Core Model for Single-Center Calculations of Electric Field Gradients. Application to LiD

Avgeropoulos, G. N.; Ebbing, Darrell D.

doi:10.1063/1.1671573

The Journal of Chemical Physics

1969

DOI: 10.1063/1.1671573

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Core Model for Single-Center Calculations of Electric Field Gradients. Application to LiD

G. N. Avgeropoulos

Darrell D. Ebbing

Abstract: The nuclear quadrupole coupling constant provides an example of a property which is sensitive to the form of the electronic wavefunction in the region of the quadrupolar nucleus. A method is discussed in which the wavefunction is separated into a core and a portion surrounding the quadrupolar nucleus. This latter portion of the wavefunction is determined by means of a single-center expansion. Calculations of the electric field gradient at the deuteron in LiD are presented. The dependence of the calculations on… Show more

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Cited by 2 publications

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Core model calculation of the electric field gradient: Projection operator formalism with application to NH₃

Cook

Ebbing

1973

Int J of Quantum Chemistry

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AbstractsA core model approach to the calculation of deuteron quadrupole coupling constants is investigated using NH, as an example. First the deuteron quadrupole coupling constant is calculated from a CNDO wave function. This result is subsequently improved by recomputing the N-D bond orbital by means of a variational calculation using the CNDO function to construct a core potential for the bond Hamiltonian. In order to simplify integrations a single-center basis is chosen to represent the variational wave function. A projection operator formalism is used as a computational scheme to maintain orthogonality of the bond orbital to core orbitals. Excellent agreement with experiment is obtained. 'The procedure is applicable to more complicated molecules.On ttudie un proctdt, bask sur un modile de coeur, pour le calcul des constantes de couplage quadrupolaire du deuteron avec NH, comme exemple. D'abord la constante de couplage quadrupolaire du deuteron a CtC calculte d'une fonction d'onde CNDO. Ce rtsultat est ensuite amtliorC en recalculant l'orbitale de la liaison N-D par un calcul variationnel; la fonction CNDO est employte pour construire un potentiel de coeur pour 1'Hamiltonien de liaison. Pour simplifier les inttgrations on choisit une base A un centre pour la reprtsentation de la fonction d'onde variationneile. Des optrateurs de projection sont employes dans les calculs pour maintenir l'orthogonalitt entre l'orbitale de liaison et les orbitales de coeur. On obtient un accord excellent, avec les donntes exptrimentales. Le proctdt peut &re appliquC a des moltcules plus compliqutes. Ein Rumpfmodellverfahren fur die Berechnung von Deuteron-Quadrupolkopplungskonstanten wird mit NH, als Beispiel untersucht. Zuerst wird die Quadrupolkopplungskonstante von einer cNDo-Wellenfunktion berechnet. Dieses Ergebnis wird dann durch eine neue Variationsberechnung des N-D-Bindungsorbitals verbessert, wobei die CNDO-Funktion fur die Konstruktion des Rumpfpotentials fur den Bindungs-Hamiltonoperator benutzt wird. Um die Integrationen zu vereinfachen wird eine Einzentrum-Basis fur die Darstellung der Variationsfunktion gewahlt. Projektionsoperatoren w-erden im Berechnungsverfahren benutzt um die Orthogonalitat zwischen dem Bindungsorbital und den Rumpforbitalen zu bewahren. Vortreffliche Ubereinstimmung mit den Experimentaldaten wird erhalten. Das Verfahren ist auf kompliziertere Molekule anwendbar.

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Core model calculation of the electric field gradient: Projection operator formalism with application to NH₃

Cook

Ebbing

1973

Int J of Quantum Chemistry

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Calculations of deuterium quadrupole coupling constants employing semiempirical molecular orbital theory

Barfield

Gottlieb

Doddrell

1978

The Journal of Chemical Physics

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Articles you may be interested inFast, accurate semiempirical molecular orbital calculations for macromolecules Deuterium quadrupole coupling constants (DQCC) for deuterium nuclei in a variety of bonding situations have been obtained by means of semiempirical molecular orbital wavefunctions in the INDO approximation. All integrals of the operator entering the electronic contributions have been included with no approximations in their evaluation. Analytical expressions are tabulated for the relevant two-center integrals; three-center integrals were obtained by numerical integration techniques. The factors responsible for the very strong dependence of deuterium QCC on internuclear distance, and the relative constancy of the parameters for a given bonding situation are discussed with regard to the types of terms which enter the integral expressions and the molecular electronic distributions. Some interesting and possibly useful predictions are also included in the tabulated results; the DQCC for the bridging deuterium in diborane is predicted to have a value of -110 kHz. which may be the first negative value for a DQCC; the effects of hydrogen bonding can be significant. the result of lengthening of the D-X bond on hydrogen bond formation.4504

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Core Model for Single-Center Calculations of Electric Field Gradients. Application to LiD

Cited by 2 publications

References 23 publications

Core model calculation of the electric field gradient: Projection operator formalism with application to NH₃

Core model calculation of the electric field gradient: Projection operator formalism with application to NH₃

Calculations of deuterium quadrupole coupling constants employing semiempirical molecular orbital theory

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Core Model for Single-Center Calculations of Electric Field Gradients. Application to LiD

Cited by 2 publications

References 23 publications

Core model calculation of the electric field gradient: Projection operator formalism with application to NH3

Core model calculation of the electric field gradient: Projection operator formalism with application to NH3

Calculations of deuterium quadrupole coupling constants employing semiempirical molecular orbital theory

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Core model calculation of the electric field gradient: Projection operator formalism with application to NH₃

Core model calculation of the electric field gradient: Projection operator formalism with application to NH₃