This is the eighth 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 Electronic energies beyond Density Functional Theory

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 8. Title and abstract of talks

Strategies to deal with the many-body problem in materials: a unified view on functionals

Lucia Reining, École Polytechnique, Palaiseau

Materials are many-body systems made of electrons and nuclei. Their properties can be expressed in terms of expectation values using many-body wavefunctions. In practice, unfortunately, these expressions cannot be straightforwardly evaluated, because one cannot calculate or store the wavefunctions, even if one decouples electron and nuclei.  Alternatively to using many-body wavefunctions, in principle one can also describe properties in terms of simpler  quantities, such as the density or a one-body Green’s function.  However, the exact expressions, i. e., the exact  functionals of the density, or of the Green’s function, are most often unknown, and it is not easy to find good approximations.

In this talk, we will focus on general strategies that are common to different approaches relying on functionals. We will discuss ideas and major general concepts. We will investigate the difficulties of finding good approximations, and some strategies for improvement. In particular, we will consider Density Functional Theory, Many-Body Perturbation Theory, and Dynamical Mean Field Theory on the same footing, in order to highlight common ideas and different choices.

On the background of these considerations, selected examples of our recent work will illustrate the state-of-the art of applications in spectroscopy [1,2] and of the search for better approximations [3]. 

References

[1] J. Zhou, L. Reining, A. Nicolaou, A. Bendounan, K. Ruotsalainen, M. Vanzini, J. Kas, J. Rehr, M. Muntwiler, V. Strocov, F. Sirotti, M. Gatti, Proc. Natl. Acad. Sci. U.S.A., 117, 28596-28602 (2020)
[2] V. Gorelov, L. Reining, M. Feneberg, R. Goldhahn, A. Schleife, W. Lambrecht, M. Gatti, npj. Comput. Mater., 8, 94 (2022)
[3] M. Vanzini, A. Aouina, M. Panholzer, M. Gatti, L. Reining, npj. Comput. Mater., 8, 98 (2022)

Theoretical investigation of the molecular structure, vibrational spectra, thermodynamics and non linear optical properties of 4,5-dibromo-2,7-dinitro-Fluorescein

Jean Baptiste Fankam Fankam, University of Yaounde I