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

Coriani, Sonia; Koch, Henrik

doi:10.1063/1.4935712

Cited by 219 publications

(350 citation statements)

References 38 publications

Supporting

Mentioning

341

Contrasting

Order By: Relevance

“…Therefore, we expect a negligibly weak time-resolved (TR) NEXAFS signature from the photoexcited ππ* state to transform into a strong nπ* state signature as the molecule undergoes ππ*/nπ* internal conversion, largely independent of geometry changes during the dynamics. For the isolated molecules used in this study, computationally demanding high level coupled cluster (CC) simulations (16)(17)(18) are now feasible and confirm the spectroscopic attribution based on orbital localization. and electron density projections onto the molecular plane for the three valence orbitals (Hartree-Fock/6-311G) involved in the characters of the two lowest lying excited states of thymine and a core orbital localized at oxygen (8).…”

supporting

confidence: 53%

Probing ultrafast ππ/nπ internal conversion in organic chromophores via K-edge resonant absorption

et al. 2017

View full text Add to dashboard Cite

Many photoinduced processes including photosynthesis and human vision happen in organic molecules and involve coupled femtosecond dynamics of nuclei and electrons. Organic molecules with heteroatoms often possess an important excited-state relaxation channel from an optically allowed ππ* to a dark nπ* state. The ππ*/nπ* internal conversion is difficult to investigate, as most spectroscopic methods are not exclusively sensitive to changes in the excited-state electronic structure. Here, we report achieving the required sensitivity by exploiting the element and site specificity of near-edge soft X-ray absorption spectroscopy. As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrum at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ*/nπ* internal conversion takes place within (60 ± 30) fs. High-level-coupled cluster calculations confirm the method’s impressive electronic structure sensitivity for excited-state investigations.

show abstract

supporting

confidence: 53%

Probing ultrafast ππ/nπ internal conversion in organic chromophores via K-edge resonant absorption

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Table 2 shows the CVS-ODC-12 results for 36 core-level transitions of 10 molecules. For comparison, we also show best available theoretical results obtained from various formulations of coupled cluster theory, 34,39,41,43,44 as well as excitation energies measured in the experiment. [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102] For all electronic transitions, the CVS-ODC-12 method correctly reproduces the order of peaks observed in the experimental spectra with transitions shifted to higher energies.…”

Section: Excitations Energiesmentioning

confidence: 99%

“…Many of the popular excited-state methods have been adopted for simulations of X-ray absorption spectra, including linearresponse, [9][10][11][12][13][14] real-time, [15][16][17] and orthogonalityconstrained 18,19 density functional theory, configuration interaction, [20][21][22][23][24][25] algebraic diagram-matic construction (ADC), 5,[26][27][28][29][30] as well as linear-response (LR-) and equation-of-motion (EOM-) coupled cluster (CC) theories. [31][32][33][34][35][36][37][38][39][40][41][42][43][44] Among these approaches, CC methods have been shown to yield particularly accurate results for core excitation energies and intensities of small molecules.…”

Section: Introductionmentioning

confidence: 99%

Simulating X-ray Absorption Spectra with Linear-Response Density Cumulant Theory

2019

View full text Add to dashboard Cite

We present a new approach for simulating Xray absorption spectra based on linear-response density cumulant theory (LR-DCT) [Copan, A. V.; Sokolov, A. Yu. J. Chem. Theory Comput., 2018, 14, 4097-4108]. Our new method combines the LR-ODC-12 formulation of LR-DCT with core-valence separation approximation (CVS) that allows to efficiently access high-energy core-excited states. We describe our computer implementation of the CVS-approximated LR-ODC-12 method (CVS-ODC-12) and benchmark its performance by comparing simulated X-ray absorption spectra to those obtained from experiment for several small molecules. Our results demonstrate that the CVS-ODC-12 method shows a good agreement with experiment for relative spacings between transitions and their intensities, but the excitation energies are systematically overestimated. When comparing to results from excited-state coupled cluster methods with single and double excitations, the CVS-ODC-12 method shows a similar performance for intensities and peak separations, while coupled cluster spectra are less shifted, relative to experiment. An important advantage of CVS-ODC-12 is that its excitation energies are computed by diagonalizing a Hermitian matrix, which enables efficient computation of transition intensities. arXiv:1812.08827v2 [physics.chem-ph]

show abstract

“…The latter can be obtained by calculating the excitation energy for transitions to a very diffuse state, approximating excitations to the continuum. 156,192 However, for single-determinant electronic structure methods, no relaxation effects are obtained. This is as a single electron can be excited, but no electron can simultaneously be relaxed -by comparison, including doubles in the coupled cluster manifold a simultaneous excitation and relaxation can occur, as will be described later.…”

