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Sedimentation of colloidal plate-rod mixtures revisited

By: Daniel de las Heras
From: Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, D-95447 Bayreuth, Germany
At: Online - Zoom (https://videoconf-colibri.zoom.us/j/85454856626)
[2021-02-18] 10:00

Gravity has a strong effect on colloidal mixtures since gravitational and thermal energies are comparable on typical length scales in the lab. Sedimentation-diffusion equilibrium experiments can be very counter-intuitive and difficult to interpret. We study here the sedimentation of colloidal plate-rod mixtures using a rescaled Onsager density functional to obtain the bulk phase behaviour. Gravity is incorporated via a local density approximation, using the concept of sedimentation paths and stacking diagrams. Our results reproduce all experimental findings such as e.g. the observation of surprising stacking sequences with up to five different stacks. We offer a simple and intuitive theoretical explanation for the existence of such complex behaviour, make new predictions such as the formation of a floating isotropic phase, and provide guidelines towards the proper interpretation of sedimentation experiments of general colloidal mixtures.