The Psi-k Community

Psi-k is a wide network of European researchers — working closely with many friends and colleagues around the world – that is intended to help build cooperation in the field of computational electronic structure calculations, in particular for crystalline quantum systems whose wave function Ψ has an associated wave vector k defining its periodicity, hence the name.  It is co-ordinated by a series of working groups from around Europe. It produces a monthly newsletter, organizes a major conference every five years, and allows researchers to email each other regarding job openings, events, and other topics of mutual interest. The network is also able to provide some degree of financial support for small workshops and schools, and for collaborative research visits.

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.

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.

Scientific report on the CECAM/Psi-K workshop on “Quantum-chemistry methods for materials science”

CECAM-HQ-EPFL, Lausanne, Switzerland, 08-10 November 2017

OrganizersIgor Ying Zhang and Matthias Scheffler (Fritz Haber Institute of the Max Planck Society (FHI), Berlin, Germany).

Sponsors:  CECAM, Psi-k and Fritz Haber Institute of the Max Planck Society (FHI), Berlin, Germany.


The workshop “Quantum-chemistry methods for materials science” was held at Lausanne, Switzerland from Nov 08th to 10th 2017. In total, 22 participants from Europe, USA, and China attended the workshop. The workshop stimulated an interdisciplinary exchange of ideas and knowledge about the development of advanced electronic-structure methods transferring from chemistry, solid-state physics, and materials science.

The electronic-structure theory is the foundation for many developments and investigation in these fields and the corresponding methods development drives progress. Despite its small and intimate scale, the workshop will have a lasting impact on materials science, because the description of many novel materials of experimental and/or industrial interest has been out of the capability of widely used density functional approximations, while the quantum-chemistry methods have great potential to handle the complex many-body electronic correlation correctly. The workshop reviewed the current state-of-the-art, the challenge and the future of using quantum-chemistry methods in materials science and inspired new avenues for more accurate approaches and computational more efficient implementations that will facilitate future discoveries.


The workshop began with presentations on the development of sophisticated electronic-structure methods in materials science (First two sessions, 14:30 -18:00 on Nov 8th and 9:00 – 12:00 on Nov 9th ). Georg Kresse and Juerg Hutter presented the analytic gradient implementation of advanced electronic-structure methods in VASP and CP2K, respectively. Numerical convergence of quantum-chemistry methods for solids was discussed comprehensively by Denis Usvyat using Gaussian-type basis functions and by Xinguo Ren in the numeric atom-centered basis framework. Andreas Gruneis gave an overview over their recent effort to improve the computational efficiency and numerical stability of coupled-cluster theories using the plane-wave basis functions. Beate Paulus’ talk then focused on the application of quantum-chemistry methods and also density-functional methods to graphene-based systems. These talks cover all the state-of-the-art developments in the field and thus sparked a heated discussion in these two sessions. By comparing the implementation of quantum-chemistry methods in different numerical frameworks and code packages, it has led to the consensus on the challenges of using quantum-chemistry methods for solids, including the slow basis-set convergence issue, the large finite-size error in the reciprocal space, and the expensive computational cost together with a huge memory consumption for large systems. These challenges have been significantly impeding the popularization of accurate quantum-chemistry methods in materials science.

In the following two sessions (14:30 -18:00 on Nov 9th and 9:00 – 12:00 on Nov 10th), the experts from quantum chemistry shared their wisdom to solve these pressing challenges in simulating finite molecules. Edward Valeev introduced his recent work on the explicitly correlated F12/R12 approach, which has been demonstrated to be very effective to reduce the basis-set error in quantum-chemistry methods for molecules. Frank Neese, Fred Manby, and Xin Xu presented their contributions to significantly enhance the computational capacity of quantum-chemistry methods towards large and complex molecular systems, including the uses of domain-based local pair natural orbital (DLPNO) methods, embedding algorithms, and the force-based extended ONIOM approach to realize linear scaling and robust performance of these quantum-chemistry methods for molecules. Ali Alavi’s talk focused on the most accurate quantum-chemistry method, the full configuration interaction method in the quantum Monte Cario framework and its connection to the fixed-node DMC approach. Garnet Chan introduced their new electronic-structure package that allows for the coupled-cluster calculations of both molecules and solids on an equal footing.

social dinner on Nov. 9

After lively discussions in these two sessions, these current progresses in quantum chemistry found their values in materials science, which highlights the importance of deepening the coalescence of two communities to solve the timely challenges of using quantum-chemistry methods for solids in the future.

