Molecular Properties and Theoretical Spectroscopy Simulations with VeloxChem

Iulia-Emilia Brumboiu^1*, Patrick Norman²

¹Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Torun, Poland
²Theoretical Chemistry and Biology, KTH Royal Institute of Technology, Stockholm, Sweden

* Presenter:Iulia-Emilia Brumboiu, email:iubr@umk.pl

VeloxChem is an MPI/OpenMP parallel Python-driven quantum chemistry software dedicated to the efficient calculation of molecular properties and theoretical spectra for very large molecules (up to and beyond 500 second row atoms) [1]. Response properties of free-standing molecules, as well as molecules embedded in an environment are enabled by a multifrequency complex linear response equation solver. VeloxChem features electronic absorption and circular dichroism spectra, vibrational spectroscopies from infrared absorption to Raman and resonance Raman spectroscopy, as well as a quadratic response solver which can be used to determine observables related to two photon absorption (TPA) and second-harmonic generation (SHG) [2] at the Hartree–Fock and Kohn–Sham Density Functional Theory (DFT) levels. Besides its HPC aspects,VeloxChem also features interactive program access through Jupyter notebooks which makes it an education-enabling software platform for quantum molecular modeling, as illustrated in the eChem project [3]. Here, we will focus on the high performance computing (HPC) aspects of VeloxChem and illustrate various spectroscopies and molecular properties of very large systems, as well as automatic workflows for modeling complex molecular systems [4].

[1] Rinkevicius, Zilvinas et al., WIREs: Comput. Mol. Sci., 10, e1457 (2020).
[2] Ahmadzadeh, Karan et al., Electron. Struct., 4, 044004 (2022).
[3] Fransson, Thomas et al., J. Chem. Educ., 100, 1664–1671 (2023).
[4] J. A. de Garcia Triviño, J. Phys. Chem. A, 129, 7575–7587 (2025).

Keywords: VeloxChem, DFT, TDDFT, spectroscopy, HPC