论文标题
分层共价框架中的流离失所不稳定性$^†$
Band gap opening from displacive instabilities in layered covalent-organic frameworks $^†$
论文作者
论文摘要
共价有机框架（COF）具有高度的化学和结构柔韧性。有一个由2D纸建造的大型COF家族，它们堆叠成形成延伸的晶体。尽管将堆叠表示为一个重复层（“ AA”）是很常见的，但越来越多的证据表明，可以访问更多样化的堆叠序列。本文中，我们报告了两种原型COF中的层堆叠的计算研究，TP-Azo和DAAQ-TFP，该研究表现为高性能作为锂离子电池电极。我们发现，对滑动结构的偏好具有惊人的偏好，其层之间的水平偏移范围从1.7至3.5Å，势能最小值，形成低能环。相关的对称破坏导致基础电子结构的明显变化。由于$π$轨道重叠的变化所解释的，因此发现了0.8-1.4 eV的带隙开口。讨论了对能源应用COF筛查和选择的影响。
Covalent organic frameworks (COFs) offer a high degree of chemical and structural flexibility. There is a large family of COFs built from 2D sheets that are stacked to form extended crystals. While it has been common to represent the stacking as eclipsed with one repeating layer ("AA"), there is growing evidence that a more diverse range of stacking sequences is accessible. Herein, we report a computational study of layer stacking in two prototypical COFs, Tp-Azo and DAAQ-TFP, which have shown high performance as Li-ion battery electrodes. We find a striking preference for slipped structures with horizontal offsets between layers ranging from 1.7 Å to 3.5 Å in a potential energy minimum that forms a low energy ring. The associated symmetry breaking results in a pronounced change in the underlying electronic structure. A band gap opening of 0.8 - 1.4 eV is found due to modifications of the underlying valence and conduction band dispersion as explained from changes in the $π$ orbital overlap. The implications for the screening and selection of COF for energy applications are discussed.
