Berlin 2012 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 13: Nonlinear Stochastic Processes
DY 13.2: Vortrag
Dienstag, 27. März 2012, 14:30–14:45, MA 004
Phase separation of binary mixtures in thin films: Effects of an initial concentration gradient across the film — •Prabhat K. Jaiswal1,2, Kurt Binder1, and Sanjay Puri2 — 1Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany — 2School of Physical Sciences, Jawaharlal Nehru University, New Delhi - 110067, India
We study the kinetics of phase separation of a binary (A,B) mixture confined in a thin film of thickness D by numerical simulations of the corresponding time-dependent Ginzburg-Landau model. The initial state consisted of 50% A : 50% B with a concentration gradient across the film, i.e., the average order parameter profile is Ψav (z,t=0)=(2z/D−1) Ψg, 0 ≤ z ≤ D, for various choices of Ψg and D. The equilibrium state consists of coexisting A-rich and B-rich domains separated by interfaces oriented perpendicular to the surfaces. However, for sufficiently large Ψg, a metastable layered state is formed with a single interface parallel to the surfaces. This phenomenon is explained in terms of a competition between domain growth in the bulk, and surface-directed spinodal decomposition that is caused by the gradient. Thus gradients in the initial state can stabilize thin-film morphologies which are not stable in full equilibrium. This offers interesting possibilities as a method for preparing novel materials.