CARBON-OXYGEN CLUSTERS AS HYPOTHETICAL HIGH ENERGY-DENSITY MATERIALS

An ab initio investigation on the hypothetical systems CnOn (n = 2, 3, 4) is presented. Calculations have been performed at SCF and MP2 leve l, using a [3s2p1d] basis set on each atom. At this level of approxima tion, two metastable structures have been found. They are C2O2 With C- 2v symmetry (an irregular tetrahedron) and C4O4 With T-d symmetry (two regular tetrahedra copenetrating each other). On the other hand, the search of local minima with C-nv structures has failed for n = 3, 4. F or the two metastable structures also larger basis sets have been used , up to [4s3p2d1f] (in the case of C4O4, at SCF level only. The comput ed energy release of the dissociation reaction (CnOn --> n CO) of the two metastable structures is very high (about 100 kcal per mole of CO produced). It is of the same magnitude of the energy computed for the corresponding isoelectronic structures N-4 and Ns. If these or similar CO-clusters could be synthesized, these systems are candidates to be high energy-density materials (HEDM). (C) 1997 Elsevier Science B.V.