Insight into Hydrazinium Nitrates, Azides, Dicyanamide, and 5- Azidotetrazolate Ionic Materials from Simulations and Experiments

摘要

A transferrable, polarizable quantum chemistry-based force field has been developed for hydrazinium , monomethylhydrazinium, and dimethylhydrazinium cations in combination with the nitrate, azide, dicyanamide, and 5- azidotetrazolate anions. Quantum chemistry calculations were performed on the neutral precursors, ions and cation-anion complexes employing aug-ccpvDz (cc- pvTz) basis functions at MP2 level or in conjunction with M05-2X density functional. Inclusion of a lone-pair on hydrazinium-based cations significantly improved ion electrostatic description and prediction of the crystal structure in molecular dynamics (MD). Seven different ionic systems have been investigated: N2H5NO3, (CH3)N2H4NO3, (CH3)2N2H3NO3, N2H5CN7, (CH3)N2H4N3, (CH3)2N2H3N3, N2H5N(CN)2. For all but the (CH3)2N2H3NO3 and N2H5N(CN)2, QC calculations of a single, gas phase ion pair predicts spontaneous deprotonation of the cation. Crystal lattice parameters obtained from MD simulations were compared with experiments for ionic crystals of these seven systems, with the experimentally determined crystal structure of N2H5N(CN)2 also presented here, enabling comparison of simulation and experiment for that compound. In general, MD simulations predicted crystal lattice vectors/angles (volumes) within a 5% (3%) absolute margin of error from experiments, with outlying values of 5-6.6 % for three crystals (CH3)N2H4N3, N2H5NO3, (CH3)N2H4NO3 with combinations of particularly small anions and/or cations. Structural comparisons between ionic materials in the liquid and crystalline state are made, including the observation of two crystalline systems where the crystalline state induces conformational changes in the methylated hydrazinium cations compared to the gas phase and liquid states. The matrices of elastic constants were extracted from MD simula.