液态结构弛豫动力学非指数性的研究进展

Studies of non-exponentiality of structural relaxation in glass forming liquids:a review

结构弛豫的非指数性是过冷液体3个最基本的动力学特征之一。本文对多种玻璃形成体系在液相区内的结构弛豫非指数性进行了系统研究,涉及到的研究体系包括小分子、金属与合金、高分子、无机网络、离子等5类玻璃形成液体。研究发现,对于绝大部分玻璃形成液体,非指数因子KWW在玻璃转变附近的低频(或低温)区间符合时间-温度叠加原理(TTS);TTS区的宽度与液体的强弱性相关;在弛豫频率接近1011Hz(或者弛豫时间1.6×1012s)时,所有液体的结构弛豫达到纯指数性(KWW=1)。本文讨论了非指数因子与液体强弱性参数和TTS区宽度的关联,以及焓弛豫非指数因子与介电弛豫非指数因子之间的相关性。

The non-exponential behavior is one of the three canonical characters of structural relaxation dynamics in supercooled liquids.The non-exponential dynamics of various glass-formers covering molecular,metallic,polymeric,network and ionic systems is reviewed across the whole liquid region from glass transition.General rules are outlined from the glass forming liquids.It is found that the majority of glass forming liquids is subject to the time-temperature-superposition（TTS） law at low dynamic regimes,while the width of the TTS regime depends on liquid fragility.The exponential mode is reached for all the liquids at fast dynamic regions with a critical relaxation frequency of ～1011 Hz（equivalent to a relaxation time of 1.6×10 12 s）.The correlations of the non-exponential parameter with liquid fragility and the width of TTS regimes are discussed,and dielectric and enthalpy relaxations are highlighted.