Pseudo Jahn-Teller effect in Ge4X4 (X=F, Cl, Br) molecules: A theoretical investigation

The instabilityof planar rings in Ge4X4 (X=F, Cl, Br, I)moleculesdue to the pseudo Jahn-Teller effect (PJTE) was investigated as anoriginal PJTE study. Optimization and the following frequency calculations in these molecules illustratedthat all of these compounds were unstable in highsymmetry planar (with D4hsymmetry) geometry and their structures were puckered to lower C2hsymmetry stable geometry. Moreover, the vibronic couplinginteraction between 1A1g ground and the first 1Eg excited states via (1A1g + 1Eg) ⊗eg PJTE problem was the reasons for the symmetry breaking phenomenon and non-planarity of the four-member ring in those series.