Ab Initio Valence Bond Description of Diatomic Dications

Ab Initio Valence Bond Description of Diatomic Dications  

Harold Basch, Pinchas Aped, Shmaryahu Hoz and Moshe Goldberg Department of Chemistry, Bar Han University, Ramat Gan 52100, Israel 

An alternative model description of dication energy curves has been given by several groups 11 17 . Based directly on the VB method, this model attributes the origin of the barrier in the ground state energy curve of diatomic dications AB2+ to an avoided crossing between a purely repulsive covalent 

As noted above, the helium diatomic dication has been well studied11 7,17,19,321. The standard three configuration VB wave function for the singly-bonded (He,-Heb)2+ consists of a linear combination of configurations (1) to (3)  

022+ is isoelectronic and isovalent with N2 and both have a formal triple bond. The 14 electrons in the dication are divided into a six electron active space and an eight electron passive space. The latter consist essentially of the doubly-occupied Is and 2s atomic orbitals on each center. In molecular orbital theory the electronic configuration of the active or triple bond part of 

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