Static second hyperpolarizabilities γ of nitroxide radical and formaldehyde: evaluation of spatial contributions to γ by a hyperpolarizability density analysis

The static second hyperpolarizability (γ) for a small size open-shell system containing a nitroxide radical group, H2NO, is studied by using ab initio molecular orbital and density functional methods. The static γ of H2CO is also evaluated as a reference closed-shell system. Remarkable changes in the spatial contributions of the third derivatives of the charge densities to the γ of H2NO, in contrast to those of H2CO, are observed in plots obtained by using various basis sets and correlation methods.