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

Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

doi:10.1063/1.4766356

Cited by 91 publications

(109 citation statements)

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“…also been presented in recent years. [25][26][27] To the best of our knowledge, this is the first study exploring the applicability of the CVS approximation at the CC level of theory. We note nonetheless a very recent study by Peng et al 9 where an alternative, and much more elaborate, approach to target core excitation energies within the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) ansatz is presented.…”

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

227

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

227

328

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“…We adopt the computational protocol in ref. 55. All REW-TDDFT calculations were performed with a locally modified version of NWChem code (56) at the CAM-B3LYP (57)/6-311G** level of theory and within the Tamm-Dancoff approximation (58).…”

Section: Methodsmentioning

confidence: 99%

Watching energy transfer in metalloporphyrin heterodimers using stimulated X-ray Raman spectroscopy

Biggs

Zhang

Healion

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the excitation energy transfer mechanism in multiporphyrin arrays is key for designing artificial light-harvesting devices and other molecular electronics applications. Simulations of the stimulated X-ray Raman spectroscopy signals of a Zn/Ni porphyrin heterodimer induced by attosecond X-ray pulses show that these signals can directly reveal electron-hole pair motions. These dynamics are visualized by a natural orbital decomposition of the valence electron wavepackets.chromophore aggregates | core transitions | REW-TDDFT | nonlinear P orphyrin rings are pyrole-based cyclic conjugated systems that serve as the main building blocks in many devices that depend on their high excitation energy transfer (EET) efficiency (1-4). Because of their stability and interesting structural, electronic, and optical properties, porphyrin compounds have a wide range of uses as chemical sensors (5), photosensitizers in photodynamic therapy for cancer (6), nonlinear optical materials (7-9), and molecular electronic (10-12) and spintronic devices (13,14).Porphyrin-based molecules hold a pivotal position in the chemistry of engineered photoactive organic compounds, and extensive electronic structure calculations of monomeric (15) and oligomeric (16, 17) porphyrin molecules, porphyrin structures in biomacromolecules (18,19), and quasi-1D and -2D porphyrin systems with infinite sizes have been carried out (13,14,(20)(21)(22)(23). Most applications involve multiporphyrin arrays, either in linear or in cyclic shape, or dendrimers (24). Porphyrin dimers, which are still small enough to be treated with relatively high-level modern quantum chemistry methods, can offer basic clues to track down the more complicated EET dynamics in multiporphyrin arrays.The kinetics of EET in multiporphyrin systems have long been studied by time-resolved fluorescence anisotropy decay (25) and pump-probe techniques, using visible light (26).Here we present a simulation study that shows how recently developed attosecond sources of X-ray pulses may be used to probe the energy transfer dynamics in a porphyrin dimer. Intense attosecond X-ray pulses, recently made available by new X-ray free electron laser (XFEL) (27, 28) and higher harmonic generation (29, 30) sources, have bandwidths covering multiple electron volts and can prepare coherent superpositions of valence electronically excited states through an impulsive Raman process (31). The short durations of these pulses make them ideal for tracing valence electronic dynamics that evolve with extremely short periods. X-ray pulses can also exploit the spectrally isolated coreexcitation frequencies to create valence excitations in the neighborhood of a selected atom, a type of localized excitation not generally accessible using visible or UV pulses. An experimental realization of a two-color pump-probe X-ray source from XFEL radiation was recently reported (32). These new sources have also been used in time-dependent X-ray diffraction studies (33), to monitor ultrafast changes in the conductivity of se...

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“…Inserting the functional of the system of non-interacting particles in the energy functional 32) which is the total electronic energy to be calculated. Applying the variational…”

Section: Density Functional Theory 25mentioning

confidence: 99%

X-ray spectroscopies through damped linear response theory

Fransson¹

2016

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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...

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

Cited by 91 publications

References 93 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

Watching energy transfer in metalloporphyrin heterodimers using stimulated X-ray Raman spectroscopy

X-ray spectroscopies through damped linear response theory

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