摘要:

A general self-consistent perturbation formalism is developed for two interacting closed-shell molecules. The zero-order many-electron wavefunction of the coupled system is represented by an antisymmetrized product of the mutually orthogonal single-determinant wavefunctions of the constituent parts. The method involves the application of perturbation theory directly to the Fock-Dirac density matrix and thus avoids the calculation of perturbed orbitals. Self-consistency to first order is maintained by an iterative determination of the matrix elements of the Hartree-Fock perturbation operator. Explicit expressions are given for the matrix elements of the one-electron and two-electron perturbations and for the energy changes to first and second order.

ISSN:0026-8976    

DOI:10.1080/00268977100100011

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The self-consistent perturbation theory of the preceding paper is simplified for the use in semi-empirical valence-shell SCF calculations. The validity and limitations of the procedure are tested for the combination of two methylene moieties to ethylene by comparing the numerical results of the perturbation treatment with valence-shell calculations of elongated ethylene. The application to the cycloaddition of the unconjugated dienophile cyclopropene to cyclopentadiene yields qualitative and quantitative information about the factors determining the stereochemical course of such additions, a hitherto poorly understood aspect of the Diels-Alder reaction.

ISSN:0026-8976    

DOI:10.1080/00268977100100021

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

General matrix expressions for solution properties such as the chemical potential, partial molal volume and compressibility are developed in terms of (radial) pair distribution functions and of direct correlation functions.

ISSN:0026-8976    

DOI:10.1080/00268977100100031

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

All the proton hyperfine splittings in the E.S.R. spectrum of the biacetyl semidione radical CH3Ċ(OH)COCH3are temperature and solvent dependent. These effects are a consequence of the restricted motion about the Ċ-OH bond which causes changes in the electron spin density throughout the radical. McLachlan S.C.F. spin density calculations successfully predict the changes in the three proton hyperfine splittings and, combined with the observed methyl proton splittings give a constant value forQCCH3Hequal to 25·0 ± 0·1 gauss for the solventsi-propanol,n-butanol, cyclohexane and dibenzyl ether from 250 to 400 K.

ISSN:0026-8976    

DOI:10.1080/00268977100100041

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The temperature dependence of the proton hyperfine splittings in the E.S.R. spectra of the biacetyl semidione radical CH3C(OH)COCH3is interpreted in terms of the restricted motion about the C-OH bond. An exact analysis of the restricted rotation gives values of the potential barrier of 2·3 to 2·8 kcal mol-1for the solvents dibenzeyl ether, cyclohexene,n-butanol andi-propanol. It is suggested that the main contribution to the potential barrier is the energy gained from delocalization of the electrons into the hydroxyl oxygen orbitals and that this effect is largely independent of the nature of the solvent.

ISSN:0026-8976    

DOI:10.1080/00268977100100051

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

We consider the Henry law adsorption of diatomic molecules on a uniform surface. Effects of hindered rotation are specifically included in the adsorption isotherm equation. Methods of applying these results to the analysis of experimental data are discussed, and a model calculation presented.

ISSN:0026-8976    

DOI:10.1080/00268977100100061

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Ortho-para separation factors for H2and D2are discussed in terms of two models of hindered rotation in the adsorbed phase. Although the available experimental data do not provide a definitive test of the models, it appears that both rotational modes are perturbed, and that a model incorporating hindrance of both modes is capable of fitting both the observed magnitude and temperature dependence of the separation factors.

ISSN:0026-8976    

DOI:10.1080/00268977100100071

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Electronic relaxation in solutions of solvated Fe3+, Mn2+(S=5/2) and Cr3+(S=3/2) is controlled by modulation of the quadratic zero field splitting interaction. The modulation is caused by collisions of the hydrated complex with bulk solvent molecules. Theoretical expressions are derived for the electronic transversal and longitudinal relaxation timesT2eandT1eand are used to interpret the E.S.R. data of these ions. The analysis yields results for the zero field splitting constants and for the mean lifetime between collisions. The latter are found to be in the range 4–9 × 10-12s.

ISSN:0026-8976    

DOI:10.1080/00268977100100081

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Potential energy surfaces have been calculated for various configurations of the CH5+ion using a non-empirical LCAO SCF MO method with a minimum basis set of Slater-type orbitals. Emphasis has been placed on a wide coverage of the surface rather than on accurate values for the extrema. The approach of H2along theC3axis of CH3+leads to a stableCsconfiguration and no activation energy is required. TheD3handC4vconfigurations can be considered as limiting forms of a C2vmolecule in which H2approaches the CH3+along aC2axis. We have shown that the formation of CH5+by this route requires a high activation energy.

ISSN:0026-8976    

DOI:10.1080/00268977100100091

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Infra-red emission has been detected from hydrogen fluoride formed in the gas-phase atom-molecule exchange reactions of atomic fluorine with hydrogen and methane. Emission was limited to that from vibrational levelsv′ˇ-3 in each case. An extrapolation technique has been used to obtain relative rate constants for direct chemical population of the various vibrational levels. The values found werek3tk2=0·76,k2tk1=3·4 for the F + H2reaction andk3tk2=0·23,k2k1=3·0 for the F + CH4case.

ISSN:0026-8976    

DOI:10.1080/00268977100100101

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor