Translational Eigenstates of Noble Gas Endofullerenes

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• Kripa Panchagnula, University of Cambridge
• Wednesday 16 October 2024, 14:30-15:30
• Unilever Lecture Theatre, Yusuf Hamied Department of Chemistry.

If you have a question about this talk, please contact Lisa Masters.

Endofullerenes (EFs) are complexes where a chemical species A, is trapped within a cavity encompassed by a fullerene cage Cn, denoted A@Cn. Recent advances in the synthesis and characterisation of these species has produced a wealth of spectroscopic data.[1] These measurements unveil information about the nuclear energy levels of the species, which due to its entrapment, has its translational motion quantised.[2]

Theoretical calculation of these nuclear energy levels is broken down into two phases. Firstly, the potential energy surface (PES) needs to be generated. However, as these EFs are bound through non-covalent interactions, they pose challenges on the electronic structure (ES) techniques with respect to achieving spectroscopic accuracy. Due to the high cost of these calculations, the PES is usually approximated as a Lennard-Jones summation, or interpolated from sparse data.

Secondly, once the PES has been generated, the endohedral eigenstates can be found by diagonalising the nuclear Hamiltonian matrix, within a specified nuclear basis set. Comparison of the energy gaps allows for scrutinisation of the PES and underlying ES. Access to the wavefunction also allows for calculation of experimentally observable properties, alongside visualisation of the nuclear orbitals.

In this talk, we investigate two noble gas endofullerenes: He@C60 and Ne@C70, using a plethora of ES techniques, with the PES interpolated using Gaussian Process Regression. The former has been recently synthesised and characterised,[3] proving invaluable in order to validate our choice of techniques and methods.[4] We then apply these to the larger Ne@C70 which required the development of a new basis set and wavefunction classification.[5] Experimental data on this species is lacking, allowing us to push the boundaries for theoretical predictions on EFs.

[1] S. Bloodworth and R. J. Whitby, Commun. Chem., 2022, 5, 1–14. [2] Z. Bacic, J. Chem. Phys., 2018, 149, 100901 [3] G. R. Bacanu, T. Jafari, M. Aouane et al., J. Chem. Phys., 2021,155, 144302 [4] K. Panchagnula, D. Graf, F. E. A. Albertani and A. J. W. Thom, J. Chem. Phys., 2024, 160, 104303 [5] K. Panchagnula, D. Graf, E. R. Johnson and A. J.W. Thom, J. Chem. Phys., 2024, 161, 054308

This talk is part of the Theory - Chemistry Research Interest Group series.

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