Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.5: Poster

Montag, 27. März 2006, 14:00–17:45, P1

First-Principles Electronic Structure Study of Layered TB₂C₂ Compounds (T = Y, La, Lu) — •Alim Ormeci and Helge Rosner — MPI for Chemical Physics of Solids, Dresden, Germany

Metal borocarbides TB₂C₂, where T = Y and rare earth (R) metals, are layered compounds with metal atom layers alternating with the (B₂C₂) layers. The RB₂C₂ compounds crystallize in the tetragonal LaB₂C₂-type structure with symmetry P4/mbm (SG 127). CaB₂C₂ also has the same crystal structure and is isoelectronic to MgB₂. However, due to heteropolar B-C bonds it is an insulator. The compound YB₂C₂, on the other hand, is a metal and a superconductor. Although there are some ambiguities about its crystal structure [1], it can be regarded as an electron-doped version of CaB₂C₂. Consequently, both the crystal and electronic structure of YB₂C₂, as well as the electron-phonon interactions in the (B₂C₂) layers are of interest.

We use the FPLO method to investigate the above mentioned aspects in YB₂C₂. In particular, we find that YB₂C₂ has the LaB₂C₂-type structure in agreement with the FP-LAPW results [1]. Furthermore, we study the effects of (i) possible disorder in the B-C network, and (ii) different stacking orders on the electronic properties. LaB₂C₂ and LuB₂C₂ are included in the study for comparative reasons.

[1] S. Khmelevskyi, et al. Supercond. Sci. Technol. 18 422 (2005)