News

• 21-10-2024: Honoured to have been invited to become a member of the JPC A/B/C Editorial Advisory Board (EAB) for a term starting January 2025 and ending December 2027.

• 27-09-2024: New preprint out today on arXiv: “Transferability of Atom-Based Neural Networks” (arXiv: 2409.17575). Frederik and I study the transferability of both invariant and equivariant neural networks when training these either exclusively on total molecular energies or in combination with data from different atomic partitioning schemes.

• 20-09-2024: Our new paper, “Exploiting Non-Abelian Point-Group Symmetry to Estimate the Exact Ground-State Correlation Energy of Benzene in a Polarized Split-Valence Triple-Zeta Basis Set”, is now out in JPCL: DOI: 10.1021/acs.jpclett.4c02267 

• 20-08-2024: Thrilled to have been invited to this year's Löwdin Symposium in Uppsala, Sweden. Thanks to Roland for the kind invitation.

• 10-08-2024: Excited to have been invited to take part in this year's International Society for Theoretical Chemical Physics (ISTCP) meeting in Qingdao, China. Thanks to Wenjian for the invitation.

• 01-08-2024: Yet another preprint out on arXiv today with a somewhat lengthy title, “Exploiting Non-Abelian Point-Group Symmetry to Estimate the Exact Ground-State Correlation Energy of Benzene in a Polarized Split-Valence Triple-Zeta Basis Set” (arXiv: 2407.21576). Alongside Jürgen Gauss (Mainz) and his excellent PhD student, Jonas Greiner, we provide estimates of the frozen-core, full configuration interaction (FCI) energy of the benzene benchmark system to within unprecedented accuracy in polarized split-valence basis sets of both double- and triple-zeta quality. These high-accuracy estimates of the exact ground-state correlation energy of benzene have been made possible by leveraging the full, non-Abelian point group of the system and exploiting redundancies among symmetrized, spatially localized molecular orbitals.

• 14-07-2024: Luna's first work from her PhD project is out on arXiv today, “Atomic Decompositions of Periodic Electronic-Structure Simulations” (arXiv: 2407.10148). In the study, we present a novel theory for partitioning simulations of periodic and solid-state systems into physically sound atomic contributions at the level of Kohn-Sham density functional theory.

• 18-06-2024: New preprint out on arXiv today, “Error Control and Automatic Detection of Reference Active Spaces in Many-Body Expanded Full Configuration Interaction” (arXiv: 2406.11343), in which we present a wealth of improvements to our MBE-FCI method. Long-lasting collaboration with Jürgen Gauss (Mainz) and his PhD student, Jonas Greiner.

• 29-05-2024: Our new paper, “MBE-CASSCF Approach for the Accurate Treatment of Large Active Spaces”, is now out in JCTC: DOI: 10.1021/acs.jctc.4c00388

• 08-05-2024: Honoured to have been awarded the 2024 JPC A - PHYS Lectureship. I'm looking forward to the award ceremony at the ACS Fall Meeting in August in Denver, where I'll also speak about our ongoing research as part of the PHYS division program.

• 06-05-2024: I'm looking forward to take part in next year's workshop on emerging excited-state and general electronic-structure methods in lovely Toulouse, France. Thanks to Titou for the invitation.

• 26-03-2024: New preprint out on arXiv today (arXiv: 2403.17836). In “An MBE-CASSCF Approach for the Accurate Treatment of Large Active Spaces” - in collaboration with the groups of Filippo Lipparini (Pisa) and Jürgen Gauss (Mainz) - we couple two standard first-order CASSCF algorithms with a massively parallel implementation of MBE-FCI theory, resulting in a powerful new method to treat arbitrary and large active spaces.

• 24-01-2024: I'm on paternal leave through March 2024.

• 15-12-2023: The forthcoming ESCMQC-2024 meeting in CPH (26-28 June 2024) will now be sponsored in full by the Novo Nordisk Foundation through a generous conference grant (€ 35k), effectively removing any direct fees associated with attending the meeting for all regular participants. Registration is expected to open by early 2024.

• 05-12-2023: Frederik's paper, “Properties of Local Electronic Structures”, is now out in JCTC. DOI: 10.1021/acs.jctc.3c00963

• 16-11-2023: I'm honoured to have been invited by the DFG-Research Training Group BENCh (Prof. Ricardo Mata) to present a institute seminar at the Faculty of Chemistry of the University of Göttingen on 09 January 2024.

• 08-11-2023: I'm grateful to NordForsk for providing generous funding (€ 20k) in support of next year’s meeting of the young academies of the Nordic and Baltic countries in Copenhagen (2-3 April 2024).

