A model for phosphate glass topology considering the modifying ion sub-network
A model for phosphate glass topology considering the modifying ion sub-network
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DOI：
10.1063/1.4870764
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发表时间：
2014-04-21
影响因子：
4.4
通讯作者：
Yue, Yuanzheng
中科院分区：
文献类型：
--
作者：
Hermansen, Christian;Mauro, John C.;Yue, Yuanzheng
本文建立了碱金属磷酸盐玻璃的温度约束模型，考虑了碱金属离子及其非键氧配位球构成的改性离子子网络的结构和拓扑作用。该模型与NMR和分子动力学模拟的结构数据以及玻璃化转变温度（Tg）和液体脆性（m）等动态数据一致。碱金属磷酸盐玻璃是用于开发约束模型的示例性系统，因为除了初级磷酸盐网络之外，改性阳离子网络也起着重要作用。该拓扑模型预测了碱金属磷酸盐玻璃的Tg和m随碱金属氧化物含量的变化趋势，并在20mol%左右出现一个异常极小值碱金属氧化物含量我们发现，在T-g和m的最小值是由增加的连接性的改性离子子网络，碱金属离子必须共享非键合氧，以满足其在较高的碱金属氧化物含量的配位要求。我们认为，系统地降低碱金属磷酸盐玻璃的Tg值从Li_2O到Na_2O到Cs_2O可能是由于改性离子子网络的削弱，并且可以通过较低的约束起始温度来解释。(C)2014 AIP Publishing LLC.
In the present paper we establish a temperature dependent constraint model of alkali phosphate glasses considering the structural and topological role of the modifying ion sub-network constituted by alkali ions and their non-bonding oxygen coordination spheres. The model is consistent with available structural data by NMR and molecular dynamics simulations and with dynamic data such glass transition temperature (T-g) and liquid fragility (m). Alkali phosphate glasses are exemplary systems for developing constraint model since the modifying cation network plays an important role besides the primary phosphate network. The proposed topological model predicts the changing trend of the T-g and m with increasing alkali oxide content for alkali phosphate glasses, including an anomalous minimum at around 20 mol.% alkali oxide content. We find that the minimum in T-g and m is caused by increased connectivity of the modifying ion sub-network, as the alkali ions must share non-bonding oxygen to satisfy their coordination requirements at higher alkali oxide contents. We argue that the systematically decreasing the T-g values of alkali phosphate glasses from Li2O to Na2O to Cs2O could be caused by a weakening of the modifying ion sub-network and can be accounted for by lower constraint onset temperatures. (C) 2014 AIP Publishing LLC.