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Core model calculation of the electric field gradient: Projection operator formalism with application to NH 3
Author(s) -
Cook Earl C.,
Ebbing Darrell
Publication year - 1973
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560070408
Subject(s) - cndo/2 , hamiltonian (control theory) , wave function , quadrupole , coupling constant , chemistry , atomic orbital , quantum mechanics , basis function , bond length , physics , computational chemistry , molecule , mathematics , mathematical optimization , electron
A core model approach to the calculation of deuteron quadrupole coupling constants is investigated using NH 3 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.