On the anharmonic force field and equilibrium structure of HNC

Abstract

A tentative anharmonic force field, including quadratic, cubic and quartic terms, has been determined for HNC. The force field is based on observed vibration-rotation data for HNC and DNC, a previous ab initio SCF calculation of the quadratic and cubic force constants, and the anharmonic force fields determined earlier for HCN and HCP. Using α constants calculated from the force field, the zero-point rotational constants B 0 for the eight stable isotopic species have been converted to B e, and hence an improved equilibrium structure has been derived. The equilibrium bond lengths are found to be r e(HN) = 0·9940(8) A and r e(NC) = 1·1689(2) A.