Ab initio study on intermolecular interactions of energetic clusters

Abstract

Ab initio SCF and Møller-Plesset correlation correction methods (MP2) in combination with counterpoise procedure for BSSE correction have been applied to R2N-NO2 (R˭H, Me), hydrazine and difluoroamine clusters. Of all the stable structures found for each polymer with the same degree of polymerization, only the most stable one is reported. The corrected binding energies of the most stable clusters are predicted to be −32.93, −20.11, −24.68, −18.39 and −9.19 kJ/mol for dimers of nitramine, methylnitramine, dimethylnitramine (DMNA), hydrazine and difluoroamine, and −47.27 and −19.22 kJ/mol for trimers of DMNA and difluoroamine respectively. The proportion of correlated interaction energy to their total interaction energy for all clusters is at least 18.1 percent, and the BSSE of ΔE (MP2) is at least 9.2 kJ/mol. Dispersion and/or electrostatic force are dominant in DMNA and difluoroamine clusters, whereas the H-bonds exist in nitramine, methylnitramine and hydrazine dimers. There exist cooperative effects in the trimers. As for R2 N-NO2 dimers, the vibrational frequencies associated with N-O stretches or wags exhibit slight red shifts, but the modes associated with the motion of hydrogen atoms of the methyl group show somewhat blue shifts with respect to those of monomer. The N-H stretch mode exhibits large red shifts when it connects with other submolecules by H-bond as in the dimers of nitramine and hydrazine, otherwise it exhibits slight blue shifts.