AI 中文总结
本研究揭示氧化学计量比作为动力学控制参数调控TiO₂₋ₓ的锐钛矿-金红石相选择，通过模拟明确其成核势垒及中间壳层基元演化机制，建立的模型可预测成分耦合结晶的目标相。
AI 中文摘要
目标多晶型物的合成至今仍更多依赖经验而非预测，因为结晶过程通常会选择最易接近的成核路径，而非热力学上最稳定的相。本研究表明，氧化学计量比可将这一经验合成变量转化为TiO₂₋ₓ中锐钛矿-金红石选择的动力学控制参数。增强采样模拟显示，氧含量会改变成核势垒景观，即使金红石仍为热力学优势相，也会切换锐钛矿与锐钛矿的相对可及性。分子动力学模拟表明，晶核周围存在弥散的中间壳层，氧缺失会改变Ti-O配位与连接性，驱动壳层局部基元从类锐钛矿向类金红石环境演化。结合势垒竞争与壳层介导的附着/交换的耦合通量模型，得到的相对成核速率图与已报道的氧依赖合成趋势一致。这些结果确立了化学计量比控制的中间壳层基元演化为多晶型选择的动力学起源，并为成分耦合结晶中预测目标相提供了框架。
英文摘要
Synthesis of a target polymorph remains more empirical than predictive because crystallization often selects the most accessible nucleation pathway rather than the thermodynamically most stable phase. Here, we show that oxygen stoichiometry converts this empirical synthesis variable into a kinetic control parameter for anatase-rutile selection in TiO$_{2-x}$. Enhanced-sampling simulations reveal that oxygen content alters the nucleation-barrier landscape, switching the relative accessibility of anatase and rutile, even while rutile remains thermodynamically favored. Molecular dynamics simulations show the presence of a diffuse intermediate shell around the nucleus, where oxygen deficiency alters Ti-O coordination and connectivity and drives shell-local motif evolution from anatase-like toward rutile-like environments. A coupled-flux model that integrates barrier competition with shell-mediated attachment/exchange yields a relative nucleation-rate map consistent with reported oxygen-dependent synthesis trends. These results establish stoichiometry-controlled intermediate-shell motif evolution as a kinetic origin of polymorph selection and provide a framework for predicting target phases in composition-coupled crystallization.
