The dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, and due to the global use of plaster of Paris in the construction industry. The dehydration kinetics of gypsum strongly depend on temperature and water vapour pressure. Here, we perform fast, time-resolved synchrotron X-ray scattering on natural alabaster samples, finding that a small elastic load accelerates the dehydration reaction significantly. The mechanical acceleration of the reaction consumes about 10,000 times less energy than that due to heating. We propose that this thermodynamically surprising finding is caused by geometry-energy interactions in the microstructure, which facilitate nucleation and growth of the new crystalline phase. Our results open research avenues on the fundamental thermo-mechanics of crystal hydrates and the interaction of stress and chemical reactions in crystalline solids with a wide range of implications, from understanding dehydration-triggered earthquakes to the energy-efficient design of calcination processes.

石膏脱水成半水合物已经进行了数十年的研究，这是因为石膏是理解流体触发地震的重要模型反应，并且由于巴黎在建筑行业中的石膏使用在全球范围内。石膏的脱水动力学在很大程度上取决于温度和水蒸气压。在这里，我们对天然雪花石膏样品进行快速，时间分辨的同步加速器X射线散射，发现较小的弹性载荷显着加速了脱水反应。反应的机械加速所消耗的能量比加热所消耗的能量少约10,000倍。我们建议，这种热力学上令人惊讶的发现是由微观结构中的几何能量相互作用引起的，该相互作用促进了新结晶相的成核和生长。