Liquid state elasticity and the onset of activated transport in glass formers.
Liquid state elasticity and the onset of activated transport in glass formers.
复制标题
液态弹性和玻璃形成体中激活运输的开始。
DOI：
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发表时间：
2012
影响因子：
3.3
通讯作者：
V. Lubchenko
中科院分区：
文献类型：
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作者：
Pyotr Rabochiy;V. Lubchenko
我们证明了玻璃形成液体中激活输运的交叉温度可以用它们的有限频率弹性常数和融合熵来预测。后一种量决定了液体中化学刚性分子单元作为温度函数的振动运动的大小。利用这一概念，在交叉时，这种振动位移与相应晶格间距的“林德曼比”几乎与系统无关，可以估计交叉温度。对于9种特定物质，结果预测与动力学交叉温度的实验估计一致，也与随机一阶跃迁（RFOT）理论的预测一致，该理论预测了由于在临界构型熵下发生的分形相关重排而导致的无障输运的开始。特别是，脆性指数与交叉温度和玻璃化转变温度的比值呈负相关。这一预测与大多数观测结果一致，除了氧化硼B2O3偏离一般趋势。这种例外是由于B2O3中温度降低时增加了局部有序。最后，我们表明考虑弹性常数的温度依赖性对于准确估计交叉温度至关重要。
We show that the crossover temperature to activated transport in glass-forming liquids can be predicted using their finite-frequency elastic constants and the fusion entropy. The latter quantities determine the size of the vibrational motions of chemically rigid molecular units in the liquid as a function of temperature. Using the notion that, at the crossover, the "Lindemann ratio" of this vibrational displacement to the corresponding lattice spacing is nearly system-independent, one can estimate the crossover temperature. For nine specific substances, the resulting predictions are consistent with experimental estimates of the dynamical crossover temperature and also with the predictions of the random first order transition (RFOT) theory for the onset of barrierless transport owing to fractal correlated rearrangements that occur at a critical configurational entropy. In particular, the fragility index is found to inversely correlate with the ratio of the crossover and glass transition temperatures. This prediction agrees with most observations except for boron oxide B2O3, which deviates from the common trend. This exception is argued to result from additional local ordering with lowering temperature in B2O3. Finally, we show that taking into account the temperature dependence of the elastic constants is crucial for accurate estimates of the crossover temperature.