An ab initio journey into the electronic structure of Be3.

In the present study, we concisely report on Be₃'s ground and several excited states of singlet, triplet, quintet, and septet spin symmetry at the MRCI/aug−cc−pV5Z computational level. We have constructed potential energy cuts along the bending coordinate under both C_2v and C_s symmetry constraints. Both linear and bent configurations have been calculated that span an energy range of nearly 160 kcal/mol. The excited states result by promoting one, two or three valence electrons from the ground state's electronic configuration. This electronic promotion destroys its sigma (2center – 2e⁻) bond(s) and the resulting asymmetry is at the very heart of the Jahn–Teller distortion. [ABSTRACT FROM AUTHOR]