Identifying quasi-2D and 1D electrides in yttrium and scandium chlorides via geometrical identification

Abstract

Developing and understanding electron-rich electrides offers a promising opportunity for a variety of electronic and catalytic applications. Using a geometrical identification strategy, here we identify a new class of electride material, yttrium/scandium chlorides Y(Sc)(x)Cl-y (y:x < 2). Anionic electrons are found in the metal octahedral framework topology. The diverse electronic dimensionality of these electrides is quantified explicitly by quasi-two-dimensional (2D) electrides for [YCl](+).e-and [ScCl](+).e(-) and one-dimensional (1D) electrides for [Y2Cl3](+).e(-), [Sc7Cl10](+).e(-), and [Sc5Cl8](2+). 2(e-) with divalent metal elements (Sc2+:3d(1) and Y2+:4d(1)). The localized anionic electrons were confined within the inner-layer spaces, rather than inter-layer spaces that are observed in A(2)B-type 2D electrides, e.g. Ca2N. Moreover, when hydrogen atoms are introduced into the host structures to form YClH and Y2Cl3H, the generated phases transform to conventional ionic compounds but exhibited a surprising reduction of work function, arising from the increased Fermi level energy, contrary to the conventional electrides reported so far. Y2Cl3 was experimentally confirmed to be a semiconductor with a band gap of 1.14 eV. These results may help to promote the rational design and discovery of new electride materials for further technological applications.