Structure and optical properties of - and -cerium sesquisulfide

Windiks, René; Wimmer, E.; Pourovskii, L. V.; Biermann, Silke; Georges, Antoine

doi:10.1016/j.jallcom.2007.04.306

Cited by 17 publications

(7 citation statements)

References 47 publications

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“…However, more frequently U eff is chosen in such a way as to reproduce with reasonable accuracy an experimentally measured quantity like cell volume, bulk modulus, etc. 24,31,55 We are not aware of any prior publication related to LDA+U type calculations for Ce-doped insulators of the type used for scintillator detectors. Fortunately, experimental measurements of Ce 4f -VBM gap are known for a few scintillators so we chose the U eff parameter to closely match these known gaps.…”

Section: Resultsmentioning

confidence: 99%

First-principles study of luminescence in Ce-doped inorganic scintillators

et al. 2011

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Luminescence in Ce doped materials corresponds to a transition from an excited state where the lowest Ce 5d level is filled (often called the (Ce 3+ ) * state) to the ground state where a single 4f level is filled. We have performed theoretical calculations based on Density Functional Theory to calculate the ground state band structure of Ce-doped materials as well as the (Ce 3+ ) * excited state. The excited state calculations used a constrained occupancy approach by setting the occupation of the Ce 4f states to zero and allowing the first excited state above them to be filled. These calculations were performed on a set of Ce doped materials that are known from experiment to be scintillators or non-scintillators to relate theoretically calculable parameters to measured scintillator performance. From these studies we developed a set of criteria based on calculated parameters that are necessary characteristics for bright Ce activated scintillators. Applying these criteria to about a hundred new materials we developed a list of candidate materials for new bright Ce activated scintillators. After synthesis in powder form one of these new materials (Ba2YCl7:Ce) was found to be a bright scintillator. This approach, involving first-principles calculations of modest computing requirements was designed as a systematic, high-throughput method to aid in the discovery of new bright scintillator materials by prioritization and down-selection on the large number of potential new materials.

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Section: Resultsmentioning

confidence: 99%

First-principles study of luminescence in Ce-doped inorganic scintillators

et al. 2011

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“…This problem can be solved within the LDA + DMFT (dynamical mean-field theory) [10,11] and the Hubbard-I approximation [11,12]. There were several attempts to calculate the optical properties within the LDA + DMFT using the Kubo formula for optical conductivity [13][14][15]. However, in all these calculations the vertex contributions were not taken into account and the two-particle Green functions were calculated as a convolution of two single-particle Green functions (for a review of the LDA + DMFT see [16]).…”

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confidence: 99%

Theory of optically forbidden d–d transitions in strongly correlated crystals

Katsnelson¹,

Lichtenstein²

2010

J. Phys.: Condens. Matter

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A general multiband formulation of the linear and nonlinear optical response functions for realistic models of correlated crystals is presented. Dipole-forbidden d-d optical transitions originate from vertex functions, which we consider assuming the locality of an irreducible four-leg vertex. The unified formulation for second- and third-order response functions in terms of the three-leg vertex is suitable for practical calculations in solids. We illustrate the general approach by consideration of intra-atomic spin-flip contributions, with an energy of 2J, where J is a Hund exchange, in the simplest two-orbital model.

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“…Similarly to many other Ce-based semiconductors (for example, the sesquioxide Ce 2 O 3 [24], or the sesquisulfide Ce 2 S 3 [25][26][27]) the absorption edge in CeSF has been previously ascribed to the Ce intra-atomic 4f to 5d transitions [5]. We will call this the "f-d scenario", in contrast to the true "p-f" scenario established by our GW calculations for CeSF (see above).…”

Section: F-d Intra-atomic Scenario For the Absorption Edge In Cesf: E...mentioning

confidence: 68%

“…Other parameters entering in Eqs. (26,27) were chosen as follows: ∆=2.1 eV, n ≈ 2 was obtained from the full complex optical conductivity of CeSF, the average Fermi velocity can be estimated to be v = V pf • δ Ce−S ∼ 0.3 eV Å, where δ Ce−S ≈ 3 Å is the distance between next-nearest Ce and S sites in CeSF, and V pf is a hybridization matrix element between the involved orbitals.…”

Section: Interband Absorption In Two-band Modelmentioning

confidence: 99%

Rare-earth vs. heavy metal pigments and their colors from first principles

Tomczak

Pourovskii

Vaugier

et al. 2013

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

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Many inorganic pigments contain heavy metals hazardous to health and environment. Much attention has been devoted to the quest for nontoxic alternatives based on rare-earth elements. However, the computation of colors from first principles is a challenge to electronic structure methods, especially for materials with localized f-orbitals. Here, starting from atomic positions only, we compute the colors of the red pigment cerium fluorosulfide as well as mercury sulfide (classic vermilion). Our methodology uses many-body theories to compute the optical absorption combined with an intermediate length-scale modelization to assess how coloration depends on film thickness, pigment concentration, and granularity. We introduce a quantitative criterion for the performance of a pigment. While for mercury sulfide, this criterion is satisfied because of large transition matrix elements between wide bands, cerium fluorosulfide presents an alternative paradigm: the bright red color is shown to stem from the combined effect of the quasi-2D and the localized nature of 4f states. Our work shows the power of modern computational methods, with implications for the theoretical design of materials with specific optical properties.functional materials | strongly correlated electrons | Mott insulator | dynamical mean field theory L ight propagating inside a heterogeneous solid experiences (i) absorption and (ii) scattering. The light that is not absorbed is diffusely reflected and responsible for the perceived color. The visual appearance of a material is, hence, determined by selective absorption of light and sufficient (back)scattering. For a material to be, e.g., a luminous red pigment, two criteria must, thus, be satisfied. First, its absorption edge should be located at the appropriate energy (∼2.1 eV) so that the red component of the visible spectrum is not absorbed. Second, the absorption edge should be sharp so that most other photons within the visible range (green and blue) are absorbed.The computation of these effects from first principles is faced with three fundamental difficulties. First, in view of the sensitivity of the human eye, the optical gap must be obtained with a precision of at least 100 meV. Conventional electronic structure methods yield a well-documented underestimation of the gap of conventional semiconductors. Second, the localized 4f states, which play a crucial role in optical properties of rare earth-based pigments (1-3), are poorly described by standard density-functional theory (4) or even GW approaches (5). Third, a realistic assessment of the coloration of a pigment must take into account scattering properties depending on concentration, granularity, and film thickness. Ab initio simulations so far have not ventured beyond calculating the optical conductivity of infinite bulk samples (refs. 6 and 7 discuss organic molecules). In this article, we address all these issues and develop a general methodology for the prediction of the color of narrow-band materials.We investigate cerium fluorosulfide (CeSF...

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Structure and optical properties of - and -cerium sesquisulfide

Cited by 17 publications

References 47 publications

First-principles study of luminescence in Ce-doped inorganic scintillators

First-principles study of luminescence in Ce-doped inorganic scintillators

Theory of optically forbidden d–d transitions in strongly correlated crystals

Rare-earth vs. heavy metal pigments and their colors from first principles

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