Ab initio calculations of the structure and harmonic force fields for the amine forms of dinitramine and methyldinitramine. Vibrational spectra and their interpretation using a scaling procedure

Abstract

Ab initio geometries and vibrational spectra have been calculated for the amine structures of dinitramine and methyldinitramine, HN(NO2)2 and CH3N(NO2)2. It is shown at the RHF and MP2 levels with the use of the 6-31G* and 6-31G** basis sets that these molecules have different symmetries in their equilibrium states,CsandC1 respectively. The quantum chemical RHF/6-31G* force fields were scaled with the set of transferable factors previously obtained by the authors to assign the available experimental vibrational bands and predict the positions of bands for the unmeasured spectral regions. Some common patterns of the geometrical parameters, vibrational spectra, and force fields of the simplest nitramines are discussed.