Bose Tushar Kanti, Saha Jayashree
Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700009, India.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Oct;92(4):042503. doi: 10.1103/PhysRevE.92.042503. Epub 2015 Oct 12.
The realization of a spontaneous macroscopic ferroelectric order in fluids of anisotropic mesogens is a topic of both fundamental and technological interest. Recently we demonstrated that a system of dipolar achiral disklike ellipsoids can exhibit long-searched ferroelectric liquid crystalline phases of dipolar origin. In the present work, extensive off-lattice Monte Carlo simulations are used to investigate the phase behavior of the system under the influences of the electrostatic boundary conditions that restrict any global polarization. We find that the system develops strongly ferroelectric slablike domains periodically arranged in an antiferroelectric fashion. Exploring the phase behavior at different dipole strengths, we find existence of the ferroelectric nematic and ferroelectric columnar order inside the domains. For higher dipole strengths, a biaxial phase is also obtained with a similar periodic array of ferroelectric slabs of antiparallel polarizations. We have studied the depolarizing effects by using both the Ewald summation and the spherical cutoff techniques. We present and compare the results of the two different approaches of considering the depolarizing effects in this anisotropic system. It is explicitly shown that the domain size increases with the system size as a result of considering a longer range of dipolar interactions. The system exhibits pronounced system size effects for stronger dipolar interactions. The results provide strong evidence to the novel understanding that the dipolar interactions are indeed sufficient to produce long-range ferroelectric order in anisotropic fluids.
在各向异性介晶流体中实现自发的宏观铁电有序是一个具有基础和技术意义的课题。最近我们证明了一个偶极非手性盘状椭球体系统可以展现出长期以来一直在寻找的偶极起源的铁电液晶相。在当前工作中，广泛的非晶格蒙特卡罗模拟被用于研究该系统在限制任何全局极化的静电边界条件影响下的相行为。我们发现该系统会形成以反铁电方式周期性排列的强铁电板状畴。通过探索不同偶极强度下的相行为，我们发现在畴内存在铁电向列相和铁电柱状有序。对于更高的偶极强度，还会得到一个双轴相，其具有类似的反平行极化铁电板的周期性阵列。我们通过使用埃瓦尔德求和法和球形截断技术研究了去极化效应。我们展示并比较了在这个各向异性系统中考虑去极化效应的两种不同方法的结果。明确表明，由于考虑了更长程的偶极相互作用，畴尺寸随系统尺寸增加。对于更强的偶极相互作用，该系统展现出明显的系统尺寸效应。这些结果为偶极相互作用确实足以在各向异性流体中产生长程铁电有序这一新颖认识提供了有力证据。
