Li Jianfu, Geng Yanlei, Xu Zhenzhen, Zhang Pinhua, Garbarino Gaston, Miao Maosheng, Hu Qingyang, Wang Xiaoli
School of Physics and Electronic Information, Yantai University, Yantai264005, P.R. China.
School of Physics and Electronic Engineering, Linyi University, Linyi276005, P.R. China.
JACS Au. 2023 Jan 12;3(2):402-408. doi: 10.1021/jacsau.2c00550. eCollection 2023 Feb 27.
External mechanical stress alters the nature of chemical bonds and triggers novel reactions, providing interesting synthetic protocols to supplement traditional solvent- or thermo-based chemical approaches. The mechanisms of mechanochemistry have been well studied in organic materials made of a carbon-centered polymeric framework and covalence force field. They convert stress into anisotropic strain which will engineer the length and strength of targeted chemical bonds. Here, we show that by compressing silver iodide in a diamond anvil cell, the external mechanical stress weakens the Ag-I ionic bonds and activate the global diffusion of super-ions. In contrast to conventional mechanochemistry, mechanical stress imposes unbiased influence on the ionicity of chemical bonds in this archetypal inorganic salt. Our combined synchrotron X-ray diffraction experiment and first-principles calculation demonstrate that upon the critical point of ionicity, the strong ionic Ag-I bonds break down, leading to the recovery of elemental solids from a decomposition reaction. Instead of densification, our results reveal the mechanism of an unexpected decomposition reaction through hydrostatic compression and suggest the sophisticated chemistry of simple inorganic compounds under extreme conditions.
外部机械应力会改变化学键的性质并引发新的反应，从而提供有趣的合成方案来补充传统的基于溶剂或热的化学方法。机械化学的机制在以碳为中心的聚合物框架和共价力场构成的有机材料中已得到充分研究。它们将应力转化为各向异性应变，进而改变目标化学键的长度和强度。在此，我们展示了通过在金刚石对顶砧池中压缩碘化银，外部机械应力会削弱Ag-I离子键并激活超离子的整体扩散。与传统机械化学不同，机械应力对这种典型无机盐中化学键的离子性施加了无偏向的影响。我们结合同步加速器X射线衍射实验和第一性原理计算表明，在离子性的临界点，强离子性的Ag-I键会断裂，导致分解反应中元素固体的恢复。我们的结果揭示的不是致密化，而是通过静水压力压缩引发意外分解反应的机制，并表明了简单无机化合物在极端条件下复杂的化学性质。
