X2C Hamiltonian Models in ReSpect: Bridging Accuracy and Efficiency
Since its inception, the ReSpect program has been evolving to provide powerful tools for simulating spectroscopic processes and exploring emerging research areas, all while incorporating relativistic effects, particularly spin-orbit interactions, in a fully variational manner. Recent developments have focused on exact two-component (X2C) Hamiltonian models that go beyond the standard one-electron X2C approach by incorporating two-electron picture-change corrections. This paper presents the theoretical foundations of two distinct atomic mean-field X2C models, amfX2C and extended eamfX2C, which offer computationally efficient and accurate alternatives to fully relativistic four-component methods. These models enable simulations of complex phenomena such as time-resolved pump-probe spectroscopies and cavity-modified molecular properties, which would otherwise be computationally prohibitive. ReSpect continues to evolve, providing state-of-the-art quantum chemical methods and postprocessing tools, all available free of charge through our Web site (www.respectprogram.org) to support researchers exploring relativistic effects across various scientific disciplines.
Authors
- Torsha Moitra (ORCID: https://orcid.org/0000-0001-7228-7678)
- Marc Joosten (ORCID: https://orcid.org/0009-0000-3436-2622)
- Olga L. Malkina (ORCID: https://orcid.org/0000-0003-1044-3799)
- Michal Repiský (ORCID: https://orcid.org/0000-0003-0776-4137)
- Marius Kadek (ORCID: https://orcid.org/0000-0001-6524-2711)
- Lukas Konecny (ORCID: https://orcid.org/0000-0002-4073-7045)
- Kenneth Ruud (ORCID: https://orcid.org/0000-0003-1006-8482)
- Debora Misenkova (ORCID: https://orcid.org/0000-0003-0593-6150)
- Martin Kaupp (ORCID: https://orcid.org/0000-0003-1582-2819)
- Vladimir G. Malkin (ORCID: https://orcid.org/0000-0001-6568-3701)
- Stanislav Komorovský (ORCID: https://orcid.org/0000-0002-5317-7200)
- Rasmus Vikhamar-Sandberg
Institutions
- Institute of Chemistry of the Slovak Academy of Sciences (SK)
- Universität Hamburg (DE)
- Norwegian Defence Research Establishment (NO)
- Slovak Academy of Sciences (SK)
- Centre for Arctic Gas Hydrate, Environment and Climate (NO)
- Czech Academy of Sciences, Institute of Inorganic Chemistry (CZ)
- Institute of Inorganic Chemistry of the Slovak Academy of Sciences (SK)
- Institute of Theoretical Physics (CN)
- Center for Free-Electron Laser Science (DE)
- Max Planck Institute for the Structure and Dynamics of Matter (DE)
- Technische Universität Berlin (DE)
- Comenius University Bratislava (SK)
- UiT The Arctic University of Norway (NO)
Publication Details
- Journal
- The Journal of Physical Chemistry A
- Published
- 2025-08-18
- DOI
- https://doi.org/10.1021/acs.jpca.5c02990
- Citations
- 2
- Primary Topic
- Advanced Chemical Physics Studies
- Type
- article
- Field-Weighted Citation Impact
- 2.49
Funders
- Agentúra na Podporu Výskumu a Vývoja
- Norges Forskningsråd
- Vedecká Grantová Agentúra MŠVVaŠ SR a SAV
- H2020 Marie Skłodowska-Curie Actions
- HORIZON EUROPE Marie Sklodowska-Curie Actions