THE STRUCTURE OF SMALL DOUBLY NEGATIVE CARBON CLUSTERS

Recently, experimental evidence has been obtained for the existence of dianionic carbon clusters as small as C7(2-). So far, no theoretical evidence has been achieved for the electronic stability of C-7(2-) , w hich is attributed to the underlying assumption of C-7(2-) having a li near structure. Linear, quasi-linear and trigonal planar atomic arrang ements for C-7(2-) are discussed. At the latter 7 structure C-7(2-) is predicted to be both stable with respect to vertical and adiabatic el ectron autodetachment and stable with respect to all fragmentation pat hways. The reasons leading to the electronic stability of the trigonal C-7(2-) dianion are discussed and illuminated by drawing a connection with the structurally related MX3(2-) alkali halides. Some remarks ar e made on larger dianionic carbon clusters.