Dr. Stefan Knecht

Welcome to the Knecht Group webpage. Here you will find information about our research interests and our latest software developments.

Our research is centred around the density matrix renormalization group (DMRG) approach, which is on the edge of becoming a well-established electronic structure method in chemistry to tackle the exponential scaling problem of solving a full-configuration-interaction type problem. We are particularly interested in developing DMRG-based ab initio wave function methods – possibly combined with density functional theory (DFT) – that allow for the prediction of electronic and magnetic properties such as X-ray, UV-Vis, EPR and NMR spectra of closed and open-shell molecules covering any element of the periodic table of elements.

Other research interests include the (range-separated) ensemble DFT method for the calculation of ground- and excited states (properties) formulated in a time-independent framework as opposed to the widely used time-dependent (TD)-DFT approach, the implementation and development of relativistic multiconfigurational methods, the description of excited-state (reaction) dynamics and the implementation of embedding approaches for (DMRG-based) ab initio wave function methods, aiming towards the study of chemical reactions including solvent and/or protein matrix effects.

Further information about our research and publications can also be found at ResearcherID and ResearchGate.


  • 25-09-2019: Looking forward to write an “invited Perspective review” article on relativistic (multi-configuration) electron correlation approaches and their application to heavy-element chemistry for PCCP.
  • 07-05-2019: New paper submitted: Analytical gradients and nonadiabatic couplings for the state-average density matrix renormalization group self-consistent field method. A giant leap forward towards ab initio dynamics with DMRG-SCF wave functions. πŸ™‚
  • 28-03-2019: Exciting news on my (long-term) project regarding state-averaged DMRG-SCF in a relativistic framework. The implementation is done and I am writing the paper right now. So look forward to read more soon. As a byproduct, the code also works with an external magnetic field applied. See below one of the bonding “Ο€u” orbitals in N2+ when applying an external magnetic field of B = 20 000 Tesla…

  • 22-01-2019: Back from Kobe/Japan with good inspirations for new projects to work on in 2019. We even had a chance to see the year 2012-fastest supercomputer (“K computer”) in the TOP 500 list.
The K supercomputer at RIKEN/KOBE in the back
Our work on U2 is featured on the cover of Nature Chemistry
(cover design by Tulsi Voralia)
  • 22-12-2018: Stay tuned for upcoming news on relativistic DMRG…
  • 05-12-2018: I will present our recent efforts on large-scale multiconfigurational quantum chemical approaches for ALL elements in the periodic table of elements on February 7th 2019 in a joint seminar of the Theoretical and Nuclear Chemistry institutes at the U Mainz/Germany.
  • 05-12-2018: I will present our recent efforts on large-scale multiconfigurational quantum chemical approaches in January 2019 at the RIKEN institute in Kobe/Japan.
  • 23-11-2018: Our paper on “Density Matrix Renormalization Group Pair-Density Functional Theory (DMRG-PDFT): Singlet-Triplet Gaps in Polyacenes and Polyacetylenes” has been accepted for publication in Chemical Science. That’s my 50th paper in the making and my first (but hopefully not last) collaboration with Laura. Stay tuned for further news. πŸ™‚
  • 12-11-2018: Our work on U2 is featured in ACS’s C&EN journal!
  • 21-09-2018: Looking forward to write a “Trendbericht 2018” for the “Nachrichten aus der Chemie” in the Theoretical Chemistry section.
  • 13-09-2018: HOT NEWS! Our paper “Relativistic Quantum Chemical Calculations Show that the Uranium Molecule U2 Has a Quadruple Bond” has been accepted for publication in Nature Chemistry.
    A couple of years in the making — the molecule had been following me since my PhD — this work marks my first paper in the Nature journal family. πŸ™‚
  • 08-05-2018: Our relativistic DMRG work is featured on the cover of JCTC.

JCTC May 2018 issue
  • 25-04-2018: Personal note: Family grows, today my wife and I welcomed our second son into this world. πŸ™‚
  • 03-04-2018: Roger Kloditz (PhD student under the supervision of my friend and colleague Dr. Michael Patzschke) from the Helmholtz Research Centre Dresden/Rossendorf is visiting our group for five weeks to work with me on various exciting projects within actinide chemistry. Stay tuned for more news in due time.
  • 23-03-2018: Personal note: I received confirmation today from the rector of ETH that I will receive the “Venia Legendi” for Theoretical Chemistry starting (officially) Aug 1st 2018. This marks the end of my “Habilitation”. πŸ™‚
  • 20-03-2018: Our paper on “An efficient relativistic density-matrix renormalization group implementation in a matrix-product formulation” has been accepted for publication in J. Chem. Theory Comput..
    Preprint available on arXiv: 1710.08301
  • 14-02-2018: Software news: A new version of our DMRG program QCMaquis has been released and is available also within OpenMolcas. For further details, check out our QCMaquis homepage.
  • 09-02-2018: I will present our latest research on multiconfigurational relativistic quantum chemical approaches at the MQM2019 – 9th Molecular Quantum Mechanics Conference in Heidelberg (Germany), Jun. 30 – 5 July, 2019.
  • 26-01-2018: I will become a “Notizenautor” for the GDCh-members journal (German chemical society) “Nachrichten aus der Chemie” reporting hot papers in Theoretical Chemistry starting in March 2018.
  • 28-11-2017: Our paper on “Combining extrapolation with ghost interaction correction in range-separated ensemble density functional theory for excited states” has been published in J. Chem. Phys..
    Preprint available on arXiv: 1708.03478
  • 10-10-2017: Our paper on “Generalized Pauli constraints in small atoms” has been submitted to Phys. Rev. Lett. for publication.
    Preprint available on arXiv: 1710.03074
  • 25-09-2017 — 05-10-2017: Sophie Kervazo (PhD student) from U Lille was visiting our group for two weeks to work with me on the thermochemistry of Pu compounds with DMRG-based approaches. Stay tuned for more news in due time.
  • 03-09-2017: I presented our latest research on multiconfigurational relativistic quantum chemical approaches for the calculation of (magnetic) properties in actinide compounds at the REHE-2017: “12th International Conference on Relativistic Effects in Heavy-Element Chemistry and Physics in Marburg (Germany), Sep. 2-6, 2017.
  • 15-06-2017: Our paper on “Excited state characterization of carbonyl containing carotenoids: a comparison between single and multireference descriptions” has been accepted for publication in Phys. Chem. Chem. Phys., 16, 17156-17166 (2017).
    Preprint available on arXiv:1705.01939
  • 15-06-2017: Our paper on “Laplace-transformed multi-reference second-order perturbation theories in the atomic and active molecular orbital basis” has been published in J. Chem. Phys., 146, 224101 (2017).
    see also on arXiv:1703.07204.
  • 09-05-2017: Our paper on “Second-order self-consistent-field density-matrix renormalization group.” has been published in J. Chem. Theory Comput., 13, 2533–2549 (2017).
  • 03-04-2017: I presented our latest research on multiconfigurational quantum chemical approaches for large active orbital spaces at the “Molecular Properties and Computational Spectroscopy” birthday symposium of Antonio Rizzo in Pisa (Italy), April 10-12, 2017.
  • 30-03-2017: Our paper “Electron correlation within the relativistic no-pair approximation” has been selected as a 2016 Editors’ Choice article in J. Chem. Phys.!