Anisotropic Impact Sensitivity and Shock Induced Plasticity of TKX-50 (Dihydroxylammonium 5,5′-bis(tetrazole)-1,1′-diolate) Single Crystals: From Large-Scale Molecular Dynamics Simulations

Abstract

Dihydroxylammonium 5,5′-bis(tetrazole)-1,1′-diolate (TKX-50) is a newly synthesized energetic material with high energy storage, low impact sensitivity, and low toxicity. These features make it a viable candidate to replace such commonly used energetic materials as RDX and CL-20 in the next generation of explosives. Sensitivity determines the engineering application of energetic materials (EMs) and has been widely studied for various EMs. To understand the origin of the anisotropic sensitivity and properties of this new synthesized EM, we report a flexible classical force field for TKX-50 developed to reproduce the molecular properties (geometry, vibrational frequencies and torsion barriers) and the crystal properties (cell parameters and lattice energy). We then used this force field in molecular dynamics (MD) simulations to predict such thermodynamic and mechanical properties as isothermal compressibility, thermal expansion, elastic moduli, and heat capacity. Furthermore, we carried out large scale (∼a half million atoms) MD simulations to investigate the mechanical response to shocks in the [100], [010] and [001] directions. The predicted Hugoniot elastic limits (HELs) are 6.1 GPa for [100], 14.2 GPa for [010] and 9.1 GPa for [001] shocks. Thus, single crystal TKX-50 shows anisotropic impact sensitivity with [010] as the most sensitive direction and [100] as least sensitive. The plastic deformations in shock compression along the [100] direction primary arise from the (001)/[210] and (010)/[001] slip systems of. For the [010] shock, the primary slip systems are (100)/[021] and (001)/[210]. However, no obvious slip system was observed for [001] shock.