DFT study of the intermolecular interaction of 3,4-dinitropyrazole (DNP) and H2O

In the present work, the sensitivity to the moisture (hygroscopisity) is studied for 3,4-dinitropyrazole (DNP) as a famous energetic molecule. All of the DNP-H2O complex systems (1-3) as well as individual molecules were optimized and bond lengths, bond angles, dihedral angles, charge transfer and stability via NBO analysis, corrected interaction energies with ZPE + BSSE and hydrogen bonds analysis were carried out and related data were gathered and explained with details. According to the NBO analysis, it was observed that the complex 2 was the most stable one among the others. However, on the basis of the interaction energies, complex 3 displayed more strong interactions. So, it proves the existence of the strong hydrogen bonds in complexes 2 and 3 as well as occurrence of the inconsistent manner between interaction energies and charge transfer changes. Furthermore, it shows that charge transfer is not the main and effective parameter of intermolecular interactions in complexes 1-3.