“Ab Initio” Calculation of the Quadrupole Coupling Constant of 14N in HCN, FCN, ClCN, HC2CN, CN−, OCN−, SCN− and the Examination of the Townes–Dailey Interpretation in Terms of Exclusive Orbitals

The electric field gradient at 14N nucleus in some RCN molecules or RCN− ions has been calculated using the accurate SCF wavefunctions obtained by McLean and Yoshimine. From these computed values and the experimentally known 14N quadrupole coupling constant of four molecules of this series, a value of 1.66e × 10−26cm2 for the quadrupole moment of 14N nucleus has been estimated. A check for the semi-empirical interpretative theory of Townes and Dailey is made in terms of localized orbitals (Boys exclusive orbitals). Some other characteristics of these exclusive orbitals are also displayed.