Periodic Density Functional Theory Calculations for Na-doped Quasi-one-dimensional Polyacetylene Chains

Abstract

We report periodic B3LYP/6−31G** density functional theory calculations on Na-doped quasi-one-dimensional trans-polyacetylene (PA) chains at various dopant concentrations. The chains are modeled using C2mH2mNa2 unit cells (m = 11, 13, 21, and 31). Our main purpose is to compare with previous calculations on Li-doping. Properties compared include geometries, atomic charges, dopant binding energies, band structures, densities of states, and nature of binding. In contrast with Li, the Na-doped chains are dissociative at concentrations of Na/C ≥ 1/9, and the bond length alternation is reduced for Na-doping as compared to Li-doping. The most significant differences are the binding energies and the appearance of a narrow isolated unoccupied band within the PA π−π* gap in the case of Na-doping. This intragap band is predominantly composed of Na(3s,3p) atomic orbitals.