Dynamic Barriers to Crystallization of Calcium Barium Carbonates
Dynamic Barriers to Crystallization of Calcium Barium Carbonates
复制标题
碳酸钙钡结晶的动态势垒
DOI：
10.1021/acs.cgd.1c00433
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发表时间：
2021
影响因子：
3.8
通讯作者：
Joester, Derk
中科院分区：
文献类型：
--
作者：
Whittaker, Michael L.;Sun, Wenhao;Duggins, Danielle O.;Ceder, Gerbrand;Joester, Derk
亚稳碳酸盐岩在地球化学、生物成矿作用和成核与生长的非经典理论中起着重要的作用。方解石（Ca0.5Ba0.5CO3）是一种显著的碳酸盐相，其与方解石（CaCO 3）的高温改性是同构的，但可以在环境条件下合成。在这里，我们研究的Ba-Ca-CO 3-H2O系统的结晶途径，重点是无定形碳酸钙碳酸钡（ACBC）的转变，以方解石和随后分解成平衡方解石（CaCO 3）和毒重石（BaCO 3）相。密度泛函理论计算表明，在0.17 <x< 0.5的范围内，方解石是一种不稳定的固溶体（Ca_（1-x）CO_3，R_3 ~ m），但当x <0.5时，可以通过无定形ACBC前体进入，并预测其分解为方解石和毒重石。我们通过实验证实了这一途径，但发现分层进行缓慢，即使在9个月后仍然不完整。使用微流体测定评估来自ACBC的方解石的成核动力学，其中增加钡含量导致方解石成核速率的惊人增加，尽管热力学驱动力降低。我们属性的结晶速率，显着加快随着时间的推移，在界面结构和组合物的变化，在粗化的无定形沉淀物。通过仔细量化的热力学和动力学贡献的多步结晶的亚稳碳酸盐，我们产生的见解，使我们能够更好地解释的形成和持久性的亚稳矿物在自然和合成环境。
Metastable carbonates play important roles in geochemistry, biomineralization and serve as model systems for nonclassical theories of nucleation and growth. Balcite (Ca0.5Ba0.5CO3) is a remarkable carbonate phase that is isostructural with a high-temperature modification of calcite (CaCO3), yet can be synthesized at ambient conditions. Here, we investigate crystallization pathways in the Ba–Ca–CO3–H2O system, with a focus on the transformation of amorphous calcium barium carbonate (ACBC) to balcite and subsequent decomposition into the equilibrium calcite (CaCO3) and witherite (BaCO3) phases. Density functional theory calculations show that balcite is an unstable solid solution (Ca1–xBaxCO3,R3̅m) in the range 0.17 <x< 0.5, but is accessible through the amorphous ACBC precursor forx≲ 0.5, and predict its decomposition into calcite and witherite. We confirm this pathway experimentally but found demixing to proceed slowly and remain incomplete even after 9 months. Nucleation kinetics of balcite from ACBC was assessed using a microfluidic assay, where increasing barium content led to a surprising increase in the balcite nucleation rate, despite decreasing thermodynamic driving force. We attribute crystallization rates that dramatically accelerate with time to changes in interfacial structure and composition during coarsening of the amorphous precipitate. By carefully quantifying the thermodynamic and kinetic contributions in the multistep crystallization of a metastable carbonate, we produce insights that allow us to better interpret the formation and persistence of metastable minerals in natural and synthetic environments.
Ba、Sr、Ca 三重碳酸盐的晶体结构
DOI：
--
发表时间：
1953
期刊：
影响因子：
--
作者：
Jitsuo Terada
通讯作者：
Jitsuo Terada