The Psi-k Community

MISSION: Psi-k is a Europe-based, worldwide network of researchers working on the advancement of first-principles computational materials science. Its mission is to develop fundamental theory, algorithms, and computer codes in order to understand, predict, and design materials properties and functions. Theoretical condensed matter physics, quantum chemistry, thermodynamics, and statistical mechanics form its scientific core. Applications encompass inorganic, organic and bio-materials, and cover a whole range of diverse scientific, engineering, and industrial endeavours. Key activities of Psi-k are the organization of conferences, workshops, tutorials and training schools as well as the dissemination of scientific thinking in society.

Psi-k is a bottom-up researchers’ network, established in 1994, to build strength and cooperation in the field of computational electronic structure. Psi-k activities are coordinated by a Board of Trustees, a Scientific Advisory Committee, and 16 Working Groups. These activities encompass the organization or co-sponsoring of ~30 workshops, conferences, schools or tutorials every year, an annual research conference jointly with CECAM, and a major conference covering the entire field every 5 years.

In addition, Psi-k produces a regular newsletter with extensive scientific highlights, and allows researchers to advertise job openings, events, and other topics of mutual interest through its 5000+ members mailing list.

This new website — introduced in  2015 to replace a venerable old site that provided sterling service over many years — offers a much more flexible modern design and functionality and it is to be hoped that it will provide even more stimulus for collaboration and cooperation amongst its members. Instructions regarding how to use it are here.

Psi-k is a registered charity and can only continue to operate thanks to the contributions from our member organisations and institutions. If you would like to make a donation to Psi-k please contact us to request an invoice or make a donation directly through our PayPal account…


Report for Theoretical Spectroscopy Lectures 2024

The aim of the school was to give a comprehensive introduction to the theoretical and practical aspects of the electronic excitations  that are probed by experimental techniques such as optical  absorption, EELS and photoemission (direct or inverse). From a theoretical perspective, excitations and excited state properties are out of the reach of density-functional theory (DFT), which is a ground-state theory. Over the past three decades, alternative ab-initio theories and frameworks capable of describing electronic excitations and spectroscopy, have gained popularity including 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 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. Additionally, the school provided valuable insights from an experimental perspective on spectroscopies and magnetic excitations, rarely covered in similar events. Finally, a large part of the school was devoted to getting familiar with the codes that implement such theories (ABINIT, 2Light, Lumen, DP, and EXC).

Francesco Sottile (Ecole Polytechnique, Palaiseau, France)
Valerio Olevano (CNRS Institut Neel, Grenoble, France)
Gian-Marco Rignanese (Université catholique de Louvain, Belgium)

Simo Huotari (University of Helsinki, Finland)
Valerie Veniard (Ecole Polytechnique and CNRS, Palaiseau, France)
Claudio Attaccalite (Institut Neel, CNRS, Grenoble, France)
Matteo Giantomassi (Université catholique de Louvain, Belgium)
Laura Urquiza (Ecole Polytechnique, Palaiseau, France)
Christoph Friedrich (Julich Research Centre, Germany)

Following the example of the previous edition, we have proposed a hybrid format, both online and in presence.
i) presentation of the theory and theoretical aspects of the implementation took place in the morning sessions; these sessions took place in the Aneesur Rahman room at CECAM HQ, but were also streamed over Zoom, for the online participants;
ii) the afternoon sessions were devoted to practical hands-on of the theory studied in the morning and were reserved to the onsite participants: DFT with ABINIT (Day 1), TDDFT with DP (Day 2), Non-linear response within TDDFT with 2Light and Lumen (Day 3), GW approximation to MBPT with Abinit (Day 4) and Bethe-Salpeter with EXC (Day 5). For the first time (in the Theoretical Spectroscopy Series of Lectures) we held the hands-on using the participants’ own laptop (computer room no longer available at Cecam).

Detailed description of the lectures:

