Excitons in conjugated polymers: wavefunctions, symmetries, and quantum numbers.
We introduce a mapping from configuration interaction singles wavefunctions, expressed as linear combinations of particle-hole excitations between Hartree-Fock molecular orbitals, to real-space exciton wavefunctions, expressed as linear combinations of particle-hole excitations between localized Wannier functions. The exciton wavefunction is a two-dimensional amplitude for the exciton center-of-mass coordinate, R, and the electron-hole separation (or relative coordinate), r, having an exact analogy to one-dimensional hydrogenlike wavefunctions. We describe the excitons by their appropriate quantum numbers, namely, the principle quantum number, n, associated with r and the center-of-mass pseudomomentum quantum number, j, associated with R. In addition, for models with particle-hole symmetry, such as the Pariser-Parr-Pople model, we emphasize the connection between particle-hole symmetry and particle-hole parity. The method is applied to the study of excitons in trans-polyacetylene and poly(para-phenylene).
Barford
William
W
Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom. william.barford@chem.ox.ac.uk
Paiboonvorachat
Nattapong
N