3 data are incorporated for most elements, E. Many E-E' data inside the same group are included. For the late main groups, the system is close to that of Pauling. For other elements it is close to the methyl-based one of Suresh and Koga [J. Phys. Chem. A 2001, 105, 5940] and its predecessors. For the diatomic alkalis MM' and halides XX', separate fits give a very high accuracy. These primary data are then absorbed with the rest. The most notable exclusion are the transition-metal halides and chalcogenides which are regarded as partial multiple bonds. Other anomalies include H 2 and F 2 . The standard deviation for the 410 included data points is 2.8 pm.
1,585 citations
TL;DR: In this article, the effect of non-local gradient-type correction terms on LDA bond energies was considered and the gradient-corrected exchange-correlation functional of Langreth and Mehl, and also a semi-empirical exchange approximation was developed by the present author.
Abstract: The calculation of molecular spectroscopic properties is an interesting application of the local density approximation (LDA) for the exchange-correlation energy of many-electron systems. LDA bond lengths and vibrational frequencies agree remarkably well with experiment. Dissociation energies are also reasonably good, but tend to overestimate the experimental results. Therefore, we consider in this work the effect of non-local gradient-type correction terms on LDA bond energies. In particular, we consider the gradient-corrected exchange-correlation functional of Langreth and Mehl, and also a semi-empirical exchange approximation recently developed by the present author.
1,503 citations