Institut des sciences et technologies moléculaires d'Angers, UMR CNRS 6200, Université d'Angers, 2 Bd Lavoisier, F-49045 Angers, France.
J Chem Phys. 2012 Mar 7;136(9):094502. doi: 10.1063/1.3690094.
Coarse graining procedures are intended to well reproduce the structure of a material while increasing the simulations efficiency. However, the dynamics usually accelerates with coarse graining and a scaling procedure has to be used for dynamical data calculations. Most often a simple time-scaling coefficient is used for this purpose. However, for low temperature liquids this simple scaling procedure is questionable. Because supercooled liquids in their approach to the glass transition temperature do not follow a simple dynamics. In order to test if this scaling procedure is still pertinent at low temperature, we use molecular dynamics simulations of a coarse grain model of the methylmethacrylate molecule compared to simulations with the All atom model. We compare two different rescaling procedures, a time rescale and a temperature rescale procedure. Using these two procedures we compare the behaviors of the mean square displacements, the incoherent scattering functions, the self and distinct part of the Van Hove correlation functions and the non-Gaussian parameters. Results show that the temperature rescaling procedure reproduces well the All atom dynamical data at low temperatures, while the time rescaling procedure is correct only in the Brownian regime. We also find that the melting and the glass-transition temperatures are relatively well reproduced with the temperature rescaling procedure.
粗粒化程序旨在很好地再现材料的结构，同时提高模拟效率。然而，动力学通常随着粗粒化而加速，因此需要对动力学数据进行缩放处理。通常，为此目的使用简单的时间缩放系数。然而，对于低温液体，这种简单的缩放过程是值得怀疑的。因为过冷液体在接近玻璃化转变温度时并不遵循简单的动力学。为了测试在低温下这种缩放过程是否仍然适用，我们使用粗粒化模型的分子动力学模拟与全原子模型的模拟进行了比较。我们比较了两种不同的重新缩放过程，即时间缩放和温度缩放过程。使用这两种方法，我们比较了均方位移、非相干散射函数、自相关和互相关的范霍夫相关函数以及非高斯参数的行为。结果表明，温度缩放过程在低温下很好地再现了全原子动力学数据，而时间缩放过程仅在布朗运动区域是正确的。我们还发现，温度缩放过程相对较好地再现了熔融和玻璃化转变温度。
