Data: 26 de maio - terça-feira
Horário: 10h00 - Local: Mini-auditório do IQ.
Título: "Multiscale Modelling of Interfaces"
Dr. Dominic Tildesley,
Director CECAM, EPFL Lausanne Switzerland
President, Royal Society of Chemistry, England.
Abstract: It is now 50 years since the first molecular dynamics simulation of liquids using realistic potentials were pioneered by Aneesur Rahman. In this talk we will discuss the developments of these methods that have resulted in the accurate modelling of interfaces and to the prediction of the surface tension of a simple liquid. Here the simulation can be used to test the in two-body and three-body intermolecular potentials that describe the gas-liquid interface. The lubrication of surfaces coated with polymers is an important technological problem and one that is difficult to solve effectively using non-equilibrium molecular dynamics with atomistic models. The timescale of the simulation is such that shearing rates that can be achieved are many orders of magnitude higher than those observed in experiment. This problem can be addressed in part by switching to a mesoscale model, which still preserves the important elements such as the shape and charge of the adsorbed polymers but allows for a longer in-silico time step. We conclude that the kinetic friction coefficient between charged brushes is higher than that of neutral brushes at low compressions and smaller at high compressions. We also show that it is possible to simulate ultra-low friction coefficients, comparable with experiments, using the smallest shear rate accessible in a mesoscale simulation. The unexpected behaviour of the shear deformation-induced structural heterogeneities in charged polymer brushes calls for further experiments to elucidate this local reorganization of the ions in adsorbed charged polymers.
Docente responsável: Munir Salomão Skaf