Iranian Chemical Science and Technologies AssociationInternational Journal of New Chemistry2645-72376420191001A Computational Study to Find the Vibrational Modes Connected with Specific Molecular Structures of Calculated Compound2772883620510.22034/ijnc.2019.112593.1054ENGolrokh MahmoudzadehDepartment of Chemistry, Arak Branch, Islamic Azad University, Arak, IranJournal Article20190810The 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).http://www.ijnc.ir/article_36205_ab5beb2df30da7ec08e348eaa8dd6414.pdf