title: beta-Bi(4)(P(2)Se(6))(3): A New Ternary Selenophosphate Obtained in a P(2)Se(5) Flux.
abstract: Bi metal dissolves in excess molten phosphorus selenide at 500 degrees C to yield black, rodlike, air- and water-stable beta-Bi(4)(P(2)Se(6))(3) crystals. The phase crystallizes in the triclinic space group P&onemacr; (No. 2) with the room-temperature cell parameters a = 12.2303(8) Å, b = 6.7640(4) Å, c = 17.866 Å, alpha = 90.493(6) degrees, beta = 94.133(6) degrees, and gamma = 91.163(6) degrees. The new structure is a complicated, three-dimensional framework built from [Bi(4)Se(22)] ribbons connected to each other by sharing selenium atoms. The [P(2)Se(6)](4)(-) ethane-like units are found inside and between the [Bi(4)Se(22)] ribbons. The compound is a semiconductor with a band gap of 1.32 eV. It melts with decomposition at 512 degrees C, converting partially to Bi(2)Se(3) and a P(x)()Se(y)() glassy material. Far-IR and Raman spectra show characteristic stretches for the [P(2)Se(6)](4)(-) ligand and Bi-Se vibrations. The structural and chemical relationships of this compound with the alpha-form are discussed.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Institut des Matériaux de Nantes, B.P. 32229, 44322 Nantes Cedex 03, France.
authors.forename: Jennifer A.
authors.initials: JA
authors.lastname: Aitken
authors.forename: Shannon
authors.initials: S
authors.lastname: Brown
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Chondroudis
authors.forename: Stéphane
authors.initials: S
authors.lastname: Jobic
authors.forename: Raymond
authors.initials: R
authors.lastname: Brec
authors.forename: Mercouri G.
authors.initials: MG
authors.lastname: Kanatzidis