Theoretical studies on the structures, densities, detonation properties and thermal stability of 2,4,6-trinitropyridine N-oxide (TNPyO) and its derivatives

Abstract

In this study, a set of designed 2,4,6-trinitropyridine N-oxide (TNPyO) derivatives with different substituents were studied theoretically at the B3LYP/6-31G* level of density functional theory. The gas-phase heats of formation (HOFs) were predicted based on the isodesmic reactions. The condensed-phase HOFs and heats of sublimation were estimated in the framework of the Politzer approach. The crystal densities were computed from molecular packing which are confirmed to be able to produce a good estimation of density for TNPyO in comparison with the available experimental data. Most of the derivatives have better detonation properties than the traditional explosives RDX (hexahydro-1,3,5-trinitro-1,3,5-trizine) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane), and three compounds are even superior in performance to CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane). An analysis of the bond dissociation energies shows that all of them except compound 5 have good thermal stability. Considering the detonation performance and thermal stability, most of them are very promising candidates of high energy density materials and are worth further investigations.