Investigations of the Very Short Hydrogen Bond in the Crystal of Nitromalonamide via Car-Parrinello and Path Integral Molecular Dynamics

In this paper are presented the results of theoretical studies of the structure in proton motion in a very short O center dot center dot center dot O and two weak N-H center dot center dot center dot O intramolecular hydrogen bonds in the nitromalonamide crystal. The dynamics of proton motion in hydrogen bonds were investigated in the NVT ensemble at 298 K using the Car-Parrinello and the path integral molecular dynamics. A very large delocalization of proton in the slightly asymmetrical single well of free energy potential of O-H center dot center dot center dot O intramolecular hydrogen bond was noted especially in the path integral simulation where quantum effects are taken into account. This hydrogen bond is very strong with the estimated energy of hydrogen bond ca. -27 kcal/mol. The nature of intra- and intermolecular interactions was studied by means of quantum theory of atoms in molecules. The infrared spectra were calculated and compared with available experimental data. CPMD vibrational results appear to be in good agreement with the experimental ones.