Entropy-driven formation of chiral nematic phases by computer simulations.
Entropy-driven formation of chiral nematic phases by computer simulations.
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DOI：
10.1038/ncomms11175
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发表时间：
2016-04-12
影响因子：
16.6
通讯作者：
Dijkstra M
中科院分区：
文献类型：
--
作者：
Dussi S;Dijkstra M
从粒子的微观手性来预测液晶的宏观手性行为是非常不容易的，即使手性相互作用在性质上是纯粹的熵。在这里，我们引入了一种新的手性硬粒子模型，即具有扭曲多面体形状的粒子，并通过计算机模拟得到了稳定的全熵驱动的胆甾相。通过稍微修改粒子的三角形基座，我们能够使用相同的右手扭曲粒子模型从左手长形(卡拉米特)转变为右手扁平(盘状)胆甾相。此外，我们还发现，通过改变粒子的双轴度和手性，不仅可以得到长方形和扁圆形的手性向列相，而且还可以得到其他新型的熵驱动相，即手性蓝相、同时具有扭转和张开变形的手性向列相、具有一轴扭曲的手性双轴向列相。我们的结果允许确定稳定这些阶段的一般指导方针。胆甾型液晶是一种应用广泛的液晶相，由于其晶胞较大，其形成过程中的熵驱动机制尚未在模拟中得到解决。在这里，Dussi和Dijkstra通过引入硬粒子模型克服了这个问题，并证明了形状本身就可以稳定手性向列相。
Predicting the macroscopic chiral behaviour of liquid crystals from the microscopic chirality of the particles is highly non-trivial, even when the chiral interactions are purely entropic in nature. Here we introduce a novel chiral hard-particle model, namely particles with a twisted polyhedral shape and obtain a stable fully entropy-driven cholesteric phase by computer simulations. By slightly modifying the triangular base of the particle, we are able to switch from a left-handed prolate (calamitic) to a right-handed oblate (discotic) cholesteric phase using the same right-handed twisted particle model. Furthermore, we show that not only prolate and oblate chiral nematic phases, but also other novel entropy-driven phases, namely chiral blue phases, chiral nematic phases featuring both twist and splay deformations, chiral biaxial nematic phases with one of the axes twisted, can be obtained by varying particle biaxiality and chirality. Our results allow to identify general guidelines for the stabilization of these phases. The entropy-driven formation of cholesteric liquid crystal, one of the widely used liquid crystal phase, has not yet been addressed in simulations due to large unit cells. Here, Dussi and Dijkstra overcome this problem by introducing a hard-particle model and show that shape alone can stabilize a chiral nematic phase.