High-density electron anions in a nanoporous single crystal: [Ca24Al28O64]4+(4e-).

Matsuishi, Satoru; Toda, Yoshitake; Miyakawa, Masashi; Hayashi, Katsuro; Kamiya, Toshio; Hirano, Masahiro; Tanaka, Isao; Hosono, Hideo · Science · 2003

basic_science · Level V

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Abstract

We removed approximately 100% of clathrated oxygen ions from the crystallographic cages in a single crystal of 12CaO.7Al2O3, leading to the formation of high-density (approximately 2 x 10(21) cm-3) electrons highly localized in the cages. The resulting electron forms a structure that we interpret as an F+ center and migrates throughout the crystal by hopping to a neighboring cage with conductivity approximately 100 siemens per centimeter, demonstrating that the encaged electron behaves as an anion. The electron anions couple antiferromagnetically with each other, forming a diamagnetic pair or singlet bipolaron. The resulting [Ca24Al28O64]4+(4e-) may be regarded as a thermally and chemically stable single crystalline "electride."