Theoretical study of the quadrupole-bound anion (BeO)2−

The global minimum on the potential energy surface of (BeO)2−, calculated at the coupled-cluster level of theory with single, double, and non-iterative triple excitations, corresponds to a rhombic D2h structure, which may be considered as a quadrupole-bound anion. The rhombic isomer is separated by a Cs symmetry transition state from the linear isomer and the energy barrier amounts to 15.4 kcal/mol. The energies of the D2h and C∞v anionic isomers differ by 6.2 kcal/mol. The vertical electron detachment energies amount to 8903 and 23847 cm−1 (1.10 and 2.96 eV) for the rhombic and linear anion, respectively.