Department of Physics, Indian Institute of Science, C. V. Raman Ave,Bengaluru 560012, India.
Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617.
Phys Rev E. 2023 Mar;107(3-1):034607. doi: 10.1103/PhysRevE.107.034607.
We report phase separation in a mixture of "hot" and "cold" three-dimensional dumbbells which interact by Lennard-Jones potential. We also have studied the effect of asymmetry of dumbbells and the variation of ratio of "hot" and "cold" dumbbells on their phase separation. The ratio of the temperature difference between hot and cold dumbbells to the temperature of cold dumbbells is a measure of the activity χ of the system. From constant density simulations of symmetric dumbbells, we observe that the "hot" and "cold" dumbbells phase separate at higher activity ratio (χ>5.80) compared to that of a mixture of hot and cold Lennard-Jones monomers (χ>3.44). We find that, in the phase-separated system, the hot dumbbells have high effective volume and hence high entropy which is calculated by two-phase thermodynamic method. The high kinetic pressure of hot dumbbells forces the cold dumbbells to form dense clusters such that at the interface the high kinetic pressure of hot dumbbells is balanced by the virial pressure of cold dumbbells. We find that phase separation pushes the cluster of cold dumbbells to have solidlike ordering. Bond orientation order parameters reveal that the cold dumbbells form solidlike ordering consisting of predominantly face-centered cubic and hexagonal-close packing packing, but the individual dumbbells have random orientations. The simulation of the nonequilibrium system of symmetric dumbbells at different ratios of number of hot dumbbells to cold dumbbells reveals that the critical activity of phase separation decreases with increase in fraction of hot dumbbells. The simulation of equal mixture of hot and cold asymmetric dumbbells revealed that the critical activity of phase separation was independent of the asymmetry of dumbbells. We also observed that the clusters of cold asymmetric dumbbells showed both crystalline and noncrystalline order depending on the asymmetry of dumbbells.
我们报告了“热”和“冷”三维哑铃混合物中的相分离，这些哑铃通过 Lennard-Jones 势能相互作用。我们还研究了哑铃不对称性和“热”和“冷”哑铃比例变化对其相分离的影响。热和冷哑铃之间的温差与冷哑铃温度之比是衡量系统活性 χ 的一个标准。从对称哑铃的恒密度模拟中，我们观察到“热”和“冷”哑铃在较高的活性比（χ>5.80）下发生相分离，而不是热和冷 Lennard-Jones 单体混合物（χ>3.44）。我们发现，在相分离系统中，热哑铃具有较高的有效体积，因此具有较高的熵，熵是通过两相热力学方法计算的。热哑铃的高动力学压力迫使冷哑铃形成密集的团簇，使得在界面处，热哑铃的高动力学压力被冷哑铃的维里压力平衡。我们发现，相分离促使冷哑铃团簇具有固态有序性。键取向序参数表明，冷哑铃形成了主要由面心立方和六方密堆积组成的固态有序，但单个哑铃具有随机取向。在不同热哑铃与冷哑铃数量比的非平衡系统的对称哑铃模拟中，我们发现相分离的临界活性随热哑铃分数的增加而降低。热和冷不对称哑铃的等混合物的模拟表明，相分离的临界活性与哑铃的不对称性无关。我们还观察到，冷不对称哑铃的团簇表现出晶体和非晶体有序性，这取决于哑铃的不对称性。
