title: Site occupancy of interstitial deuterium atoms in face-centred cubic iron.
abstract: Hydrogen composition and occupation state provide basic information for understanding various properties of the metal-hydrogen system, ranging from microscopic properties such as hydrogen diffusion to macroscopic properties such as phase stability. Here the deuterization process of face-centred cubic Fe to form solid-solution face-centred cubic FeDx is investigated using in situ neutron diffraction at high temperature and pressure. In a completely deuterized specimen at 988 K and 6.3 GPa, deuterium atoms occupy octahedral and tetrahedral interstitial sites with an occupancy of 0.532(9) and 0.056(5), respectively, giving a deuterium composition x of 0.64(1). During deuterization, the metal lattice expands approximately linearly with deuterium composition at a rate of 2.21 Å(3) per deuterium atom. The minor occupation of the tetrahedral site is thermally driven by the intersite movement of deuterium atoms along the ‹111› direction in the face-centred cubic metal lattice.
authors.affiliation: Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Machida
authors.affiliation: Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Saitoh
authors.affiliation: Department of Physics, Chuo University, 21-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Sugimoto
authors.affiliation: 1] Quantum Beam Science Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan [2] J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Hattori
authors.affiliation: 1] Quantum Beam Science Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan [2] J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: Asami
authors.initials: A
authors.lastname: Sano-Furukawa
authors.affiliation: Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Naruki
authors.initials: N
authors.lastname: Endo
authors.affiliation: Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Katayama
authors.affiliation: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cyo, Matsuyama, Ehime 790-8577, Japan.
authors.forename: Riko
authors.initials: R
authors.lastname: Iizuka
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Toyoto
authors.initials: T
authors.lastname: Sato
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Motoaki
authors.initials: M
authors.lastname: Matsuo
authors.affiliation: 1] Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan [2] WPI-Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Orimo
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Aoki