High-Pressure Structural and Electronic Properties of Potassium-Based Green Primary Explosives
Recently synthesized green primary explosives potassium 4,4′-bis(dinitromethyl)-3,3′-azofurazanate (K2BDAF) and potassium 1,1′-dinitramino-5,5′-bistetrazolate (K2DNABT) offer fast, powerful initiation capacity and high-performance detonation characteristics to replace the long-standing toxic primary explosives. In the present study, we report the structural and electronic properties of the emerging green primary explosives K2BDAF and K2DNABT under hydrostatic pressure up to 10 GPa. We observed that dispersion correction methods are important for capturing weak intermolecular interactions in order to accurately describe the geometries of the primary explosives. The computed ground state structural properties using optB86b-vdW method are in good agreement with the experimental results. The pressure-dependent lattice constants and bond parameters show anisotropic nature and also a sharp discontinuity around 4–5 GPa. The obtained equilibrium bulk modulus shows that K2BDAF is softer than K2DNABT. Bonding analysis revealed that the C-NO2 energetic functional groups are more sensitive than the stable ring structure under hydrostatic pressure. The calculated electronic structure of K2BDAF using the Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential shows a direct-to-indirect band gap transition around 5 GPa, which is consistent with the aforementioned discontinuity of the structure, while K2DNABT is found to be a direct-band-gap insulator in the studied pressure range of 1–10 GPa. The abnormal trends in the structural and electronic properties suggest that K2BDAF may undergo a structural transition/distortion around 4–5 GPa of pressure.