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Title: Local vibrational dynamics of hematite (α-Fe{sub 2}O{sub 3}) studied by extended x-ray absorption fine structure and molecular dynamics

The local vibrational dynamics of hematite (α-Fe{sub 2}O{sub 3}) has been investigated by temperature-dependent extended x-ray absorption fine structure spectroscopy and molecular dynamics simulations. The local dynamics of both the short and long nearest-neighbor Fe–O distances has been singled out, i.e., their local thermal expansion and the parallel and perpendicular mean-square relative atomic displacements have been determined, obtaining a partial agreement with molecular dynamics. No evidence of the Morin transition has been observed. More importantly, the strong anisotropy of relative thermal vibrations found for the short Fe–O distance has been related to its negative thermal expansion. The differences between the local dynamics of short and long Fe–O distances are discussed in terms of projection and correlation of atomic motion. As a result, we can conclude that the short Fe–O bond is stiffer to stretching and softer to bending than the long Fe–O bond.
Authors:
 [1] ; ;  [2]
  1. Dipartimento di Fisica e Astronomia - Università di Padova, Padova (Italy)
  2. ESRF - European Synchrotron Radiation Facility, Grenoble (France)
Publication Date:
OSTI Identifier:
22420095
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ABSORPTION SPECTROSCOPY; ANISOTROPY; ATOMIC DISPLACEMENTS; DISTANCE; FERRITES; FINE STRUCTURE; HEMATITE; IRON OXIDES; MOLECULAR DYNAMICS METHOD; MORIN; SIMULATION; TEMPERATURE DEPENDENCE; THERMAL EXPANSION; X RADIATION; X-RAY SPECTROSCOPY