title: A-site-ordered perovskite MnCu3V4O12 with a 12-coordinated manganese(II).
abstract: A novel cubic perovskite MnCu3V4O12 has been synthesized at a high pressure and high temperature of 12 GPa and 1373 K. This compound crystallizes in the A-site-ordered perovskite structure (space group Im3) with lattice constant a = 7.26684(10) Å at room temperature. The most notable feature of this compound lies in the fact that the Mn(2+) ion is surrounded by 12 equidistant oxide ions to form a regular icosahedron; the situation of Mn(2+) is unprecedented for the crystal chemistry of an oxide. An anomalously large atomic displacement parameter U(iso)= 0.0222(8) Å(2) is found for Mn(2+) at room temperature, indicating that the thermal oscillation of the small Mn(2+) ion in a large icosahedron is fairly active. Magnetic susceptibility and electric resistivity measurements reveal that 3d electrons of Mn(2+) ions are mainly localized, while 3d electrons in Cu(2+) and V(4+) ions are delocalized and contribute to the metallic conduction.
authors.affiliation: Department of Material Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Akizuki
authors.forename: Ikuya
authors.initials: I
authors.lastname: Yamada
authors.forename: Koji
authors.initials: K
authors.lastname: Fujita
authors.forename: Norimasa
authors.initials: N
authors.lastname: Nishiyama
authors.forename: Tetuo
authors.initials: T
authors.lastname: Irifune
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yajima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kageyama
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Tanaka