向列相(N)-各向同性相(I)相变为弱一级相变,其相变潜热大约比溶化的相变潜热小2个数量级.在这种弱一级相变附近焓随温度的变化表明:各向同性相最低过冷温度T*、N-I相变温度TC和向列相最高过热温度T**彼此十分接近.本文通过分子统计理论研究这一现象.形成单轴向列相的液晶分子并不具有D∞对称性.在分子场近似下和二粒子集团近似下,随分子双轴性参数增大,T*/T**增大并趋近于1.
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