Speaker: Sascha Jähnigen, Freie Universität Berlin

The chirality of molecular crystals arises from space-group symmetry, which defines the supramolecular organisation and collective vibrational modes of the solid. Vibrational circular dichroism (VCD), the chiral analogue of infrared absorption, provides a direct spectroscopic probe of this structural enantiomorphism, extending chiroptical analysis beyond isolated molecules. In the solid state, VCD intensities reflect the interplay between local intramolecular contributions and non-local terms arising from lattice vibrations, long-range intermolecular couplings, and Davydov splitting. Their interpretation therefore requires a fully periodic theoretical framework.
Within periodic boundary conditions, nuclear velocity perturbation theory (NVPT) provides a rigorous response formalism, implemented with plane-wave basis sets and pseudopotentials in Kohn–Sham density functional theory (KS-DFT). This imports the non-adiabatic couplings required for computing the magnetic response to nuclear dynamics. Maximally localised Wannier functions (MLWFs) enable the decomposition of electric and magnetic dipole operators, disentangling molecular and supramolecular components of the response.
The integration of periodic electronic-structure theory, NVPT-based response, vibrational dynamics, and a well-defined magnetic gauge establishes the foundation for quantitative interpretation of solid-state VCD in chiral crystals and polymorphic systems, as will be shown in this talk.

References:
[1] S. Jähnigen, Angew. Chem. Int. Ed. 62 (2023), e202303595.
[2]  J. Bloino, S. Jähnigen, C. Merten, J. Phys. Chem. Lett. 15 (2024), 8813-8828.
[3]  S. Jähnigen, R. Vuilleumier, A. Zehnacker, Chem. Sci. 16 (2025), 9833-9842.
[4]  S. Jähnigen et al., Angew. Chem. Int. Ed. 62 (2023), e202215599.
[5]  S. Jähnigen et al., J. Phys. Chem. Lett. 12 (2021), 7213-7220.
[6] A. Scherrer et al., J. Chem. Theory Comput. 9 (2013), 5305-5312.