非晶碳酸钙结构复杂性的几何阻碍作用
Geometrically-frustrated interactions drive structural complexity in amorphous calcium carbonate
摘要：
无定形碳酸钙（ACC）是海洋生物体内重要的生物矿化前体。关于ACC的关键未决问题之一是如何最好地理解其结构，以及如何合理化其作为非晶相的亚稳性。在这里，我们报告高品质的原子模型ACC产生的使用国家的最先进的原子间的潜力，以帮助指导适合X射线总散射数据。利用最近开发的反演方法，我们从这些模型中提取有效的钙$\boldsymbol\cdots$钙相互作用的潜力，ACC的形成。该电位在两个竞争距离处包含最小值，对应于碳酸根离子桥接Ca $^{2+}$ -离子对的两种不同方式。我们揭示了一个意想不到的映射到Lennard-Jones-Gauss（LJG）模型通常在计算软物质的背景下进行研究，ACC的经验LJG参数取已知的值，以促进结构的复杂性。以这种方式，我们表明，ACC的复杂结构和它的弹性结晶实际上是编码在几何挫折有效的相互作用之间的钙$^{\boldsymbol 2+}$离子。
英文摘要：
Amorphous calcium carbonate (ACC) is an important precursor for biomineralisation in marine organisms. Among the key outstanding problems regarding ACC are how best to understand its structure and how to rationalise its metastability as an amorphous phase. Here, we report high-quality atomistic models of ACC generated by using state-of-the-art interatomic potentials to help guide fits to X-ray total scattering data. Exploiting a recently-developed inversion approach, we extract from these models the effective Ca$\boldsymbol\cdots$Ca interaction potential governing ACC formation. This potential contains minima at two competing distances, corresponding to the two different ways in which carbonate ions bridge Ca$^{2+}$-ion pairs. We reveal an unexpected mapping to the Lennard-Jones--Gauss (LJG) model normally studied in the context of computational soft-matter, with the empirical LJG parameters for ACC taking values known to promote structural complexity. In this way we show that both the complex structure of ACC and its resilience to crystallisation are actually encoded in the geometrically-frustrated effective interactions between Ca$^{\boldsymbol 2+}$ ions.
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