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Polarized–unpolarized ground state of small polycyclic aromatic hydrocarbons
Author(s) -
SanFabiín E.,
Moscardó F.
Publication year - 2012
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24090
Subject(s) - wave function , ground state , coupled cluster , antiferromagnetism , chemistry , density functional theory , spin (aerodynamics) , molecule , atomic physics , molecular physics , computational chemistry , physics , condensed matter physics , thermodynamics , organic chemistry
Do polyacenes, circumacenes, periacenes, nanographenes, and graphene nanoribbons show a spin polarized ground state? In this work, we present monodeterminantal (Hartree–Fock (HF) and density functional theory (DFT) types), and multideterminantal calculations (Møller–Plesset and Coupled Cluster), for several families of unsaturated organic molecules ( n ‐Acenes, n ‐Periacenes and n ‐Circumacenes). All HF calculations and many DFT show a spin‐polarized (antiferromagnetic) ground state, in agreement with previous calculations. Nevertheless, the multideterminantal calculations, carried out with perturbative and variational wavefunctions, show that the more stable state is obtained starting from the unpolarized HF wavefunction. The trend of the stabilization of wavefunctions (polarized or unpolarized) with respect to exchange and correlation potentials, and to the number of benzene rings, has been analyzed. A study of the spin (〈Ŝ 2 〉) and the spin density on the carbon atoms has also been carried out. © 2012 Wiley Periodicals, Inc.