Wed, 09 Jul 2008 13:28:24 BST CiteULike: dchens Kob http://www.citeulike.org/user/dchen/author/Kob CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2563522 <i>Physical Review Letters, Vol. 98, No. 2. (2007)</i><br /><br />We use molecular dynamics computer simulations to investigate the relaxation dynamics of a simple model for a colloidal gel at a low volume fraction. We find that due to the presence of the open spanning network this dynamics shows at low temperature a nontrivial dependence on the wave vector which is very different from the one observed in dense glass-forming liquids. At high wave vectors the relaxation is due to the fast cooperative motion of the branches of the gel network, whereas at low wave vectors the overall rearrangements of the heterogeneous structure produce the relaxation process. Length-Scale-Dependent Relaxation in Colloidal Gels Emanuela Del Gado Walter Kob doi:10.1103/PhysRevLett.98.028303 Physical Review Letters, Vol. 98, No. 2. (2007) 2008-03-19T17:19:20-00:00 2007 Physical Review Letters 98 2 APS 2007 colloids gel relaxation simulation http://www.citeulike.org/user/dchen/article/1875705 <i>Physical Review E, Vol. 60, No. 3. (1999), 3107.</i><br /><br />Using extensive molecular dynamics simulations of an equilibrium; glass-forming Lennard-Jones mixture; we characterize in detail the local atomic motions. We show that spatial correlations exist among particles undergoing extremely large (“mobile”) or extremely small (“immobile”) displacements over a suitably chosen time interval. The immobile particles form the cores of relatively compact clusters; while the mobile particles move cooperatively and form quasi-one-dimensional; stringlike clusters. The strength and length scale of the correlations between mobile particles are found to grow strongly with decreasing temperature; and the mean cluster size appears to diverge near the mode-coupling critical temperature. We show that these correlations in the particle displacements are related to equilibrium fluctuations in the local potential energy and local composition. Spatial correlations of mobility and immobility in a glass-forming Lennard-Jones liquid Claudio Donati Sharon Glotzer Peter Poole Walter Kob Steven Plimpton doi:10.1103/PhysRevE.60.3107 Physical Review E, Vol. 60, No. 3. (1999), 3107. 2007-11-07T00:33:19-00:00 1999 Physical Review E 60 3 3107 American Physical Society glass glotzer mobility 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