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 ato ms (which have PH3 sidegroups) with a linear group of six C atoms. The calculations have been performed with the density-functional linear m uffin-tin orbital method for a single, infinite, periodic chain. We di scuss, in particular, the orbitals near the Fermi energy; we also use a semiquantitative approach to estimate the effects of spin-orbit coup ling. Finally, we examine the perturbation on the band structure that are induced by polaronic defects and suggest that these may be relevan t for interpreting the experimental results on this and related polyme rs.