Knowledge Bank

A systematic study of the behavior of the $CN-$ molecule ion under the influence of an electrostatic field arising from a perturbing point charge is presented. Self-consistent-field Molecular-orbital (SCF-MO) wave functions are computed for the $CN-$ molecule ion for a variety of point charge perturbations. The polarization of the $CN-$ ion is examined by utilization of the density difference functions, $\delta p(R)=\rho 1(R)-\rho 2(R)$, where $\rho 1(R)$ and $\rho 2(R)$ represent the molecular electronic charge densities of the perturbed and unperturbed $CN-$ ion, respectively. Contour diagrams of the unperturbed and perturbed ion charge densities are analyzed. The SCF energies obtained for $CN-$ in the presence of a point charge are used to obtain potential energy curves and potential energy surfaces, from which a stretching force constant for HCN is estimated. It appears that this technique provides a useful means of examining the bonding of the CN fragment in differing chemical environments.