Departamento de Física Atómica, Molecular y Nuclear, Área de Física Teórica, Universidad de Sevilla, Apartado de Correos 1065, 41080 Sevilla, Spain.
J Chem Phys. 2012 Jul 21;137(3):034505. doi: 10.1063/1.4733974.
We perform Monte Carlo computer simulations of nematic drops in equilibrium with their vapor using a Gay-Berne interaction between the rod-like molecules. To generate the drops, we initially perform NPT simulations close to the nematic-vapor coexistence region, allow the system to equilibrate and subsequently induce a sudden volume expansion, followed with NVT simulations. The resultant drops coexist with their vapor and are generally not spherical but elongated, have the rod-like particles tangentially aligned at the surface and an overall nematic orientation along the main axis of the drop. We find that the drop eccentricity increases with increasing molecular elongation, κ. For small κ the nematic texture in the drop is bipolar with two surface defects, or boojums, maximizing their distance along this same axis. For sufficiently high κ, the shape of the drop becomes singular in the vicinity of the defects, and there is a crossover to an almost homogeneous texture; this reflects a transition from a spheroidal to a spindle-like drop.
我们使用棒状分子之间的 Gay-Berne 相互作用，对与蒸气处于平衡状态的向列型液滴进行蒙特卡罗计算机模拟。为了生成液滴，我们最初在接近向列-蒸气共存区域的 NPT 模拟中进行，让系统达到平衡，然后突然进行体积膨胀，随后进行 NVT 模拟。生成的液滴与蒸气共存，通常不是球形的，而是拉长的，棒状粒子在表面处切向排列，整体向列取向沿液滴的主轴。我们发现，液滴的偏心率随分子伸长率 κ 的增加而增加。对于小 κ，液滴中的向列织构具有双极特性，两个表面缺陷或 boojums 沿着同一轴最大化它们之间的距离。对于足够高的 κ，缺陷附近液滴的形状变得奇异，并且向几乎均匀的织构转变；这反映了从球形到纺锤形液滴的转变。
