Thermomechanical anomalies and polyamorphism in B 2 O 3 glass: A molecular dynamics simulation study
Thermomechanical anomalies and polyamorphism in B 2 O 3 glass: A molecular dynamics simulation study
复制标题
B 2 O 3 玻璃中的热机械异常和多晶现象：分子动力学模拟研究
DOI：
10.1103/physrevb.74.224107
复制
发表时间：
2006
影响因子：
3.7
通讯作者：
J. Kieffer
中科院分区：
文献类型：
--
作者：
Liping Huang;J. Kieffer
基于一种新的配位电荷转移势，采用分子动力学MD模拟方法研究了B2O3在各种热力学约束条件下的行为。这种相互作用势允许原子上的电荷在化学键形成和断裂时重新分布，并动态地调整到给定物种的多个配位状态。我们的模拟揭示了B2O3的异常热机械行为的结构起源，如膨胀后的结构的机械模量的增加。虽然在低于Tg的玻璃和高于800 °C的熔融状态下实验观察到这种现象，但我们的模拟首次预测B2O3玻璃的机械模量也会在拉伸应力下膨胀时增加。这些异常行为可以解释为两个不同刚度的图案之间的局部结构转换的结果，这些图案类似于在材料的晶体对应物中发现的图案。我们发现的B2O3的机制类似于我们之前确定的SiO2异常行为的机制，并且似乎对网络形成玻璃具有普遍性。此外，我们的模拟使我们发现了新的低密度B2O3晶体，这为理解玻璃态B2O3的反常热机械行为和这种化合物的结晶异常提供了一把钥匙。
Molecular dynamics MD simulations, based on a new coordination-dependent charge-transfer potential, were used to study the behavior of B2O3 in response to various thermal and mechanical constraints. This interaction potential allows for the charges on atoms to redistribute upon the formation and rupture of chemical bonds, and dynamically adjusts to multiple coordination states for a given species. Our simulations reveal the structural origin of the anomalous thermomechanical behaviors of B2O3, such as the increase of mechanical moduli upon expansion of the structure. While this phenomenon has been experimentally observed in the glass just below Tg and in the molten state above 800 °C, our simulations predict for the first time that the mechanical moduli of B2O3 glass also increase upon expansion under tensile stress. These anomalous behaviors can be explained as the result of localized structural transformations between two motifs of different stiffness that are similar to those found in the material’s crystalline counterparts. The mechanism we found for B2O3 is analogous to the one we identified earlier as underlying the anomalous behaviors of SiO2, and appears to be universal for network-forming glasses. Furthermore, our simulations led us to the discovery of new low-density B2O3 crystals, which provide a key to understanding the anomalous thermomechanical behaviors of vitreous B2O3 and the crystallization anomaly of this compound.