Department of Physics, Sapienza, Università di Roma, Piazzale Aldo Moro 2, I-00185 Roma, Italy.
Laboratoire Charles Coulomb, UMR 5221, CNRS and Université Montpellier 2, 34095 Montpellier, France.
J Chem Phys. 2013 Dec 28;139(24):244910. doi: 10.1063/1.4849115.
We study the phase diagram of a binary mixture of patchy particles which has been designed to form a reversible gel. For this we perform Monte Carlo and molecular dynamics simulations to investigate the thermodynamics of such a system and compare our numerical results with predictions based on the analytical parameter-free Wertheim theory. We explore a wide range of the temperature-density-composition space that defines the three-dimensional phase diagram of the system. As a result, we delimit the region of thermodynamic stability of the fluid. We find that for a large region of the phase diagram the Wertheim theory is able to give a quantitative description of the system. For higher densities, our simulations show that the system is crystallizing into a BCC structure. Finally, we study the relaxation dynamics of the system by means of the density and temperature dependences of the diffusion coefficient. We show that there exists a density range where the system passes reversibly from a gel to a fluid upon both heating and cooling, encountering neither demixing nor phase separation.
我们研究了一种具有形成可逆凝胶能力的嵌段粒子二元混合物的相图。为此，我们进行了蒙特卡罗和分子动力学模拟，以研究该系统的热力学性质，并将我们的数值结果与基于无参数 Wertheim 分析理论的预测进行比较。我们探索了定义系统三维相图的温度-密度-组成空间的广泛范围。结果，我们限定了流体热力学稳定性的区域。我们发现，在相图的很大一部分区域，Wertheim 理论能够对系统进行定量描述。对于较高的密度，我们的模拟显示系统结晶成 BCC 结构。最后，我们通过扩散系数的密度和温度依赖性来研究系统的弛豫动力学。我们表明，在系统从凝胶到流体的可逆转变过程中，存在一个密度范围，在这个范围内，系统在加热和冷却过程中既不会发生相分离也不会发生离析。
