摘要:

AbstractA series of excited electronic states of AH2molecules having extremely small bond angles has been discovered theoretically. Systems which have shown this characteristic to date include H2O+, NH2, CH2+, and NH2+. In the present researchab initiostudies were carried out using a double zeta plus polarization basis set. Configuration interaction including all Hartree‐Fock interacting single and double excitations was performed. For the2B2state of CH2+, the predicted equilibrium geometry isθe(HCH) = 35.2°,re(C‐H) = 1.41 A. This state is bound by 20.3 kcal/mole relative to the separated C++ H2ground electronic state. The analogous state of BH2is not substantially bound, but the neutral C + H2system shows some very interesting features. All of these results may be qualitatively understood in the context of Walsh's

ISSN:0021-2148    

DOI:10.1002/ijch.198000012

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThis paper gives a survey of results pertaining to the electronic structures of metal atom cluster compounds. The development of progressively more complete and accurate calculations, from the simpled‐orbital overlap model of Cotton and Haas (1964) through approximate Hartree–Fock (Fenske–Hall) calculations to recent SCF‐Xα‐SW calculations incorporating corrections for relativistic effects. It is shown that the qualitative essentials of the bonding are apparent even in the simplest treatment but that the more sophisticated methods are required to interpret spectra and other experimental data quan

ISSN:0021-2148    

DOI:10.1002/ijch.198000013

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractComplexes [(C2H2X2)2M]nwith ligating atoms X = O, S and central atoms M = Li (n= 0, ± 1) and Be (n= 0, ± 2) have been studied by quantum chemicalab initiocalculations. Total energies, relative binding energies and orbital energies of mainly planar complexes of standard geometry have been studied. The effect of variation of geometry including non‐planarity has also been considered. The primary binding region is found to contain appreciable interactions not only within pairs MX but for the sulfur case also of the type XX'. The chelate form of the ligands is shown to be essential to the properties of the comple

ISSN:0021-2148    

DOI:10.1002/ijch.198000014

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractMetal containing models of the active site of the metalloenzyme carboxypeptidase were studied by quantum chemicalab initiocalculations. The comparative properties of [Zn(OH)(NH3)2]+and [Be(OH)(NH3)2]+indicate some of the characteristics of the role of transition metals in biological systems: the Zn complex, but not the Be complex, generates directionality constraints for an incoming ligand that are compatible with the geometrical features identified in the crystal structure of the active site — substrate complex. Moreover, an incoming ligand (H2O) is perturbed more strongly by the Zn complex than by the Be complex. This perturbation (a charge transfer and a characteristic polarization of the electronic density along the metal–ligand axis) is in good agreement with the proposed effect of the metal in the active site on the reactivity of a carbonyl carbon in a peptide bond. The perturbation caused by the incoming ligand in the electronic structure of the metal containing complex is also larger for the Zn complex than for the Be complex. These findings indicate that while the Be complex may simulate some of the purely electrostatic effects of the Zn containing model of the active site, it does not represent as well as the Zn complex some of the reactivity elements that have been implicated in the role of the metal in the catalytic mechanism of carboxypeptid

ISSN:0021-2148    

DOI:10.1002/ijch.198000015

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe gauge properties of exact solutions, and of optimal variational solutions for static magnetic fields are reviewed. Also various other topics are discussed, including the optimal choice of gauge, gauge factors, gauge invariance and current conservation, minimal variance gauges, and the Thomson bound.

ISSN:0021-2148    

DOI:10.1002/ijch.198000016

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractWe present a brief account of methods of deriving lower and upper bounds to energy eigenvalues, overlap integrals, expectation values, transition elements and properties of atoms and molecules (such as dynamic polarizabilities) which are related to second order perturbation theory.

