Electron localizationdelocalization transitions in dissociation of the C_{4}^{} anion: A largeD analysis
Abstract
We present a study, employing high level ab initio methods, of electron localizationdelocalization transitions along the dissociation path of the C4 anion to C_{2} and C2. We find that at the equilibrium geometry, the symmetrical and nonsymmetrical configurations of the linear C4 anion are almost isoenergetic. However, along a collinear dissociation path, the dipole moment drops abruptly to zero when the separation between the two middle carbon nuclei reaches about R=2.15 Å. The dipole moment remains zero until about R=2.78 Å, and then continuously increases as dissociation proceeds. This behavior is analogous to critical phenomena: The abrupt drop to zero of the dipole moment resembles a firstorder phase transition, the later steady rise resembles a continuous phase transition. We show that a simple subHamiltonian model, corresponding to the largedimension limit for an electron in the field of four collinear carbon atoms, exhibits both kinds of phase transitions along the dissociation path.
 Publication:

Journal of Chemical Physics
 Pub Date:
 February 2004
 DOI:
 10.1063/1.1637581
 Bibcode:
 2004JChPh.120.2199S
 Keywords:

 82.37.Np;
 33.15.Fm;
 33.15.Bh;
 82.30.Lp;
 33.15.Kr;
 31.15.Ar;
 31.15.Ne;
 31.25.Qm;
 31.15.Dv;
 Single molecule reaction kinetics dissociation etc.;
 Bond strengths dissociation energies;
 General molecular conformation and symmetry;
 stereochemistry;
 Decomposition reactions;
 Electric and magnetic moments polarizability and magnetic susceptibility;
 Ab initio calculations;
 Selfconsistentfield methods;
 Electron correlation calculations for polyatomic molecules;
 Coupledcluster theory