Singh Jalim, Jose Prasanth P
School of Basic Sciences, Indian Institute of Technology Mandi, Kamand, Himachal Pradesh 175005, India.
J Phys Condens Matter. 2020 Nov 5;33(5). doi: 10.1088/1361-648X/abbbc4.
Molecular dynamics simulations are performed on a system of model linear polymers to look at the violations of Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations near the mode coupling theory transition temperatureat three (one higher and two lower) densities. At low temperatures, both lower density systems show stable gas-supercooled-liquid coexistence whereas the higher density system is homogeneous. We show that monomer density relaxation exhibits SE violation for all three densities, whereas molecular density relaxation shows a weak violation of the SE relation nearin both lower density systems. This study identifies disparity in monomer mobility and observation of jumplike motion in the typical monomer trajectories resulting in the SE violations. In addition to the SE violation, a weak SED violation is observed in the gas-supercooled-liquid coexisting domains of the lower densities. Both lower density systems also show a decoupling of translational and rotational dynamics in this polymer system.
对模型线性聚合物系统进行分子动力学模拟，以研究在模式耦合理论转变温度附近，三种密度（一种较高密度和两种较低密度）下斯托克斯 - 爱因斯坦（SE）关系和斯托克斯 - 爱因斯坦 - 德拜（SED）关系的违背情况。在低温下，两种较低密度的系统都显示出稳定的气体 - 过冷液体共存，而较高密度的系统是均匀的。我们表明，对于所有三种密度，单体密度弛豫都表现出对SE关系的违背，而在两个较低密度系统中，分子密度弛豫在附近表现出对SE关系的微弱违背。本研究确定了单体迁移率的差异以及在典型单体轨迹中观察到的跳跃式运动，这导致了对SE关系的违背。除了对SE关系的违背外，在较低密度的气体 - 过冷液体共存区域还观察到了对SED关系的微弱违背。两个较低密度的系统在该聚合物系统中还表现出平动和转动动力学的解耦。
