Pseudo Jahn–Teller effect in stacked benzene molecules

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Chemically bound structures of several benzene molecules are studied both analytically and numerically. The bonds in these structures are established by replacing the intra π-bonds of C6 rings by the inter σ-bonds. The rearrangements of different π-bonds may take place differently which causes distortions of C6 rings. The reason of the distortions is the pseudo-Jahn–Teller effect (PJTE). In the case of two chemically bound benzene molecules in a hollow position (with direct on-top stacking), called as bi-benzene, three different distorted states in addition to the undistorted one are found to exist. PJTE leads also to a chemical bonding of three and more benzene molecules stacked directly on-top of each other. These bound structures do not exist for undistorted molecules. All bound states, although being metastable are separated from the unbound ones by energy barriers ≳2eV. It is found that the height of the barrier for symmetric bi-benzene is essentially affected by the Jahn–Teller effect.