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

P7.120Thu 811:10-14:00Phase transitions in a Gaussian-core model undergeometrical confinementTakamichi Terao 11 Gifu university, Yanagido 1-1, 501-1193, Gifu, JapanThe Gaussian-core model (GCM) gives a good approximation for the effective interaction betweenthe centers of mass of two polymer coils due to the entropic repulsion. It is known that thismodel exhibits a reentrant melting at sufficiently low temperature. As the density of the systemincreases, there is a fluid-solid transition and a bcc-fcc transition in the solid phases, and a fluidphase appears again at much higher densities. The effects of geometrical confinement on GCMraise an interesting topic. The nature of the structural transition in confined GCM has not yetbeen clarified, and it is worth investigating the characteristics of its phase behaviors, for example,to clarify whether there is an ordered phase with multilayer structures. In this study, the orderdisordertransition of a GCM confined between parallel walls is investigated by a Monte Carlosimulation. When the density of the system is changed, the system shows successive layeringtransitions. It is also confirmed that there are ordered structures with a square lattice symmetryand with hexagonal lattice symmetry in the direction parallel to the walls. Such positional orderremains beyond the critical temperature, at which ordered states disappear at all densities in a threedimensionalsystem without confinement. Different from hard-sphere suspensions, the positionalorder of this model remains relatively stable, despite the polydispersity of the system. The natureof the melting transition in this system is also discussed.120