title: The effect of vacancy ordering on quadrupole shifts in Mössbauer spectra of maghemite.
abstract: Electric field gradient (EFG) lattice sums for the vacancy-disordered and vacancy-ordered forms of maghemite were evaluated using a point charge model. The calculated EFGs produced a wide range of magnitudes and principal directions for the quadrupole interaction for both forms of maghemite. Small perturbations of the crystallographic parameters were shown to have a significant effect on the quadrupole shift. The effects observed were significant enough to show that quadrupole shifts should be considered when fitting the Mössbauer spectra of maghemite.
authors.affiliation: School of Physics, Monash University, Victoria 3800, Australia. Kathryn.Spiers@monash.edu
authors.forename: K M
authors.initials: KM
authors.lastname: Spiers
authors.forename: D M
authors.initials: DM
authors.lastname: Paganin
authors.forename: J D
authors.initials: JD
authors.lastname: Cashion