The metal-insulator transition of : An embedded Peierls instability

Institut für Physik, Universität Augsburg - 86135 Augsburg, Germany

Corresponding author: eyert@physik.uni-augsburg.de

Received: 11 February 2002
Accepted: 2 April 2002

Abstract

Results of first-principles augmented spherical-wave electronic-structure calculations for niobium dioxide are presented. Both metallic rutile and insulating low-temperature , which crystallizes in a distorted rutile structure, are correctly described within density functional theory and the local density approximation. Metallic conductivity is carried by metal orbitals, which fall into the one-dimensional band and the isotropically dispersing bands. Hybridization of both types of bands is almost negligible outside narrow rods along the line X-R. In the low-temperature phase splitting of the band due to metal-metal dimerization as well as upshift of the bands due to increased p - d overlap remove the Fermi surface and open an optical band gap of about 0.1 eV. The metal-insulator transition arises as a Peierls instability of the band in an embedding background of electrons. This basic mechanism should also apply to , where, however, electronic correlations are expected to play a greater role due to stronger localization of the 3d electrons.