Two inherent crossovers of the diffusion process in glass-forming liquids
Two inherent crossovers of the diffusion process in glass-forming liquids
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DOI：
10.1103/physreve.98.042601
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发表时间：
2018-10-05
影响因子：
2.4
通讯作者：
Yamamuro, Osamu
中科院分区：
文献类型：
--
作者：
Kofu, Maiko;Faraone, Antonio;Yamamuro, Osamu
我们报告了非相干准弹性中子散射测量，检查了两种玻璃形成液体（即分子液体（3-甲基戊烷）和离子液体[1-丁基-3-甲基咪唑双（三氟甲磺酰基）亚胺]）中的自扩散过程。我们通过实验证明，两种液体在自相关函数的动量传递 (Q) 依赖性方面表现出两个交叉，该自相关函数基本上由拉伸指数函数 exp[-(t/tau)(beta)] 描述。第一个交叉点（Q 近似于 0.2 埃（-1））对应于归因于动态相关性的从菲克扩散（β = 1）到非菲克扩散（β 不等于 1）的交叉。另一方面，Q 处的第二个近似为 0.8 埃(-1) 与从高斯行为到非高斯行为的交叉相关。值得注意的是，拉伸指数 beta 在两个交叉点之间逐渐变化。我们认为这两种交叉是玻璃形成液体的普遍特征。
We report on incoherent quasielastic neutron scattering measurements examining a self-diffusion process in two types of glass-forming liquids, namely a molecular liquid (3-methylpentane) and an ionic liquid [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide]. We have experimentally demonstrated that both liquids exhibit two crossovers in the momentum transfer (Q) dependence of the self-correlation function, which is basically described by the stretched exponential function, exp[-(t/tau)(beta)]. The first crossover point (Q approximate to 0.2 angstrom(-1)) corresponds to a crossover from Fickian (beta = 1) to non-Fickian (beta not equal 1) diffusion attributed to dynamical correlation. On the other hand, the second one at Q approximate to 0.8 angstrom(-1) is associated with the crossover from Gaussian to non-Gaussian behavior. It is remarkable that the stretching exponent beta gradually changes in between the two crossover points. We consider that the two crossovers are the universal feature for glass-forming liquids.