Dr. Giovanni Li Manni, Electronic Structure Theory Department, Max Planck Institute for Solid State Research, Stuttgart, Germany, https://www.fkf.mpg.de/person/38639/5567042

Spin structures of biological and bio-mimetic catalysts are of paramount importance for gaining
control over their spectacular reactivity, such as the water splitting reaction at the oxygen
evolving center of photosystem II or the nitrogen fixation catalyzed by ferredoxins in nitrogenase
enzymes. Spin structures are also key to the magnetic properties of solid states materials,
including superconductivity and spin-orbital separation in Mott insulators.

Quantum chemical simulations of spin structures of poly-nuclear transition metal (PNTM) clusters
represent one of the most challenging tasks in modern quantum chemistry, due to (1) the
vast number of nearly-degenerate electronic states, (2) long-range spin interactions, and (3)
spin-frustration effects that often characterize ground and excited electronic states of these
systems. Multi-configurational (MC) strategies are unavoidable for this class of systems. Cheap
and almost-accurate strategies are just a lie!

I will show that local symmetries exist for exchange-coupled PNTM clusters that can be revealed
by a conceptual strategy based on simple unitary orbital transformations (Quantum Anamorphosis).
This strategy (a) greatly reduces the multi-reference character of strongly correlated
electronic states, (b) allows for unprecedented state-specific optimizations of excited states, and
(c) vastly simplify the characterization of the spin interactions. The strategy is generally applicable
to ab initio Hamiltonians (commonly used for molecular clusters) and to model Hamiltonians
(Heisenberg chains, J12 Heisenberg 2D and 3D models).

I will show this conceptual strategy in practice on Fe4(III)S4, Mn3(IV)O4, and Co3(II)Er(III)O4 clusters.
For the challenging Fe8-sulfur clusters (FeMoco and P-cluster), travelling salesman problem
(TSP) strategies, based for example on Genetic Algorithms, are utilized to reveal Quantum
Anamorphosis.

[1] G. Li Manni, W. Dobrautz, and A. Alavi, J. Chem. Theory Comput. 16, 2202 (2020).
[2] G. Li Manni, Phys. Chem. Chem. Phys. 23, 19766 (2021).
[3] G. Li Manni,W. Dobrautz, N. A. Bogdanov, K. Guther, and A. Alavi, J. Phys. Chem. A 125, 4727
(2021).
[4] W. Dobrautz, O. Weser, N. A. Bogdanov, A. Alavi, and G. Li Manni, J. Chem. Theory Comput.
17, 5684 (2021).
[5] W. Dobrautz, V. M. Katukuri, N. A. Bogdanov, D. Kats, G. Li Manni,and A. Alavi Phys. Rev. B
105, 195123 (2022).
[6] N. Liebermann, D. Kats, and G. Li Manni 10.26434/chemrxiv-2022-rfmhk-v2 (just accepted).
[7] R. Han, S. Luber, and G. Li Manni 10.26434/chemrxiv-2023-xd0wv (under review).