Experimental and calculated second harmonic generation of a guanidinium salt in the solid state

A new salt containing both dipolar and octupolar molecules has been synthesized and its structural features fully revealed, namely, its noncentrosymmetry. The microscopic optical properties of a neutral cluster were calculated probing several functionals; a better performance was observed for functionals with high percentage of Hartree-Fock exchange. The vector and septor irreducible components, for individual ions, were also calculated in order to evaluate their ratio and the dipolar/octupolar character. The optical properties of the solid state were computed, using the oriented gas model and two different local field factors. For the SHG generation, the calculated value compares well with the experimental value measured for the powder form, of the order of magnitude of the urea signal.