Phase Diagram of a Reentrant Gel of Patchy Particles

Sandalo Roldan-Vargas (1) , Frank Smallenburg (1) , Walter Kob (2) , Francesco Sciortino (1)

1 Dipartimento di Fisica [Roma La Sapienza]
2 L2C - Laboratoire Charles Coulomb

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.

Domaines: Chimie-Physique [physics.chem-ph]; Matière Molle [cond-mat.soft]

Sandalo Roldan-Vargas, Frank Smallenburg, Walter Kob, Francesco Sciortino. Phase Diagram of a Reentrant Gel of Patchy Particles. Journal of Chemical Physics, 2013, 139 (24), pp.244910. ⟨10.1063/1.4849115⟩. ⟨hal-00923977⟩