Electronic structure of Pt in polyyne

We present results of first-principles calculations on [Pt(PH3)(2)C-6](x), which is a linear-chain compound consisting of alternating Pt atoms (which have PH3 sidegroups) with a linear group of six C atoms. The calculations have been performed with the density-functional linear muffin-tin orbital method for a single, infinite, periodic chain. We discuss, in particular, the orbitals near the Fermi energy; we also use a semiquantitative approach to estimate the effects of spin-orbit coupling. Finally, we examine the perturbation on the band structure that are induced by polaronic defects and suggest that these may be relevant for interpreting the experimental results on this and related polymers.