title: Local vibrational dynamics of hematite (α-Fe₂O₃) studied by extended x-ray absorption fine structure and molecular dynamics.
abstract: The local vibrational dynamics of hematite (α-Fe2O3) 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.affiliation: Dipartimento di Fisica e Astronomia - Università di Padova, Padova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sanson
authors.affiliation: ESRF - European Synchrotron Radiation Facility, Grenoble, France.
authors.forename: O
authors.initials: O
authors.lastname: Mathon
authors.affiliation: ESRF - European Synchrotron Radiation Facility, Grenoble, France.
authors.forename: S
authors.initials: S
authors.lastname: Pascarelli