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

P5.68Wed 711:10-14:00A hexatic phase and order parameters in quasi-2dNadezda Gribova 1 and Axel Arnold 21 ITT, University of Stuttgart, Pfaffenwaldring 9, 70569, Stuttgart, Germany2 ICP, University of Stuttgart, Stuttgart, GermanyA quasi-2d system, a 3d system confined in one of the dimensions, is expected to be an intermediatecase between 3d and a 2d. One of the differences between 2d and 3d systems is a type of the solidliquidtransition. The transition in the 3d is of first order, while in 2d a system melts via twosecond-order transitions and an intermediate hexatic phase, a phase with an orientational order,but without any translational order. How close to 2d should a quasi-2d system be to go through ahexatic phase? What order parameters are a reliable signature of this phase? In our work we reporta computer simulation study of a Lennard-Jones liquid confined between two structureless wallswith a tunable attraction. To check for the existence of a hexatic phase we study a broad rangeof order parameters that were previously used to characterize 2d systems. We find that the Bindercumulant [1] is the most reliable parameter. Signs of a hexatic phase appear only in a one-layersystem with very attractive walls, i. e. when the quasi-2d system is very close to a pure 2d system.This might explain contradictory experimental findings on the existence and nature of the hexaticphase.[1] K. Binder, Z. Phys. B 43, 119 (1981).68