We organized a nice social dinner on Nov. 9, which complemented the scientific program, by promoting further exchange among the organizers, the invited speakers, and the participants.

List of invited talks

  1. Georg Kresse (Univ. Vienna): Analytic gradients for the RPA: using the relation between total energies and self-energies
  2. Juerg Hutter (University of Zurich): MP2, RPA and GW within the Gaussian and Plane Waves Method
  3. Denis Usvyat (Humboldt-Universität zu Berlin):  Wave-function-based methodology as a route to controllable accuracy in solid state applications
  4. Andreas Grüneis (Max-Planck-Institute for Solid State Research, Germany):  Recent progress in applying coupled cluster theories to the study of ground and excited state properties of solids
  5. Beate Paulus (Free University Berlin):  Electron correlation effects in graphene-based systems
  6. Xinguo Ren (University of Science and Technology of China): Periodic RPA and GW within a numeric atom-centered basis framework
  7. Edward Valeev (Virginia Tech, USA):  Recent work on reduced-scaling explicitly correlated many-body methods
  8. Fred Manby (University of Bristol):  Multiscale embedding methods for accurate quantum chemistry of complex systems
  9. Garnet Chan (Caltech, USA):  Reduced scaling methods for materials
  10. Xin Xu (Fudan University, China):  Embedding approaches for large complex systems, including the extended ONIOM method XO and the DCMB method

The workshop booklet, the program with the abstracts of the talks and the posters, and some supplemental materials can be found on the official workshop’s webpage:



Scientific report on the “Interface Morphology Prediction with Robust and Efficient Structure Search” (IMPRESS) Workshop

Interface Morphology Prediction with Robust and Efficient Structure Search (IMPRESS)

Aalto University, Finland, 7-9 June 2017

Organisers: Dr Milica Todorović (Aalto University, Finland), Dr Oliver T. Hofmann (Technical University of Graz, Austria), Prof. Patrick Rinke (Aalto University, Finland)

Funding: CECAM, Psi-K, NOMAD CoE, Aalto University CMMP doctoral network


Determining or predicting the structure of organic ensembles on surfaces is a challenging problem that occupies basic science and engineering alike. Recently, novel machine-learning approaches have started to compete with more traditional, stochastic methods, such as basin hoping or simulated annealing. In IMPRESS, we took an interdisciplinary stance and brought together assorted experts to focus on the challenges of organic/inorganic interfaces: this is the first workshop to unite different electronic structure methods, structure search approaches and machine learning.

Continue reading Scientific report on the “Interface Morphology Prediction with Robust and Efficient Structure Search” (IMPRESS) Workshop

Psi-k Volker Heine Young Investigator Award 2018

“For research excellence in all fields involving electronic structure calculations”

Young computational science researchers are invited to put themselves forward for the Psi-k Volker Heine Young Investigator Award 2018.  The finalists will compete at a special session of the joint EPS Condensed Matter Division and German Physical Society (CMD/DPG) Spring Meeting in Berlin, during March 11-16, 2018.

The Volker Heine Award session will be part of the Symposium:
Frontiers of Electronic Structure Theory: Correlated Electron Materials

Purpose: The purpose of the Psi-k Volker Heine Young Investigator Award is to recognize an individual for her or his outstanding computational work in any type of condensed-matter, materials, or nanoscience research involving electronic structure calculations. In 2018 there will be one award of 2500 Euro and four runner-up prizes of 500 Euro each. The prize is sponsored by Nature Publishing Group.

Regulations and Procedure:

1) Applicants may be of any nationality working anywhere in the world.

