Dresden 2014 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 8: Critical Phenomena and Phase Transitions
DY 8.8: Vortrag
Montag, 31. März 2014, 17:15–17:30, ZEU 118
Dynamic scaling and superdiffusion in a critical binary mixture — Dipanjan Chakraborty1,2, Siegfried Dietrich1, and •Felix Höfling1 — 1Max Planck Institute for Intelligent Systems, Stuttgart, and Institute for Theoretical Physics IV, Universität Stuttgart, Germany — 2IISER Mohali, SAS Nagar, India
A binary mixture near its consolute point exhibits critical fluctuations of the local composition. The static properties of the mixture are well described by the 3D Ising universality class [1], the dynamic properties involving conservation of particles, energy, and momentum are classified as model H′. So far, theoretical work on the critical dynamics has focused on transport coefficients, while studies of the relaxation dynamics of the spatially resolved order parameter are missing.
We present numerical results for the dynamic structure factor S(k,t) of a symmetric binary Lennard-Jones mixture near its demixing transition. Employing the computing resources of high-end GPUs [2], we have performed microcanonical molecular dynamics simulations which cover system sizes of up to 216,000 particles and 4 non-trivial orders of magnitude in time. We explore the crossover of the k-dependent relaxation time from diffusion-like to critical behaviour and find nice agreement with theoretical predictions. Dynamic scaling of S(k, t) at criticality is tested and scaling functions are deduced. For interdiffusion, we have evidence that the vanishing of the diffusion constant is accompanied by superdiffusion within intermediate time windows.
[1] S. K. Das et al., J. Chem. Phys. 125, 024506 (2006)
[2] P. Colberg and F. Höfling, Comp. Phys. Comm. 182, 1120 (2011)