arXiv subjects

Yannick J. Franzke

Publications and source records attributed to Yannick J. Franzke.

5 recordsLinked to original sources

arXiv2026

Application of SAP-X2C to Spectroscopy and Comparison to Screened Nuclear Spin-Orbit Approximations

Recently, Surjuse and Valeev [J. Chem. Theory Comput. 22, 3443-3452 (2026).] suggested to use a simple superposition of atomic potentials to account for the two-electron picture-change error in one-electron exact two-component (SAP-X2C) theory. Herein, we generalize this ansatz to analytical derivative theory and apply SAP-X2C to molecular spectroscopy. The accuracy is assessed for NMR, EPR, Mössbauer, UV/vis, as well as X-ray absorption spectroscopy. A thorough comparison with four-component results and the even simpler screened nuclear spin-orbit (SNSO) approximation reveals that both SNSO-X2C and SAP-X2C perform excellently for spectroscopic properties, with SAP-X2C yielding slightly lower errors. Another major advantage is its well defined thermodynamic limit and less empirical nature. Therefore, SAP-X2C may be expected to become the default choice to mitigate the two-electron picture-change error in density functional theory approaches for spectroscopy thanks to its accuracy, simplicity, and efficiency. More complicated approaches to account for this error based on atomic mean-field ansätze may still be relevant for high-level correlated methods and highly accurate thermochemistry.

physics.chem-ph↗

arXiv2025

A Guide to Molecular Properties from the Bethe-Salpeter Equation

The Bethe-Salpeter equation (BSE) combined with the Green's function GW method has successfully transformed into a robust computational tool to describe light-matter interactions and excitation spectra for molecules, solids, and materials from first principles. Thanks to its ability to accurately describe charge-transfer and Rydberg excitations, the GW-BSE already forms an established and cost-efficient alternative to time-dependent density functional theory. This raises the question whether the GW-BSE approach can become a more general framework for molecular properties beyond excitation energies. In this mini-review, we recapitulate recent endeavors along this point in terms of both theoretical and practical developments for quantum chemistry, physical chemistry, and related fields. In doing so, we provide guidelines for current applications to chemical challenges in collaboration with experimentalists as well as to future developments to extended the GW-BSE toolkit.

physics.chem-ph↗

arXiv2024

A General and Transferable Local Hybrid Functional for Electronic Structure Theory and Many-Fermion Approaches

Density functional theory has become the workhorse of quantum physics, chemistry, and materials science. Within these fields, a broad range of applications needs to be covered. These applications range from solids to molecular systems, from organic to inorganic chemistry, or even from electrons to other fermions such as protons or muons. This is emphasized by the plethora of density functional approximations that have been developed for various cases. In this work, a new local hybrid exchange-correlation density functional is constructed from first principles, promoting generality and transferability. We show that constraint satisfaction can be achieved even for admixtures with full exact exchange, without sacrificing accuracy. The performance of the new functional for electronic structure theory is assessed for thermochemical properties, excitation energies, Mössbauer isomer shifts, NMR spin--spin coupling constants, NMR shieldings and shifts, magnetizabilities, as well as EPR hyperfine coupling constants. Here, the new density functional shows excellent performance throughout all tests and is numerically robust only requiring small grids for converged results. Additionally, the functional can be easily generalized to arbitrary fermions as shown for electron-proton correlation energies. Therefore, we outline that density functionals generated in this way are general purpose tools for quantum mechanical studies.

physics.chem-ph↗

arXiv2024

Current density functional framework for spin-orbit coupling: Extension to periodic systems

Spin-orbit coupling induces a current density in the ground state, which consequently requires a generalization for meta-generalized gradient approximations. That is, the exchange-correlation energy has to be constructed as an explicit functional of the current density and a generalized kinetic energy density has to be formed to satisfy theoretical constraints. Herein, we generalize our previously presented formalism of spin-orbit current density functional theory [Holzer et al., J. Chem. Phys. 157, 204102 (2022)] to non-magnetic and magnetic periodic systems of arbitrary dimension. Besides the ground-state exchange-correlation potential, analytical derivatives such as geometry gradients and stress tensors are implemented. The importance of the current density is assessed for band gaps, lattice constants, magnetic transitions, and Rashba splittings. For the latter, the impact of the current density may be larger than the deviation between different density functional approximations.

physics.chem-ph↗

arXiv2024

Efficient Treatment of Relativistic Effects with Periodic Density Functional Methods: Energies, Gradients, and Stress Tensors

The implementation of an efficient self-consistent field (SCF) method including both scalar relativistic effects and spin-orbit interaction in density functional theory (DFT) is presented. We make use of Gaussian-type orbitals (GTOs) and all integrals are evaluated in real space. Our implementation supports density functional approximations up to the level of meta-generalized gradient approximations (mGGAs) for SCF energies and gradients. The latter can be used to compute the stress tensor and consequently allow us to optimize the cell structure. Considering spin-orbit interaction requires the extension of the standard procedures to a two-component (2c) formalism and a non-collinear approach for open-shell systems. Here, we implemented both the canonical and the Scalmani-Frisch non-collinear DFT formalisms, with hybrid and range-separated hybrid functionals being presently restricted to SCF energies. We demonstrate both efficiency and relevance of spin-orbit effects for the electronic structure of discrete systems and systems periodic in one to three dimensions.

physics.chem-ph↗