  • Introduction to spectroscopy
    This thorough introductory lecture was given by an expert in the field: Simo Huotari, an experimentalist from Finland with an outstanding record of activity in electronic excitations and spectroscopy spectra especially at synchrotron facilities. Several experimental techniques used to investigate the spectroscopic properties of matter are presented, ranging from scattering (EELS, IXS) to absorption (optical, XANES, EXAFS), from photoemission (and inverse-photoemission) to Auger spectroscopy. For all methods, a link has been given to the quantities that can be computed using the theoretical methods in the subsequent lectures, in particular the spectral function and the inverse dielectric function ε1 or screening function.
  • Density-Functional Theory (DFT)
    This lecture (presented by G.-M. Rignanese) covered the basics of DFT: formalism and implementation. A special care was taken to present the shortcomings of DFT regarding its use for the computation of band structures, and, on the other hand, its usefulness as a starting point for more elaborate theories. The topics covered were: the electronic N-body problem, functionals of the density, the Kohn-Sham approach, approximations and new functionals, and the band-gap problem. In addition, more technical concepts (related to the plane-wave approach to be followed in the hands-on) were explained: plane-wave basis set, Brillouin zone integration, pseudopotentials, relaxation via computing the forces, and iterative algorithms. And of course, the ABINIT code was presented. This year’s important addition was related to the high throughput and its importance to machine learning approaches. The lecture was followed by hands-on on Abinit, in the afternoon.
  • Micro-Macro connection
    One-hour lecture (by F. Sottile) on the connection between measurable quantities (macroscopic) and calculated quantities (microscopic). This is a crucial concept that is often disregarded. We find that this micro-macro connection needs to be better explained in textbooks or articles, rather than given for granted, in particular for what concerns optical absorption.
  • Time-Dependent Density Functional Theory (TDDFT)
    A review (by V. Olevano) of TDDFT and its fundamental assumptions, theorems, caveats and drawbacks has been presented. In particular, we have illustrated the linear-response TDDFT in an actual implementation which is in the frequency domain, reciprocal space and on a plane-wave basis, as implemented in the DP (Dielectric Properties, code. This scheme is well suited to EELS and optical spectroscopy calculations, and particularly convenient for infinite periodic bulk solids, but also semi-infinite systems like surfaces, wires and tubes by the use of supercells. A critical analysis of all the classical approximations (RPA, Adiabatic LDA, with and without local-field effects) as well as the most recent ones (long-range contribution only, Nanonoquanta kernel, Bootstrap, etc.) has been presented, together with illustrating examples of spectra on prototype condensed matter systems, like bulk silicon, graphite, nanotubes, etc. This lecture was followed by a practical session on the use of DP code.
  • Non-linear response: perturbative approach
    In this lecture (by V. Veniard) the perturbative approach for non-linear spectroscopy is presented, with a description of second- and third-order responses. In particular, the intrinsic difficulties of the inclusion of local fields and the exchange and correlation (xc) contribution beyond RPA (with terms like the third -or fourth-derivatives of the xc energy with respect to the density) were emphasized. Exercises with 2light in the afternoon to calculate the second harmonic generation of Silicon Carbide.Event website (with program, and list of participants):

    General Remarks:

    • This year’s event was particularly international: in addition to the 9 European nationalities, we welcomed 2 students from India, 1 from Morocco, 1 from Ethiopia, and 1 from the USA.
    • We had secured addition funding for this event from the GDR-REST and Psi-k. Futhermore, we obtained extra funding from the CECAM initiative for underrepresented and underprivileged groups within the CECAM Community (special thanks to Sara Bonella and Andrea Cavalli for this).
    • All participants attended the social dinner on Tuesday, and almost all attended the (exceptional) second social dinner that we managed to organize on Thursday.
    • For the first time, we decided to award a poster prize. Due to the exceptional quality of the posters, we chose to award two poster prizes ex-aequo on Friday. The two winners received a certificate and a 200 CHF award.
    • We extend our warm thanks to the organizing staff in Lausanne. The smooth running of this event was thanks to Aude Merola Failletaz, Bogdan Nichita, Nathalie Carminati, and Carole Albonico.
    • We hope that the feedback from the Survey compiled by the students is positive and we look forward to organizing another such event.
  • Non-linear response: time evolution approach.
    Together with the perturbative approach, also the real time evolution approach was presented (by C. Attaccalite), in which all orders are automatically included. This permits both to tackle non-perturbative regimes (like high-harmonic generation) and to introduce important concepts (dephasing, Berry phase, etc.). Again, several points of view have been given: the theoretical explanation and derivation, as well as the implementation technical details. Exercises with the Lumen code in the afternoon.
  • Many-Body Perturbation Theory
    In this (and next) lecture, presented by F. Sottile, we introduced the theoretical basics of many-body Green’s functions theory. Starting from the very basic concept of the Green’s function as a general strategy to solve a linear differential problem and later motivated by spectroscopic reasons (what is an electron? How do we measure the energy of an electron?), the lectures introduced the Hedin’s equations and, finally, the most popular approximations on the self-energy: Hartree-Fock, CohSex, and GW approximation. The latter is very successful in predicting the band gaps of solids. It improves significantly over the standard density-functional approaches for the electronic structure. The central quantities are the Green’s function G and the screened Coulomb interaction W. In this framework, the GW approximation appears naturally as a first-order approximation in the “small” quantity W. But, together with the formal derivation of the GW approximation, and in order to elucidate the physical content of the GW approximation, we show that the GW approximation is a natural improvement over the well-known Hartree-Fock method.
  • The GW approximation in practice
    The second of this series of lectures (presented by M. Giantomassi) introducing MBPT is devoted to practical aspects: creation of the ground state with a correct pseudo-potential and the RPA screening file, convergence with respect to many parameters (bands, k-points, plane waves, G-vectors, self-consistent iterations, etc.), aspects of self-consistency (QPSCGW, self-consistent cohsex, only-energy self-consistency, etc.).
  • Bethe-Salpeter Equation (BSE)
    This lecture (by L. Urquiza) presents the many-body approach for the description of the polarizability. Within the Green’s functions formalism, the linear response polarizability is given by the 2-particle Green’s function which obeys a Dyson-like equation, similar to the linear response TDDFT equation. The derivation of the Bethe-Salpeter equation as well as all the approximations involved in the (several) steps are illustrated in this lecture, before presenting the numerical aspects useful for the afternoon hands-on with the EXC code.
  • Magnetic Response in MBPT
    This lecture (given by C. Friedrich) covers many aspects that are often neglected in all the other lectures: spin-polarized calculations, spin-orbit coupling, exchange splitting, and single-particle and collective magnetic excitations (Stoner and magnons). Besides the important connection to the relevant experiments, the link between magnetic and charge response functions in a unified and clear notation was particularly appreciated. The lecture was divided into two main parts: the theoretical (and implementation) details within the many-body approach via the GWT approximation, were followed by recent results on the electron-magnon interaction and band anomalies in iron.

