Communication: Application of state-specific multireference coupled cluster methods to core-level excitations

Brabec, Jiří; Bhaskaran‐Nair, Kiran; Govind, Niranjan; Pittner, Jiřı́; Kowalski, Karol

doi:10.1063/1.4764355

Cited by 48 publications

(52 citation statements)

References 42 publications

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“…The interest in accurate ab initio procedures to compute spectroscopic parameters related to X-ray absorption and ionization has significantly grown over the past five years, [1][2][3][4][5][6][7][8][9][10] concurrently with the advances on the experimental side, in particular the advent of third-generation synchrotron radiation sources for the measurement of high-quality X-ray absorption spectra, and the ongoing development of fourth-generation synchrotron facilities (e.g., free-electron lasers) and their perspective opportunities for novel experimental studies on the interaction of matter and X-ray radiation.…”

Section: Introductionmentioning

confidence: 99%

Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework

Coriani

Koch

2015

The Journal of Chemical Physics

217

328

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Accurate ab initio based multisheeted double many-body expansion potential energy surface for the three lowest electronic singlet states of The Journal of Chemical Physics 126, 074309 (2007); 10.1063/1.2566770Erratum: "Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework" [J. Chem. Phys. 143, 181103 (2015) Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework We present a simple scheme to compute X-ray absorption spectra (e.g., near-edge absorption fine structure) and core ionisation energies within coupled cluster linear response theory. The approach exploits the so-called core-valence separation to effectively reduce the excitation space to processes involving at least one core orbital, and it can be easily implemented within any pre-existing coupled cluster code for low energy states. We further develop a perturbation correction that incorporates the effect of the excluded part of the excitation space. The correction is shown to be highly accurate. Test results are presented for a set of molecular systems for which well converged results in full space could be generated at the coupled cluster singles and doubles level of theory only, but the scheme is straightforwardly generalizable to all members of the coupled cluster hierarchy of approximations, including CC3. C 2015 AIP Publishing LLC.[http://dx

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Section: Introductionmentioning

confidence: 99%

Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework

Coriani

Koch

2015

The Journal of Chemical Physics

217

328

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“…Other high level ab initio methods such as the equation of motion coupled cluster (EOM-CC) method, 38 the symmetry-adapted-cluster configuration interaction (SAC-CI) method, [39][40][41][42][43] and multireference coupled cluster approaches 44 have also been applied to study core excited states. They are very accurate (error less than 0.1 eV) but their computational scaling is not favorable.…”

Section: Introductionmentioning

confidence: 99%

Core and valence excitations in resonant X-ray spectroscopy using restricted excitation window time-dependent density functional theory

Zhang

Biggs

Healion

et al. 2012

The Journal of Chemical Physics

Self Cite

107

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We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen, and sulfur K and L 2,3 edges. Comparison of the simulated XANES signals with experiment shows that the restricted window time-dependent density functional theory is more accurate and computationally less expensive than the static exchange method. Simulated RIXS and 1D SXRS signals give some insights into the correlation of different excitations in the molecule.

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“…In contrast to CI, the extension of the CC idea to the MR case is nontrivial due to the problem with definition of a proper vacuum state leading to a number of technical complications, for review see Reference . However, various flavors of MR CC have been applied to core spectra of small main group molecules recently …”

Section: Theoretical Methodsmentioning

confidence: 99%

Theoretical X‐ray spectroscopy of transition metal compounds

Bokarev

Kühn

2019

WIREs Comput Mol Sci

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X-ray spectroscopy is one of the most powerful tools to access structure and properties of matter in different states of aggregation as it allows to trace atomic and molecular energy levels in course of various physical and chemical processes. Xray spectroscopic techniques probe the local electronic structure of a particular atom in its environment, in contrast to ultraviolet/visible (UV/Vis) spectroscopy, where transitions generally occur between delocalized molecular orbitals. Complementary information is provided by using a combination of different absorption, emission, scattering as well as photo-and autoionization X-ray methods. However, interpretation of the complex experimental spectra and verification of experimental hypotheses is a nontrivial task and powerful first principles theoretical approaches that allow for a systematic investigation of a broad class of systems are needed. Focusing on transition metal compounds, L-edge spectra are of particular relevance as they probe the frontier d-orbitals involved in metal-ligand bonding. Here, neardegeneracy effects in combination with spin-orbit coupling lead to a complicated multiplet energy level structure, which poses a serious challenge to quantum chemical methods. Multiconfigurational self-consistent field (MCSCF) theory has been shown to be capable of providing a rather detailed understanding of experimental X-ray spectroscopy. However, it cannot be considered as a "blackbox" tool and its application requires not only a command of formal theoretical aspects, but also a broad knowledge of already existing applications. Both aspects are covered in this overview.

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Communication: Application of state-specific multireference coupled cluster methods to core-level excitations

Cited by 48 publications

References 42 publications

Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework

Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework

Core and valence excitations in resonant X-ray spectroscopy using restricted excitation window time-dependent density functional theory

Theoretical X‐ray spectroscopy of transition metal compounds

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