An ab initio study of the structures and the harmonic and anharmonic stretching force constants of the cyanides HCN, LiCN, FCN, ClCN and isocyanides HNC, LiNC, FNC, ClNC

Equilibrium structures and both harmonic and anharmonic stretching force constants have been calculated ab initio for the four cyanides HCN, LiCN, FCN, and C1CN, and the four isocyanides HNC, LiNC, FNC, and ClNC, using several basis sets of about triple-zeta quality. The CN and NC bond lengths, as well as diagonal stretching force constants, are nearly the same throughout both series. Trends in the off-diagonal stretching force constants are discussed, and dipole moment values are correlated with the structural type, XCN and XNC, and the electronegativity of the ligand X.