Liquid polymorphism and double criticality in a lattice gas model

VERA B. HENRIQUES, N. GUISONI, M.A. BARBOSA, M. THIELO, M.C. BARBOSA

MOLECULAR PHYSICS

Taylor & Francis

Año: 2005 vol. 103 p. 3001 - 3007

0026-8976

We analyse the possible phase diagrams of a simple model for an associating liquid proposed previously. Our two-dimensional lattice model combines orientational ice-like interactions and van der Waals interactions which may be repulsive, and in this case represent a penalty for distortion of hydrogen bonds in the presence of extra molecules. These interactions can be interpreted in terms of two competing distances, but not necessarily soft-core. We present mean-field calculations and an exhaustive simulation study for different parameters which represent the relative strength of the bonding interaction to the energy penalty for its distortion. As this ratio decreases, a smooth disappearance of the double criticality occurs. Possible connections to liquid-liquid transitions of molecular liquids are suggested.