Understanding the Correlation between Impact Sensitivity and Elasticity of Energetic Crystals via Dispersion-Corrected Density Functional Theory Calculations

Impact
sensitivity and elasticity are among the most important
properties of energetic materials. Both properties are related to
the mechanical stress. Understanding elasticity and impact sensitivity
is crucial for predicting the mechanical response and failure of energetic
materials, thus establishing a correlation between the elasticity
mechanics and the initiation and detonation of energetic materials.
However, it is unclear how elasticity influences the impact sensitivity
of energetic crystals. Herein, the elastic properties of 19 typical
energetic crystals with impact sensitivity varying from low to high
are studied by using dispersion-corrected density functional theory.
We demonstrate that the elastic stiffness tensors predicted in this
work satisfy the necessary and sufficient stability conditions for
elastic stability. A thorough comparison with literature data further
shows that while the results are in general agreement with literature
data, large discrepancies are found for certain elastic tensor elements.
By probing the correlation between impact sensitivity and elasticity,
we show that higher elastic moduli and elastic anisotropy generally
lead to lower impact sensitivity. The underlying mechanism is that
higher elastic moduli and higher elastic anisotropy lead to easy absorption
of impact energy in the form of elastic deformation and dissipation
of impact energy through thermal conductivity and shear sliding, thus
lowering the probability of impact-induced formation and growth of
hotspots. These findings facilitate our fundamental understanding
of the elastic properties and structure–property relationships
of energetic crystals.

冲击感度（impact sensitivity）与弹性是含能材料（energetic materials）最为重要的性能之一，二者均与机械应力密切相关。明晰含能材料的弹性与冲击感度，对于预测其力学响应与失效模式至关重要，进而可建立弹性力学与含能材料起爆、爆轰之间的内在关联。然而目前学界仍未明确弹性如何影响含能晶体的冲击感度。本文针对19种冲击感度覆盖低至高区间的典型含能晶体，采用色散校正密度泛函理论（dispersion-corrected density functional theory）开展弹性性能研究。本研究所预测的弹性刚度张量（elastic stiffness tensors）满足弹性稳定性的充要条件。通过与已有文献数据的全面比对可知，尽管整体结果与文献报道基本吻合，但部分弹性张量元素存在显著偏差。通过系统探究冲击感度与弹性性能的关联，本文发现更高的弹性模量（elastic moduli）与弹性各向异性（elastic anisotropy）通常对应更低的冲击感度。其内在作用机制为：更高的弹性模量与弹性各向异性可使材料更易以弹性变形形式吸收冲击能量，并通过热传导与剪切滑移耗散冲击能量，从而降低冲击诱导热点（hotspots）形成与生长的概率。上述研究结果有助于深化对含能晶体弹性性能及构效关系（structure–property relationships）的基础认知。