The accurate simulation of x-ray spectroscopy has become a very important tool, enabling the analysis and interpretation of complex structural dynamics often seen in experimental spectra. The GW approximation is prominent among the theoretical methods used for such simulations due to its relatively low computational cost and good accuracy profile. The extant popularity of the GW approximation in periodic calculations has recently transferred to isolated systems, with many molecular GW implementations available nowadays.<br/>Here, we will show that a molecular GW implementation, based on the contour-deformation technique, can be efficiently paired with the MINRES linear equation solver in order to reduce the overall computational scaling of the approach. We use this new implementation to predict core-level ionization spectra of clusters with up to a few hundred water molecules, with results in very good agreement to those obtained from Green’s function coupled-cluster method. We will also show that basis set extrapolation techniques can often fail in core-level GW calculations of first-row atoms, if standard basis sets are used. Finally, we will show that the GW approximation can also be used for the accurate prediction of valence ionization spectra of open-shell transition metal hexaaqua complexes.

Scalable molecular core and valence GW calculations

ACS Spring 2022

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