A study of the ground state wave function of carbon monoxide

Siu, Albert K. Q.; Davidson, Ernest R.

doi:10.1002/qua.560040302

Cited by 72 publications

(20 citation statements)

References 18 publications

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“…It has been argued that strong orthogonality is too severe of an approximation. 4,13,47 We think that some deficiencies associated with strongly orthogonal geminals were due to the incomplete optimization of the geminal wave function in earlier studies. 15 The best way to evaluate the quality of approximations used in the SSG model is, in our view, to examine all perturbative corrections.…”

Section: Quality Of Ssg Reference Wave Functionmentioning

confidence: 99%

Geminal model chemistry II. Perturbative corrections

Rassolov

Garashchuk

2004

The Journal of Chemical Physics

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We introduce and investigate a chemical model based on perturbative corrections to the product of singlet-type strongly orthogonal geminals wave function. Two specific points are addressed ͑i͒ Overall chemical accuracy of such a model with perturbative corrections at a leading order; ͑ii͒ Quality of strong orthogonality approximation of geminals in diverse chemical systems. We use the Epstein-Nesbet form of perturbation theory and show that its known shortcomings disappear when it is used with the reference Hamiltonian based on strongly orthogonal geminals. Application of this model to various chemical systems reveals that strongly orthogonal geminals are well suited for chemical models, with dispersion interactions between the geminals being the dominant effect missing in the reference wave functions.

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Section: Quality Of Ssg Reference Wave Functionmentioning

confidence: 99%

Geminal model chemistry II. Perturbative corrections

Rassolov

Garashchuk

2004

The Journal of Chemical Physics

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“…The pair energies resulting from the two-body perturbation calculations are compared with the pair-excitation energies obtained by the method of configuration interaction [7] in Table IV. In all three calculations, the matrix …”

Section: Comparison Of Pair Energies With Configuration Interactionmentioning

confidence: 99%

“…The present study represents one of the first applications of the third-order many-body perturbation expansion for a molecule not containing a hydrogen atom, and it does permit some comparison with configuration interaction. Although the configuration interaction calculation reported by Siu and Davidson [7] employs a larger basis set, and includes single-excitations which third-order MBPT does not, a comparison between the two results is nevertheless useful. A comparison of two-body perturbative and certain pair-restricted configuration interaction calculations [2,7] is presented first.…”

Section: Introductionmentioning

confidence: 99%

“…Although the configuration interaction calculation reported by Siu and Davidson [7] employs a larger basis set, and includes single-excitations which third-order MBPT does not, a comparison between the two results is nevertheless useful. A comparison of two-body perturbative and certain pair-restricted configuration interaction calculations [2,7] is presented first. This comparison is presented because the two-body perturbative results are obtained simultaneously as a by-product of the full many-body calculations, because pair configuration interaction calculations are quite common, and because a pair-bypair analysis can be made.…”

Section: Introductionmentioning

confidence: 99%

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Third‐order many‐body perturbation theory for the ground state of the carbon monoxide molecule

Bartlett

Wilson

Silver

1977

Int J of Quantum Chemistry

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AbstractsMany-body perturbation calculations have been performed for the ground state of the carbon monoxide molecule at its equilibrium internuclear separation. The calculations are complete through third order within the algebraic approximation; i.e., the state functions are parameterized by expansion in a finite basis set. All two-, three-, and four-body terms are rigorously determined, and many-body effects are found to be very important. A detailed comparison is made with a previously reported configuration interaction study. Pad6 approximants to the energy expansion are constructed. The many-body perturbative wave function is used in the Rayleigh quotient to produce upper bounds to the electronic energy.La thtorie des perturbations a N corps a ete appliqute I'ttat fondamental de la molicule CO a la distance d'tquilibre. Les calculs sont complets jusqu'au troisikme ordre dans le cadre de I'approximation algebrique; c'est-a-dire les fonctions d'ttat sont paramttriskes par un dtveloppment dam une base finie. Tous les termes ii deux, trois et quatre corps sont ddtermints rigoureusement. II s'avere que les effets a N corps sont tr&s importants. Une cornparaison dttaillte a Ctt faite avec un calcul de type CI. Des approximants de Pad6 pour I'tnergie ont t t t construits. La fonction de perturbation a e t B utilide dans le quotient de Rayleigh pour obtenir des bornes sup6rieures de I'Cnergie electronique.Vielteilchenstorungsrechnungen sind fur den Grundzustand des CO-Molekiils am Gleichgewichtskernabstand ausgefuhrt worden. Die Berechnungen sind bis zur dritten Ordnung vollstandig; d.h. die Zustandsfunktionen sind durch eine Entwicklung in einem endlichen Basissatz parametrisiert worden. Alle Zwei-, Drei-und Vierkorperglieder sind streng bestimmt worden und es zeigt sich, dass die Vielteilcheneffekte sehr wichtig sind. Ein detaillierter Vergleich mit einer CI-Berechnung ist ausgefiihrt worden. Padt-Approximanten fur die Energieentwicklung sind konstruiert worden. Die Storungsfunktion ist in einem Rayleigh-Verhaltnis benutzt worden um obere Schranken der elektronischen Energie zu geben.

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“…Thus we can be quite confident that the energy lowering from the SCF observed in the subsequent calculations is predominantly a correlation effect. Since our basis set is much less flexible than the one used in the recent iterative natural orbital CI calculation of Siu and Davidson [8], we cannot hope to recover as high a percentage of the total correlation energy as these authors. Previous calculations [ 1, 31 have shown that the basis set limit for the type of basis used in this work is about 50% of the correlation energy of the valence shell.…”

Section: Ds-asepc + Bclc2mentioning

confidence: 99%

The generalized separated electron pair model. III. An application to three localization schemes for CO

Robb

Csizmadia

1972

Int J of Quantum Chemistry

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AbstractsThe separated electron pair (SEP) model (strongly orthogonal geminals) and methods for its systematic extension have been applied to three different localization schemes for C-0.The optimum SEP wave function is obtained for the particular localization scheme that involves three equivalent bent bonds. The major corrections to the SEP model arise from one-electron transfer terms. Two-electron transfer terms were important only for those pairs that were not well localized. I t was found that the separate definitions of the total intrapair and interpair correlation energies did not depend strongly on the choice of localization scheme. worden. Die optimale sEP-Welenfunktion ist fur das besondere Lokalisierungsverfahren erhalten, das drei aquivalente "gebogene" Bindungen enthalt. Die wichtigsten Verbesserungen zum sEP-Modell entstehen aus den Einelektronenuberfihrungsgliedern. Zweielektronenuberfuhrungsglieder sind nur fur solche Paare wichting, die nicht gut lokalisiert sind. Die Definitionen der totalen Intrapaar-und Interpaarkorrelations-energien hangen von der M'ahl des Lokalisierungs-verfahren nicht stark ab.

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A study of the ground state wave function of carbon monoxide

Cited by 72 publications

References 18 publications

Geminal model chemistry II. Perturbative corrections

Geminal model chemistry II. Perturbative corrections

Third‐order many‐body perturbation theory for the ground state of the carbon monoxide molecule

The generalized separated electron pair model. III. An application to three localization schemes for CO

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