The prediction of nuclear quadrupole moments fromabinitioquantum chemical studies on small molecules. I. The electric field gradients at the14N and2H nuclei in N2, NO, NO+, CN, CNminus;, HCN, HNC, and NH3

摘要

Electric field gradients (efgrsquo;s) at the nitrogen nuclei in N2, NO+, NO, CN, and CNminus;and at the nitrogen and hydrogen nuclei in HCN, HNC, and NH3, calculated usingabinitioquantum chemical methods, are reported. Employing extensive Gaussian basis sets, the efgrsquo;s were computed at the selfhyphen;consistent field (SCF), singles and doubles configuration interaction lsqb;CI(SD)rsqb;, and coupled pair functional (CPF) levels of theory as the expectation values of the efg operator and also as the energy derivatives of the appropriate perturbed Hamiltonian using the finite field method. Corrections due to zero point vibrational motions were also calculated. The effect of basis set incompleteness on the calculated efgrsquo;s, together with the experimental nuclear quadrupole coupling constants, are used to estimate the14N and2H nuclear quadrupole moments, and to test the quality of the correlated wave functions generated by the CI(SD) and CPF methods. The recommended values, on the basis of the present calculations, are 2.05plusmn;0.02 and 0.29plusmn;0.01 fm2, respectively, for the14N and2H quadrupole moments.