First-principles calculation of the conformation and electronic structure of polyparaphenylene

Abstract

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers J. Chem. Phys. 120, 8608 (2004) In this article, an all-electron first-principles total energy calculation with Gaussian-type functions for the wave functions, for the exchange correlation potential, and for the charge density has been applied for single chains of polyparaphenylene ͑PPP͒. A local-density approximation within a helical band structure approach has been used. The calculated torsional potential shows a minimum at the torsion angle of 34.8°. The internal coordinates were optimized in the equilibrium conformation and are in good agreement with experimental and other theoretical results. The calculated direct band gap is 2.54 eV compared with the experimental result from UPS spectra of 3.4 eV for the gas phase. The band structure strongly depends on the conformation which suggests that the electronic properties can be modified in a wide range through doping or addition of side groups.

Resolving Band-Structure Evolution and Defect-Induced States of Single Conjugated Oligomers by Scanning Tunneling Microscopy and Tight-Binding Calculations

“…The reported theoretical values, however, span a wide range from 1.46 eV (TBA) to 5.60 eV (HF) [5,11,20,[22][23][24][25][26][27]. Considering that the dihedral angle in our case is 28 , the 4.5 eV CB bandwidth reported here is consistent with the theoretical prediction of Champagne et al [27].…”

“…Using linear extrapolation, the band gap eventually approaches 3:1 AE 0:2 eV (or 2:3 AE 0:2 eV) for an infinitely long PPP polymer. Like CB bandwidth, the band gap value of PPP is also debated in the literature [22,23,[30][31][32][33]. Our experimental data were acquired by measuring well-defined single oligomers, many uncertainties encountered in other experimental methods, for example, interchain effects or defect influence, can be excluded.…”

Substrate‐Mediated Electronic Structure and Properties of Sexiphenyl Films

“…The band structure calculations for a single polyparaphenylene chain indicate a 0.5 eV lowering of the ionization potential on reduction of the torsional angle from 50 to 0. [15] Sexiphenyl is known to be twisted in the gas phase with a torsional angle of 40±45. In the solid state it is generally accepted that the molecule is planar, and it has been shown to be on average planar in a single crystal X-ray diffraction study of Baker et al [19] The coplanarity of type I 6P is certainly indicated by its large p-band spread.…”

Calculation of the total energy per unit cell and of the band structures of the five nucleotide base stacks using the local-density approximation

“…5,11 The local density approximation is used with a Kohn-Sham exchange term 16 and a Ceperley-Alder correlation term, 17 using the Perdew-Zunger analytic fit. 18 The helicity of the polymer system is described by a screw operator S, with the one-electron wave functions transforming under S according to Bloch's theorem.…”

“…Because there are correlation-corrected Hartree-Fock band structure calculations ͑using the inverse Dyson equation in the diagonal approximation 7 with a Mo "ller-Plesset 8 self energy in the framework of the electronic polaron model 9 ͒ on the base stacks, 10 it seemed interesting and useful to compare these band structures with the LDA ones. Further, having already performed LDA calculations on different chemical bond chains, 6,11,12 we wanted to see how the LDA program works for periodic molecular stacks in a helical arrangement.…”