Wilkinson Collin J, Potter Arron R, Welch Rebecca S, Bragatto Caio, Zheng Qiuju, Bauchy Mathieu, Affatigato Mario, Feller Steven A, Mauro John C
Department of Materials Science and Engineering , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States.
Department of Materials Science and Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States.
J Phys Chem B. 2019 Aug 29;123(34):7482-7489. doi: 10.1021/acs.jpcb.9b06512. Epub 2019 Aug 15.
The mixed alkali effect, the deviation from expected linear property changes when alkali ions are mixed in a glass, remains a point of contention in the glass community. While several earlier models have been proposed to explain mixed alkali effects on ionic motion, models based on or containing discussion of structural aspects of mixed-alkali glasses remain rare by comparison. However, the transition-range viscosity depression effect is many orders in magnitude for mixed-alkali glasses, and the original observation of the effect (then known as the Thermometer Effect) concerned the highly anomalous temperature dependence of stress and structural relaxation time constants. With this in mind, a new structural model based on topological constraint theory is proposed herein which elucidates the origin of the mixed alkali effect as a consequence of network strain due to differing cation radii. Discussion of literature models and data alongside new molecular dynamics simulations and experimental data are presented in support of the model, with good agreement.
混合碱效应，即在玻璃中混合碱离子时偏离预期线性性能变化的现象，仍然是玻璃学界争论的焦点。虽然此前已经提出了几种模型来解释混合碱对离子运动的影响，但相比之下，基于混合碱玻璃结构方面或包含相关讨论的模型仍然很少。然而，混合碱玻璃的转变范围粘度降低效应有多个数量级，并且该效应最初的观察结果（当时称为温度计效应）涉及应力和结构弛豫时间常数高度异常的温度依赖性。考虑到这一点，本文提出了一种基于拓扑约束理论的新结构模型，该模型阐明了混合碱效应的起源是由于不同阳离子半径导致的网络应变。文中呈现了文献模型和数据的讨论，以及新的分子动力学模拟和实验数据，以支持该模型，结果吻合良好。
