Speaker: Marco Bauer, PhD: Universität Heidelberg, now: KTH Stockholm

Excitonic renormalization (XR) [1-4] is a novel fragmentation scheme, in which the electronic structure of fully isolated fragments is calculated by a method of choice, which can differ between individual fragments. The interaction is then recovered by contracting the correlated monomer information in form of transition densities with computationally cheap integrals in an ab-initio manner. To account for the non-orthogonality of the orbitals between different fragments a biorthogonal framework is used. This methodology is particularly useful for rather weakly bound fragments with several multi-reference centers, as e.g. encountered a lot in the field of small molecule activation. Here I will show how the Hamiltonian can be built efficiently, by expanding the overlap between non-orthogonal states in orders of orbital overlaps, leading to smooth and fast convergence and how to optimize the monomer information in a compact manner.

References:

[1] A. D. Dutoi & Y. Liu, Mol. Phys. 117, 431 (2019).
[2] Y. Liu & A. D. Dutoi, Mol. Phys. 117, 446 (2019).
[3] M. Bauer, A. Dreuw, A. D. Dutoi, J. Chem. Phys. 161 (2024)
[4] M. Bauer, P. Norman, A. Dreuw, A. D. Dutoi, arXiv:2507.23484 (2025)