skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Extended vs. Local Structure in Sb-Pyrochlores: An Illustration of the Valuable Interplay between Crystallography and XAFS

Abstract

The convergence between extended structure provided by X-ray diffraction and local structure of antimony extracted from spectroscopic data is reached through an alternative crystallographic description for a Sb-pyrochlore arrangement within the same space group symmetry of pyrochlore structure-type. A full account on this description is presented, along with a calculated diffraction pattern matching experimental data and conforming to Sb 1s XANES data.

Authors:
 [1]
  1. Crystallography and Mineralogy Center, IICT / INETI, and CENIMAT, Department of Materials Science, Faculty of Sciences and Technology, Nova University of Lisbon, Quinta da Torre, 2829-516 Caparica (Portugal)
Publication Date:
OSTI Identifier:
21054595
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644475; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ANTIMONY; CONVERGENCE; CRYSTAL STRUCTURE; CRYSTALS; FINE STRUCTURE; PYROCHLORE; SYMMETRY; X-RAY DIFFRACTION; X-RAY SPECTRA; X-RAY SPECTROSCOPY

Citation Formats

Figueiredo, Maria-Ondina. Extended vs. Local Structure in Sb-Pyrochlores: An Illustration of the Valuable Interplay between Crystallography and XAFS. United States: N. p., 2007. Web. doi:10.1063/1.2644475.
Figueiredo, Maria-Ondina. Extended vs. Local Structure in Sb-Pyrochlores: An Illustration of the Valuable Interplay between Crystallography and XAFS. United States. doi:10.1063/1.2644475.
Figueiredo, Maria-Ondina. Fri . "Extended vs. Local Structure in Sb-Pyrochlores: An Illustration of the Valuable Interplay between Crystallography and XAFS". United States. doi:10.1063/1.2644475.
@article{osti_21054595,
title = {Extended vs. Local Structure in Sb-Pyrochlores: An Illustration of the Valuable Interplay between Crystallography and XAFS},
author = {Figueiredo, Maria-Ondina},
abstractNote = {The convergence between extended structure provided by X-ray diffraction and local structure of antimony extracted from spectroscopic data is reached through an alternative crystallographic description for a Sb-pyrochlore arrangement within the same space group symmetry of pyrochlore structure-type. A full account on this description is presented, along with a calculated diffraction pattern matching experimental data and conforming to Sb 1s XANES data.},
doi = {10.1063/1.2644475},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • The combined techniques of surface extended x-ray-absorption fine structure (SEXAFS) and high-resolution core and valence photoelectron spectroscopy have been used to study the local bonding structure of the Sb/Si(111) interface. From photoemission, we find that the Sb atoms adsorb in a unique environment that completely saturates the dangling bonds of the Si(111) surface and that completely eliminates the surface components of the Si 2{ital p} core-level spectrum. The Sb-induced Si 2{ital p} interfacial core level is found to be shifted 0.20{plus minus}0.02 eV towards higher binding energy with an intensity that corresponds to the top monolayer of surface atoms. Themore » SEXAFS determination of the absolute surface coordination numbers and bond lengths within the first Sb shell is 2.1{plus minus}0.3 Sb atoms at 2.86{plus minus}0.02 A and 2.0{plus minus}0.4 Si atoms at 2.66{plus minus}0.03 A. Combined, these results indicate that Sb trimers occupy the threefold atop sites of the Si(111) surface, where each Sb atom is bonded to two Si atoms in a modified bridge configuration.« less
  • We have performed fluorescence x-ray-absorption fine-structure (XAFS) measurements from 20{endash}200 K on a 5000-A {ital c}-axis film of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) on MgO ({ital T}{sub {ital c}}=89 K) using photons polarized perpendicular to the film. The quality of the data is high out to 16 A{sup {minus}1}. The data from 3{endash}15.5 A{sup {minus}1} were transformed into {ital r} space and fit to a sum of theoretical standards out to 4.0 A. These data are compared to YBCO data from a single crystal and from a film on LaAlO{sub 3} with the same {ital T}{sub {ital c}}. The mainmore » difference between the single crystal and the film data is that while the single-crystal data are well described by a two-site axial oxygen [O(4)] distribution, we see no evidence for such a distribution in either thin-film sample. We place an upper limit on the size of the axial oxygen distribution splitting for the film on MgO at {Delta}{sub {ital r}}{approx_lt}0.09 A. Therefore, the magnitude of any possible splitting is not directly related to {ital T}{sub {ital c}}. Fits to the temperature-dependent data from the YBCO film on MgO indicate that all bonds show a smooth change of their broadening factor {sigma}, except the Cu-O(4) bonds, which show an increase in {sigma} in the vicinity of {ital T}{sub {ital c}}, followed by a decrease of the same magnitude. Such a feature does not occur in diffraction measurements. Since XAFS measurements of {sigma} include any correlation between the atoms in a given bond, we conclude that the O(4) position becomes less correlated with the Cu positions near {ital T}{sub {ital c}}. Correlation measurements of these and several further near neighbors are also reported. {copyright} {ital 1996 The American Physical Society.}« less
  • We present a quasielastic neutron scattering (QENS) study of single-particle dynamics in pure water, measured at temperatures between 256 and 293 K along an isobaric path at 200 MPa. A thorough analysis of the spectral line shapes reveals a departure from simple models of continuous or jump diffusion, with such an effect becoming stronger at lower temperatures. We show that such a diverging trend of dynamical quantities upon cooling closely resembles the divergent (anomalous) compressibility observed in water by small-angle diffraction. Such an analogy suggests an interesting interplay between single-particle diffusion and structural arrangements in liquid water, both bearing witnessmore » of the well-known water anomalies. In particular, a fit of dynamical parameters by a Vogel-Tammann-Fulcher law provides a critical temperature of about 220 K, interestingly close to the hypothesized position of the second critical point of water and to the so-called Widom line.« less