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arXiv · 2212.04369

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

Meng Huang·Francesco A. Evangelista
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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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Meng Huang, Francesco A. Evangelista. 2022-12-19. A benchmark study of core-excited states of organic molecules computed with the generalized active space driven similarity renormalization group. https://doi.org/10.1063/5.0137096

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