First-principles study on crystal structure, mechanical thermodynamics, and electronic properties of perovskite energetic materials under high pressure

Abstract

Based on first-principles calculations, the (H₂dabco)[NH₂NH₃(ClO₄)₃] (DAP-7) compound was studied in depth using the dispersion-corrected density functional theory (DFTD) method, and the influence of pressure on its impact sensitivity and stability was evaluated. Analysis of the characteristic bond angles and torsion angles within the crystal revealed that at 11 GPa, the skeleton structure of the A-site cation H₂dabco²⁺ became distorted. The calculated average fractional coordinates and Euler angles of the centroids for the A-site and X-site structures structures showed that throughout the entire pressure range, the crystal only underwent a slight rotational transformation with the space group remaining unchanged. According to the first-principles band gap criterion and the trend of bandgap changes under different pressures, it was found that around 25 GPa, the decrease in the bandgap value of DAP-7 changed significantly. Additionally, the elastic constants (Cij), elastic moduli (B, E, G), and Cauchy pressure (C12-C44) all increased with increasing pressure, indicating that the rigidity and ductility of the crystal are significantly enhanced under pressure. The calculation results of intermolecular interactions showed that the largest proportion of total interaction is hydrogen bonding H⋯O(O⋯H), which decreases as pressure increases, thus leading to an increase of impact sensitivity of materials.