Phase diagram of the two-dimensional symmetric associating lattice gas

We use extensive Monte Carlo simulations to investigate the phase diagram of the symmetric associating lattice gas (ALG) model. The ALG is defined on a triangular lattice in which each site can be either empty or occupied by a single molecule. Molecules have four bonding and two non-bonding arms. The model exhibits three phases: gas/disordered, low-density liquid (LDL), and high-density liquid (HDL) [1]; as well as water-like anomalous behavior. Recently, new results for the ALG [2] raised some questions about the structure of the phase diagram. Our results show a new continuous HDL-gas line which starts at finite chemical potential μ and extends to infinite μ [2]. For the LDL-gas transition, the scenario is controversial. Previous simulation results revealed a continuous transition [3], while Husimi Lattice calculations resulted in a discontinuous one [4]. Our simulations show that this transition is discontinuous.

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[2] A. P. Furlan, T. J. Oliveira, J. F. Stilck, and R. Dickman, Phys. Rev. E 100, 022109 (2019).
[3] A. P. Furlan, C. E. Fiore, and M. C. Barbosa, Phys. Rev. E 92, 032404 (2015).
[4] T. J. Oliveira, J. F. Stilck, and M. A. A. Barbosa, Phys. Rev. E 82, 051131 (2010).