Regensburg 2004 – wissenschaftliches Programm

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M: Metallphysik

M 18: Postersitzung

M 18.23: Poster

Dienstag, 9. März 2004, 14:30–16:30, Saal C

Covalent bonding in approximants of Quasicrystals and the electronic transport — •Torsten Schmidt, Heinrich Solbrig, and Philipp Plaenitz — Technische Universitaet Chemnitz, Institut fuer Physik, D-09107 Chemnitz, Germany

Recent X-Ray diffraction data indicates the existance of well pronounced inhomogenities of the elctronic charge density acting as covalent interatomic bonds[1]. The present work attemps to prove these findings by ab-initio calculations of the electronic density in 1/1-approximants.

For Al-TM systems (TM = Mn,Fe,Re,Ru) it is shown that covalent charge bridges (i) stabilize the typical clusters (comparison with free clusters) and (ii) connect them to establish a network of clusters.We see these bonding properties as an essential source of the observed transport anomalies. These idea is proved upon examining the changes in both: the bonding and the electronic transport after introducing arbitrary defects of chemical decoration and structure.

Transport parameters are obtained by means of the Kubo-Greenwood formula employing the elctronic states as produced by the ASA-LMTO method. Valence charge densities are calculated by the ABINIT structure code and by GAMESS for isolated molecule clusters, respectively.

[1] K. Kirihara (et.al), Covalent bond and their crucial effects on pseudogap formation in alpha-Al(Mn,Re)Si icosahedral quasicrystalline approximant, Phys. Rev. B 68, 014205, (2003)