Revisiting the slow dynamics of a silica melt using Monte Carlo simulations
Revisiting the slow dynamics of a silica melt using Monte Carlo simulations
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DOI：
10.1103/physreve.76.011507
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发表时间：
2007-07-01
影响因子：
2.4
通讯作者：
Berthier, Ludovic
中科院分区：
文献类型：
--
作者：
Berthier, Ludovic
我们实现了一个标准的蒙特卡罗算法来研究硅熔体在从6100 K到2750 K的宽温度范围内的缓慢平衡动力学。我们发现系统的平均动力学行为与分子动力学模拟的结果在定量上是一致的，至少在与α -弛豫相对应的长时间内是如此。相比之下，在分子动力学中与玻色子峰相关的短时间强热振动被蒙特卡罗算法有效地抑制。这使我们能够在模式耦合理论的背景下重新考虑二氧化硅动力学，因为该理论的几个缺点以前归因于热振动。对我们的数据进行的模式耦合理论分析在定性上是正确的，但该理论的定量测试失败了，这引起了人们对该系统中是否存在可避免的奇点的怀疑。我们讨论了动态非均质性的出现，并报告了平动扩散和结构弛豫之间解耦的详细测量结果，以及不断增长的四点动态磁化率。动态异质性似乎比更脆弱的玻璃形成模型不那么明显，但在性质上没有不同。
We implement a standard Monte Carlo algorithm to study the slow, equilibrium dynamics of a silica melt in a wide temperature regime, from 6100 K down to 2750 K. We find that the average dynamical behavior of the system is in quantitative agreement with results obtained from molecular dynamics simulations, at least in the long-time regime corresponding to the alpha-relaxation. By contrast, the strong thermal vibrations related to the boson peak present at short times in molecular dynamics are efficiently suppressed by the Monte Carlo algorithm. This allows us to reconsider silica dynamics in the context of mode-coupling theory, because several shortcomings of the theory were previously attributed to thermal vibrations. A mode-coupling theory analysis of our data is qualitatively correct, but quantitative tests of the theory fail, raising doubts about the very existence of an avoided singularity in this system. We discuss the emergence of dynamic heterogeneity and report detailed measurements of a decoupling between translational diffusion and structural relaxation, and of a growing four-point dynamic susceptibility. Dynamic heterogeneity appears to be less pronounced than in more fragile glass-forming models, but not of a qualitatively different nature.