Cube‐like double four‐ring (d4r) cages are among the most frequent building units of zeolites and zeotypes. In materials synthesised in fluoride‐containing media, the fluoride anions are preferentially incorporated in these cages. In order to study the impact of framework composition and organic structure‐directing agents (OSDAs) on the possible occurrence of local distortions of fluoride‐containing d4r cages, density functional theory (DFT) calculations and DFT‐based molecular dynamics simulations were performed for AST‐type zeotypes, considering four different compositions (SiO₂, GeO₂, AlPO₄, GaPO₄) and two different OSDA cations (tetramethylammonium [TMA] and quinuclidinium [QNU]). All systems except SiO₂‐AST show significant deformations, with a pyritohedron‐like distortion of the d4r cages occurring in GeO₂‐ and GaPO₄‐AST, and a displacement of the fluoride anions towards one of the corners of the cage in AlPO₄‐ and GaPO₄‐AST. While the distortions occur at random in TMA‐containing zeotypes, they exhibit a preferential orientation in systems that incorporate QNU cations. In addition to providing detailed understanding of the local structure of a complex host‐guest system on the picosecond timescale, this work indicates the possibility to stabilise ordered distortions through a judicious choice of the OSDA, which might enable a tuning of the material's properties.

中文翻译：

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包含双四环笼的原型沸石框架中的局部变形：框架组成和有机客体的作用**

立方体状的双四环（d4r）笼子是沸石和分子型最常见的建筑单元之一。在含氟介质中合成的材料中，氟阴离子优先掺入这些笼中。为了研究骨架组成和有机结构导向剂（OSDA）对含氟d4r笼子局部变形可能发生的影响，针对AST进行了密度泛函理论（DFT）计算和基于DFT的分子动力学模拟类型的型型，考虑了四种不同的成分（SiO ₂，GeO ₂，AlPO ₄，GaPO ₄）和两种不同的OSDA阳离子（四甲基铵[TMA]和奎宁环己酮[QNU]）。除SiO ₂ -AST以外的所有系统均显示出明显的变形，在GeO _2-和GaPO ₄ -AST中d4r笼发生类似吡六面体的形变，并且氟阴离子向AlPO ₄笼中的一个角位移‐和GaPO ₄-AST。尽管扭曲在包含TMA的分子型中随机发生，但在包含QNU阳离子的系统中它们表现出优先的取向。除了可以在皮秒级的时间内详细了解复杂的主客体系统的局部结构外，这项工作还表明可以通过明智地选择OSDA来稳定有序畸变，从而可以调节材料的性能。