title: Synthesis, structure, and properties of BaAl2Si2.
abstract: Single crystals of BaAl2Si2 were grown from an Al molten flux and characterized using single-crystal X-ray diffraction at 10 and 90 K and neutron diffraction at room temperature. BaAl2Si2 crystallizes with the alpha-BaCu2S2 structure type (Pnma), is isostructural with alpha-BaAl2Ge2, and is an open 3D framework compound, where Al and Si form a covalent cagelike network with Ba2+ cations residing in the cages. BaAl2Si2 has a unit cell of a=10.070(3) A, b=4.234(1) A, and c=10.866(3) A, as determined by room-temperature single-crystal neutron diffraction (R1=0.0533, wR2=0.1034). The structure as determined by single-crystal neutron and X-ray diffraction (10 and 90 K) indicates that BaAl2Si2 (Pnma) is strictly isostructural to other (alpha)-BaCu2S2-type structures, requiring site specificity for Al and Si. Unlike BaAl2Ge2, no evidence for an alpha to beta (BaZn2P2-type, I4/mmm) phase transition was observed. This compound shows metallic electronic resistivity and Pauli paramagnetic behavior.
authors.affiliation: Department of Chemistry, One Shields Avenue, University of California, Davis, California 95616, USA.
authors.forename: Cathie L
authors.initials: CL
authors.lastname: Condron
authors.forename: Håkon
authors.initials: H
authors.lastname: Hope
authors.forename: Paula M B
authors.initials: PM
authors.lastname: Piccoli
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Schultz
authors.forename: Susan M
authors.initials: SM
authors.lastname: Kauzlarich