Real-time equation-of-motion CC cumulant and CC Green's function simulations of photoemission spectra of water and water dimer

Fernando D Vila; John J Rehr; Himadri Pathak; Bo Peng; Ajay Panyala; Erdal Mutlu; Nicholas P Bauman; Karol Kowalski

doi:10.1063/5.0099192

Real-time equation-of-motion CC cumulant and CC Green's function simulations of photoemission spectra of water and water dimer

J Chem Phys. 2022 Jul 28;157(4):044101. doi: 10.1063/5.0099192.

Authors

Fernando D Vila¹, John J Rehr¹, Himadri Pathak², Bo Peng², Ajay Panyala², Erdal Mutlu², Nicholas P Bauman², Karol Kowalski²

Affiliations

¹ Department of Physics, University of Washington, Seattle, Washington 98195, USA.
² Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, USA.

PMID: 35922363
DOI: 10.1063/5.0099192

Abstract

Newly developed coupled-cluster (CC) methods enable simulations of ionization potentials and spectral functions of molecular systems in a wide range of energy scales ranging from core-binding to valence. This paper discusses the results obtained with the real-time equation-of-motion CC cumulant (RT-EOM-CC) approach and CC Green's function (CCGF) approaches in applications to the water and water dimer molecules. We compare the ionization potentials obtained with these methods for the valence region with the results obtained with the coupled-cluster with singles, doubles, and perturbative triples formulation as a difference of energies for N and N - 1 electron systems. All methods show good agreement with each other. They also agree well with the experiment with errors usually below 0.1 eV for the ionization potentials. We also analyze unique features of the spectral functions, associated with the position of satellite peaks, obtained with the RT-EOM-CC and CCGF methods employing single and double excitations, as a function of the monomer OH bond length and the proton transfer coordinate in the dimer. Finally, we analyze the impact of the basis set effects on the quality of calculated ionization potentials and find that the basis set effects are less pronounced for the augmented-type sets.