Golrokh Mahmoudzadeh - Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran

The purpose of this research is to provide a deeper understanding of the planar high- symmetry configuration instability. In the ideal case, the distortion corresponds to the movements of nuclei along normal modes that belong to non-totally symmetric irreps of the high symmertry (HS) point group of molecule. The analysis of the structural distortion from the HS nuclear arrangements of the JT active molecules presents a challenge because of the superposition of the effects produced by many different normal modes. It is shown that the instability of planar configurations of Tetrafluoroethylene radical anion, CF2 = CF2− molecule, leading to symmetry breaking and distortions is induced by the pseudo Jahn-Teller effect (PJTE). It was proved that the PJTE is the only source of instability of high-symmetry configurations of molecules . Therefore, the instability of planar configuration leading to symmetry breaking and distortions is induced by the pseudo Jahn-Teller effect (PJTE). In other words, in the studied molecule, descent in symmetry is associated with increasing the stability of molecule, i.e. the more curvature of the lower of curve have played a major role in stabilization energy so that the increasing of stability is attributed to the pseudo Jahn-Teller effect stablization energy (PJTE stabilization energy).

Symmetry Breaking, Imaginary Frequencies and Trans-bent configuration, pseudo Jahn-Teller effect (PJTE)