Scientific Report for the workshop “Astrochemistry meets Surface Science: Theoretical Frontiers”

April 5th – 8th 2022

Aarhus Institute of Advanced Studies, Aarhus University, Denmark

Objectives:

The goal of the workshop was to bring closer together the research communities of theoretical Astrochemistry and theoretical (under Earth conditions) Surface Science. These two fields often address very similar questions, while using the exact same techniques and methodologies (e.g. electronic structure methods such as density functional theory, molecular dynamics or kinetic Monte Carlo simulations). And yet, despite these similarities, a noticeable communication gap exists between the two communities. Our multidisciplinary workshop aimed to bridge this gap and help establish new networking and collaboration ties between these fields.

The workshop covered a broad range of topics ranging from surface reaction networks and kinetic models to the characterization of interstellar ices and questions of energy dissipation and heat transport. In parallel to the underlying scientific questions, special focus was placed on theoretical and methodological aspects, as well as computational and numerical tools that are used in either one or both of the fields of astrochemistry and Earth-related surface science.

Continue reading Report for the workshop “Astrochemistry meets Surface Science: Theoretical Frontiers” →

ICTP, Trieste (Italy), 16-27 May 2022

The last two decades have witnessed a tremendous growth in the use of Wannier functions (WFs) for first-principles electronic structure calculations. Beyond providing fundamental insights on several aspects of the electronic structure, from chemical bonding to electrical polarisation, topological invariants, Berry curvature and more, WFs have found applications in a plethora of different domains. 

The software package WANNIER90 has become a reference for calculating maximally-localised Wannier functions (MLWFs) [1,2] and related properties [2,3,4]. As Wannier functions are independent from the basis sets used to represent the electronic structure in the underlying first-principles calculations, WANNIER90 can be interfaced to virtually any electronic-structure code. Indeed, most of the major electronic-structure packages have already an interface to WANNIER90, including Quantum ESPRESSO, ABINIT, VASP, Siesta, Wien2k, Fleur and Octopus. 

The availability of a robust MLWF code that is connected to several ab-initio engines has acted as a fertiliser for the birth of independent computational efforts aimed at calculating complex materials properties by leveraging WFs. Several independent packages exploiting MLWFs and WANNIER90 exist nowadays, targeting a number of properties, from electron-phonon coupling [5] (EPW) to topological invariants [6] (Z2Pack), surface spectral densities [7] (WannierTools), Berry-phase related properties [8] (Wannier Berri), tight-binding models (PythTB, TBModels), high-throughput calculations [9] (AiiDA-Wannier90), dynamical mean field theory (TRIQS), just to mention a few.

Wannier 2022 has been an event that put together the community behind these symbiotic packages that form a research and software ecosystem built upon the concept of MLWFs. The workshop has served the two-fold objective of teaching several techniques enabled by Wannier functions to young researchers and fostering an integration between all the packages composing the Wannier ecosystem, contrasting fragmentation and duplication of efforts.

This workshop has been generously funded by ICTP, Psi-k, MaX, NCCR MARVEL and CECAM. The computational infrastructure to run the hands-on tutorials has been provided by ICTP through their ICTP Cloud.   

The workshop was run by 6 directors:

• Antimo Marrazzo, University of Trieste
• Roxana Margine, Binghamton University
• Sinisa Coh, University of California Riverside
• Stepan Tsirkin, University of Zurich
• Giovanni Pizzi, EPFL
• Nicola Seriani, ICTP (local organiser)

The event comprised two parts, a summer school (first week) and a developers meeting (second week). 

Continue reading Scientific Report on the Wannier 2022 Workshop →

Scientific Report for the
Theoretical Spectroscopy Lectures
March 21-25, 2022
CECAM-HQ-EPFL, Lausanne, Switzerland

Objectives:
The aim of the school was to give a deep introduction to the theoretical and practical aspects of the electronic excitations which are probed by experimental techniques such as optical absorption, EELS, and photoemission (direct or inverse). From the theory point of view, excitations and excited state properties are out of the reach of density-functional theory (DFT), which is a ground-state theory. In the last thirty years, other ab-initio theories and frameworks, which are able to describe electronic excitations and spectroscopy, have become more and more used: time-dependent density-functional theory (TDDFT) and many-body perturbation theory (MBPT) or Green’s function theory (GW approximation and Bethe-Salpeter equation BSE). In fact, computational solutions and codes have been developed in order to implement these theories and to provide tools to calculate excited state properties. The present school focused on these points, covering theoretical, practical, and also numerical aspects of TDDFT and MBPT, non-linear response, and real-time spectroscopies. For the first time, this year we also covered theoretical aspects of magnetic excitations. Finally, a large part of the school was devoted to the codes implementing such theories (ABINIT, 2Light, DP, EXC). Continue reading Report on the Theoretical Spectroscopy Lectures →

The virtual Psi-k GreenALM Hands-on Tutorial 2021 took place from Oct. 11-14, 2021 in virtual form (https://greenalmtutorial.mcl.at/). It was organized by the Materials Center Leoben Forschung GmbH (www.mcl.at) together with the team from the Vienna Scientific Cluster and Co-organizers from KTH Stockholm and Montanuniversität Leoben and was additionally funded by Psi-k and EuroCC Austria. Continue reading Report on the Virtual Psi-k GreenALM Hands-on Tutorial 2021 →

The workshop Integration of ESL modules into electronic-structure codes was held in Lausanne February 17 2020 to February 28 2020. It was joined by 21 participants from a large fraction of the electronic structure codes. We had an initial 2 day discussion round followed by coding sessions for 10 days. Discussions were focused on how ESL should proceed in the future and we invite all to join our monthly meetings for a chat, contact us at esl <at> cecam.org for more information.

Sponsors: CECAM and Psi-K

The workshop was a continuation of a series of workshops in the ESL spirit, see here focused on integrating currently available ESL libraries into existing electronic structure codes.
Some of the goals achieved were:

• Integration of Psolver into Octopus and SIESTA
• Improving ESL bundle usability and maintainability. Patches for packages part of the ESL bundle improved the bundles capacity to build more easily.
• Several bugs found in packages were reported up stream which will eventually go down to the bundle packages (temporary patches are distributed with the ESL bundle).
• Ensured OMM package has an official release.
• ELSI-RCI was fully integrated into DFTB+
• FHI-AIMS integration with LibXC was greatly improved and MGGA can now be used.
• Preparation of two more ESL bundle packages, abinit-common and libPAW
• Expand the collaborations of the ESL towards more DFT codes and methodologies

Workshop details, such as the program, participant list and organizers may be found here. The final report will be made available here (not currently available, but will be once a follow-up meeting has finished).