"Glass and Time," IMFUFA, Department of Science and Environment, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark.
Department of Chemical Engineering, University of Rhode Island, Kingston, Rhode Island 02881, USA.
J Chem Phys. 2018 Jan 21;148(3):034503. doi: 10.1063/1.4986569.
This paper studies the dynamics of relaxation phenomena in the standard dissipative particle dynamics (DPD) model [R. D. Groot and P. B. Warren, J. Chem. Phys. 107, 4423 (1997)]. Using fluctuating hydrodynamics as the framework of the investigation, we focus on the collective transverse and longitudinal dynamics. It is shown that classical hydrodynamic theory predicts the transverse dynamics at relatively low temperatures very well when compared to simulation data; however, the theory predictions are, on the same length scale, less accurate for higher temperatures. The agreement with hydrodynamics depends on the definition of the viscosity, and here we find that the transverse dynamics are independent of the dissipative and random shear force contributions to the stress. For high temperatures, the spectrum for the longitudinal dynamics is dominated by the Brillouin peak for large length scales and the relaxation is therefore governed by sound wave propagation and is athermal. This contrasts the results at lower temperatures and small length scale, where the thermal process is clearly present in the spectra. The DPD model, at least qualitatively, re-captures the underlying hydrodynamical mechanisms, and quantitative agreement is excellent at intermediate temperatures for the transverse dynamics.
本文研究了标准耗散粒子动力学（DPD）模型[R. D. Groot 和 P. B. Warren，J. Chem. Phys. 107, 4423（1997）]中弛豫现象的动力学。使用涨落流体力学作为研究的框架，我们专注于集体横向和纵向动力学。结果表明，与模拟数据相比，经典流体力学理论在相对较低的温度下很好地预测了横向动力学；然而，对于较高的温度，理论预测在相同的长度尺度上不太准确。与流体力学的一致性取决于粘度的定义，在这里我们发现横向动力学与应力的耗散和随机剪切力贡献无关。对于高温，纵向动力学的谱主要由大尺度的布里渊峰主导，因此弛豫由声波传播控制，是非热的。这与低温和小尺度的结果形成对比，在低温和小尺度下，谱中明显存在热过程。DPD 模型至少在定性上再现了潜在的流体力学机制，并且在中间温度下横向动力学的定量一致性非常好。
