NUCLEAR-QUADRUPOLE COUPLING-CONSTANT ASSIGNMENTS FOR A SERIES OF AZOLES AND AZINES BY HARTREE-FOCK SCF-CLUSTER AND LATTICE CALCULATIONS

We present ab initio Hartree-Fock lattice calculations on a series of heterocyclic and other compounds. Some of these have previously been s tudied by cluster calculations with the same DZ basis sets at the SCF level. The electric field gradients at the nitrogen centres, are relat ed to NQR experimental determinations of nuclear quadrupole coupling c onstants. The compounds studied include imidazole and pyrazole, 4-nitr oimidazole, 4-nitropyrazole, pyrazine, and tetramethylpyrazine, pyridi nium chloride, and N-methylpyridinium iodide, and pyridine-N-oxide.