The practical exercises took place in the afternoon. Given the necessity for the participants to use their laptop, we devised a double strategy: i) on one side, we provided all the necessary tools (executables, doc, input files, reference results) for all those who wanted to use their laptops for all calculations; ii) on the other, we installed the codes (and all related and useful softwares and libraries, visualization tools) on the EPFL cluster, for a remote connection. The great majority chose the first strategy, while the latter was followed by those few without a Linux operative system. The exercises were very varied, ranging from the simple codes’ tutorials (available on the web pages of the codes) to more realistic calculations (converged results for a system of choice by the student).


  1.  Monday 21 March
    Welcome: objectives of the school (F.Sottile)
    Introduction on Spectroscopy (S.Huotari)
    Coffee Break
    Density Functional Theory (G.-M. Rignanese)
    Lunch break
    Hands-on with Abinit (tutors)
    Poster session and Aperitif
  2.  Tuesday 22 March
    Micro-Macro Connection (F.Sottile)
    Time Dependent DFT (V. Olevano)
    Coffee Break
    Linear response and the DP code (V. Olevano)
    Hands-on with DP (tutors)
    Social Dinner
  3.  Wednesday 23 March
    Non-linear approaches to TDDFT :: second and third order (V. Veniard)
    Coffee Break
    Spectroscopies in real-time (C. Attaccalite)
    Hands-on with 2Light and Lumen (tutors)
  4. Thursday 24 March
    Many-Body Perturbation Theory (F. Sottile)
    Coffee Break
    GW in practice (M. Giantomassi)
    Hands-on with Abinit (tutors)
    2nd Social Dinner
  5. Friday 21 March
    Bethe-Salpeter Equation (L. Urquiza)
    Coffee Break
    Magnetism in Spectroscopies (C. Friedrich)
    Hands-on with EXC (tutors)

Event website (with program, and list of participants):

General Remarks:

  • This year’s event was particularly international: in addition to the 9 European nationalities, we welcomed 2 students from India, 1 from Morocco, 1 from Ethiopia, and 1 from the USA.
  • We had secured additional funding for this event from the GDR-REST and Psi-k. Furthermore, we obtained extra funding from the CECAM initiative for underrepresented and underprivileged groups within the CECAM Community (special thanks to Sara Bonella and Andrea Cavalli for this).
  • All participants attended the social dinner on Tuesday, and almost all attended the (exceptional) second social dinner that we managed to organize on Thursday.
  • For the first time, we decided to award a poster prize. Due to the exceptional quality of the posters, we chose to award two poster prizes ex-aequo on Friday. The two winners received a certificate and a 200 CHF award.
  • We extend our warm thanks to the organizing staff in Lausanne. The smooth running of this event was thanks to Aude Merola Failletaz, Bogdan Nichita, Nathalie Carminati, and Carole Albonico.
  • We hope that the feedback from the Survey compiled by the students is positive and we look forward to organizing another such event.

