Nuclear Quadrupole Coupling in Polyatomic Molecules

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Abstract
The Gaussian‐transform method has been applied to the evaluation of the deuteron and nitrogen‐14 quadrupole coupling constant (eqQ/h) with the various minimal and extended basis‐set SCF—LCAO—MO functions that are available for the linear polyatomic molecules DCN, C2D2, DF2—, and N3—. Comparisons are made between calculations neglecting and including the three‐center integral contributions. The coupling constant is found to be quite sensitive to the choice of basis orbitals, particularly those responsible for the form of the valence‐shell charge density. This suggests that the quadrupole coupling constant in polyatomic molecules is a useful criterion for testing the wavefunction obtained in approximate calculations. Of particular interest is the variation in the (eqQ/h)D results for DF2—, which points out the need for an experimental coupling constant measurement for this hydrogen‐bonded species.