Authors: Niklas Göllmann, Matthew R. Ludwig, Peter Wind, Laura E. Ratcliff, and Luca Frediani.
Results
Core-ionisation energies are the main quantities involved in the resolution of X-Ray photoelectron spectroscopy, where molecules are ionised by extracting core-electrons with an X-Ray beam. Interpreting such spectra requires a reliable computational protocol.
A big challenge in computing core-ionisation energies is to identify the core-hole state correctly, avoiding either its collapse or its delocalisation. We prevent this collapse by using the (initial) maximum overlap method to stabilise this state without resorting to pseudopotentials as done previously and thus keeping an all-electron description of the system.
By using this method combined with Multiwavelets in MRChem, we have shown that one can obtain precise core binding energies for a variety of molecules of different sizes.
Publication in the journal: Physical Chemistry Chemical Physics, 2nd October 2025; https://doi.org/10.1039/D5CP01544H
Funding
We are grateful for computational support from the UK national high performance computing service, ARCHER2, for which access was obtained via the UKCP consortium and funded by EPSRC grant ref EP/X035891/1.
MRL acknowledges support from the Engineering and Physical Sciences Research Council (EP/W524414/1).
LER thanks Anna Regoutz for useful discussions.
The financial support from the Research Council of Norway through its Centres of Excellence scheme (Hylleraas centre, 262695) and the FRIPRO scheme (ReMRChem, 324590) is acknowledged.
The support from Sigma2, The National Infrastructure for High Performance Computing and Data Storage in Norway, under the NN14654K grant of computer time is also acknowledged.