title: Rattling in the Quadruple Perovskite CuCu3 V4 O12.
abstract: Of particular interest is a peculiar motion of guest atoms or ions confined to nanospace in cage compounds, called rattling. While rattling provides unexplored physical properties through the guest-host interactions, it has only been observed in a very limited class of materials. Herein, we introduce an A-site-ordered quadruple perovskite, CuCu3 V4 O12 , as a new family of cage compounds. This novel AA'3 B4 O12 -type perovskite has been obtained by a high-pressure synthesis technique and structurally characterized to have cubic Im$\bar 3$ symmetry with an ionic model of Cu(2+) Cu(2+) 3 V(4+) 4 O12 . The thermal displacement parameter of the A-site Cu(2+) ion is as large as Uiso ≈0.045 Å(2) at 300 K, indicating its large-amplitude thermal oscillations in the oversized icosahedral cages. Remarkably, the presence of localized phonon modes associated with rattling of the A-site Cu(2+) ion manifests itself in the low-temperature specific heat data. This work sheds new light on the structure-property relations in perovskites.
authors.affiliation: Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan).
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Akizuki
authors.affiliation: Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, 1-2 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531 (Japan). i-yamada@21c.osakafu-u.ac.jp.|JST-PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan). i-yamada@21c.osakafu-u.ac.jp.
authors.forename: Ikuya
authors.initials: I
authors.lastname: Yamada
authors.affiliation: Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan). fujita@dipole7.kuic.kyoto-u.ac.jp.
authors.forename: Koji
authors.initials: K
authors.lastname: Fujita
authors.affiliation: Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan).
authors.forename: Kazuya
authors.initials: K
authors.lastname: Taga
authors.affiliation: College of Humanities and Sciences, Nihon University, Tokyo 156-8550 (Japan).
authors.forename: Takateru
authors.initials: T
authors.lastname: Kawakami
authors.affiliation: Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5148 (Japan).
authors.forename: Masaichiro
authors.initials: M
authors.lastname: Mizumaki
authors.affiliation: Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan).
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Tanaka
keywords: cage compounds; high-pressure chemistry; perovskites; rattling; transition metals