ISSN:0021-2148    

DOI:10.1002/ijch.198000017

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractStandard concepts of information theory, including Shannon's entropy, Fisher's information, Jaynes' principle of entropy maximization, Fisher's locality information matrix, and Kullback and Leibler's information measure, are described and extended to many dimensions as appropriate, to establish precise connections between the many body quantum‐mechanical kinetic energy functionalT[Ψ] and information measures. Implications for density functional theory of electronic structure are discussed, and elementary examples are displayed to illustrate the argument. Among the several exact relations obtained, one of special interest is the identity\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm T}[\psi ] = {\rm T}[\rho ,{\rm f}] = \left( {\frac{{\rm N}}{8}} \right)\int {\frac{{\nabla \rho (1) \cdot \nabla \rho (1)}}{{\rho (1)}}} d_{{\rm T}_{\rm 1} } + \left( {\frac{{\rm N}}{{\rm 8}}} \right)\int {\rho \left( 1 \right)[I_F^1 (x_1 ,y_1 ,z_1 )]d_{{\rm T}_1 } } $$\end{document}where the first term is the intrinsic accuracy or Fisher's information for locality of the one‐particle density (normalized to 1),\documentclass{article}\pagestyle{empty}\begin{document}$ \rho \left( 1 \right) = \int { \cdot \cdot \cdot \int {|{\rm \psi |}^{\rm 2} d_{{\rm T}_2 } \cdot \cdot \cdot } } \,d_{{\rm T}_{\rm N} ,} $\end{document}, and the second term is the average over the one‐particle density of Fisher's information associated with the conditional density\documentclass{article}\pagestyle{empty}\begin{document}$ f\left( {2,\;3,\; \cdot \cdot \cdot ,\;N|1} \right) \equiv \,|\psi |^2 /\rho \left( 1 \right) $\end{document}that is, the second term is the average over the marginal distribution ρ(1) of the trace of Fisher's information matrix for the distributionf(2,3, …,N|1). Because of this formula, the quantum mechanical variation principle may be precisely stated as a principle of minimal in

ISSN:0021-2148    

DOI:10.1002/ijch.198000018

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe evidence for a definite number of electrons occurring in a partly filled shell (consisting of f or d‐like orbitals) in gaseous molecules and in condensed matter (including metallic lanthanides) is reviewed, based on the analysis of atomic spectra. Comparison is made with competing descriptions (mainly useful outside the transition‐groups), and inner shells are discussed, accompanied by recent evidence from photo‐electron spectra. The importance of the local kinetic energy, and of the total symmetry of closed shells as the neutral element of Hund vector‐coupling, is emphasized. Critical analysis is made of real angular functions, Schrödinger's equation written on conservative form, and of the cardinal numberKof electrons in an atom as an approximate quantum number (likeS) in c

ISSN:0021-2148    

DOI:10.1002/ijch.198000019

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractA coupled Hartree–Fock theory for diamagnetic susceptibilities χ and chemical shifts σ in terms of localized MO's and individual gauge origins for the different MO's is derived. The new coupled Hartree–Fock equations and expressions for χ and σ differ from the traditional ones by the presence of “exchange coupling terms” (ECT) and “resonance coupling terms” (RCT). For the ECT, that are expected to be very small, a simple approximation is proposed. Both the ECT and the RCT can be decomposed into “diamagnetic” and “paramagnetic” contributions. Spurious paramagnetic terms due to inappropriate choices of the gauge origin are avoided in the present scheme. The possibility to include correlati

ISSN:0021-2148    

DOI:10.1002/ijch.198000020

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe unitary group formulation of many‐electron theory provides an accurate and vivid picture of many‐electron states called theGel'fand labelwhich exhibits both the electron configuration and the spin and which permits a facile correlation of molecular orbital and valence bond states. In addition it provides a convenient method of computation of matrix elements which is competitive with more conventional me

ISSN:0021-2148    

DOI:10.1002/ijch.198000021

出版商:WILEY‐VCH Verlag    

年代:1980

数据来源: WILEY