Virtual space reduction in quasi-particle electron propagator calculations: Applications to polycyclic aromatic hydrocarbons



Recently developed techniques of virtual space reduction in quasi-particle electron propagator calculations are applied to naphthalene, anthracene, phenanthrene, naphthacene, pentacene, and hexacene. Electron density difference matrices corresponding to second-order transition energies are used to reduce the rank of the virtual orbital space for further electron propagator calculations in the partial third-order approximation. Within this approach, only minor deviations from ionization energies obtained with the full virtual orbital space are introduced. Comparison is made with a conventional, energy-based virtual orbital space contraction. No more than 0.14 eV of the calculated ionization energy is lost when the virtual space's dimension is reduced by 50%. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008