2) The applicant’s PhD certificate must not be dated more than 5 years before the first day of the joint CMD/DPG – EPS Conference (March 11, 2018). Those who have not yet completed a PhD can also apply.

3) Young investigators who wish to compete for the Psi-k Volker Heine Young Investigator Award 2018 must submit:

  • abstract (in the format of the abstracts for the conference)
  • two-page description making the case for her/his outstanding scientific contribution
  • extended CV (incl. list of publications and talks/posters)
  • evidence of satisfying the conditions of regulation (2) above.

These items must be submitted by email, as a pdf attachment, to the chairperson of Psi-k whose address is given below. It must be received not later than December 1, 2017. The abstract must also be submitted as a regular contribution to the CMD/DPG Conference.

4) The candidate must arrange for two confidential support letters to be sent directly by to the Psi-k chairperson (see below). These letters (sent by email) need to be received before December 1, 2017. One of the letters must certify that the candidate meets the requirements of regulations (2) above.

5) The Psi-k Trustees will select five finalists who will get an invitation to present their work at the CMD/DPG Conference (25 min. talk + 5 min. discussion). After these presentations, the award committee will select the award winner.

6) The award winner will receive her or his award of 2500 Euro and the four runner-up their prizes of 500 Euro each, together with a certificate, at a presentation on the Psi-k Scientific Get-Together during the conference.

Award Committee: The award committee will consist of selected invited speakers of the CMD/DPG Conference and three members of the Psi-k Trustees.

Risto Nieminen
Psi-k Chairman
[email protected]

Scientific report of the international workshop on ‘New challenges in Reduced Density Matrix Functional Theory: Symmetries, time-evolution and entanglement’

Group photo.
CECAM-HQ-EPFL, Lausanne, Switzerland, 26-29 September 2017

Organizers:  Carlos L. Benavides-Riveros (Martin-Luther Universität Halle-Wittenberg, Germany), E. K. U. Gross (Max Planck Institute of Microstructure Physics, Germany), Miguel A. L. Marques (Martin-Luther Universität Halle-Wittenberg, Germany), and Christian Schilling (University of Oxford, United Kingdom).

Sponsors:  CECAM, Psi-k and Max Planck Institute of Microstructure Physics.


This international workshop discussed and explored new aspects and challenges in Reduced Density Matrix Functional Theory (RDMFT). The main aim was to bring together leading experts in the field to address and carefully discuss open challenges in RDMFT such as implementations of 1-particle symmetries, extensions to open-shell atoms and molecules, time-evolution, temperature dependency and new insights about RDMFT from recent progress on the 1- and 2-body N-representability problems and density matrix renormalization group. The list of speakers was carefully chosen to include experts in various disciplines required for the accomplishment of the proposed scientific program. To maximize the success of the workshop, we asked all speakers to provide rather informal and interactive presentations. We also asked them to share their slides and other supplemental materials with all the participants in advance, allowing them to prepare the workshop accordingly. This ‘homework’ enabled not only fruitful and stimulating scientific discussions, but also more involved questions. Continue reading Scientific report of the international workshop on ‘New challenges in Reduced Density Matrix Functional Theory: Symmetries, time-evolution and entanglement’


Location: Abdus Salam International Centre for Theoretical Physics, Trieste (Italy), 3-7 July 2017

Organizers:  David M. Ceperley (University of Illinois at Urbana-Champaign); Michele Ceriotti (Ecole Polytechnique Fédérale de Lausanne); Thomas E. Markland (Stanford University).

Local Organizers: Ali Hassanali (The Abdus Salam International Centre for Theoretical Physics); Sebastiano Pilati (University of Padova).

