title: Electron Confinement in Channel Spaces for One-Dimensional Electride.
abstract: Electrides are characteristic of anionic electrons trapped at the structural voids in the host lattice. Electrides are potentially useful in various technological applications; however, electrides, particularly their inorganic subgroup, have been discovered only in limited material systems, notably zero-dimensional [Ca24Al28O64](4+):4e(-) and two-dimensional [Ca2N](+):e(-) and [Y2C](1.8+):1.8e(-). Here, on the basis of density functional theory calculations, we report the first one-dimensional (1D) electride with a [La8Sr2(SiO4)6](4+):4e(-) configuration, in which the four anionic electrons are confined in the channel spaces of the host material. According to this theoretical prediction, an insulator-semiconductor transition originating from electron confinement in the crystallographic channel sites was demonstrated experimentally, where 10.5% of the channel oxygen was removed by reacting an oxygen stoichiometric La8Sr2(SiO4)6O2 precursor with Ti metal at a high temperature. This study not only adds an unprecedented role to silicate apatite as a parent phase to a new 1D electride, but also, and more importantly, demonstrates an effective approach for developing new electrides with the assistance of computational design.
authors.affiliation: Materials Research Center for Element Strategy, Tokyo Institute of Technology , Yokohama 226-8503, Japan.|ACCEL Project, Japan Science and Technology Agency (JST) , Tokyo 102-8666, Japan.
authors.forename: Yaoqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Materials Research Center for Element Strategy, Tokyo Institute of Technology , Yokohama 226-8503, Japan.|Materials and Structures Laboratory, Tokyo Institute of Technology , Yokohama 226-8503, Japan.
authors.forename: Zewen
authors.initials: Z
authors.lastname: Xiao
authors.affiliation: Materials Research Center for Element Strategy, Tokyo Institute of Technology , Yokohama 226-8503, Japan.|Materials and Structures Laboratory, Tokyo Institute of Technology , Yokohama 226-8503, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kamiya
authors.affiliation: Materials Research Center for Element Strategy, Tokyo Institute of Technology , Yokohama 226-8503, Japan.|Materials and Structures Laboratory, Tokyo Institute of Technology , Yokohama 226-8503, Japan.|ACCEL Project, Japan Science and Technology Agency (JST) , Tokyo 102-8666, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Hosono
keywords: EPR; apatite; calculations; oxygen conductor; oxygen reduction