STUDIES OF TRANSPOLYACETYLENE CHAIN USING THE 1ST-PRINCIPLES DENSITY-FUNCTIONAL THEORY

we report a self-consistent linear-combination-of-Gaussian-orbitals st udy of the dimerization of a single, infinite chain of trans-polyacety lene 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 angstrom and 7 meV per dimer, respectively. The most essential c ontributions for lowering the total energy and forming the electron de nsity difference between the single and double bonds in the dimerizati on come from the pi valence states at the Brillouin zone boundaries ma king the results sensitive to the k sampling here. The dimerization te ndency becomes partly or totally suppressed if minor amounts of electr ons are removed from the pi valence band edge.