Regensburg 2010 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 51: Electronic Properties I
MM 51.2: Vortrag
Donnerstag, 25. März 2010, 10:30–10:45, H5
First-principles electronic structure and chemical bonding studies of type I clathrates Ba8TxE46−x (T: late transition metals; E: Si, Ge; x= 0–6) — •Alim Ormeci, Umut Aydemir, Wilder Carrillo-Cabrera, Michael Baitinger, and Yuri Grin — Max Planck Institute for Chemical Physics of Solids, Dresden
In recent years type I clathrates doped with transition metals have attracted a lot interest largely due to the expectations that such materials may have interesting electronic and transport properties. The cubic unit cell of type I clathrates contains two 20- and six 24-framework atom cages. The voids enclosed by these cages can be filled with alkali, alkaline-earth or rare earth metals, while transition metals or Ga can substitute some of the framework atoms yielding three-component compounds. Here, the interest is confined to Si or Ge as main framework atoms, Ba as filler, and some late transition metals selected from Groups 9-12 as dopants. The dopants usually occupy the 6c Wyckoff position (space group Pm3n, no. 223), however the range of 6c site occupation fraction depends on the dopant and the framework atom, Si or Ge. Vacancies at 6c sites are a possibility and observed mostly in Ge clathrates rather than in Si ones. Using the full-potential local orbital (FPLO) method and supercells containing up to 216 atoms, electronic structures, chemical bonding and heats of formation will be investigated for the systems Ba8TxE46−x with E: Si, Ge and for x= 0–6 allowing also for the possibility of vacancies, as well. Theoretical results will be compared with experimental findings.