A Method for Estimating Electronic Repulsion Integrals Over LCAO MO'S in Complex Unsaturated Molecules

Parr, Robert G.

doi:10.1063/1.1700802

Cited by 201 publications

(27 citation statements)

References 3 publications

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“…It is very likely that the interaction of this dipole with the field will orient the molecule in the field direction, the energy of the interaction being --400 cm-I for a field of this To estimate the quadrupole moment of a n, orbital we make the crude approximation that the p, orbitals may be replaced by a point model, where a half unit charge is placed at an average distance di/2 from the nucleus. The values of di for nitrogen and oxygen, dN and do, were obtained from the approximation used by Parr (27). He approximated the p orbital by two tangential uniform spheres of diameter di = 4.597 2,-' x lo-' cm, where Z , is the effective nuclear charge as defined by Slater's rules (28).…”

Section: As Follows X (E($ioir Cosmentioning

confidence: 99%

Electron spin resonance spectra of nitric oxide adsorbed on zeolites

Gardner¹,

Weinberger²

1970

Can. J. Chem.

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Electron spin resonance (e.s.r.) spectra of N O adsorbed on the 4 zeolites Linde 4A, 5A, 13X, and hydrogen mordenite were measured at 77 OK. N o e.s.r. signal was observed for NO on silica gel. By use of expressions for the line shapes of polycrystalline samples, assuming axially symmetric g-tensors, and taking into account also isotropic coupling, values of g , , , g,, and line width were derived by an iterative procedure. From these, the crystal field splitting, A, of the 2pz levels, which become non-degenerate on adsorption, were calculated. By relating A to the interaction of the non-axial components of the quadrupole moment with the corresponding electric field gradients, the non-axial component of the latter is estimated for the surface fields of the zeolites.

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Section: As Follows X (E($ioir Cosmentioning

confidence: 99%

Electron spin resonance spectra of nitric oxide adsorbed on zeolites

Gardner¹,

Weinberger²

1970

Can. J. Chem.

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“…The first approximation in the semi-empirical methods was the ''zero-differential overlap'' in which the products v l v m are neglected in most of overlap integrals S lm ¼ v l v m and the application to p electrons of conjugated organic molecules (Pariser-Parr-Pople theory [16][17][18][19]; Hückel HMO (reference2, p. 67 in [2]). The second progress was the extension of these methods to all valence electrons of a molecule.…”

Section: Methodsmentioning

confidence: 99%

From Democritus to Schrödinger: a reflection on quantum molecular modeling

Vasilescu

Adrian-Scotto

2010

Struct Chem

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This review describes the saga of the atom and molecules, from the atomic concept as it was introduced 25 centuries ago by Leucippus and Democritus, to the modern Quantum Molecular Modeling. Quantum methods that have given rise to the contemporary Molecular Modeling are briefly presented. Chosen examples illustrate the performance and the predictions of Quantum Modeling in the following topics: conformational analysis, electrostatics, molecular spins and radicals, infrared and Raman spectra, thermochemistry, and electrophilicity properties derived from the molecular chemical potential.

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“…The latter is regarded as an experimental parameter and assumed as -1.20 ev for both formamide and acroleint. Two-centre repulsion integrals of the type (4), are calculated by combining Pariser and Parr's [10] and Pariser's [16] approximation for the one-centre repulsion integral with the uniformly charged sphere approximation [17]. Valence-state ionization potentials and electron affinities for carbon, oxygen, and nitrogen necessary for evaluating one-centre repulsion integrals are taken from Pritchard and Skinner's table [18].…”

Section: Methods Of Calculationmentioning

confidence: 99%

Intramolecular charge-transfer absorption spectra of formamide and acrolein

Nagakura

1960

Molecular Physics

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To test further Nagakura and Tanaka's conception of intramolecular charge-transfer absorption, an improved calculation based on LonguetHiggins and Murrell's method was carried out for the w-electron structures of formamide and acrolein. This shows that the 1717 ~, band of formamide and 1935 ~, band of acrolein can be regarded as intramolecuIar charge-transfer absorption bands in the sense that the excited state wave functions for these two bands are mainly constructed of the charge-transfer configuration, and that the transitions corresponding to these bands are accompanied by a large amount of electron transfer from electron donor towards acceptor. The 1717 A band of formamide can not be interpreted as a shifted 1560 ~, formaldehyde band. The latter band must shift to shorter wavelengths as the result of interaction with non-bonding electrons of the nitrogen atom. Similar blue shifts occur in acrolein for the C = C and C ---O zr -~Tr ~ bands relative to the corresponding bands of ethylene and formaldehyde. Similar causes operate in the blue shifts of the non-charge-transfer bands of donor-acceptor molecular complexes.

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A Method for Estimating Electronic Repulsion Integrals Over LCAO MO'S in Complex Unsaturated Molecules

Cited by 201 publications

References 3 publications

Electron spin resonance spectra of nitric oxide adsorbed on zeolites

Electron spin resonance spectra of nitric oxide adsorbed on zeolites

From Democritus to Schrödinger: a reflection on quantum molecular modeling

Intramolecular charge-transfer absorption spectra of formamide and acrolein

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