Group photo of the Workshop on “Understanding Quantum Phenomena with Path Integrals: from Chemical Systems to Quantum Fluids and Solids”, ICTP – Trieste, July 2017



The main goal of this interdisciplinary workshop was to gather together physicists and chemists who employ computer-simulation methods based on path integrals to investigate different systems, ranging from chemical and biochemical compounds, to quantum fluids/solids, to ultracold gases. This event allowed a broad community of researchers to create a platform for exchanging knowledge and know-how on path-integral technology and on other approaches to the combined quantum simulation of electrons and nuclei. Furthermore, speakers had the opportunity to showcase the most recent applications to various intriguing quantum phenomena, including, e.g., isotope effects in aqueous systems, quantum fluctuations in enzyme catalysis, quantum phase transitions due to strong correlations, and tunnelling phenomena in molecular systems and in adiabatic quantum computers (alias quantum annealers), thus creating a new bridge between quantum chemistry and quantum computing.

This event took place at the ICTP Adriatico Guesthouse, in a warm and sunny Trieste, allowing participants to enjoy the view of the Adriatic sea and the Miramare park. The format included 24 (long) oral presentations given by invited speakers, 7 short talks selected from contributed abstracts, 21 flash presentations (meant to advertise the content of a poster), and a total of 24 poster presentations. The workshop was attended by a total of 80 participants (including directors and speakers) from 29 countries.

This event has been sponsored by ICTP and by the Psi-k Network.



Psi-k workshop on
“Atomic scale materials microscopy: theory meets experiment”
National Railway Museum, York (UK)
26-28 June 2017


Atomic scale materials characterization is now one of the major drivers of technological innovation in areas such as nanoelectronics, catalysis, medicine, clean energy generation and energy storage. This can in a large part be attributed to advances in electron and scanning probe microscopies, which are now able to provide atomically resolved structural, chemical and electronic characterization of a wide range of functional materials. However, the types of systems relevant to applications, which include surfaces, interfaces, nanocrystals and two-dimensional materials, are complex and interpreting experimental images and spectra is often extremely challenging. On the other hand, parallel advances in theoretical approaches means that theory can often offer invaluable guidance. These approaches include first principles methods for structure prediction, simulation of scanning probe and electron microscopy images, and prediction of various spectroscopic signatures (e.g. EELS and STS). Some of the most impressive examples of this kind of research in recent years have combined complementary theoretical and experimental approaches in a synergistic way to unravel the complex structure of materials. This type of integrated approach is increasingly being recognised as critical to advanced materials research and development by both industry and research funders.

It was in this context that the Psi-k workshop: “Atomic scale materials microscopy: theory meets experiment” was held between the 26th and 28th of June 2017 at the National Railway Museum in York (UK). The scientific focus was on the application and development of first principles methods that, in synergy with advanced microscopy techniques (e.g. TEM, EELS, STM, AFM), can help to unravel the structure and properties of materials at the atomic scale. Open to both experts and newcomers the aim was to provide a rounded overview of emerging methods and challenges in the field, and provide an opportunity for in-depth discussion and exchange of ideas. Continue reading SCIENTIFIC REPORT ON THE PSI-K WORKSHOP: “ATOMIC SCALE MATERIALS MICROSCOPY: THEORY MEETS EXPERIMENT”

Scientific Report regarding the CECAM Workshop: “Tackling complexity of the nano/bio interface – computational and experimental approaches”

Organizers:   Thomas Frauenheim (University of Bremen)

Qiang Cui (University of Wisconsin, Madison, USA)

Bob Hamers, University of Wisconsin, Madison, USA)

Joel Pedersen, University of Wisconsin, Madison, USA)

Location:       University of Bremen, Germany,

12th June until 16th June 2017

  1. Summary

The workshop “Tackling Complexity of the Nano/Bio Interface – Computational and Experimental Approaches” was held at the University of Bremen, Germany from June 12th to 16th 2017. In total, 72 participants from Belgium, Brazil, Finland, Ireland, Luxemburg, The Netherlands, Portugal, Slovenia, Spain, Sweden, Switzerland, Russia, France, Germany, UK and US attended the workshop.

