title: Remarkable rare-earth metal silicide oxides with planar Si6 rings.
abstract: New rare-earth silicide oxides, La10Si8O3 (1) and Ce10Si8O3 (2), were synthesized through high-temperature reactions of the pure elements under controlled oxygen atmosphere conditions. The remarkable silicides crystallize in a unique crystal structure (space group P6/mmm; a = 10.975(3) A (La) and 10.844(1) A (Ce); c = 4.680(1) A (La) and 4.561(1) A (Ce)) that features a 3-D framework of corner-shared O-centered (La/Ce)6 octahedra, reminiscent of hexagonal tungsten bronzes, with planar Si6 rings enclosed within its hexagonal channels. Band structure calculations indicate the compounds are metallic, with optimized La-Si bonds, and a benzene-like [Si6]6- anion. Compound 1 exhibits temperature independent paramagnetism. Compound 2 exhibits Curie-Weiss paramagnetism, and an antiferromagnetic ordering below 7 K.
authors.affiliation: Department of Chemistry and the Texas Center for Superconductivity, University of Houston, Houston, Texas 77204-5003, USA.
authors.forename: Limin
authors.initials: L
authors.lastname: Wang
authors.forename: Zhongjia
authors.initials: Z
authors.lastname: Tang
authors.forename: Bernd
authors.initials: B
authors.lastname: Lorenz
authors.forename: Arnold M
authors.initials: AM
authors.lastname: Guloy