A benchmark study of core-excited states of organic molecules computed with the generalized active space driven similarity renormalization group

Abstract

This work examines the accuracy and precision of X-ray absorption spectra computed with a multireference approach that combines generalized active space (GAS) references with the driven similarity renormalization group (DSRG). We employ the X-ray absorption benchmark of organic molecules (XABOOM) set, consisting of 116 transitions from mostly organic molecules [T. Fransson et al., J. Chem. Theory Comput. 17, 1618 (2021)]. Several approximations to a full-valence active space are examined and benchmarked. Absolute excitation energies and intensities computed with the GAS-DSRG truncated to second-order in perturbation theory are found to systematically underestimate experimental and reference theoretical values. Third-order perturbative corrections significantly improve the accuracy of GAS-DSRG absolute excitation energies, bringing the mean absolute deviation from experimental values down to 0.32 eV. The ozone molecule and glyoxylic acid are particularly challenging for second-order perturbation theory and are examined in detail to assess the importance of active space truncation and intruder states.

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Cited by in corpus (2)

• Simulating Transient X-ray Photoelectron Spectra of Fe(CO)5 and Its Photodissociation Products With Multireference Algebraic Diagrammatic Construction Theory
• Generalization of one-center non orthogonal configuration interaction singles to open shell singlet reference states: Theory and application to valence-core pump-probe states in acetylacetone