The response of ettringite under sorption is critical for the utilization of this mineral as an energy storage material and to understand the concrete durability problems associated with ettringite formation. We report molecular simulations directly sampling the osmotic ensemble to understand the sorption processes and structural changes in ettringite-metaettringite transition. Desorption branch and sorption-induced volume changes from simulations agree with the experiments. The structural changes at low relative humidity are analyzed, revealing for the first time details of metaettringite structure. The reversibility under sorption observed experimentally is captured by simulation in the ettringite domain. The reversibility in the conversion of metaettringite into ettringite is not captured by the direct simulations in the osmotic ensemble due to the large volume changes associated with ettringite desorption. Finally, we discuss the role of hydrogen bonds on the hysteresis in ettringite.

钙矾石在吸附作用下的响应对于将这种矿物用作储能材料并了解与钙矾石形成相关的混凝土耐久性问题至关重要。我们报告了直接对渗透系综进行采样的分子模拟，以了解钙矾石-偏钙矾石转变的吸附过程和结构变化。来自模拟的解吸分支和吸附引起的体积变化与实验一致。分析了低相对湿度下的结构变化，首次揭示了偏钙矾石结构的细节。实验观察到的吸附下的可逆性通过钙矾石域中的模拟获得。由于与钙矾石解吸相关的大体积变化，渗透系综中的直接模拟没有捕捉到偏钙矾石转化为钙矾石的可逆性。最后，我们讨论了氢键对钙矾石磁滞的作用。