title: Absence of superconductivity in fluorine-doped neptunium pnictide NpFeAsO.
abstract: X-ray diffraction, specific heat, magnetic susceptibility and inelastic x-ray scattering measurements on the transurarium oxypnictides NpFeAsO and NpFeAsO0.85F0.15 are presented. No superconductivity down to 2 K was observed upon fluorine doping, contrary to the structurally analogous rare-earth pnictides. No modification of the phonon density of states was observed upon doping with fluorine. We discuss our results in light of the latest experimental and theoretical studies on the role of phonons in the superconducting pnictide compounds.
authors.affiliation: Diamond Light Source Limited, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK.
authors.forename: A C
authors.initials: AC
authors.lastname: Walters
authors.forename: H C
authors.initials: HC
authors.lastname: Walker
authors.forename: R
authors.initials: R
authors.lastname: Springell
authors.forename: M
authors.initials: M
authors.lastname: Krisch
authors.forename: A
authors.initials: A
authors.lastname: Bosak
authors.forename: A H
authors.initials: AH
authors.lastname: Hill
authors.forename: C E
authors.initials: CE
authors.lastname: Zvorişte-Walters
authors.forename: E
authors.initials: E
authors.lastname: Colineau
authors.forename: J-C
authors.initials: JC
authors.lastname: Griveau
authors.forename: D
authors.initials: D
authors.lastname: Bouëxière
authors.forename: R
authors.initials: R
authors.lastname: Eloirdi
authors.forename: R
authors.initials: R
authors.lastname: Caciuffo
authors.forename: T
authors.initials: T
authors.lastname: Klimczuk