Stability properties of C-4(2+)

The carbon tetramer dication C-4(2+) is studied by multireference configura tion-interaction calculations. Equilibrium geometries of C-4(2+) are identi fied and their stability properties discussed. Although for the tetramer io n the negative dissociation energy -D-c turns out to be smaller than for th e dications C-n(2+) with n = 2, 3, thermochemical stability is not yet achi eved. The size of the involved potential barriers, however, entails a high degree of metastability for C-4(2+). (C) 2000 Elsevier Science B.V. All rig hts reserved.