This is the third session of the second season of the Mixed-Gen on-line series aimed mainly at PhD students and researchers in their first post-doc. Our goal is to continue providing a new venue for these young scientists to share their work, get expert feedback and have an opportunity to strengthen scientific relations within the CECAM community.

The general area for this session is Simulating colloidal systems

To participate

If you are a PhD student or a post-doc:

Please use the Participate Tab on this page to start the application. You will have to login using your CECAM account to access the application form. If you don't have a CECAM account yet, use the register option on the top right corner of the login page...and welcome to CECAM!

If you are a more senior scientist:

Please contact the organisers and we shall process your registration.

Submission of posters

(Please note that - at least for the time being - we shall accept posters only from PhD students or researchers in their first post-doc)

After your application is accepted, you will be able to submit a poster. In the CECAM page for this event, go to “My participation” tab and click on “Add a poster”, providing title and abstract following the recommended format. On the same form you can upload your poster file in png or jpg as soon as it is ready. These formats are strict to enable showing of the poster in the Gather session. If the poster file is not ready at the moment of submitting your abstract, you can upload it later by editing your submission (Go to “My participation” tab and click three vertical dots on “Actions” column on table “My posters”). Please upload your poster as soon as possible to enable a decision from the selection committee - see below.

Please note that posters will be visible in the Gather room associated with this session until the end of the series (June 2022) unless otherwise requested.

DEADLINE FOR SUBMISSION: TEN DAYS BEFORE THE EVENT

Selection of posters

Posters will be selected by the event organisers with the support of our main speaker and experts who will take place in the poster session. 

Selection of the two talks by PhD or first year postdocs

These contributions, to be broadcasted in the Zoom webinar in the first part of the event, will be selected, after a preliminary screening by the organisers, the main speaker and guest experts, via a lottery from the posters selected for the Gather session. Please tick “No” to the question “Upgrade to talk?” in your application if you DO NOT WANT your poster to be considered for this lottery. 

THE DECISION ON THE POSTER AND THE OUTCOME OF THE LOTTERY SELECTION WILL BE COMMUNICATED ONE WEEK BEFORE THE EVENT

POSTER SUBMISSIONS BEYOND THIS DEADLINE WILL BE ACCEPTED BUT NOT CONSIDERED FOR UPGRADE TO TALK. SUBMISSION WILL BE DEFINITELY CLOSED FOUR DAYS BEFORE THE EVENT.

SESSION 3. Title and abstract of talks

Anomalous slow dynamics in soft matter

Emanuela Zaccarelli, La Sapienza University, Rome

Colloidal suspensions form a wide variety of arrested states, from gels to glasses of various kinds. After a short introduction, I will focus on examples where slow dynamics becomes "anomalous", i.e. not characterized by a classical two-step behavior, but by a logarithmic dependence of the density auto-correlation functions and by a power-law (subdiffusive) behavior of the mean-squared displacement. I will describe a few case studies, from short-ranged attractive colloids to binary mixtures, where this behavior has been reported, highlighting the important role of computer simulations.

Cooperative effects driving the multi-periodic response of cyclically sheared amorphous solids

Asaf Szulc, Ben-Gurion University

Plasticity in amorphous materials, such as glasses, colloids, or granular materials, is mediated by local rearrangements called "soft spots." Experiments and simulations have shown that soft spots are two-state entities interacting via quadrupolar displacement fields generated when they switch states. When the system is subjected to cyclic strain driving, the soft spots can return to their original state after one or more driving cycles. The response is multi-periodic when the system repeats after more than one driving cycle. To better understand the physical mechanisms behind multi-periodicity, we use a model of interacting hysterons. Each hysteron is a simplified two-state element representing hysteretic soft-spot dynamics. We show how interactions generate cooperative effects that allow multi-periodic cycles to emerge. The nature of the mechanisms that we uncovered has significant implications for the understanding, the modeling, and the uses of plasticity in amorphous solids.

Reference

[1] A. Szulc, M. Mungan, and I. Regev, arXiv:2111.14155 (2021)

Crystallisation and polymorph selection in active Brownian particles

Fergus Moore, University of Bristol

We explore crystallisation and polymorph selection in active Brownian particles with numerical simulation. In agreement with previous work (Wysocki et al. in Europhys Lett 105:48004, 2014), we find that crystallisation is suppressed by activity and occurs at higher densities with increasing Péclet number (Pe). While the nucleation rate decreases with increasing activity, the crystal growth rate increases due to the accelerated dynamics in the melt. As a result of this competition, we observe the transition from a nucleation and growth regime at high Pe to “spinodal nucleation” at low Pe. Unlike the case of passive hard spheres, where preference for FCC over HCP polymorphs is weak, activity causes the annealing of HCP stacking faults, thus strongly favouring the FCC symmetry at high Pe. When freezing occurs more slowly, in the nucleation and growth regime, this tendency is much reduced and we see a trend towards the passive case of little preference for either polymorph.

Reference

[1] F. Moore, C. Royall, T. Liverpool, J. Russo, Eur. Phys. J. E, 44, 121 (2021)

Diffusion of globular macromolecules in liquid crystals of colloidal cuboids

Luca Tonti, University of Manchester

It is already known that macrmolecular motion in intracellular environment is strongly hindered by the crowded environment in which they display, and this effect is know as macromolecular crowding. However, less effort has been invested in how the structural organisation of environment influences the motion of guest particles. To this end, we investigated the dynamics of a model system of colloidal small hard spheres (HSs) immersed in isotropic and nematic suspensions of prolate and oblate hard board-like particles (HBPs), i.e. cuboids, performing Dynamic Monte Carlo simulations [1]. We found similar features in the dynamics of both HBPs and HSs: from slower diffusion in denser systems, to anisotropic diffusion in anisotropic phases. Anomalous diffusion has been observed at intermediate and long time scales for both HSs and HBPs, with deviation from expected Gaussian particle displacement distributions for some cases, also in isotropic phases. We also found nematic-like cluters of HBPs in isotropic phases, whose local preferential orientation we suppose can explain observed non-Gaussian behaviour [2].

References

[1] A. Patti, A. Cuetos, Phys. Rev. E, 86, 011403 (2012)
[2] L. Tonti, F. García Daza, A. Patti, Journal of Molecular Liquids, 338, 116640 (2021)