Nanochemistry Research Institute, Department of Chemistry, Curtin University, P.O. Box U1987, Perth, WA 6845, Australia.
J Am Chem Soc. 2010 Dec 15;132(49):17623-34. doi: 10.1021/ja108508k. Epub 2010 Nov 19.
Calcium carbonate is a ubiquitous mineral that represents one of the most significant biominerals, a major contributor to carbon sequestration through geological deposits, and a technological hindrance as a result of scale formation. Amorphous calcium carbonate is intimately involved in the nucleation and growth of this material, yet much remains undiscovered regarding the atomic detail. Through dynamical simulation we demonstrate that nucleation of amorphous calcium carbonate follows a nonclassical pathway. This arises from the addition of ion pairs to clusters exhibiting a consistently exothermic free energy that persists with increasing particle size. Furthermore, the disruption of the surrounding water of solvation by the atomically rough surface reduces the barrier to growth to the order of ambient thermal energy, thereby allowing the amorphous phase to grow faster than crystalline polymorphs. Amorphous calcium carbonate nanoparticles are also found to exploit size-dependent water content to render itself more stable than the favored bulk phase, calcite, below a critical diameter of close to 4 nm.
碳酸钙是一种无处不在的矿物质，它是最重要的生物矿物之一，是通过地质沉积物进行碳封存的主要贡献者，也是由于结垢而形成的技术障碍。无定形碳酸钙在这种物质的成核和生长过程中起着重要作用，但关于其原子细节，仍有许多尚未被发现。通过动力学模拟，我们证明了无定形碳酸钙的成核遵循非经典途径。这是由于离子对的添加到表现出持续放热的自由能的簇，该自由能随着粒径的增加而持续。此外，原子粗糙表面对溶剂化水的破坏降低了生长的势垒，使其接近环境热能，从而使无定形相比晶型多形体生长得更快。还发现无定形碳酸钙纳米颗粒利用尺寸依赖性的含水量使自身比优选的块状相方解石更稳定，低于接近 4nm 的临界直径。
