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Title: Benchmark theoretical study of the ionization threshold of benzene and oligoacenes
Authors: DELEUZE, Michael
FRANCOIS, Jean-Pierre
Issue Date: 2003
Citation: JOURNAL OF CHEMICAL PHYSICS, 119(6). p. 3106-3119
Abstract: In straightforward continuation of Green's function studies of the ultraviolet photoelectron spectra of polycyclic aromatic compounds [Deleuze , J. Chem. Phys. 115, 5859 (2001); M. S. Deleuze, ibid. 116, 7012 (2002)], we present a benchmark theoretical determination of the ionization thresholds of benzene, naphthalene, anthracene, naphthacene (tetracene), pentacene, and hexacene, within chemical accuracy [0.02-0.07 eV]. The vertical ionization potentials of these compounds have been obtained from series of single-point calculations at the Hartree-Fock, second-, third-, and partial fourth-order Moller-Plesset (MP2, MP3, MP4SDQ) levels, and from coupled cluster calculations including single and double excitations (CCSD) as well as a perturbative estimate of connected triple excitations [CCSD(T)], using basis sets of improving quality, introducing up to 510, 790, 1070, 1350, 1630, and 1910 basis functions in the computations, respectively. A focal point analysis of the convergence of the calculated ionization potentials has been performed in order to extrapolate the CCSD(T) results to an asymptotically (cc-pVinfinityZ) complete basis set. The present results confirm the adequacy of the outer-valence Green's function scheme for strongly correlated systems. Adiabatic ionization energies have been further determined by incorporating Beck-three-parameter Lee-Yang-Parr functional corrections for zero-point vibrational energies and for geometrical relaxations. Extension of the analysis to the CCSD(T)/cc-pVinfinityZ level shows that the energy minimum form of the benzene radical cation is an obtuse structure related to the B-2(2g) state. Isotopic shifts of the adiabatic ionization potentials, due to deuterium substitution of hydrogens, have also been discussed. (C) 2003 American Institute of Physics.
Notes: Limburgs Univ Centrum, Dept SBG, B-3590 Diepenbeek, Belgium. Bogoliubov Inst Theoret Phys, UA-03143 Kiev 143, Ukraine.Deleuze, MS, Limburgs Univ Centrum, Dept SBG, Univ Campus, B-3590 Diepenbeek, Belgium.
URI: http://hdl.handle.net/1942/2240
DOI: 10.1063/1.1589731
ISI #: 000184350300019
ISSN: 0021-9606
Category: A1
Type: Journal Contribution
Validation: ecoom, 2004
Appears in Collections: Research publications

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