Dataset Information

Local vs Nonlocal States in FeTiO₃ Probed with 1s2pRIXS: Implications for Photochemistry.

ABSTRACT: Metal-metal charge transfer (MMCT) is expected to be the main mechanism that enables the harvesting of solar light by iron-titanium oxides for photocatalysis. We have studied FeTiO₃ as a model compound for MMCT with 1s2pRIXS at the Fe K-edge. The high-energy resolution XANES enables distinguishing five pre-edge features. The three first well distinct RIXS features are assigned to electric quadrupole transitions to the localized Fe* 3d states, shifted to lower energy by the 1s core-hole. Crystal field multiplet calculations confirm the speciation of divalent iron. The contribution of electric dipole absorption due to local p-d mixing allowed by the trigonal distortion of the cation site is supported by DFT and CFM calculations. The two other nonlocal features are assigned to electric dipole transitions to excited Fe* 4p states mixed with the neighboring Ti 3d states. The comparison with DFT calculations demonstrates that MMCT in ilmenite is favored by the hybridization between the Fe 4p and delocalized Ti 3d orbitals via the O 2p orbitals.

SUBMITTER: Hunault MOJY

PROVIDER: S-EPMC5636175 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Publications

Local vs Nonlocal States in FeTiO<sub>3</sub> Probed with 1s2pRIXS: Implications for Photochemistry.

Hunault Myrtille O J Y MOJY Khan Wilayat W Minár Jan J Kroll Thomas T Sokaras Dimosthenis D Zimmermann Patric P Delgado-Jaime Mario U MU de Groot Frank M F FMF

Inorganic chemistry 20170905 18

Metal-metal charge transfer (MMCT) is expected to be the main mechanism that enables the harvesting of solar light by iron-titanium oxides for photocatalysis. We have studied FeTiO<sub>3</sub> as a model compound for MMCT with 1s2pRIXS at the Fe K-edge. The high-energy resolution XANES enables distinguishing five pre-edge features. The three first well distinct RIXS features are assigned to electric quadrupole transitions to the localized Fe* 3d states, shifted to lower energy by the 1s core-hol ...[more]

PMID: 28872322

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Project description:BackgroundMultienergy computed tomography (MECT) is a promising imaging modality for material decomposition, lesion detection, and other clinical applications. However, there is an urgent need to design efficient and accurate algorithms to solve the inverse problems related to spectral reconstruction and improve image quality, especially under low-dose and incomplete datasets. The key issue for MECT reconstruction is how to efficiently describe the interchannel and intrachannel priors in multichannel images.MethodsIn this model, in order to correlate the similarities of interchannel images and regularize the multichannel images, the global, local, and nonlocal priors are jointly integrated into the low-dose MECT reconstruction model. First, the subspace decomposition method first employs the global low-rankness to map the original MECT images to the low-dimensional eigenimages. Then, nonlocal self-similarity of the eigenimages is cascaded into the optimization model. Additionally, the L0 quasi-norm on gradient images is incorporated into the proposed method to further enhance the local sparsity of intrachannel images. The alternating direction method is applied to solve the optimization model in an iterative scheme.ResultsSimulation, preclinical, and real datasets were applied to validate the effectiveness of the proposed method. From the simulation dataset, the new method was found to reduce the root-mean-square error (RMSE) by 42.31% compared with the latest research fourth-order nonlocal tensor decomposition MECT reconstruction (FONT-SIR) method under 160 projection views. The calculation time of an iteration for the proposed method was 23.07% of the FONT-SIR method. The results of material decomposition in real mouse data further confirmed the accuracy of the proposed method for different materials.ConclusionsWe developed a method in which the global, local, and nonlocal priors are jointly used to develop the reconstruction model for low-dose MECT, where the global low-rankness and nonlocal prior are cascaded by subspace decomposition and block-matching, and the L0 sparsity is applied to express the local prior. The results of the experiments demonstrate that the proposed method based on subspace improves computational efficiency and has advantages in noise suppression and structure preservation over competing algorithms.

Dataset Information

Local vs Nonlocal States in FeTiO₃ Probed with 1s2pRIXS: Implications for Photochemistry.

Publications

Local vs Nonlocal States in FeTiO<sub>3</sub> Probed with 1s2pRIXS: Implications for Photochemistry.

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Local vs Nonlocal States in FeTiO3 Probed with 1s2pRIXS: Implications for Photochemistry.

Publications

Local vs Nonlocal States in FeTiO<sub>3</sub> Probed with 1s2pRIXS: Implications for Photochemistry.

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OmicsDI is part of the ELIXIR infrastructure

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Local vs Nonlocal States in FeTiO₃ Probed with 1s2pRIXS: Implications for Photochemistry.