Structural, Mechanical and Electronic Properties of Dihydroxylammonium 5, 5'-Bistetrazole-1, 1'-diolate (TKX-50) under High Pressures: A First-principles Study

The structures and mechanical and electronic properties of dihydroxylammonium 5, 5'-Bistetrazole-1, 1'-diolate(TKX-50) were examined over a pressure range to clarify its structural and chemical stability at high pressures with a first-principles method based on density functional theory using PBE functional plus vdW corrections(DFT-D). The intermolecular interactions under high pressures were analyzed with the Hirshfeld surfaces and 2D fingerprint plots to clarify its change trend. The calculated lattice constants, axial compressibility, and equation of state are in good accordance with the available experimental results. For the first time, we predict the elastic constants of TKX-50 using a first-principles method. The predicted stiffness constants are ordered as C₃₃(61.9 GPa>C₁₁(58.1 GPa)>C₂₂(36.9 GPa). The electronic energy band structures show that the band gap changes from a direct one (B-B) at 0 GPa to an indirect one at 50 GPa. The band gap at 100 GPa is also indirect (from G to B). The band gap decreases with respect to an increase in pressure, implying that the impact sensitivity increases with compression.