Dynamics of supercooled liquids: excess wings, β peaks, and rotation–translation coupling
Dynamics of supercooled liquids: excess wings, β peaks, and rotation–translation coupling
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过冷液体动力学：多余翼、β峰和旋转-平移耦合
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发表时间：
2005
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通讯作者：
H. Cummins
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文献类型：
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作者：
H. Cummins
冷却到液态-玻璃化转变的液体的介电磁化率谱在α峰和磁化率最小值之间的频率范围内经常表现出二级结构，其形式要么是“多余翼”，要么是二级峰--Johari-Goldstein β峰。最近，Götze和Sperl（2004 Phys. Rev. Lett. 92 105701）表明，一个简单的示意性模式耦合理论模型，其中包括旋转平移（RT）耦合，成功地描述了光学克尔效应数据中观察到的近对数衰减。该模型也表现出多余的翼和β峰的特点，定性地类似于实验的介电数据。它还预测了机翼的超量斜率随温度的降低而减小，并随着RT耦合的增加而逐渐演变成β峰。因此，我们建议，这些功能和它们所观察到的随温度的演变可能是RT耦合的后果。
Dielectric susceptibility spectra of liquids cooled towards the liquid–glass transition often exhibit secondary structure in the frequency region between the α peak and the susceptibility minimum, in the form of either an ‘excess wing’ or a secondary peak—the Johari–Goldstein β peak. Recently, Götze and Sperl (2004 Phys. Rev. Lett. 92 105701) showed that a simple schematic mode coupling theory model, which incorporates rotation–translation (RT) coupling, successfully describes the nearly logarithmic decay observed in optical Kerr effect data. This model also exhibits both excess wing and β peak features, qualitatively resembling experimental dielectric data. It also predicts that the excess wing slope decreases with decreasing temperature and gradually evolves into a β peak with increasing RT coupling. We therefore suggest that these features and their observed evolution with temperature may be consequences of RT coupling.