• 10-10-2023: Looking forward to take part in Assoc. Prof. Ida-Marie Høyvik's Young CAS workshop, A Wave Function Based Framework for Describing Photoactivated Redox Processes, taking place in Trondheim, Norway, from 15-18 January 2024.

• 16-08-2023: New paper, “Properties of Local Electronic Structures”, from Frederik and I out on arXiv today (arXiv: 2308.07780). In our work, we show how computational simulations of local rather than global electronic structures can allow for changes to these under reactions to be directly related to key concepts in physical, organic chemistry.

• 05-06-2023: Presented some of our ongoing work on extensions of the MBE-FCI method today at the Numerical Methods in Quantum Chemistry 2023 meeting in Tromsø, Norway.

• 25-04-2023: Thrilled for Frederik - one of my first two PhD students @ DTU - who has today been awarded a Fulbright scholarship to visit Prof. Heather J. Kulik's group @ MIT later this year. 

• 11-04-2023: Jonas' paper, “Symmetrization of Localized Molecular Orbitals”, is now out in JPCA. DOI: 10.1021/acs.jpca.3c01371

• 17-03-2023: Frederik's paper, “Decomposing Chemical Space: Applications to the Machine Learning of Atomic Energies”, is now out in JCTC. DOI: 10.1021/acs.jctc.2c01290

• 01-03-2023: Together with Andreas H. Laustsen-Kiel (Technical University of Denmark), Kirsten M. Ø. Jensen (University of Copenhagen), Sandra W. Thrane (Bactolife), and Lia Leffland (Danish Academy of Technical Sciences), we have been granted 675k EUR from  The VILLUM Foundation towards the establishment and 5-year operation of a new Young Academy of Technology, Science, and Innovation (YATSI).

• 28-02-2023: Together with Jonas Greiner, a PhD student from the Gauss group in Mainz, I have a new paper, “Symmetrization of Localized Molecular Orbitals”, on arXiv today (arXiv: 2302.13654). In our study, we present a novel algorithm for (i) detecting approximate symmetries present amongst spatially localized MOs and (ii) enforcing these in numerically exact manners by means of unitary optimization techniques.

• 01-02-2023: Thrilled to have been promoted to the level of associate professor @ DTU following positive external recommendations.

• 19-01-2023: I'm pleased to have been invited by the organizers to speak at the workshop, Numerical Methods in Quantum Chemistry 2023, taking place in Tromsø, Norway, from 5-8 June 2023.

• 20-12-2022: Frederik and I have a new paper, “Decomposing Chemical Space: Applications to the Machine Learning of Atomic Energies”, on arXiv today (arXiv: 2212.09489). In our study, we inspect how different atomic partitioning schemes expose the composition & diversity of chemical space, and we examine the possibility of training custom machine models directly on atomic, rather than molecular energies.

• 29-11-2022: I'm thrilled to have been named among this year's cohort of Sapere Aude Research Leaders with a grant of 835k EUR from the Independent Research Fund Denmark. My research project will be concerned with focused decompositions of optical properties for improving upon the convergence of QM/MM simulations with respect to the extent of the QM region. In the process, we'll initiate a new collaboration with Filippo Lipparini and his group in Pisa, Italy.

• 28-07-2022: I presented some of our most recent work on the MBE-FCI method and its potential use of (non-)Abelian point group symmetries at the 1st Annual PySCF Developers' Meeting @ Caltech.

• 25-05-2022: Honoured to have been elected as a new member of the Young Academy of Denmark under the Royal Danish Academy of Sciences and Letters. I can't wait to meet everybody & get involved.

• 13-02-2022: Pleased to have been invited to present my recent work on decomposed mean-field quantum chemistry at this year's WATOC 2020 conference.

• 11-02-2022: My paper on mean-field decompositions of electronic excitations is now published as a communication in JCP, as part of the 2022 JCP Emerging Investigators Special Collection: DOI: 10.1063/5.0082938.

• 20-12-2021: A new paper on “Electronic Excitations Through the Prism of Mean-Field Decomposition Techniques” by Eriksen (arXiv: 2112.09508) has appeared on arXiv today. The paper extends our recently proposed theory for decomposing the results of Kohn-Sham density functional theory [Eriksen, JCP 153, 214109 (2020)] to stationary excited states, and we show how to rigorously partition energies and dipole moments for orbital-optimized excited states amongst the individual atoms of a system.

• 15-10-2021: The first talented cohort of PhD students have joined my new lab @ DTU Chemistry - Luna Zamok & Frederik Ørsted Kjeldal. Very much looking forward to 3 years of interesting scientific endeavours.

• 23-08-2021: Pleased to have been invited to present my recent work on decomposed mean-field quantum chemistry at this year's annual meeting of the Danish Chemical Society.

• 28-06-2021: My paper on local condensed-phase properties has now been published in JPCL: DOI: 10.1021/acs.jpclett.1c01375.

