The structure, vibrational spectra and nonlinear optical properties of neutral melamine and singly, doubly and triply protonated melaminium cations-theoretical studies

The restricted Hartree-Fock (RHF) methods were used for calculation of the hyperpolarizability for each ion. For comparison, analogous calculations were carried out for the closed-shell neutral melamine. The theoretical results can be used in design of new molecular compounds with nonlinear optical properties.