Prediction of structures and properties of 2,4,6-triamino-1,3,5-triazine-1,3,5-trioxide (MTO) and 2,4,6-trinitro-1,3,5-triazine-1,3,5-trioxide (MTO3N) green energetic materials from DFT and ReaxFF molecular modeling

Abstract

2,4,6-Triamino-1,3,5-triazine-1,3,5-trioxide (MTO) and 2,4,6-trinitro-1,3,5-triazine-1,3,5-trioxide (MTO3N) were suggested by Klapötke et al. as candidates for green high energy density materials (HEDM), but a successful synthesis has not yet been reported. In order to predict the properties of these systems, we used quantum mechanics (PBE flavor of density functional theory) to predict the most stable conformations of MTO and MTO3N and their optimum packing into the most stable crystal structures. We found that MTO has the P2₁ space-group with a density of ρ = 1.92 g cm⁻³ while MTO3N has the P2₁/c space-group with a density of ρ = 2.10 g cm⁻³. The heats of reaction (ΔH_rxn) were computed to be 1036 kcal kg⁻¹ for MTO, 1412 kcal kg⁻¹ for MTO3N, and 1653 kcal kg⁻¹ for a mixture of them. These properties are comparable to those of such other useful energetic materials as RDX (ρ = 1.80 g cm⁻³, ΔH_rxn = 1266 kcal kg⁻¹), HMX, and PETN, making MTO and MTO3N excellent candidates for environmentally friendly HEDMs. In addition, we predicted the stability of –NH₂, –NO, and –NO₂ groups in water solution. We also show that the ReaxFF-lg reactive FF leads to an accurate description of the structural properties of MTO and MTO3N crystals making it practical to carry out large-scale reactive molecular dynamics simulations practical for these systems to determine the sensitivity and performance (CJ point calculation and velocity) under shear, shock, and thermal loads.