A PRIMITIVE MODEL FOR HEXAMETHYLPARAROSANILINE (CRYSTAL VIOLET) MONOMOLECULAR ADLAYER - A MONTE-CARLO SIMULATION STUDY

The NVT Monte Carlo simulation results are reported for a model of two -dimensional (2D) chemically associating fluid with six attractive sit es per monomer disc. Three of these sites are of the type alpha and th e other three of the type beta. The sites alpha and beta are fixed ins ide a hard core, they follow each other anticlockwise, with a 'valence ' angle of 60 degrees. It is assumed that only alpha+beta site-site as sociation of two different discs occurs. Complex formation, dependent on the density and association energy, is much more sophisticated, in comparison to previously studied models of dimerizing and polymerizing discs. An analysis of complexes in terms of the fractions of singly, doubly,..., hers-bonded particles is performed, and the dimensions and distributions of complexes are studied. We obtained the pair distribu tion functions of particles and structure factor in the fluid layer. T he model was inspired by experiments on visualization of organic monol ayers in the framework of scanning tunneling microscopy (STM). Current ly it yields a preliminary insight into the molecular organization of crystal violet molecules on the iodine covered (111) single-crystal su rface plane observed experimentally. Extensions of the model and metho dology are discussed. (C) 1998 Elsevier Science S.A. All rights reserv ed.