First-principles XANES simulation for oxygen-related defects in Si-O amorphous materials

Katayama, Wataru; Tamura, Tomoyuki; Nishino, Yuya; Hirose, Takakazu

doi:10.1016/j.commatsci.2021.110555

Cited by 4 publications

(2 citation statements)

References 23 publications

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“…The variable O-K edge and intense ~532 eV peak can also be related to potential reactions during solar wind irradiation and heating. Simulations of amorphous and crystalline SiO 2 have demonstrated that oxygen-excess defects produce a pre-edge peak at ~532 eV 49 , as seen in this apatite grain. Molecular O 2 has a similar pre-peak and has been identified in vesicles in an interplanetary dust particle 47 , although the O or O 2 here is not confined to the vesicles.…”

Section: Discussionmentioning

confidence: 68%

Hydrogen-bearing vesicles in space weathered lunar calcium-phosphates

Burgess,

Cymes,

Stroud

2023

Commun Earth Environ

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Water on the surface of the Moon is a potentially vital resource for future lunar bases and longer-range space exploration. Effective use of the resource depends on developing an understanding of where and how within the regolith the water is formed and retained. Solar wind hydrogen, which can form molecular hydrogen, water and/or hydroxyl on the lunar surface, reacts and is retained differently depending on regolith mineral content, thermal history, and other variables. Here we present transmission electron microscopy analyses of Apollo lunar soil 79221 that reveal solar-wind hydrogen concentrated in vesicles as molecular hydrogen in the calcium-phosphates apatite and merrillite. The location of the vesicles in the space weathered grain rims offers a clear link between the vesicle contents and solar wind irradiation, as well as individual grain thermal histories. Hydrogen stored in grain rims is a source for volatiles released in the exosphere during impacts.

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Section: Discussionmentioning

confidence: 68%

Hydrogen-bearing vesicles in space weathered lunar calcium-phosphates

Burgess,

Cymes,

Stroud

2023

Commun Earth Environ

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“…The O1 site coordinating with two Si atoms connects two SiO 4 tetrahedrons, and the distances to the nearest Yb atoms are larger than 3.5 Å. Despite the large Yb-O distances, the hybridization effects with Yb orbitals may persist since the spectral shape is largely different from those of SiO 2 and Si-O amorphous[49]. The K-edge spectra of O2…”

mentioning

confidence: 99%

Oxygen K-edge spectra of Yb2O 3 polymorphs, Yb2SiO5, and Yb2Si2O7: First-principles simulations and EELS measurements

Ogawa

Miao

Bao

et al. 2022

Preprint

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First-principles calculations, along with a core-hole technique, are adopted to simulate oxygen K-edge spectra for three polymorphs of Yb2O3 and two types of ytterbium silicates (i.e., Yb2SiO5 and Yb2Si2O7). The twe Yb silicates are compared with experimental spectra, which are measured via electron energy-loss spectroscopy for a polycrystalline sample including both phases. The simulated O K-edge spectra of cubic, monoclinic, and hexagonal Yb2O3 exhibit characteristic twin peaks, which resulted from crystal fi eld splitting of unoccupied Yb5 d orbitals in Yb-O polyhedra. Spacing between the two peaks refl ects a degree of distortion of the polyhedra and local coordination environments around O atoms. The simulated and experimental O K-edge spectra of Yb2SiO5 and Yb2Si2O7 also show twin peaks, where lower-energy peaks are signifi cantly reduced compared to those of Yb2O3. A small diff erence in the lower-energy peaks, which refl ect the local environments of O atoms, enables us to identify Yb silicate phases from an O K-edge spectrum. The derived insights could be widely extended to rare-earth oxides.

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