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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework
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Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework

机译：多孔材料的固有挠性;理论，建模和EMT沸石骨架的柔性窗口

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摘要

Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves – as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si-O-Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the 'rigid unit mode' (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the 'flexibility window' phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework.
机译：框架材料的结构包含通过其顶点连接的原子的强键多面体基团。通常，改变多面体之间的几何形状所需的能源成本远低于多面体本身变形的成本–如硅酸盐的情况，SiO4四面体基团的几何结构比Si-O受更强的约束-Si桥接角。结果，框架材料经常表现出固有的柔性，并且它们的动态和静态特性受到多面体的低能量集体运动的强烈影响。可以通过“刚性单位模式”（RUM）模型在对等空间中获得这些运动的洞察力，而通过基于模板的几何模拟可以在真实空间中获得洞察力。我们简要回顾了与能量有关的材料（包括离子导体，钙钛矿和沸石）中的骨架柔韧性现象。特别是，我们研究了沸石中的“柔韧性窗”现象，并在EMT框架的柔韧性窗上提出了新颖的结果，从而揭示了结构导向剂的作用。我们的主要发现是，冠醚尽管体积大，但不限制骨架的几何柔性。

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