CECAM Flagship Workshop: Electronic Structure Software Development: Advancing the Modular Paradigm

CECAM Flagship Workshop: Electronic Structure Software Development: Advancing the Modular Paradigm

Held at CECAM-HQ, EPFL, Lausanne, February 19-24, 2024

This workshop continues the successful trajectory of the CECAM Electronic Structure Library initiative, aimed at supporting and connecting developers of shared libraries and software tools in support of electronic structure simulations across our entire community. As always, CECAM’s professionalism and remarkable organization, as well as their truly welcoming hospitality, deserve the highest praise.


Shared computational libraries that provide key functionality are now firmly established parts of the electronic structure software ecosystem. As electronic structure methods and codes diversify and mature, the development of libraries strengthens collaborations and avoids reimplementing the same methods in the context of a different, monolithic code. Over the years, a modular paradigm has emerged in which central pieces can be shared and reused between different projects.

Many efforts carried out so far have focused on making this paradigm successful and sustainable, by building robust software components with stable interfaces, offering the best possible performance on a broad range of hardware architectures, and sharing development practices between developers with sometimes very different backgrounds. Among the most important ongoing challenges are (1) training and educating new developers to take advantage of existing developments where that is appropriate and (2) continuously evolving library software to be useful, current, and usable by end users in often complex environments like HPC systems.

The scientific reach of electronic structure theory continues to expand rapidly, including by generalisation of high-throughput calculations, creation of complex workflows, and rapid growth of data-driven methods and machine learning. All these developments now attract participants beyond academia. On the computational side, the involvement of industrial partners is growing steadily, bringing feedback and insights from engineers. Globally, several key collaborative efforts develop shared software, including the MaX and NOMAD Centers of Excellence (CoE), the UK ExCALIBUR exascale project, the Swiss THEOS and MARVEL projects, the U.S. based Molecular Sciences Software Institute, DoE’s Exascale initiative, or DoE funded centers such as MiCCOM. Connections with other communities, like quantum chemistry, are getting stronger because of shared needs, as illustrated by the TREX CoE. The Swiss Scientific Computing Center (CSCS), the U.K.’s Daresbury Laboratory, and many other individual institutions likewise act as lighthouses for shared developments within the broad electronic structure software ecosystem.

The CECAM Electronic Structure Library (ESL) initiative ( is a key venue that connects developers from electronic structure codes across the community (contributors represent, e.g., SIESTA, BigDFT, DFTB+, Quantum Espresso, Octopus, FHI-aims, and several others). It provides a space for coordination between developers, new library developments and enhancements of existing libraries, as well as interaction with the broader ecosystem of library developments for electronic structure theory. Especially through its workshops, the ESL also acts as a venue that brings together developers across the many broader centers and collaborative efforts (see above) providing a common ground to exchange information and coordinate developments.


Major outcomes:

  • Unifying practices and tools to build software. We have agreed on using CMake in all ESL modules and created a repository to share good CMake recipes:
  • On top of this, we have agreed on further promoting the use of Spack and EasyBuild.
  • Create a new section in the programme for early career colleagues to expose their research.
  • Identified potential new partners for reviving a planned COST action, meetings are planned in the coming weeks.
  • Increased participation from the US, with the help of a generous sponsorship from MOLSSI.
  • A healthy intake of newcomers, around half of the 38 participants.
  • Increased awareness of our Zulip channel to bring together the community
  • Participants from other communities that made use of electronic structure libraries, e.g. Machine Learning and experimental materials

This workshop has identified a series of problems that can and should be addressed rapidly:

  • Making use cases more accessible to newcomers. For this, we have started to upgrade the ESL Demonstrator.
  • Improving the visibility of the Continuous Integration infrastructure. It now has its own dedicated repository:
  • Sustain a collaborative chat channel (Zulip) where people can exchange ideas, and request feedback

Discussions about the future of the ESL


It is more and more difficult to keep momentum within the community and important sustainability issues are now emerging, e.g. LibXC is used by around 80 different codes but is maintained by a single person who has to deal with complex technical problems. Another prominent issue is employment churn, which limits commitments to 3 years or less. The “publish or perish” race, with a retraction rate of articles doubling every 2 years, is also adding an unnecessary pressure on young researchers, depriving the community from a strongly needed generational renewal. As a result, the spreading of code reuse and good practices is quite slower than the production of sharable and reusable software modules.