The programme consisted of 28 invited lectures, one poster session presenting 27 posters and many events (reception / conference dinner) to allow for informal exchange. The lectures were scheduled to last 40 min, including 5-10 min discussion time. In addition to this extended time for discussion, the chairpersons were instructed to introduce the subject of the session and to actively participate in the discussion. This “Gordon-conference-style” was essential to guarantee a vivid discussion. The organizers ensured that well-established scientists acted as invited speakers and chairpersons. Continue reading Scientific Report regarding the CECAM Workshop: “Tackling complexity of the nano/bio interface – computational and experimental approaches”

Scientific report on “HoW exciting! Workshop on excitations in solids Humboldt-Universität zu Berlin”, Berlin, Germany August 3 – 11, 2016


The third Berlin edition of the “HoW exciting! Workshop on excitations in solids” was a very successful event. It took place in the Campus Adlershof of the Humboldt-Universität zu Berlin. The subject of the workshop, namely excitations in solids, is extremely up-to-date, attracting the attention of a vast interdisciplinary community. Technological applications based on excitations in solids are closely interconnected with the fundamental physical mechanisms ruling them. A deep understanding of such basic properties is therefore essential and makes the role of theory crucial in this respect. Assessing the state of the art of the theoretical approaches to address excited-state properties of materials and establishing their link with the most recent experimental observations were the main goals of this workshop, which can be considered successfully achieved. Continue reading Scientific report on “HoW exciting! Workshop on excitations in solids Humboldt-Universität zu Berlin”, Berlin, Germany August 3 – 11, 2016

14th ETSF Young Researchers’ Meeting (Tarragona)

In 2017, the ETSF Young Researchers’ Meeting made its way to Tarragona, Spain for the first time. Sunny weather, great food, a beautiful old city and the kind hosts at the Catalan Institute for Chemical Research (ICIQ) provided a fantastic setting for a week of science that will stay in our memory.

The Young Researchers’ Meeting (YRM) of the European Theoretical Spectroscopy Facility (ETSF) is a workshop organised by young researchers for young researchers. Every year, postdocs, PhD students and Master students gather from all over Europe to discuss problems and recent advances in theoretical and computational methods for the study of the electronic and optical properties of materials. The YRM is where you can present your work in progress, float new ideas, and learn from others at your own level – both scientifically and personally. Talks at the YRM are 25 minutes, which gives you enough time to introduce your topic, what you did and, crucially, how you did it. Each session starts with an introductory keynote that provides an overview of the field, introduces the theoretical framework and points out open questions. Continue reading 14th ETSF Young Researchers’ Meeting (Tarragona)


18th Total Energy Workshop, ICTP, Trieste (Italy), 12-14 January 2017

Group picture from the 18th Total Energy International Workshop, ICTP, Trieste, January 2017

The “Total Energy” Workshop is held traditionally in Trieste every two years, since 1987. It is devoted to recent advances in computational condensed matter physics and materials science, based on realistic calculations of the electronic structure of complex systems. It has become one of the most popular regular events of the international ab-initio electronic-structure community. The 2017 edition confirmed this tradition, with a large number of participants, lively discussions and, furthermore, with an impressive number of contributed posters. Overview, speakers list, program with the relevant material (Conference Book, abstracts, list of attendees, …) are available on the web page:


The Workshop involved 225 attendees, including Directors, Scientific Committee members, speakers, and selected participants.

Following the tradition of the previous meetings of the series, the Workshop has been structured in thematic sessions with oral presentations by invitation only. The aim was to gather speakers presenting current topics of research of broad interest as well as future research directions for the electronic structure community. The chairpersons introduced each session with a short overview (about 5 min) to set the subject and point out open problems.  The introductions were very useful, especially for those people working on other subjects. In addition, large space was devoted to discussion. This format has been greatly appreciated and contributed to create, most noteworthy, a lively atmosphere.

Selected contributions from participants have been solicited as posters. The large number of selected posters (140) has been a testament of the enthusiastic and active participation of the attendees. Consequently, two large poster sessions have been organized.

In Honor of Walter Kohn

The Workshop included one special Lecture and one entire session in honor of Walter Kohn, Continue reading SCIENTIFIC REPORT ON THE “18TH INTERNATIONAL WORKSHOP ON COMPUTATIONAL PHYSICS AND MATERIALS SCIENCE: TOTAL ENERGY AND FORCE METHODS”

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