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Ogasawara, Kazuyoshi; Iwata, Takahiro; Koyama, Yukinori; Ishii, Toshinorí; Tanaka, Isao; Adachi, Hirohiko

doi:10.1103/physrevb.64.115413

Cited by 166 publications

(117 citation statements)

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“…5) Totally relativistic first principles molecular orbital calculations were made. Electronic correlations among 2p 1=2 , 2p 3=2 and 3d electrons were rigorously calculated by taking Slater determinants of all electronic configurations made by these molecular orbitals.…”

Section: Introductionmentioning

confidence: 99%

First Principles Calculation of Fe L2,3-edge X-ray Absorption Near Edge Structures of Iron Oxides

et al. 2004

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X-ray absorption near edge structure (XANES) at L 2;3 -edge of 3d transition elements is dominated by strong correlation effects among 2p core hole and 3d electrons. In the present study, we have performed systematic configuration interaction (CI) calculations in order to reproduce and interpret Fe-L 2;3 XANES of FeO, LaFeO 3 and SrFeO 3 . Relativistic four components wave functions were obtained by solving Dirac equations with density functional theory. CI calculations were made using the relativistic molecular orbitals instead of atomic orbitals, which enables inclusion of the O-2p orbital contributions through covalency. The oscillator strength of the electric dipole transition was then computed. Experimental XANES spectra of three compounds were satisfactorily reproduced by the theoretical spectra obtained for (FeO 6 ) mÀ clusters in octahedral symmetry. Chemical shifts between compounds were quantitatively reproduced as well. Component analysis of CI was systematically made in order to analyze the origin of differences in spectral shapes.

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Section: Introductionmentioning

confidence: 99%

First Principles Calculation of Fe L2,3-edge X-ray Absorption Near Edge Structures of Iron Oxides

et al. 2004

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“…We have calculated the electronic structure of CaGa 2 S 4 , in order to obtain the knowledge on electronic transitions up to 20 eV. Our result is based on the molecular orbital calculation by the relativistic DV-X method, the methodological details of which are described [11,12]. The [Ca 9 Ga 12 S 64 ] 74-molecule was chosen as a model cluster.…”

Section: Electronic Structure Of Caga 2 S 4 By the Dv-x Calculationmentioning

confidence: 99%

Excitation processes of trivalent cerium ions in calcium thiogallate crystals by hot photocarriers

Kitaura

Ohnishi

Sasaki

et al. 2010

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. Excitation spectra for the 5d → 4f emission of Ce 3+ ions in CaGa 2 S 4 crystals have been measured at 300 K by using vacuum ultraviolet (VUV) photons, together with reflectivity and absorption-edge spectra. X-ray photoelectron spectroscopy (XPS) experiment has also been performed in order to clarify the contribution of shallow core states to the excitation and reflectivity spectra. Furthermore, cluster calculation by a relativistic discrete variational X (DV-X method has been carried out to elucidate the optical transitions resulting in the creation of multiple e-h pairs in CaGa 2 S 4 . The excitation processes of Ce 3+ ions in CaGa 2 S 4 by hot photocarriers are discussed on the basis of the electronic structure determined from the experiments and calculation. IntroductionLuminescence properties of inorganic phosphors have been studied toward applications for flat panel display and solid-state lighting. Development of inorganic phosphor devices is achieved through continuous investigation of phosphor materials. Since fundamental researches were focused on ternary compounds such as II-III-VI group for the past 10 years [1], some bright phosphors were synthesized using alkaline-earth thiogallates and thioalminates as host materials. For example, Eu 2+ -activated BaAl 2 S 4 attracts attention as a high-luminance blue-emitting phosphor which satisfies requirements for full colour display [2]. Actually, a full colour flat panel display using this phosphor was demonstrated. Therefore, it is supposed that rare-earth-activated alkaline-earth thiogallates and thioalminates are key materials for the designing of inorganic phosphor devices.Investigations of emission and excitation processes are of great importance in phosphor materials. These processes have been well investigated in Ce 3+ -doped CaGa 2 S 4 by using ultraviolet (UV) and visible (VIS) light [3][4][5][6]. The absorption band of Ce 3+ ions locates at 2.92 eV below the fundamental absorption edge of host CaGa 2 S 4 . Two emission bands are observed at 2.65 and 2.40 eV under photoexcitation in the Ce 3+ absorption band, and are attributed to the electronic transitions from the 5d state to the 4f state in Ce 3+ ions. On the other hand, the emission and excitation processes of Ce 3+ ions have not yet been investigated under photoexcitation in the fundamental absorption region. These data are essentially required to know how hot conduction electrons interact with luminescence ions or host materials. Such information would be surely useful for understanding of electroluminescence (EL) and

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“…This non-statistical branching ratio can be found for a number of systems, and has been attributed to the delicate balance of between core-hole spin-orbit interaction and electron-hole exchange interaction. 18,[204][205][206][207] If only core-hole spin-orbit interactions are in effect, the branching ratio should be the statistical 2:1, but electron-hole exchange effects change the situation. This can be demonstrated by restricting the excitation channels in a relativistic calculation to only allow excitations from 2p 1/2 or 2p 3/2 , and the results of such a division is demonstrated in panel (d).…”

Section: Spin-orbit Effectsmentioning

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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Relativistic cluster calculation of ligand-field multiplet effects on cationL2,3x-ray-absorption edges ofSrTiO

Cited by 166 publications

References 15 publications

First Principles Calculation of Fe <i>L</i><SUB>2,3</SUB>-edge X-ray Absorption Near Edge Structures of Iron Oxides

First Principles Calculation of Fe <i>L</i><SUB>2,3</SUB>-edge X-ray Absorption Near Edge Structures of Iron Oxides

Excitation processes of trivalent cerium ions in calcium thiogallate crystals by hot photocarriers

X-ray spectroscopies through damped linear response theory

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