Comparison with the climate research community

One ESL contributor is now experiencing first-hand how software activities are organised in the climate research community, through a position in the Access-NRI infrastructure ( There, software development is inherently collaborative, since all models require more than one code and have highly complex interactions. Most of the research involves both academic and non-academic institutions, which has had a great impact on the professionalisation of all software activities. Hiring Research Software Engineers (RSE) is part of the core development strategy. Access-NRI has been active since 2022 and is the result of many years of lobbying. It is currently employing 25 RSE and will expand to 35 RSE by 2025. Its activities are evaluated every 5 years to renew its funding. Such an organisation with a long-term view lets RSE serve the whole community all the time, instead of being limited to one research group / one software project as it is the case within the electronic structure community, leading to a much higher impact of the software development outcomes on society. Even if it is quite challenging, the paradigm shift it represents deserves at least to be considered and discussed.

Possible actions to increase momentum

One possible way to improve communication and ensure constant progress within the community is to set up an exchange platform for good practices. The following questions are open: How to define a list of experts? Would it be a regular call, e.g. monthly, or an on-demand call when a critical mass of interest is reached? Can this help us save time when addressing software-related issues?

How can we discuss more openly? One way is to promote the ESL discussion space on Zulip ( There, discussions can be organised in a way that will make them easy to find even after a few months of inactivity. To make it easier for people to join, the invitation link now appears prominently on the first page of the ESL website (

Another way to improve communication and visibility could be to structure our community around topics and guide new developers through the different kinds of software available: reference implementations vs. fully optimised software, and/or research/experimental software vs. production-grade software. How can the idea of an “electronic-structure ecosystem” be promoted and made more understandable?

An important aspect affecting momentum is to find ways to alleviate the current contributors to the ESL, in particular by identifying what should not be worried about. It is also essential to remember that researchers are generally not software experts and do need training regarding software engineering aspects.

There is a general consensus that the outcomes of ESL efforts should be promoted significantly more than they currently are. More outreach could be achieved by a more prominent involvement of ESL contributors in online communities like Stack Exchange. A well-defined protocol for announcements would help defining an “ESL style”.

All this being said, several new developments and connections showcased at the workshop are very encouraging and generated praise – for example, the US DOE funded infrastructure around NWChemEx, the report on Julia software for DFT development, or the experiences of the Psi4 project, to name just a few. Clearly, our software ecosystem is moving. Connecting the different, rapidly evolving developments in our community continues to be a major function of the ESL workshops and of the ESL.

Community Needs

The ESL initiative is, in fact, centered around a key community need in the experience of the organizers, i.e., a venue to communicate and (where possible) create bridges between the diverse software projects and developments surrounding electronic structure theory.

Since the inception of the ESL, it has sustained a substantial number of consistent participants from the DFT community. However, these same participants are all agreeing that the community needs to do more to bring together developments, training, and knowledge sharing. This requires close collaboration with entities with expertise, such as HPC centers.

Since GPUs has become mainstream, and we are likely to see more specialized architectures in the future. It is becoming increasingly more difficult for non-research software engineers to tackle the difficulties on achieving performant and accurate software on said architectures. The community needs a continuous communication channel with field experts, such as HPC centers, compiler vendors and hardware designers.

Societal Needs 

The Electronic Structure Library and related collaborative efforts are building a world-wide community and network within the electronic structure theory community. By bringing together developers, researchers, and practitioners from around the world, the initiative fosters a sense of community and shared purpose, facilitating collaboration, knowledge exchange, and professional networking opportunities. This can enhance the visibility and reputation of individuals and institutions involved in the initiative, leading to increased opportunities for collaboration and recognition within the scientific community. Societal benefits are emerging in 4 different areas:

  • Accelerating scientific progress: By fostering collaboration and sharing among developers from various academic, industrial, and research institutions, the ESL can foster advancements in areas such as materials science, chemistry, and condensed matter physics, which can ultimately benefit society through the development of new technologies and innovations.
  • Democratising the access to cutting-edge software: By sharing and reusing cutting-edge computational tools and libraries developed by experts in the field, as well as good programming practices, the ESL aims at make the access to advanced electronic structure methods easier, enabling researchers from diverse backgrounds, including those in academia, industry, and smaller research institutions, to utilize state-of-the-art computational techniques for their research projects.
  • Broadening education and training opportunities: By facilitating knowledge exchange and collaboration among developers with different backgrounds and levels of expertise, the ESL can help cultivate a new generation of computational scientists skilled in advanced electronic structure methods. This can contribute to the growth of the scientific workforce and empower individuals to pursue careers in STEM fields.
  • Increasing the impact of publicly-funded research: By defending the modular paradigm and avoiding repetitive efforts and errors, the ESL intends to help researchers and scientific software developers make a better use of their time and resources, which in the long run will improve the impact and returns of the related investments.

