Monomeric and self-assembled crystal phases of TNBT

(3,3′,5,5′-Tetranitro-4,4′-bi-1,2,4-Triazole) TNBT was designed and predicted more than three decades ago as a high energy material. As with many other designed molecules, TNBT has not been successfully synthesized and has not been computationally studied in detail. In this work, theoretical calculations at density functional theory (DFT) level of theory were carried out for both the gas phase molecule and its possible bulk crystal phases. Unimolecular DFT computations show that TNBT is comparable to CL-20 with high bulk density, high formation energy and high detonation velocity and detonation pressure. It is found that instead of C–NO₂ hemolytic fission, bond breaking of C–N bond in the triazole ring is the dominant initial reaction for unimolecular decomposition of TNBT, and the predicted potential activation barriers are higher than those of CL-20 and HMX. The low-lying energy bulk phases of TNBT are mostly structures that have low symmetry and low bulk modulus. It is also found that TNBT can self-assemble to linear polymeric crystals which have higher formation energies and higher bulk densities than their monomeric counterparts. Graphical abstract: (Figure presented.)