Luo Peng, Zhai Yanqin, Falus Peter, García Sakai Victoria, Hartl Monika, Kofu Maiko, Nakajima Kenji, Faraone Antonio, Z Y
Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Nat Commun. 2022 Apr 19;13(1):2092. doi: 10.1038/s41467-022-29778-4.
The relaxation behavior of glass formers exhibits spatial heterogeneity and dramatically changes upon cooling towards the glass transition. However, the underlying mechanisms of the dynamics at different microscopic length scales are not fully understood. Employing the recently developed wide-angle neutron spin-echo spectroscopy technique, we measured the Q-dependent coherent intermediate scattering function of a prototypical ionic glass former CaK(NO), in the highly viscous liquid state. In contrast to the structure modulated dynamics for Q < 2.4 Å, i.e., at and below the structure factor main peak, for Q > 2.4 Å, beyond the first minimum above the structure factor main peak, the stretching exponent exhibits no temperature dependence and concomitantly the relaxation time shows smaller deviations from Arrhenius behavior. This finding indicates a change in the dominant relaxation mechanisms around a characteristic length of 2π/(2.4 Å) ≈ 2.6 Å, below which the relaxation process exhibits a temperature independent distribution and more Arrhenius-like behavior.
玻璃形成体的弛豫行为表现出空间异质性，并且在冷却至玻璃转变温度时会发生显著变化。然而，在不同微观长度尺度下动力学的潜在机制尚未完全理解。利用最近开发的广角中子自旋回波光谱技术，我们测量了典型离子玻璃形成体CaK(NO)在高粘性液态下的Q依赖相干中间散射函数。与Q < 2.4 Å（即结构因子主峰及以下）时的结构调制动力学相反，对于Q > 2.4 Å（即结构因子主峰上方第一个最小值之外），拉伸指数不显示温度依赖性，并且弛豫时间与阿仑尼乌斯行为的偏差较小。这一发现表明，在特征长度2π/(2.4 Å) ≈ 2.6 Å附近，主导弛豫机制发生了变化，低于该长度时，弛豫过程呈现出与温度无关的分布以及更类似阿仑尼乌斯的行为。
