Theoretically Revealing the Response of Intermolecular Vibration Energy Transfer and Decomposition Process of the DNTF System to Electric Fields Using Two-Dimensional Infrared Spectra

Computational insights into the structure and decomposition behaviors of 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide under high pressure up to 10 GPa

CONTEXT

Inspired by the recent successful synthesis of the energetic compound 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102), which displayed a good balance between high energy and sensitivity, the response of the structure and decomposition behaviors of ICM-102 to high pressure was systematically investigated using first principle calculations. ICM-102 exhibited a graphite-like layer structure, with the c-axis and the a-axis mainly contributing to the distance between the molecular planes. As the pressure increased from 1 atm to 10 GPa, this distance decreased from 3.166 to 2.689 Ǻ. The hydrogen bonds had the most contribution to the non-covalent interactions within the same molecular planes, resulting in the b-axis discontinuity. However, van der Waals interactions gradually appeared between molecular planes as the pressure increased to 2.5 GPa. Based on the analysis of crystal orbitals, the distribution of π bonds and the Laplacian bond order (LBO), it was determined that the generation mechanism of H2O molecules involved the cleavage of N-Oc (coordinated oxygen atoms), followed by intermolecular hydrogen transfer reactions, and ultimately the formation of H2O molecules through competition with H atoms in the amino groups within the same molecules. More importantly, the pressure dependence of LBO values for N-Oc revealed that high pressure could inhibit the ICM-102 decomposition process due to reinforcing hydrogen bonds and van der Waals interactions. This work will deepen our understanding of the stability of ICM-102 under high pressure and provide a helpful reference for its potential detonation applications.

METHODS

All simulations, including geometry optimization and vibration analysis under quasi-hydrostatic pressure, were conducted using the CP2K code. The PBE function and the Goldk-Teter-Hutter (GTH) pseudopotential with the double-ζ-with-polarization (DZVP) basis set were employed. Additionally, the semiempirical dispersion correction D3 (BJ) was used to account for the intermolecular dispersion force. The simulations were performed under periodic boundary conditions, with a finest grid level cutoff set to 400 Ry for the Γ point. The Broyden-Flecher-Goldfarb-Shanno (BFGS) optimization method was used, with tighter convergence criteria applied for the subsequent calculations of infrared spectra. Finally, the wave-function analysis, such as non-covalent interaction and LBO, was conducted using the Multiwfn and VMD packages.

Infrared spectra and electronic structural changes of DNTF under high pressure: experimental and theoretical studies

3,4-Bis(3-nitrofurazan-4-yl)furoxan (DNTF) is a novel energetic material with an excellent performance and has attracted considerable attention. Motivated by recent theories and experiments, we had carried out experimental and theoretical studies on the high-pressure responses of vibrational characteristics, in conjunction with structural and electronic characteristics. It is found that all observed infrared spectra peaks seem to shift towards higher frequencies. And the peaks attributed to N-Oc (coordinated oxygen atom) stretching vibrations become broader due to the decrease of lattice constants and the free region of DNTF crystals with the increase of pressure, where the a-direction is more sensitive to pressure. In addition, the non-covalent interaction between adjacent DNTF molecules in the same layer changes from the van der Waals interaction to the steric effect with the increase of pressure, and that between layers also changes from the van der Waals interaction to the π-π stacking interaction. More importantly, these results highlight that the increase of pressure may lead to the stability decrease and impact the sensitivity increase of DNTF. This study can deepen the understanding of the energetic material DNTF under high pressure and is of great significance for blasting and detonation applications of DNTF.