Density-Functional Tight-Binding Molecular Dynamics Simulation of the Bending Mechanism of Molecular Crystals
Density-Functional Tight-Binding Molecular Dynamics Simulation of the Bending Mechanism of Molecular Crystals
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分子晶体弯曲机制的密度泛函紧束缚分子动力学模拟
DOI：
10.1021/acs.jpcc.2c02504
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Momoji Kubo
中科院分区：
文献类型：
--
作者：
Yusuke Ootani;Momoji Kubo
智能照相制版材料的发展需要生物分子晶体。用塑性弯曲模型解释了塑性分子晶体的弯曲，在该模型中，晶体分离成层状结构，并在彼此上滑动以消散应力。该模型已被公布为可弯曲分子晶体的设计原理：当形成晶体层的强相互作用和允许滑动的弱相互作用在晶体中共存时，晶体经历塑性弯曲。然而，也报告了一些例外情况。3，4-二氯苯甲酸（CBA）和3，4-二氯苯甲酰胺（CBAM）晶体符合设计原则。然而，当外力施加在（001）面上时，仅CBA晶体沿晶体的长边沿着弯曲。CBAM晶体虽然结构相似，但以脆性方式断裂。这个意外的结果表明，设计原理仍然是不完整的，和CBAM晶体的脆性性质的根本原因的理解，需要建立一个通用的设计原理。在这项研究中，我们进行了基于密度泛函紧束缚分子动力学的CBA和CBAM晶体的剪切/拉伸模拟，以阐明可弯曲分子晶体的设计原则。剪切模拟表明，CBA和CBAM晶体具有塑性特性，因为它们都通过滑动层或重新定向分子来耗散剪切应力。然而，在拉伸模拟中发现了一个关键的差异：CBA晶体是塑性的，而CBAM晶体是脆性的。在先前的实验中，CBAM晶体的断裂是由于CBAM晶体在受到拉伸应力时的脆性性质。在CBAM晶体中，晶体层中的强氢键阻止了分子的重新取向，并且当受到拉伸应力时使CBAM晶体变脆。基于模拟结果，我们提出了一个更新的，一般的可弯曲的塑料分子晶体的设计原则：除了传统的设计原则，晶体应该是足够灵活的拉伸应力引起塑性弯曲。
Bendable molecular crystals are required for the development of smart photomechanical materials. The bending of plastic molecular crystals has been explained by a plastic bending model in which crystals segregate into a layered structure and slide over each other to dissipate the stress. This model has been promulgated as the design principle of a bendable molecular crystal: crystals experience plastic bending when the strong interactions that form the crystal layer and weak interactions that allow the sliding coexist in the crystal. However, some exceptions have been reported. The crystals of 3,4-dichlorobenzoic acid (CBA) and 3,4-dichlorobenzamide (CBAM) conform to the design principle. However, only the CBA crystal bends along the long side of the crystal when the external force is applied on the (001) face. The CBAM crystal, although similar in structure, fractures in a brittle manner. This unexpected result shows that the design principle is still incomplete, and an understanding of the underlying cause of the brittle nature of the CBAM crystal is required to establish a general design principle. In this study, we performed density-functional tight-binding molecular dynamics-based shear/tensile simulations of CBA and CBAM crystals to elucidate the design principle for bendable molecular crystals. The shear simulations showed that both the CBA and CBAM crystals had plastic characteristics because they both dissipated a shear stress by sliding layers or reorientating molecules. A critical difference was found, however, in the tensile simulations: the CBA crystal was plastic, and the CBAM crystal was brittle. The fracture of CBAM crystals in previous experiments was due to the brittle nature of CBAM crystals when subjected to a tensile stress. In the CBAM crystal, strong hydrogen bonding in the crystal layer prevented reorientation of the molecules and made the CBAM crystal brittle when subjected to a tensile stress. Based on the simulation results, we proposed an updated, general design principle for a bendable plastic molecular crystal: in addition to the conventional design principle, the crystal should be sufficiently flexible for a tensile stress to elicit plastic bending.
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DOI：
10.1021/jp074167r
发表时间：
2007-10
期刊：
The journal of physical chemistry. A
影响因子：
--
作者：
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DOI：
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发表时间：
2019
期刊：
影响因子：
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作者：
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影响因子：
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影响因子：
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作者：
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影响因子：
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作者：
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