Semiempirical Calculations of Some 2H and 14N Nuclear Quadrupole Coupling Constants

A parameterized LCAO method for the calculation of nuclear field gradients is described. The principal difference between this and other theories concerns the treatment of the two-center contribution to the field gradient. In our method, the two-center terms are included as parameters proportional to their respective nuclear terms. Only three parameters are necessary, one for triple and double bonds, one for single bonds, and one for a bond to hydrogen. The method developed herein not only successfully reproduces 14N field gradients, but also 2H field gradients, heretofore not possible with other semiempirical methods.