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arXiv 2106.04820cond-mat.soft
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玻璃形成液体Ca0.4K 0.6(NO3)1.4的集体弛豫动力学研究

Q-dependent Collective Relaxation Dynamics of Glass-Forming Liquid Ca0.4K0.6(NO3)1.4 Investigated by Wide-Angle Neutron Spin-Echo

Peng Luo, Yanqin Zhai, Peter Falus, Victoria Garcia Sakai, Monika Hartl, Maiko Kofu, Kenji Nakajima, Antonio Faraone, Yang Zhang

摘要:

采用广角中子自旋回波光谱,我们测量了依赖于Q的相干中间散射函数的原型离子玻璃前体Ca 0.4K 0.6(NO3)1.4,在平衡和过冷液体状态超出流体动力学制度。数据揭示了一个明确的两步弛豫:一个指数快速过程,和一个拉伸指数缓慢的阿尔法过程。在α过程的所有特征变量中观察到de Gennes变窄:弛豫时间、振幅和拉伸指数。在所有的长度尺度探测,α-松弛的相对幅度随着温度的升高而降低,并在正常的液体状态下趋于平稳。的温度依赖性的拉伸指数和弛豫时间在不同的Q的表示,在本地长度尺度的弛豫机制的修改,表现为温度无关的动态异质性和较小的偏差从Arkylius行为,甚至发生以上的α-β(Johari-Goldstein)的分叉温度。

英文摘要:

Employing wide-angle neutron spin echo spectroscopy, we measured the Q-dependent coherent intermediate scattering function of the prototypical ionic glass former Ca0.4K0.6(NO3)1.4, in the equilibrium and supercooled liquid states beyond the hydrodynamic regime. The data reveal a clear two-step relaxation: an exponential fast process, and a stretched exponential slow alpha process. de Gennes narrowing is observed in all characteristic variables of the alpha process: the relaxation time, amplitude, and stretching exponent. At all length scales probed, the relative amplitude of the alpha-relaxation decreases with increasing temperature and levels off in the normal liquid state. The temperature dependence of the stretching exponent and the relaxation time at different Q's indicate that modifications of the relaxation mechanisms at the local length scales, manifested as temperature independent dynamic heterogeneity and smaller deviations from Arrhenius behavior, have occurred even above the alpha-beta (Johari-Goldstein) bifurcation temperature.

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