Machine-learning potentials (MLPs) are advantageous in modeling boron coordination and three-membered rings (3-rings) in borate glasses. In this study, the prominent ability of MLP enables us to study how boron coordination varies during deformation, and the change in microstructure circumvents the overload stress in lithium borate and lithium borosilicate glasses via molecular dynamics simulations. Under uniaxial and triaxial compressive deformations, some of the threefold coordinated boron, ${}^3\mathrm{B}$, atoms were altered to be fourfold coordinated boron (${}^4\mathrm{B}$) at a strain range beyond elastic deformations. According to the local deformation analysis, a microstructure at around ${}^4\mathrm{B}$ was determined to be rigid, specifically, that around ${}^4\mathrm{B}$ forming a 3-ring exhibited the least flexibility. Conversely, the local region at around ${}^3\mathrm{B}$ and oxygen atoms in nonring structures flexibly deformed following the entire deformation. As a result, nonbridging oxygen located in the vicinity of ${}^3\mathrm{B}$ was found to migrate to form ${}^4\mathrm{B}$ due to compression. Remarkably, most of the boron atoms became ${}^4\mathrm{B}$, and they formed abundant three membered rings in the borate glasses at a certain strain owing to the triaxial compression. Consequently, it is inferred that such a drastic structural variation can be the origin of high damage resistance of borate glasses.

中文翻译：

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在压缩下改变硼酸锂玻璃的环结构：利用机器学习潜力进行MD模拟

机器学习势 (MLP) 在模拟硼酸盐玻璃中的硼配位和三元环 (3-环) 方面具有优势。在本研究中，MLP的突出能力使我们能够通过分子动力学模拟研究硼配位在变形过程中如何变化，以及微观结构的变化规避了硼酸锂和硼硅酸锂玻璃的过载应力。在单轴和三轴压缩变形下，一些三重配位硼，${}^3\mathrm{乙}$，原子被改变为四重配位硼（${}^4\mathrm{乙}$）在超出弹性变形的应变范围。根据局部变形分析，周围的微观结构${}^4\mathrm{乙}$被确定为刚性的，具体而言，围绕${}^4\mathrm{乙}$形成三环表现出最低的灵活性。相反，当地区域在${}^3\mathrm{乙}$非环结构中的氧原子在整个变形过程中发生柔性变形。结果，非桥氧位于${}^3\mathrm{乙}$被发现迁移形成${}^4\mathrm{乙}$由于压缩。值得注意的是，大部分硼原子变成了${}^4\mathrm{乙}$，并且由于三轴压缩，在一定应变下，它们在硼酸盐玻璃中形成了丰富的三元环。因此，推测这种剧烈的结构变化可能是硼酸盐玻璃高抗损伤性的根源。