Sun, 27 Jul 2008 07:46:02 BST CiteULike: dchen's Binder http://www.citeulike.org/user/dchen/author/Binder CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2883868 <i>Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 75, No. 1. (2007)</i><br /><br />Monte Carlo simulations are used to study the effect of confinement on a crystal of point particles interacting with an inverse power law potential r−12 in d=2 dimensions. This system can describe colloidal particles at the air-water interface, a model system for experimental study of two-dimensional melting. It is shown that the state of the system (a strip of width D) depends very sensitively on the precise boundary conditions at the two “walls” providing the confinement. If one uses a corrugated boundary commensurate with the order of the bulk triangular crystalline structure, both orientational order and positional order is enhanced, and such surface-induced order persists near the boundaries also at temperatures where the system in the bulk is in its fluid state. However, using smooth repulsive boundaries as walls providing the confinement, only the orientational order is enhanced, but positional (quasi-)long range order is destroyed: The mean-square displacement of two particles n lattice parameters apart in the y direction along the walls then crosses over from the logarithmic increase (characteristic for d=2) to a linear increase with n (characteristic for d=1). The strip then exhibits a vanishing shear modulus. These results are interpreted in terms of a phenomenological harmonic theory. Also the effect of incommensurability of the strip width D with the triangular lattice structure is discussed, and a comparison with surface effects on phase transitions in simple Ising and XY models is made. Ordering of two-dimensional crystals confined in strips of finite width A Ricci P Nielaba S Sengupta K Binder doi:10.1103/PhysRevE.75.011405 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 75, No. 1. (2007) 2008-06-11T21:38:50-00:00 2007 Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 75 1 APS 2007 confinement pre simulation http://www.citeulike.org/user/dchen/article/1875802 <i>The Journal of Chemical Physics, Vol. 116, No. 12. (2002), pp. 5158-5166.</i><br /><br />We present molecular dynamics simulations of a binary Lennard-Jones mixture at temperatures below the kinetic glass transition. The "mobility" of a particle is characterized by the amplitude of its fluctuation around its average position. The 5% particles with the largest/smallest mean amplitude are then defined as the relatively most mobile/immobile particles. We investigate for these 5% particles their spatial distribution and find them to be distributed very heterogeneously in that mobile as well as immobile particles form clusters. We suggest that this dynamic heterogeneity may be due to the fact that mobile/immobile particles are surrounded by fewer/more neighbors which form an effectively wider/narrower cage. The dependence of our results on the length of the simulation run indicates that individual particles have a characteristic mobility time scale which can be approximated via the non-Gaussian parameter. ©2002 American Institute of Physics. Dynamical heterogeneities below the glass transition Vollmayr Lee W Kob K Binder A Zippelius doi:10.1063/1.1453962 The Journal of Chemical Physics, Vol. 116, No. 12. (2002), pp. 5158-5166. 2007-11-07T01:07:08-00:00 2002 The Journal of Chemical Physics 116 12 5158 5166 AIP glass-transition heterogeneity