8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Fri 911:10-14:00P6.29Melting and solid phase structure of mixedArgon-Krypton, Argon-Xenon and Krypton-Xenonsubmonolayer mixed on graphiteAndrzej Patrykiejew 1 and Stefan Sokolowski 11 Department for the Modelling of Physico-ChemicaUniversity, pl. Marii Curie-Sklodowskiej3, 20031, Lublin, PolandThe Argon and Xenon submnolayer films on graphite exhibit incommensurate structure at lowtemperatures [1], while Krypton forms the commensurate phase [1]. The structure of mixed filmsof noble gases on graphite has scarley been studied [2-4] and our understanding of such systems isnot completed yet. Using Monte Carlo simulation method we study the structure of submonolayerfilms of Ar-Kr, Ar-Xe as well as Kr-Xe submonolayers on graphite. The results obtained using 2-as well as 3-dimensional models are compared. It is shown that the melting temperature of Ar-Krmixture changes monotonously when the film composition changes from pure Argon to pureKrypton. On the other hand, the melting temperature of the Ar-Xe and Kr-Xe is demonstratedto exhibit non-monotonous changes with the film composition, and reaches the minimum valuefor the Xe mole fraction equal to about 0. 4 and 0. 5, respectively. In general, the results for theAr-Xe and Kr-Xe mixtures, are in a reasonable agreement with experimental data. In the case ofKr-Xe mixture, we have found that at sufficiently low temperatures and the Xenon mole fractionbetween about 0. 2 and 0. 6, the film exhibits a presence of the commensurate super-structure,in which each Xenon atom is surrounded by six Krypton atoms. It is also shown that for the filmdensities below the monolayer completion, the melting temperatures obtained using two- andthree-dimensional models are practically the same, independently of the film composition.[1] L. W. Bruch, M. W. Cole, and E. Zaremba, Physical Adsorption: Forces and Phenomena,(Clarendon Press, Oxford, (1977).[2] J. Bohr, M. Nielsen, J. P. McTague, J. Als-Nielsen, and K. Kjaer, Surf. Sci. 125, 181 (1983).[3] T. Ceva, M. Goldmann, and C. Marti, J. Phys. (Paris), 47, 1527 (1986).[4] P. W. Stephens, A. I. Goldman, P. A. Heiney, and P. A. Bancel, Phys. Rev. B 33 (1986) 655.29