A Esmaeili - Department of Chemistry, Education, Mahallat, Iran

The structural properties of OF2, OCl2, OBr2,OI2 have been examined by means ofB3LYP/Def2-TZVPP and LC-wPBE/ Def2-TZVPP and CCSD(T)/ Def2-TZVPP level theoryinterpretations. The results obtained showed the expected ground state structure for compound islinear.(D∞h symmetry) .The distortion of the high-symmetry configuration of compound is due tothe pseudo Jahn-Teller effect(PJTE), which is the only source of instability of high-symmetryconfiguration in nondegenerate states.The distortion is due to the mixing of the ground ∑(+)(g) andexcited II(u) states [1].

Pseudo-Jahn-Teller effect, TD-DFT , Vibronic Coupling