Okamoto Atsushi, Kuwatani Tatsu, Omori Toshiaki, Hukushima Koji
Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aramaki, Aoba-ku, Sendai 980-8579, Japan.
Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Oct;92(4):042130. doi: 10.1103/PhysRevE.92.042130. Epub 2015 Oct 12.
Metastable minerals commonly form during reactions between water and rock. The nucleation mechanism of polymorphic phases from solution are explored here using a two-dimensional Potts model. The model system is composed of a solvent and three polymorphic solid phases. The local state and position of the solid phase are updated by Metropolis dynamics. Below the critical temperature, a large cluster of the least stable solid phase initially forms in the solution before transitioning into more-stable phases following the Ostwald step rule. The free-energy landscape as a function of the modal abundance of each solid phase clearly reveals that before cluster formation, the least stable phase has an energetic advantage because of its low interfacial energy with the solution, and after cluster formation, phase transformation occurs along the valley of the free-energy landscape, which contains several minima for the regions of three phases. Our results indicate that the solid-solid and solid-liquid interfacial energy contribute to the formation of the complex free-energy landscape and nucleation pathways following the Ostwald step rule.
亚稳矿物通常在水与岩石的反应过程中形成。本文使用二维Potts模型探索了溶液中多晶型相的成核机制。该模型系统由一种溶剂和三个多晶型固相组成。固相的局部状态和位置通过Metropolis动力学进行更新。在临界温度以下，溶液中最初会形成一大簇最不稳定的固相，然后按照奥斯特瓦尔德分步规则转变为更稳定的相。作为每个固相模态丰度函数的自由能景观清楚地表明，在簇形成之前，最不稳定的相由于其与溶液的低界面能而具有能量优势，而在簇形成之后，相变沿着自由能景观的谷底发生，该谷底包含三相区域的几个最小值。我们的结果表明，固-固和固-液界面能有助于形成复杂的自由能景观和成核途径，并遵循奥斯特瓦尔德分步规则。
