Structure and properties of polymers calculated by ab initio molecular dynamics

The Car-Parrinello ab initio molecular dynamics scheme combines electronic structure calculations with complete geometry optimizations very efficiently. For the first time we apply this method to organic semiconducting polymers. Equilibrium geometries are calculated for a series of polymers: polythiophene (PTh), polypyrrole (PPy), polyisothianaphtene (PITN), polyparaphenylene (PPP), polyaniline (PANI) and polyparaphenylenesulfide (PPS). The bandgaps of these polymers, calculated with the local density functional, are shown to correctly represent the trend in the experimental optical bandgap.