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The COSY webinars will be organized every three months (each webinar will consist of two lectures):

  • March 25th, 2024
  • September 18th, 2024

The 1st Webinar:

Moderator: Kaido Sillar (University of Tartu)
Speakers: Joachim Sauer (Humboldt University of Berlin) & María Pilar de Lara-Castells (Spanish National Research Council)

Speaker 1: Joachim Sauer (Institut für Chemie, Humboldt-Universität zu Berlin, Germany)

Effect of Fe substitution in aluminium oxide gas phase clusters – a challenge for quantum chemistry

We study gas phase clusters as models for solid catalysts, “the active site in isolation”, and are interested in how the structure and reactivity of gas phase clusters differ from those of the bulk phase with the same composition. We use density functional theory (DFT) to perform global structure optimizations (genetic algorithm). To verify the global minimum structures, we calculate IR spectra and compare them with the ones obtained for mass-selected clusters by photodissociation (IRPD) and multiple photon dissociation (IRMPD) spectroscopy (cooperation with Knut Asmis, Leipzig).

Here, we focus on the effect of Fe substitution on the structure and reactivity of the aluminium oxide clusters Al3O4+ [1] and Al8O12+. For Al3O4+, the spectra predicted by DFT indicate that Fe substitution leads to a structural change which is driven by a transition from the Fe+III/O-II to the Fe+II/O-I oxidation states. DFT does not get the relative stabilities right and multireference (MR) calculations are needed. Even if the number of atoms in this cluster is not large, the MR calculations are difficult to converge with the size of the active space (number of orbitals on the O atoms in addition to the d orbitals on Fe). The relative stabilities obtained with MRCI and NEVPT2 are 52 ± 17 and 69 ± 14 kJ/mol, respectively.

In contrast to Al3O4+, Fe substitution is isomorphous in Al8O12+ and a change of the oxidation states from Fe+III/O-I to Fe+IV/O-II converts the reactive terminal Al−O•− bond into a non-reactive terminal Fe=O bond. While the DFT predictions of the IR spectrum agree with experiment for the singlet and triplet spin states, they are not the lowest energy spin states regardless the functional used (PBE performs best here). MR calculations are even more challenging because of the larger number of orbitals on O atoms that would be needed to reach convergence.

[1] Müller, F.; Stückrath, J. B.; Bischoff, F. A.; Gagliardi, L.; Sauer, J.; Debnath, S.; Jorewitz, M.; Asmis, K. R. Valence and Structure Isomerism of Al2FeO4+: Synergy of Spectroscopy and Quantum Chemistry. J. Am. Chem. Soc. 2020, 142, 18050-18059.

 

Speaker 2: María Pilar de Lara-Castells (AbinitFot Group, IFF-CSIC, Madrid)

An ab initio journey towards the molecular-level understanding of subnanometric metal clusters

Current advances in synthesizing and characterizing atomically precise monodisperse metal clusters (AMCs) at the subnanometer (Angstrom) scale have opened fascinating possibilities in new quantum materials research. Their quantized ‘molecule-like’ electronic structure showcases unique stability and physical and chemical properties different from those of nanoparticles and bulk materials. When integrated into materials that interact with environmental molecules and sunlight, AMCs may exhibit enhanced (photo)catalytic activity, electronic properties, and even optical behavior. Their tiny size (below 1 nm) makes free AMCs amenable to atomic-scale modelling using either density functional theory (DFT)-based approaches or methods at a higher level of ab initio theory, even including nonadiabatic (e.g., Jahn-Teller) effects. Surfacesupported AMCs can routinely be modelled using DFT-based single-reference methods, enabling real-time molecular dynamics simulations on the nanoseconds scale. The study of their optical properties is also possible using timedependent DFT or reduced density matrix theory. All these computational and theoretical efforts aim to achieve a molecular-level understanding of the stability and properties of AMCs as function of their chemical composition, size, and structural fluxionality in different thermodynamical conditions (temperature and pressure). These efforts bear the potential of guiding experiments to control AMCs functionalities for applications. In this webinar, the potential of state-of-the-art ab initio (DFT and beyond DFT) modelling will be emphasized through an illustrative overview of recent studies of free and surface-supported AMCs, including a comparison with experimental measurements [1-17]. Possible directions for methodological enhancements on the ab initio modelling of hybrid AMCs-materials systems will also be discussed with a focus on AMCs-support intermolecular interactions, including excited states.

References:

1. M. P. de Lara-Castells, J. Colloid Interface Sci. (2022), 612, 737.

2. M. P de Lara-Castells, C. Puzzarini, V. Bonačić-Koutecký, M. A. López-Quintela, S. Vajda, Editorial for the Themed Collection “Stability and properties of new-generation metal and metal-oxide clusters down to subnanometer scale” in Phys. Chem. Chem. Phys. (2023), 25, 15081.

3. B. Fernández, M. Pi, M. P. de Lara-Castells, Phys. Chem. Chem. Phys. (2023), 25, 16699.

4. A. O. Mitrushchenkov, M. P. de Lara-Castells, ChemPhysChem (2023), 24, e202300317

5. J. Garrido-Aldea, M. P. de Lara-Castells, Phys. Chem. Chem. Phys. (2022), 24, 24810.

6. B. Fernández, M. P. de Lara-Castells, Phys. Chem. Chem. Phys. (2022), 24, 26992.

7. L. L. Carroll, L. Moskaleva, M. P. de Lara-Castells, Phys. Chem. Chem. Phys. (2023), 25, 15729.

8. D. Buceta, S. Huseyinova, M. Cuerva, H. Lozano, L. J. Giovanetti, J. M. Ramallo-López, P. López-Caballero, A. Zanchet, A. O. Mitrushchenkov, A. W. Hauser, G. Barone, C. HuckIriart, C. Escudero, J. C. Hernández-Garrido, J. J. Calvino, M. López-Haro, M. P. de Lara-Castells, F. G. Requejo, M. Arturo López-Quintela. Chem. A European J. (2023), 29, e202301517.

9. M. P. de Lara-Castells, A. W. Hauser, J. M. Ramallo-López, D. Buceta, L. J. Giovanetti, M. A. López-Quintela, F. G. Requejo, J. Mater. Chem. A (2019), 7, 7489.

10. P. López-Caballero, J. M. Ramallo-López, L. J. Giovanetti, D. Buceta, S. Miret-Artés, M. A. López-Quintela, F. G. Requejo, J. Mater. Chem. A (2020), 8, 6842.

11. P. López-Caballero, A. W. Hauser, M. P. de Lara-Castells, J. Phys. Chem. C (2019), 123, 23064.

12. M. P. de Lara-Castells, S. Miret-Artés, Europhys. News (2022), 53, 7-9.

13. A. O. Mitrushchenkov, A. Zanchet, A. W. Hauser, J. Phys. Chem A (2021), 125,9143.

14. P. López-Caballero, R. Garsed, M. P. de Lara-Castells, ACS Omega (2021), 24, 16165

15. P. López-Caballero, S. Miret-Artés, A. O. Mitrushchenkov, M. P. de Lara-Castells, J. Chem. Phys. (2020), 153, 164702.

16. A. Zanchet, P. López-Caballero, A. O. Mitrushchenkov, D. Buceta, M. A. LópezQuintela, A. W. Hauser, M. P. de Lara-Castells, J. Phys. Chem. C (2019), 123, 27064.

17. M. P. de Lara-Castells, C. Cabrillo, D. A. Micha, A. O. Mitrushchenkov, T. Vazhapilly, Phys. Chem. Chem. Phys. (2018), 29, 19110.

 

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