Density-functional and plane-wave approach to structural properties of poly(p-phenylene) and poly(p-phenylene vinylene)

Ab initio total-energy calculations are performed in order to investigate g round-state structural properties of 1D poly(paraphenylene) (PPP) and poly( para-phenylene vinylene) (PPV). The calculations are based on local-density -functional theory, the pseudopotential method and the supercell approach w ith a plane-wave basis set, Good agreement (within a few percent) between t heory and available experimental results is obtained for a variety of param eters. Amplitudes of ring librations at room temperatures and ring-flip act ivation energies are also estimated from analysis of torsion potentials. PP V calculation with a double unit cell with alternating ring torsions indica te a small (less than 7 degrees) deviation from planarity. (C) 1999 Publish ed by Elsevier Science B.V. All rights reserved.