Disentangling the resonant Auger spectra of ozone: overlapping core-hole states and core-excited state dynamics

We report the development and benchmark of multireference algebraic diagrammatic construction theory (MR-ADC) for the simulations of core-excited states and X-ray absorption spectra (XAS). Our work features an implementation that incorporates core-valence separation into the strict and extended second-order MR-ADC approximations (MR-ADC(2) and MR-ADC(2)-X), providing efficient access to high-energy excited states without including inner-shell orbitals in the active space. Benchmark results on a set of small molecules indicate that at equilibrium geometries, the accuracy of MR-ADC is similar to that of single-reference ADC theory when static correlation effects are not important. In this case, MR-ADC(2)-X performs similarly to single- and multireference coupled cluster methods in reproducing the experimental XAS peak spacings. We demonstrate the potential of MR-ADC for chemical systems with multiconfigurational electronic structure by calculating the K-edge XAS spectrum of the ozone molecule with a multireference character in its ground electronic state and the dissociation curve of core-excited molecular nitrogen. For ozone, the MR-ADC results agree well with the data from experimental and previous multireference studies of ozone XAS, in contrast to the results of single-reference methods, which underestimate relative peak energies and intensities. The MR-ADC methods also predict the correct shape of the core-excited nitrogen potential energy curve, and are in good agreement with accurate calculations using driven similarity renormalization group approaches. These findings suggest that MR-ADC(2) and MR-ADC(2)-X are promising methods for the XAS simulations of multireference systems and pave the way for their efficient computer implementation and applications.

Section: Discussionsupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: X-ray Absorption Spectrum Of Ozone Ozone (Omentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

See 2 more Smart Citations

Core-Excited States and X-ray Absorption Spectra from Multireference Algebraic Diagrammatic Construction Theory

Mazin

Sokolov

2023

“…Given the complexity and high number of final ionic states reached, OCA turns out to be adequate for an overall description of the spectral intensities in current spectra of complex molecules. 387,390,391 The computational steps to obtain ssDCH spectral intensities and AES/RAES decay rates in OpenMolcas are summarized in Figure 20. In both cases, the two-particle Dyson matrices corresponding to either the ssDCH intensities or to the Auger amplitudes are a key ingredient.…”

Section: Ionization and Autoionization Processesmentioning

confidence: 99%

The OpenMolcas Web: A Community-Driven Approach to Advancing Computational Chemistry

Manni

Galván

Alavi

et al. 2023

Self Cite

109

The developments of the open-source chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report offers an overview of the chemical phenomena and processes can address, while showing that is an attractive platform for state-of-the-art atomistic computer simulations.

Predicting the X-ray Absorption Spectrum of Ozone with Single Configuration State Functions

Hait,

Martínez

2024

X-ray absorption spectra (XAS) of biradicaloid species are often thought to represent a challenge to theoretical methods. This has led to the testing of recently developed multireference techniques on the XAS of ozone, but reproduction of the experimental spectral profile has proven difficult. We utilize a minimal model consisting of a single configuration state function (CSF) per excited state to model core-level excitations of ozone, with the orbitals of each CSF optimized using the restricted open-shell Kohn−Sham (ROKS) method. This protocol leads to semiquantitative agreement with experimental XAS. In fact, we find that low-lying core-hole excited states in biradicaloids can be approximated with individual CSFs, despite the presence of multireference character in the ground state. We also report that the 1s → π* and 1s → σ* transitions have quite distinct widths for O 3 . This reveals the importance of sampling over a representative range of geometries from the vibrational ground state for properly assessing the accuracy of electronic structure methods against experiments instead of the popular procedure of uniformly broadening stick spectra at the equilibrium geometry.