An application of the DFT-based scaled quantum mechanical force field method to a weakly bonded system: N2O4

The adequacy of the density functional derived scaled quantum mechanical force field method of Rauhut and Pulay has been tested for a weakly bound dimer, N2O4. The Becke3–Lee–Yang–Parr/6-31G* harmonic force field has been scaled with the transferable scale factors of Rauhut and Pulay (developed originally for `commonʹ organic compounds without any reference to the N–O bond) resulting in 20.7 and 38 cm−1 for the mean and the maximal individual deviations, respectively, as compared with experimental spectra. Consequently, the force field method of Rauhut and Pulay may give reliable results for non-common compounds as well.