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Workshop on quantum dissipation by swift nuclei in condensed matter

Workshop photograph at CECAM headquarters

During 7-9 December 2022 the workshop on quantum dissipation by swift nuclei took place in Lausanne, at the CECAM headquarters. It was jointly funded by CECAM , Psi-k, and the Lawrence Livermore National Laboratory. It brought together key people in the fields of electronic stopping of nuclei in matter, non-adiabatic quantum dynamics, and density-functional theory and many-electron dynamics, to face the problem of quantum dissipation of swift nuclei in matter, from quantum friction effects of ions/molecules on surfaces and nanoconfined flow, to strong dissipation under irradiation. Invited speakers were prompted to talk about their recent work and ideas in their own topics which they thought could connect to the other subfields. The general ambition was cross-fertilisation,and exploring how connections of advances in one field might contribute to the others. In the spirit of traditional Psi-k / CECAM workshops, ample opportunity for discussion and lateral collective thinking was provided.

Full details can be found in the CECAM web page for this event.

The format consisted of three full days, including seven talks and a discussion session per day, after the afternoon coffee break. Slots of 40 min were allocated per speaker, aiming at 20-25 min of lecture and 15-20 min of discussion. Most of the talks were delivered in-person, The workshop was structured in three interconnected themes, one per day, starting with nuclei as projectiles (experiment, theory, simulation), followed by levels of theory for the dynamics of the electronic subsystem, to conclude with quantum coupled dynamics of electrons and nuclei, including connection to other non-adiabatic contexts. Each day had an associated discussion session led by one of the participants who identified important open questions to be addressed in the future, as arising from the presentations.

Key needs identified and actions proposed to address them can be summarised as follows:

  1. Promoting further interactions between modelers and experimentalists and ensuring that experimentalists’ input on relevant questions and coherence between models and experimental set up is clearly disseminated. To foster this goal, the organization of a follow-up workshop driven by experimentalists was proposed and will be pursued for 2024.
  2. Clarifying and disseminating state-of-the-art and open questions via a shared publication in the form of a roadmap paper. In particular, this work should include a more important participation by the cognate community of non-adiabatic dynamics applied to chemical processes, which has developed a number of quite advanced tools, especially in the field of photochemistry.
  3. Identify challenges and benchmark systems for currently existing techniques. In particular, an adequate description of electron thermalisation after a strong energy pulse was considered a timely and suitable challenge for the dynamical simulation techniques being used (such as TDDFT).


It was considered a quite successful meeting by all, deserving further exploration.


  • Emilio Artacho (Nanogune, DIPC, Ikerbasque, U. Cambridge),
  • Sara Bonella (CECAM, EPFL),
  • Alfredo Correa (Larence Livermore National Lab)
  • Jorge Kohanoff (U Complutense, Madrid)

Report of the E-CAM workshop “Improving the accuracy of ab-initio methods for materials”

Title: Improving the accuracy of ab-initio predictions for materials
Webpage with list of participants, schedule and slides of presentations: http://www.cecam.org/workshop-0-1643.html
Dates: September 17, 2018 to September 20, 2018
Organizers: Dario Alfè, Michele Casula, David CeperleyCarlo Pierleoni

State of the art
Improving the accuracy of ab-initio methods for materials means to devise a global strategy which integrates several approaches to provide a robust, controlled and reasonably fast methodology to predict properties of materials from first principle. Kohn-Sham DFT is the present workhorse in the field but its phenomenological character, induced by the approximations in the exchange-correlation functional, limit its transferability and reliability.
A change of paradigm is required to bring the ab-initio methods to a predictive level. The accuracy of XC functional in DFT should be assessed against more fundamental theories and not, as it is often done today, against experiments. This is because the comparison with experiments is often indirect and could be misleading. The emerging more fundamental method for materials is Quantum Monte Carlo because of: 1) its favourable scaling with system size with respect to other Quantum Chemistry methods; 2) its variational character which defines an accuracy scale and allows to progressively improve the results. However QMC being much more demanding in terms of computer resources, and intricate than DFT, a combined approach is still desirable where QMC is used to benchmark DFT approximations for specific systems before performing the production study by DFT.
A different aspect of accuracy is related to size effects: often relevant phenomena occurs at length and time scales beyond the one approachable by first-principle methods. In these cases effective force fields methods can be employed. Machine Learning methods can be used to extract those force fields from training sets provided by ab-initio calculations. Presently DFT-based training sets are used. Improving their accuracy will improve the ultimate accuracy at all scales.
This change of paradigm requires building a community of people with different expertises working in an integrated fashion. This has been the main aim of the workshop.

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