arXiv subjects

Udo Schwingenschloegl

Publications and source records attributed to Udo Schwingenschloegl.

21 records · Page 2Linked to original sources

arXiv2006

Chemical Bonding and Charge Distribution at Metallic Nanocontacts

We present results of electronic structure calculations for aluminium contacts of atomic size, based on density functional theory and the local density approximation. Addressing the atomic orbitals at the neck of the nanocontact, we find that the local band structure deviates strongly from bulk fcc aluminium. In particular, hybridization between Al 3s and 3p states is fully suppressed due to directed bonds at the contact. Moreover, a charge transfer of 0.6 electrons off the contact aluminium site is found. Both the suppressed hybridization and the violated charge neutrality are characteristic features of metallic nanocontacts. This fact has serious consequences for models aiming at a microscopic description of transport properties.

cond-mat.mes-hall↗

arXiv2005

Orbital ordering in the two-dimensional ferromagnetic semiconductor Rb_2CrCl_4

We present the results of electronic structure calculations for the two-dimensional ferromagnet Rb_2CrCl_4. They are obtained by the augmented spherical wave method as based on density functional theory and the local density approximation. In agreement with experimental data Rb_2CrCl_4 is found to be semiconducting and displays long-range ferromagnetic order of the localized Cr 3d moments. The magnetic properties are almost independent of the structural modifications arising from the Jahn-Teller instability, which leads from the parent body-centered tetragonal K_2NiF_4 structure to a side-centered orthorhombic lattice. In contrast, our calculations give evidence for a strong response of the optical band gap to the corresponding structural changes.

cond-mat.str-el↗

arXiv2004

The vanadium Magneli phases VnO(2n-1)

To compare the metal-insulator transitions (MITs) of VO2 and V2O3 we analyze the relations between the structural and electronic properties of the vanadium Magneli phases. These materials set up the homologous series VnO(2n-1) (3 <= n <= 9) and have crystal structures comprising typical dioxide-like and sesquioxide-like regions. As the MITs of the vanadium Magneli phases are accompanied by structural transformations, we are able to discuss the effects of characteristic changes in the local atomic environments. The systematic investigation of the transport properties is based on a new and unifying description of the crystal structures of the Magneli phases including VO2 and V2O3. Our results lead to a comprehensive understanding of the MITs in the Magneli class and shed new light on the role of particular electronic states for the MIT of V2O3.

cond-mat.str-el↗