Section: Ionization Potentials Along the Periodic Tablementioning

confidence: 99%

“…Since the development of the damped linear response function in CC, [I,II] it has been further developed to include environmental effects through polarizable embedding, 155 use a core-valence separation approach, 156 calculate the spectrum using a complex solver, 157 as well as used to calculated chemical shifts, [III] consider the spectrum of water [IV] and noble gases, 158 as well as modeling photoionization 159 and photodetachment 160 cross sections.…”

Section: Molecular Response Theorymentioning

confidence: 99%

X-ray spectroscopies through damped linear response theory

Fransson¹

2016

View full text Add to dashboard Cite

In order to reach a fundamental understanding of interactions between electromagnetic radiation and molecular materials, experimental measurements need to be supplemented with theoretical models and simulations. With the use of this combination, it is possible to characterize materials in terms of, e.g., chemical composition and molecular structure, as well as achieve time-resolution in studies of chemical reactions. This doctoral thesis focuses on the development and evaluation of theoretical methods with which, amongst others, X-ray absorption and X-ray emission spectroscopies can be interpreted and predicted. In X-ray absorption spectroscopy the photon energy is tuned such that core electrons are targeted and excited to either bound or continuum states, and X-ray emission spectroscopy measures the subsequent decay from such an excited state. These core excitations/de-excitations exhibit strong relaxation effects, making theoretical considerations of the processes particularly challenging. While the removal of a valence electron leaves the remaining electrons relatively unaffected, removing core electrons has a substantial effect on the other electrons due to the significant change in the screening of the nucleus. Additionally, the core-excited states are embedded in a manifold of valence-excited states that needs to be considered by some computationally feasible method. In this thesis, a damped formalism of linear response theory, which is a perturbative manner of considering the interactions of (weak) external or internal fields with molecular systems, has been utilized to investigate mainly the X-ray absorption spectra of small-to medium-sized molecular systems.Amongst the standard quantum chemical methods available, coupled cluster is perhaps the most accurate, with a well-defined, hierarchical manner of approaching the correct electronic wave function. Combined with response theory, it provides a reliable theoretical method in which relaxation effects are addressed by means of an accurate treatment of electron correlation. The first part of this thesis deals with the development and evaluation of such an approach, and it is shown that the relaxation effects can be addressed by the inclusion of double excitations in the coupled cluster manifold. However, these calculations are computationally very demanding, and in order to treat larger systems the performance of the coupled cluster approach has been compared to that of the less demanding method of timedensity dependent functional theory (TDDFT). Both methods have been used to v vi investigate the X-ray absorption spectrum of water, which has been extensively debated in the scientific community following a relatively recent hypothesis concerning the underlying structure of liquid water. Water exhibits a great number of anomalous properties that stand out from those of most compounds, and the importance of reaching a fundamental understanding of this substance cannot be overstated. It has been demonstrated that TDDFT yields excellent results for liq...

show abstract

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

Cited by 219 publications

References 38 publications

Probing ultrafast ππ/nπ internal conversion in organic chromophores via K-edge resonant absorption

Probing ultrafast ππ/nπ internal conversion in organic chromophores via K-edge resonant absorption

Simulating X-ray Absorption Spectra with Linear-Response Density Cumulant Theory

X-ray spectroscopies through damped linear response theory

Contact Info

Product

Resources

About

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

Cited by 219 publications

References 38 publications

Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

Simulating X-ray Absorption Spectra with Linear-Response Density Cumulant Theory

X-ray spectroscopies through damped linear response theory

Contact Info

Product

Resources

About

Probing ultrafast ππ/nπ internal conversion in organic chromophores via K-edge resonant absorption

Probing ultrafast ππ/nπ internal conversion in organic chromophores via K-edge resonant absorption