Detailed Program, Speakers and Participants, Event Website, Abstracts and Further Information


LOBSTER School on Chemical Bonding Analysis

The LOBSTER School on Chemical Bonding Analysis took place at Aalto University, Finland on 12-14 March 2024 and gathered over 30 participants. The purpose of the School was to introduce the theory and practicalities, as well as recent developments on both, behind the LOBSTER code. LOBSTER is a popular code that allows the user to perform “electronic structure reconstruction” in terms of localized projections of plane-wave-based wavefunctions, allowing a quantitative interpretation of the nature of chemical bonding in solids.

The School was organized locally by Dr Miguel Caro, Dr Rina Ibragimova and Dora Javor at Aalto University, as well as by the LOBSTER team led by Prof Richard Dronskowski (RWTH Aachen University). The LOBSTER team that visited Aalto was formed by Prof Dronskowski, Dr David Schnieders and Peter Mueller (all from Aachen). They presented the theory behind bonding analysis and gave practical tutorials on running the code. The core LOBSTER team was joined at the School by Prof Janine George (Jena University) and Prof Volker Deringer (University of Oxford) who gave lectures on how LOBSTER has been applied in materials research problems to understand bonding in these materials.

The School was sponsored by the Finnish CECAM node, the Psi-K charity and Aalto University’s Department of Chemistry and Materials Science.

The schedule and full list of participants are given below.


Tuesday 12 March Wednesday 13 March Thursday 14 March
9:00 – 9:30 Registration and welcome addresses (9:20 Miguel Caro & 9:25 Richard Dronskowski)
9:30 – 10:30 Chemical Bonding 101 (Richard Dronskowski) Charges, Madelung, Bond Indices, Polarizations (Peter Mueller) Defects, nanomaterials, amorphous matter (Volker Deringer)
10:30 – 11:00 Coffee break Coffee break Coffee break
11:00 – 12:30 Practical session: LOBSTER installation, first steps Practical session: advanced features and visualization Practical session: application of the previous session
12:30 – 14:00 Lunch break (participants pay for their own lunch – Maukas space reservation at 12:45) Lunch break (participants pay for their own lunch – Maukas space reservation at 12:45) Lunch break (participants pay for their own lunch – Arvo space reservation at 12:45)
14:00 – 15:00 LOBSTER nuts-and-bolts, plane waves & orbitals, projection to atomic orbitals (Daniel Schnieders) LOBSTER advanced, projection to molecular orbitals, other basis sets, magnetism LOBSTER automation (Janine George)
15:00 – 15:30 Coffee break Coffee break Coffee break
15:30 – 17:00 Practical session: basic features Practical session: more advanced features Practical session: application of the previous session
17:30 – 19:00 Poster session (takes place at the School of Chemical Engineering building’s upstairs lobby, Kemistintie 1)
18:30 – 20:30 Dinner @ Fat Lizard Restaurant Otaniemi


Note: these are the participants who agreed to have their details shared online.

Name Institution Contact
Miguel Caro Aalto University [email protected]
Peter Müller RWTH Aachen University [email protected]
Hanwen Zhang University of Oxford
Javier Sanz Rodrigo DTU [email protected]
Rajeev Dutt University of Warwick [email protected]
Linh Tong Aalto University [email protected]
Volker Deringer University of Oxford [email protected]
Wanja Schulze University of Jena [email protected]
Nityasagar Jena Linköping University [email protected]
Ransel Barzaga Instituto de Astrofísica de Canarias
Scott Simpson St. Bonaventure University [email protected]
Alyssa Santos St. Bonaventure University
Anson Thomas Indian Institute of Technology Roorkee [email protected]
M.D. Hashan C. Peiris Binghamton University – State University of New York [email protected]
Richard Dronskowski RWTH Aachen University
Divya Srivastava Turku University [email protected]
Pablo Castro Latorre University of Barcelona [email protected]
Elisa Damiani University of Bologna [email protected]
Madhavi Dalsaniya Warsaw University of Technology [email protected]
YiXu Wang RWTH Aachen University [email protected]
Edith Simmen ETH Zurich [email protected]
Rafael Nunez Aalto University [email protected]
Aleksandra Oranskaia KAUST [email protected]
David Schnieders RWTH Aachen University [email protected]
Neeraj Mishra Ben-Gurion University of the Negev [email protected]
Madhavi Dalsaniya Warsaw University of Technology [email protected]
Rina Ibragimova Aalto University [email protected]
Munavvar Husain University of Warsaw
Janine George BAM Berlin


CECAM/Psi-k Flagship School on Machine Learning Interatomic Potentials for Young and Early-Career Researchers (ML-IP 2023)

Machine learning interatomic potentials (ML-IPs) have now established themselves as a key technique in atomistic modeling. They allow the simulation of many diverse types of systems, from the molecular to the solid state, at the accuracy of highly sophisticated electronic structure methods but at a greatly reduced cost. While the general methodology of training and validating a machine learning potential has been well established, many codes and integrated software applications exist to perform these tasks. Since many of these come with a high entry barrier, there is still a need to educate young and early-career researchers in these tasks, as well as provide a pathway to enter the field and make valuable contributions for researchers who have promising ideas that could benefit from the application of ML-IPs.

