Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), University of California, Los Angeles, California 90095-1593, USA.
Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark.
J Chem Phys. 2017 Aug 21;147(7):074501. doi: 10.1063/1.4998611.
Although molecular dynamics (MD) simulations are commonly used to predict the structure and properties of glasses, they are intrinsically limited to short time scales, necessitating the use of fast cooling rates. It is therefore challenging to compare results from MD simulations to experimental results for glasses cooled on typical laboratory time scales. Based on MD simulations of a sodium silicate glass with varying cooling rate (from 0.01 to 100 K/ps), here we show that thermal history primarily affects the medium-range order structure, while the short-range order is largely unaffected over the range of cooling rates simulated. This results in a decoupling between the enthalpy and volume relaxation functions, where the enthalpy quickly plateaus as the cooling rate decreases, whereas density exhibits a slower relaxation. Finally, we show that, using the proper extrapolation method, the outcomes of MD simulations can be meaningfully compared to experimental values when extrapolated to slower cooling rates.
尽管分子动力学（MD）模拟通常用于预测玻璃的结构和性质，但它们本质上受到时间尺度的限制，需要使用快速冷却速率。因此，将 MD 模拟结果与在典型实验室时间尺度下冷却的玻璃的实验结果进行比较具有挑战性。基于不同冷却速率（从 0.01 到 100 K/ps）的钠硅酸盐玻璃的 MD 模拟，我们在此表明，热历史主要影响中程有序结构，而在模拟的冷却速率范围内短程有序基本不受影响。这导致焓和体积弛豫函数解耦，其中随着冷却速率的降低，焓迅速达到平台，而密度则表现出较慢的弛豫。最后，我们表明，通过使用适当的外推方法，可以将 MD 模拟的结果与实验值进行有意义的比较，当外推到较慢的冷却速率时。
