Atomic picture of structural relaxation in silicate glasses
Atomic picture of structural relaxation in silicate glasses
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DOI：
10.1063/1.5095529
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发表时间：
2019-06
影响因子：
4
通讯作者：
Weiying Song;Xin Li;Bu Wang;N. A. Anoop Krishnan;S. Goyal;M. Smedskjaer;J. Mauro;C. Hoover;M. Bauchy
中科院分区：
文献类型：
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作者：
Weiying Song;Xin Li;Bu Wang;N. A. Anoop Krishnan;S. Goyal;M. Smedskjaer;J. Mauro;C. Hoover;M. Bauchy
作为非平衡材料，玻璃不断地向过冷液态弛豫。然而，玻璃弛豫的原子尺度起源和机制仍然不清楚。在这里，基于分子动力学模拟的硅酸钠玻璃淬火与不同的冷却速率，我们表明，结构松弛发生通过转化成较大的小硅酸盐环。我们证明了这种机制是由小环（<6元）拓扑过约束和经历一些内应力的事实驱动的。在原子水平上，这种应力表现为径向和角度约束之间的竞争，其中较弱的键弯曲约束屈服于较强的键拉伸约束。这些结果与晶粒生长理论中冯·诺依曼的N − 6规则相呼应，并表明原子环和二维晶粒的稳定性在本质上是完全拓扑的。
As nonequilibrium materials, glasses continually relax toward the supercooled liquid state. However, the atomic-scale origin and mechanism of glass relaxation remain unclear. Here, based on molecular dynamics simulations of sodium silicate glasses quenched with varying cooling rates, we show that structural relaxation occurs through the transformation of small silicate rings into larger ones. We demonstrate that this mechanism is driven by the fact that small rings (<6-membered) are topologically overconstrained and experience some internal stress. At the atomic level, such stress manifests itself by a competition between radial and angular constraints, wherein the weaker bond-bending constraints yield to the stronger bond-stretching ones. These results strongly echo von Neumann's N − 6 rule in grain growth theory and suggest that the stability of both atomic rings and two-dimensional crystal grains is fully topological in nature.