We organized the ML-IP 2023 school at Aalto University, Finland, from 6–10 November 2023 with the broader goal of educating young researchers working on machine learning for materials and molecules on diverse topics, including structural representations, fitting ML models for potentials as well as properties beyond the ground-state potential energy surface, dataset generation and curation, and software frameworks. This was done keeping in mind the applicants’ interest and familiarity with scientific applications, to facilitate the “on-boarding” into the field. This endeavor was supported by funding from both Psi-k and CECAM, aided by additional contributions from Aalto University Department of Chemistry and Materials Science as well as from EPFL’s COSMO laboratory through the ERC-FIAMMA grant.

Applications and participants

Owing to the broad interest in the field, we received an impressive number of applications, over 120 total for in-person participation alone. From this number, 40 were shortlisted to attend the meeting in person; up to 80 more applicants were selected for online participation. In the spirit of supporting early-career researchers, we prioritized those who could benefit the most from attending the workshop in person. To foster diversity amongst participants, both in terms of experience levels in the field and backgrounds, we gave preference to younger researchers (doctoral students and early postdocs) and selected applicants based on motivation and potential to learn from the workshop. While a good proportion of participants were women researchers and those from other traditionally underrepresented groups, we note that we are still far from fair representation of these groups (e.g. gender equality and good representation of non-European researchers), which is an ongoing issue in our research field that we all have a responsibility to address.

We note, especially given the current political climate, that visa issues hindered travel amongst several participants of non-European nationality, in a few cases resulting in the cancellation of their on-site participation, ultimately harming the workshop’s goals of open scientific exchange.

Workshop format

As the workshop was organized in a hybrid format, talks and hands-on tutorials were given by 13 invited speakers in-person at Aalto University, with 3 more speakers joining remotely. Tutorials were held at the end of each workshop day, with sufficient time for both the speaker to present their tutorial and the attendees to work through the tutorials on their own. Despite the preparation work done in advance, technical issues (especially joining and using the supercomputer infrastructure made available to attendees) did pose a barrier for many of the workshop attendees in these sessions.

All of the workshop attendees were provided the opportunity to present and discuss their own work at a poster session. Several presentation slots were also made available for the attendees, and the speakers for these slots were chosen based on the poster abstracts. The poster session was held both in person and online (on Gather Town). This dual format of the poster session provided another opportunity to facilitate the interactions among online and offline participants, although the overall participation in the online poster session was quite low. Nonetheless, enforcing the hybrid format enabled contributions from speakers who were otherwise unable to join the workshop to these sessions. Awards were presented for the three best contributed talks and three in-person poster presentations.

Finally, a Slack workspace served as an additional opportunity for participants and speakers to have discussions, pose questions, and continue to strengthen the community of young and early-career researchers in the field of machine learning potentials. Many of the speakers kindly participated in these interactions, which further catalyzed the learning process of the attendees.

The scientific program was complemented by social events that gave participants a chance for informal networking in a more relaxed setting, which was appreciated by many.

Feedback and future planning

To conclude the workshop, a focus session was held to receive feedback and suggestions for future editions of this workshop. The feedback from the workshop participants, obtained in-person and over Slack during the workshop and in a survey circulated after the workshop, was enthusiastically positive. Participants particularly valued the high proportion of early-career researchers, the ability to actively interact with the speakers, in an atmosphere that encouraged a flat hierarchy and interactions between researchers with different experience levels.

Most attendees considered the scientific level of the talks as appropriate overall, although some expressed the need for more in-depth and introductory lectures at the graduate level as opposed to the working-level knowledge of most practitioners in the field.
The tutorials, however, posed some issues, most of which were technical, starting from hassles with registration and accounts on the cluster to long queuing times on clusters, which significantly impacted the intended interactive nature of these sessions and left the participants with little time to fully engage with the contents of the tutorial and instructions from the speakers.

The online poster session was useful for some people, but the overall participation was quite low. In the future, requiring or strongly encouraging on-site participants to also add their posters online could help with this problem.

Due to the continuing growth of this field, the number of applicants who had to be turned away, and the interest explicitly expressed by attendees, we expect a future edition of this workshop to be well-received. In the discussion session on the “future of ML-IP” held at the end of the workshop, a need was expressed for a written guide to the organization of future events, as well as a need to rethink the online portion of the event, given the significant additional organizational effort needed to run the online part of the conference.

