Studies of trans-polyacetylene chain using the first-principles density-functional theory

We report a self-consistent linear-combination-of-Gaussian-orbitals study of the dimerization of a single, infinite chain of trans-polyactylene using the first-principles density-functional theory in the local-density approximation. As the result we get a weakly dimerized ground state with a dimerization amplitude and stabilization energy of about 0.01 Å and 7 meV per dimer, respectively. The most essential contributions for lowering the total energy and forming the electron density difference between the single and double bonds in the dimerization come from the π valence states at the Brillouin zone boundaries making the results sensitive to the k sampling here. The dimerization tendency becomes partly or totally suppressed if minor amounts of electrons are removed from the π valence band edge.