• 27-04-2021: I've got a new paper, “Decomposed Mean-Field Simulations of Local Properties in Condensed Phases” by Eriksen, on arXiv today (arXiv: 2104.12480). In the letter, I've used my recent theory for decomposing Kohn-Sham DFT simulations [Eriksen, J. Chem. Phys. 153, 214109 (2020)] to separate out local solvation properties (monomer ground-state energies and dipole moments) within liquid, ambient water.

• 01-03-2021: I've now officially commenced my new position as an assistant professor at DTU Chemistry. See Contact for my new e-mail and physical address and please don't hesitate to get in touch.

• 28-02-2021: Our new invited review on incremental approaches to the exact diagonalization problem in electronic structure theory, “Incremental Treatments of the Full Configuration Interaction Problem” by Eriksen & Gauss, has been published in WIREs Comput. Mol. Sci.: DOI: 10.1002/wcms.1525.

• 22-01-2021: Over the moon to be named among this year's Villum Young Investigators. I can't wait to get started at DTU Chemistry in March, embarking on five years of research on decomposed quantum chemistry. Truly grateful to The VILLUM Foundation for this starting grant and the support. At the same time, I'll unfortunately have to relinquish my recent Reintegration Fellowship from The Carlsberg Foundation as a consequence.

• 25-12-2020: My invited perspective on near-exact electronic structure theory is now out in JPCL, subtly disguised as an homage to the late and great Ornette Coleman: DOI: 10.1021/acs.jpclett.0c03225.

• 15-12-2020: I've been invited to write a short review on the MBE-FCI approach to exact electronic structure theory for WIREs Comput. Mol. Sci.: “Incremental Treatments of the Full Configuration Interaction Problem” by Eriksen & Gauss (arXiv: 2012.07371). As always, feedback is welcome. Our work will hopefully work to clarify what the pros & cons of this sort of method are in various practical applications.

• 04-12-2020: More good news - my paper on mean-field decompositions by means of localized orbitals, “Mean-Field Density Matrix Decompositions” by Eriksen, has now been published in JCP, as part of their 2020 JCP Emerging Investigators Special Collection: DOI: 10.1063/5.0030764.

• 03-12-2020: I'm truly honoured to have been named among this year's recipients of a Carlsberg Foundation Reintegration Fellowship, which will allow me to return back home to Denmark (DTU Chemistry) in March 2021 and further develop my scientific career. Huge thanks to The Carlsberg Foundation for the support. 

• 26-10-2020: I've been invited to write a perspective on modern-day exact electronic structure theory, which has now appeared on arXiv: “The Shape of FCI to Come” by Eriksen (arXiv: 2010.12304). The paper provides a (hopefully) succinct account of today's state-of-the-art as well as my personal views on what's to come.

• 22-10-2020: The foreword to this year's Mol. Phys. Festschrift in honour of Jürgen Gauss, which I've had the privilege of guest-editing alongside Stella Stopkowicz (Mainz), Thomas Jagau (Leuven) & Trygve Helgaker (Oslo), has now appeared online. DOI: 10.1080/00268976.2020.1817247.

• 16-10-2020: Our new paper on the extension of MBE-FCI theory to properties for ground and excited states, “Ground and Excited State First-Order Properties in Many-Body Expanded Full Configuration Interaction Theory” by Eriksen & Gauss, has been published in JCP: DOI: 10.1063/5.0024791.

• 07-10-2020: Our new paper on the benzene blind challenge, “The Ground State Electronic Energy of Benzene” by Eriksen et al., has been published in JPCL: DOI: 10.1021/acs.jpclett.0c02621.

• 24-09-2020: A new paper on “Mean-Field Density Matrix Decompositions” by Eriksen (arXiv: 2009.10837) has appeared on arXiv today. The paper introduces a new way of decomposing mean-field electronic structure theories (with applications to HF & KS-DFT) by means of localized MOs and various charge population protocols. I further demonstrate how decomposed mean-field theory makes it possible to expose and amplify compositional features in the context of machine-learned quantum chemistry.

• 11-08-2020: Two new papers have appeared on arXiv within the past week. In arXiv: 2008.02678 (“The Ground State Electronic Energy of Benzene” by Eriksen et al.), we report on a blind challenge devoted to the determination of the FCI ground state energy for the benzene/cc-pVDZ system, with involvement from most of the current state-of-the-art approaches from all around the world. In arXiv: 2008.03610 (“Ground and Excited State First-Order Properties in Many-Body Expanded Full Configuration Interaction Theory” by Eriksen & Gauss), MBE-FCI theory is extended to excited states and static first-order properties different from total, ground state correlation energies. Both papers have been submitted for publication.

• 13-07-2020: Our new paper on the PySCF program has been published in JCP: DOI: 10.1063/5.0006074.