Key future improvements

Based on this participant feedback and our collective experience as organizers, we identified some key areas of improvement for the next editions of the workshop:

  • Increase the geographic diversity of participants (as the current demographic was mostly Europe-based). While the hybrid nature of the event helped expand the reach to other countries, this representation must also be reflected on-site, even while working under the current restrictions.
  • Actively encourage people from under-represented groups (women, people of color, and LGBTQ+ people, for example) to apply and participate, and additionally become involved in the conference organization. Also, begin gathering demographic data to support this goal.
  • Foster collaboration with industry by more proactively reaching out to industrial contacts for scientific contributions and sponsorship. This could also help support travel costs for those traveling from less-resourced countries.

Quantum Monte Carlo HPC Applications in Condensed Matter, Quantum Chemistry and Materials Science 25 January 2024 | 09:30 -12:30 CET

Join us for a deep dive into the cutting edge of quantum materials research and quantum chemistry at the upcoming webinar on “Quantum Monte Carlo HPC Applications in Condensed Matter, Quantum Chemistry, and Materials Science” on January 25, 2024, from 09:30 to 12:30 CET. The webinar is a collaborative effort between the Targeting Real Chemical Accuracy at the EXascale (TREX) project and CECAM (Centre Européen de Calcul Atomique et Moléculaire).

Overview and objectives

The webinar will be exploring the frontiers of quantum materials research and quantum chemistry,  by means of Quantum Monte Carlo (QMC) calculations, owing to their unique suitability in solving complex many-body problems as well as in harnessing the parallelism offered by upcoming exascale supercomputer architectures.

The agenda covers a spectrum of key topics, including magnetism, surface physics, layered materials, energy excitations, and high-pressure hydrogen. Participants will gain a deeper insight into high-performance computing applications via quantum Monte Carlo simulations.

Target Audience

This webinar caters for researchers, students and professionals in the fields of quantum chemistry, condensed matter physics, and materials science.


Theoretical Spectroscopy Lectures :: Cecam School March 2024

dear colleagues and friends,
it is with pleasure that we announce the forthcoming

Theoretical Spectroscopy Lectures

that are going to take place in CECAM, Lausanne
March 11, 2024 – March 15, 2024.

The deadline for registering is 5 February 2024.

The event is going to take place at the CECAM HQ in Lausanne. Please take note that in order to participate to the hands-on sessions, you are required to come with a laptop (better if running under Linux).

Please find here the details of the school

We thank Psi-k and the gdr REST for extra funding.

Looking forward to seeing you in Lausanne.

The organisers,

Francesco Sottile
Gian-Marco Rignanese
Valerio Olevano

New Psi-k Chair

As we move into a new year Psi-k is delighted to announce the election of a new Chair, Professor Arash Mostofi of Imperial College London. Professor Mostofi will follow on from previous Chair, Professor Peter Haynes, who has now come to the end of his term.

Arash Mostofi is Professor of Theory and Simulation of Materials in the Departments of Materials and Physics at Imperial College London. His research is dedicated to the development and application of first-principles modelling tools for the theory and simulation of materials. He is an original author and developer of the Wannier90 and ONETEP codes and his research interests include electronic structure software development, 2D materials, defects and interfaces, and perovskite and layered perovskite oxides.

We would like to take this opportunity to thank Professor Haynes for his leadership of Psi-k over the last three years and look forward to working with him as the Chair of the next Psi-k Conference that will be held in Lausanne, Switzerland in 2025.

Summer School “Towards exascale solutions in Green function methods and advanced DFT” Paphos, Cyprus, October 3-8, 2023

This summer school targeted an audience consisting of PhD students and young postdocs, industry-based researchers as well as researchers from countries without tier 0 supercomputing facilities. There were 45 participants, among which 9 ladies. The school covered a wide range of topics to show the challenges and opportunities of exascale computing in ab initio materials science. Lectures provided in-depth information on the fundamentals of advanced exchange-correlation functionals, many-body perturbation theory based on Green functions, and coupled-cluster method applied to solids. Special focus was on libraries and software applications developed in the NOMAD Center of Excellence, for which training was provided, including on LUMI,, a powerful pre-exascale European Union high-performance computer. Fundamentals and recent developments in the field were presented by recognized experts, and there was plenty of room for open exchange between the young scientists and established international experts. Continue reading Summer School “Towards exascale solutions in Green function methods and advanced DFT” Paphos, Cyprus, October 3-8, 2023

Ab initio (from electronic structure) calculation of complex processes in materials