弹性形变对丝状相液晶相变的影响

应用Saupe形式的弹性自由能，研究了简单的扭曲，展曲和弯曲形变对相变的影响.结果表明，弹性形变可以产生从各向同性相至双轴丝状相的一级相变，对螺状相液晶，当系统手征性增加并超过某一临界值时，一级相变可过渡到二级相变. 关键词：

PHASE TRANSITION IN NEMATICS INDUCED BY ELASTIC DISTORTION

With elastic constants as functions of the order parameters, we have obtained a Landau's elastic free energy expression for biaxial nematic liquid crystals similar to that used by Govers. The relationship between this Govers form and the Saupe form for biaxial nematics is obtained. It shows that simple distortion, splay, twist or bend, may lead to a first order phase transition from isotropic phase to biaxial nematic phase. However, in the case of cholesteric liquid crystal, there exists a critical chirality, above which, instead of first order, the phase transition becomes second order.