Electronic structure of GaInN semiconductors investigated by x-ray absorption spectroscopy

Guo, Qi; Senda, H.; Saito, Katsuhiko; Tanaka, Tooru; Nishio, Mitsuhiro; Ding, Junjie; Fan, Tongxiang; Zhang, D.; Wang, Xinqiang; Liu, S. T.; Shen, Bo; Ohtani, Ryota

doi:10.1063/1.3583461

Cited by 18 publications

(16 citation statements)

References 21 publications

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Section: Introductionmentioning

confidence: 99%

“…NEXAS has been successfully applied to large biological systems, 2 small molecules in the gas phase, 3 organic thin-films, 4 and semiconducting materials. 5 This wide range of applications is possible because synchrotron light sources can span an energy range that goes from a few electron volt (eV) 6 to hundreds of MeV. 7 As NEXAS experiments are becoming more feasible, there is a growing need to develop accurate theoretical approaches to aid the interpretation of experimental spectra.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of X-ray absorption spectra with orthogonality constrained density functional theory

Derricotte

Evangelista

2015

Phys. Chem. Chem. Phys.

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Orthogonality constrained density functional theory (OCDFT) is a variational time-independent approach for the computation of electronic excited states. In this work we extend OCDFT to compute core-excited states and generalize the original formalism to determine multiple excited states. Benchmark computations on a set of 13 small molecules and 40 excited states show that unshifted OCDFT/B3LYP excitation energies have a mean absolute error of 1.0 eV. Contrary to time-dependent DFT, OCDFT excitation energies for first- and second-row elements are computed with near-uniform accuracy. OCDFT core excitation energies are insensitive to the choice of the functional and the amount of Hartree–Fock exchange. We show that OCDFT is a powerful tool for the assignment of X-ray absorption spectra of large molecules by simulating the gas-phase near-edge spectrum of adenine and thymine.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulation of X-ray absorption spectra with orthogonality constrained density functional theory

Derricotte

Evangelista

2015

Phys. Chem. Chem. Phys.

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“…X-ray spectroscopy [1][2][3] is a powerful spectroscopic tool for the elucidation of structural and electronic properties of materials [4][5][6] and (bio-)molecular systems [7][8][9]. X-ray absorption spectroscopy (XAS) probes the excitation of core electrons.…”

Section: Introductionmentioning

confidence: 99%

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

Bernadotte

Atkins

Jacob

2012

The Journal of Chemical Physics

147

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For electronic excitations in the ultraviolet and visible range of the electromagnetic spectrum, the intensities are usually calculated within the dipole approximation, which assumes that the oscillating electric field is constant over the length scale of the transition. For the short wavelengths used in hard X-ray spectroscopy, the dipole approximation may not be adequate. In particular, for metal K-edge X-ray absorption spectroscopy (XAS), it becomes necessary to include higher-order contributions. In quantum-chemical approaches to X-ray spectroscopy, these socalled quadrupole intensities have so far been calculated by including contributions depending on the square of the electric-quadrupole and magnetic-dipole transition moments. However, the resulting quadrupole intensities depend on the choice of the origin of the coordinate system. Here, we show that for obtaining an originindependent theory, one has to include all contributions that are of the same order in the wave vector consistently. This leads to two additional contributions depending on products of the electric-dipole andelectric-octupole and of the electric-dipole and magnetic-quadrupole transition moments, respectively. We have implemented such an origin-independent calculation of quadrupole intensities in XAS within timedependent density-functional theory, and demonstrate its usefulness for the calculation of metal and ligand K-edge XAS spectra of transition metal complexes.2

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“…Recent advances in experimental techniques for generating and detecting X-ray radiation have spurred the development of NEXAS and its applications in chemistry and biology. [1][2][3][4][5][6][7] Theoretical simulations of X-ray absorption play a critical role in interpretation of the NEXAS spectra. 8 However, computations of the core-level excitations are very challenging as they require simulating excited states selectively in the high-energy spectral region and a balanced treatment of electron correlation, orbital relaxation, and relativistic effects, often combined with large uncontracted basis sets.…”

Section: Introductionmentioning

confidence: 99%

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

2019

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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]

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Electronic structure of GaInN semiconductors investigated by x-ray absorption spectroscopy

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Cited by 18 publications

References 21 publications

Simulation of X-ray absorption spectra with orthogonality constrained density functional theory

Simulation of X-ray absorption spectra with orthogonality constrained density functional theory

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

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

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