title: BaRh2Si9--a new clathrate with a rhodium-silicon framework.
abstract: The semiconducting compound BaRh2Si9 is a new kind of intermetallic clathrate. It was obtained by reacting BaSi, Rh and Si at 950 °C. The crystal structure (space group C2/c; Pearson symbol mC48, a = 6.2221(5) Å, b = 21.399(2) Å, c = 6.2272(5) Å, β = 90.306(7)°) displays a covalently bonded Rh-Si framework, in which four-connected Si atoms partly show unusually small bond angles. The Ba atoms are encapsulated in large polyhedral cages formed by 18 Si and 4 Rh atoms. The compound is a diamagnetic p-type semiconductor, which is in agreement with band structure calculations resulting in a band gap of 0.12 eV. Quantum chemical calculations reveal positively charged Ba atoms (Ba(+1.3)) and negatively charged Rh atoms (Rh(-1)). Si atoms with neighboring Rh atoms are positively charged, while those connected only with Si atoms are negatively charged.
authors.affiliation: Max Planck Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Jung
authors.forename: Alim
authors.initials: A
authors.lastname: Ormeci
authors.forename: Walter
authors.initials: W
authors.lastname: Schnelle
authors.forename: Hong Duong
authors.initials: HD
authors.lastname: Nguyen
authors.forename: Michael
authors.initials: M
authors.lastname: Baitinger
authors.forename: Yuri
authors.initials: Y
authors.lastname: Grin