This is the first 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 Multiscale simulations of complex materials

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 1. Title and abstract of talks

Polymer simulations across multiple scales

Friederike Schmid, Johannes Gutenberg University, Mainz

Polymers, i.e., macromolecules, are omnipresent in nature and technology, yet their simulation still represents a challenge. This is because the behavior of polymeric systems is governed by processes on a multitude of length scales ranging from Angstrom (chemical structure) to micrometers or more (morphologies of polymeric materials). By now, many decades of research efforts have been dedicated to developing efficient simulation methods for polymeric systems, yet new ideas and methods still keep emerging. In the lecture I will give a brief introduction into some basic concepts of polymer theory and then discuss polymer models on different scales, with some bias towards polymer field theory.

Mori-Zwanzig projection technique in coarse-grained modelling

Nicodemo Di Pasquale, University of Manchester

Despite their successes, Fine-Grained (FG) or atomistic models suffer severe limitations in terms of the time- and length-scale accessible to investigation. Therefore, many real- world applications, especially in the class of soft matter materials, remain inaccessible to fully resolved simulations, due to their unsustainable computational costs, and must rely on semiempirical Coarse-Grained (CG) models. Significant efforts have been devoted in the last decade towards improving the predictivity of these CG models and providing a rigorous justification of their use, through a combination of theoretical studies and data- driven approaches.

In this talk, we will explore one of the most promising frameworks to obtain such rigorous justification, the projection operator technique, developed by Mori and Zwanzig (MZ) in the context of non-equilibrium statistical mechanics. The Mori-Zwanzig (MZ) projection is a generic, yet systematic, theoretical tool for deriving coarse-grained models.

We will show that the dynamics of the beads is described by a Generalized Langevin Equation (GLE) obtained from the full FG description, in which a precise physical meaning can be given to each of its terms. In particular, we derive the fact that some of the well known bottom-up methodologies used to obtain the CG interactions (i.e., IBI models [1], force matching[2] , relative entropy models [3]) are all included within such MZ description [4]. We will then explore the problem of the memory in CG models, and propose a rational basis for a data-driven approach to an approximation of the memory and fluctuating terms in such GLE, which can be considered included in the class of the Markovian models [5].

References

[1] D. Reith, M. Pütz, F. Müller-Plathe, J. Comput. Chem., 24, 1624-1636 (2003)
[2] W. Noid, J. Chu, G. Ayton, V. Krishna, S. Izvekov, G. Voth, A. Das, H. Andersen, The Journal of Chemical Physics, 128, 244114 (2008)
[3] M. Shell, The Journal of Chemical Physics, 129, 144108 (2008)
[4] N. Di Pasquale, T. Hudson, M. Icardi, Phys. Rev. E, 99, 013303 (2019)
[5] N. Di Pasquale, T. Hudson, M. Icardi, L. Rovigatti, and M. Spinaci, arXiv preprint arXiv:2011.00996, (2020).

Co-assembly of block copolymers and anisotropic nanoparticles

Javier Diaz, École Polytechnique Fédérale de Lausanne

Block copolymer (BCP) melts can self-assemble into ordered periodic morphologies (lamellar, BCC spheres, hexagonal cylinders, …), which has been exploited to control the localization of colloidal nanoparticles (NPs). Additionally, BCP domains can template the alignment of NPs with orientational degrees of freedom such as nanorods. In this work we computationally study the role of shape anisotropy with a generalized model that simulates colloids with a variety of shapes (spheroids, rhomboids, nanorods). Simulation results are compared with experimental setups both in 2D and in 3D, finding good agreement and novel co-assembled structures, thanks to the rich phase behavior of BCP melts and the various NP length scales.  

Highly elongated ellipsoids are shown to induce a sphere-to-cylinder phase transition in the BCP, due to the symmetry-breaking effect in the vicinity of the nanoellipsoid. 

Multiscale Modeling of Polymer-Nanoparticle Systems

Constantinos J. Revelas, National Technical University of Athens

We present a multiscale simulation strategy for the prediction of the structure and thermodynamics of polymeric interphases (i.e., polymer-vacuum, polymer-polymer and polymer-solid) and polymer nanocomposites. The hierarchical multiscale strategy comprises three levels of description: i) atomistic Monte Carlo and Molecular Dynamics simulations, ii) mesoscopic self-consistent field calculations, and iii) macroscopic hybrid particle-field simulations. The intermediate level of the multiscale strategy is based on self-consistent field calculations, which enable derivation of the potential of mean force that describes the repulsion and agglomeration tendencies of bare or polymer-grafted nanoparticles. Using these potentials one could undertake hybrid particle-field simulations to describe the phase behavior at macroscopic time and length scales.