• 16-03-2020: My forthcoming seminar at King's College London has been cancelled/rescheduled due to COVID-19. Bummer.

• 02-03-2020: A new preprint on recent developments in the PySCF program package has been submitted for publication in a special issue of JCP on electronic structure software. A preprint is available on arXiv: 2002.12531.

• 20-02-2020: I've been invited by George Booth @ the Department of Physics, King's College London to present a seminar on MBE-FCI theory on Tuesday, March 31st. Looking very much forward to the visit! (UPDATE 16-03-2020: Cancelled/rescheduled due to COVID-19).

• 13-02-2020: I am pleased to announce that our proposal for the 2020 HPC Call @ Johannes Gutenberg-Universität Mainz, Germany, has been awarded a total of 10.0M core-hours on their MogonII system. The project will be concerned with the application of our MBE-FCI method to the field of computational thermochemistry and the allocation will run for the next year.

• 11-12-2019: I've been invited by Nick Blunt & Alex Thom @ the Department of Chemistry, University of Cambridge to present a seminar on MBE-FCI theory on Wednesday, February 2nd next year. Looking very much forward to the visit!

• 27-11-2019: Our paper entitled “Generalized Many-Body Expanded Full Configuration Interaction Theory” (Eriksen & Gauss) is out now in JPCL. DOI: 10.1021/acs.jpclett.9b02968

• 09-10-2019: Our paper entitled “Generalized Many-Body Expanded Full Configuration Interaction Theory” (Eriksen & Gauss) has been submitted for publication. A preprint is available on arXiv: 1910.03527.

• 07-10-2019: The PyMBE code is now open source: https://gitlab.com/januseriksen/pymbe

• 09-09-2019: I'm contributing to this month's C&EN Magazine with an essay (Nomadic Tales) on my postdoctoral experience. Link: https://cen.acs.org/careers/postdocs/Postdoc-perspective-Tales-nomadic-postdoc/97/i35

• 05-08-2019: Our “Many-Body Expanded Full Configuration Interaction. II. Strongly Correlated Regime” (Eriksen & Gauss) paper is out now in JCTC. DOI: 10.1021/acs.jctc.9b00456

• 09-05-2019: Our paper entitled “Many-Body Expanded Full Configuration Interaction. II. Strongly Correlated Regime” (Eriksen & Gauss) has been submitted for publication. A preprint is available on arXiv: 1905.02786.

• 10-04-2019: My abstract for an oral contribution at the MQM2019 meeting (Heidelberg, Germany) later this year has been accepted. I intend to talk about recent enhancements of the MBE-FCI method and its application to increasingly larger system sizes.

• 27-03-2019: I am pleased to announce that my proposal for the 18th PRACE Project Access Call has been awarded a total of 26.4M core-hours on the MARCONI system @ Cineca, Bologna, Italy. The project will be concerned with the application of our MBE-FCI method to the field of computational thermochemistry and the allocation will run for the next year.

• 11-02-2019: After 2.5 fruitful and truly enjoyable years in Mainz, I am relocating to Bristol, UK to start a new leg of postdoctoral research by 01-03-2019, this time generously funded by the Independent Research Fund Denmark. My new host for the coming 2 years will be Prof. Fred Manby and we will work towards accelerating and enhancing the MBE-FCI method even further in continued close collaboration with Prof. Jürgen Gauss in Mainz.

• 22-10-2018: I will present our latest research on MBE-FCI at the Methods and Algorithms in Quantum Chemistry conference (Aarhus, Denmark), December 13-16, 2018.

• 20-08-2018: Our “Many-Body Expanded Full Configuration Interaction. I. Weakly Correlated Regime” (Eriksen & Gauss) paper is out now in JCTC. DOI: 10.1021/acs.jctc.8b00680

• 07-08-2018: I will present our latest research on MBE-FCI at the joint Mainz-Kobe workshop on Solving the Full Configuration Interaction Problem (Kobe, Japan), November 26-27, 2018.

• 04-07-2018: Our paper entitled “Many-Body Expanded Full Configuration Interaction. I. Weakly Correlated Regime” (Eriksen & Gauss) has been submitted for publication. A preprint is available on arXiv: 1807.01328.

• 01-07-2018: I will present our latest research on MBE-FCI at the Molecular Electronic Structure conference (Metz, France), August 28-31, 2018.

• 28-06-2018: I presented our latest research on MBE-FCI at the 16th ICQC satellite meeting on Strong correlation in electronic structure theory (Strasbourg, France), June 24-27, 2018.

• 08-06-2018: I presented our latest research on MBE-FCI at the Low-scaling and Unconventional Electronic Structure Techniques conference (Telluride, CO, US), June 04-07, 2018.