Static electronic and vibrational first hyperpolarizability of meta-dinitrobenzene as studied by quantum chemical calculations

In the present study, we report on the results of computations of the electronic and the vibrational contributions to the static first hyperpolarizability ( β ) of meta-dinitrobenzene molecule. It turned out that the electron correlation effects are much more important for reliable prediction of the electronic counterpart than for determining vibrational corrections: β e value is increased by about 500% passing from the HF to the CCSD(T) level of theory. The preliminary assessment of density functional theory in determination of hyperpolarizabilities shows that harmonic contributions to β , contrary to the purely electronic contributions, are substantially underestimated in comparison with the wave function theory results. Another important finding of this study is that long-range corrected functionals tend to improve upon traditional functionals both in determining electronic as well as vibrational hyperpolarizabilities. It is also demonstrated that the vibrations of the nitro groups have a predominant influence on the vibrational contributions to β vib . The mechanical and electrical anharmonicity correction terms to the vibrational hyperpolarizability were found to be substantially larger than the lowest-order harmonic term.