Title: Equilibrium properties of the lattice system with SALR interaction potential on a square lattice: quasi-chemical approximation versus Monte Carlo simulation
Author(s):

	Ya.G. Groda (Belarusian State Technological University, 13a Sverdlova St., 220006 Minsk, Belarus) ,
	V.S. Vikhrenko (Belarusian State Technological University, 13a Sverdlova St., 220006 Minsk, Belarus) ,
	D. di Caprio (Chimie ParisTech, PSL Research University, CNRS, Institute of Research of Chimie Paris (IRCP), 11 Pierre and Marie Curie St., 75231 Paris, France)

The lattice system with competing interactions that models biological objects (colloids, ensembles of protein molecules, etc.) is considered. This system is the lattice fluid on a square lattice with attractive interaction between nearest neighbours and repulsive interaction between next-next-nearest neighbours. The geometric order parameter is introduced for describing the ordered phases in this system. The critical value of the order parameter is estimated and the phase diagram of the system is constructed. The simple quasi-chemical approximation (QChA) is proposed for the system under consideration. The data of Monte Carlo simulation of equilibrium properties of the model are compared with the results of QChA. It is shown that QChA provides reasonable semiquantitative results for the systems studied and can be used as the basis for next order approximations.

Key words: lattice fluid model, competing interaction, order-disorder phase transition, Monte Carlo simulation, quasi-chemical approximation, phase diagram
PACS: 05.10.Ln, 64.60.De, 64.60.Cn

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