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arXiv 1002.0191cond-mat.stat-mech
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受限液晶中的各向同性-向异性转变：一种非普适现象

The isotropic-to-nematic transition in confined liquid crystals : an essentially non-universal phenomenon

J. M. Fish, R. L. C. Vink

备注：
To appear in Phys. Rev. E
发表信息：
Phys. Rev. E 81, 021705 (2010)
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摘要：

本文用计算机模拟了两个相距H的平行平板间的液晶从各向同性到双折射的转变。板是中性的，并且不对颗粒施加任何锚定。根据粒子之间作用的对势的形状，我们发现，过渡要么从一阶到连续的临界膜厚度H=Hx的变化，或过渡保持一阶无关H。这表明，各向同性的限制几何过渡，是不具有任何普适类，而是它的命运是由微观细节决定的。由此产生的毛细管相图可以假设两种拓扑结构：一种是各向同性和双结点分支在H=Hx处相遇，另一种是它们保持分离。对于H值的转变是强烈的一阶转变的转变温度的移位DT是在良好的协议与开尔文方程。不仅恢复了DT~1/H的关系，而且使位移的前因与独立测量的本体潜热和界面张力定量一致。

英文摘要：

Computer simulations are presented of the isotropic-to-nematic transition in a liquid crystal confined between two parallel plates a distance H apart. The plates are neutral and do not impose any anchoring on the particles. Depending on the shape of the pair potential acting between the particles, we find that the transition either changes from first-order to continuous at a critical film thickness H=Hx, or that the transition remains first-order irrespective of H. This demonstrates that the isotropic-to-nematic transition in confined geometry is not characterized by any universality class, but rather that its fate is determined by microscopic details. The resulting capillary phase diagrams can thus assume two topologies: one where the isotropic and nematic branches of the binodal meet at H=Hx, and one where they remain separated. For values of H where the transition is strongly first-order the shift DT of the transition temperature is in excellent agreement with the Kelvin equation. Not only is the relation DT~1/H recovered but also the prefactor of the shift is in quantitative agreement with the independently measured bulk latent heat and interfacial tension.

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