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PP-III-20PHASE BEHAVIOR OF ORIENTABLE DIMERS ADSORBED ONSURFACES WITH DIFFERENT GEOMETRYFefelov V.F. 1 , Gorbunov V.A. 1 , Myshlyavtsev A.V. 1,2 , Myshlyavtseva M.D. 11 Omsk State Technical University, Omsk, Russia2 Institute of Hydrocarbons Processing SB RAS, Omsk, RussiaFefelov_Vasiliy@mail.ruAdsorption of gases on solid surfaces is an important problem in physicalchemistry and chemical engineering [1]. Works belonging to this topic are based onLangmuir’s model of adsorption, where adsorbed molecule occupies one adsorptionsite of surface. However the most of adsorbates are polyatomic molecules and theirssize can significantly exceed size of adsorption site therefore multisite-occupancytheory must be considered. Moreover polyatomic molecules usually don’t havespherical symmetry and can have different orientation in adsorbed monolayer withrespect to the interface [2]. It leads to absolutely different statistic from one ofLangmuir’s model [3,4]. It is convenient to investigate such systems through model ofdimer adsorption, because dimer is the simplest model of adsorbate which has allrequired properties (multisite adsorption, horizontal and vertical orientation withrespect to interface). Adsorption of dimers actively has been used in last decade [5],but the most of theoretical works, with few exceptions, don’t take into accountpossibility of different orientations of adsorbed dimer with respect to the interface.The aim of present work is study of phase behavior of orientable dimers adsorbed onsquare, triangular and honeycomb lattices.Fig. 1. Types of lattices (square, triangular, honeycomb) and dimers adsorbed on one andtwo sites (black circles), prohibited for adsorption sites due to infinity strong repulsiveinteractions (red circles).To construct the model we used lattice gas (LG) model. In the framework of LGmodel surface is represented as array of M=L×L adsorption sites in square, triangularor honeycomb arrangement (Fig.1), where L is linear size of the array. As a model ofmolecule-adsorbate we use dimer composed of 2 identical units with constant bondlength equal to the lattice constant. Dimer is the simplest adsorbate, which hasn’tspherical symmetry and can adsorb occupying one or two lattice sites (Fig.1). To476