Abstract: Using a first-principles method based on density functional theory, together with the generalised gradient approximation, the structures and electronic properties of Cn(n= 2-9) clusters have been determined, and their highest occupied molecular orbital-lowest unoccupied molecular orbital energy gaps and their binding energies have been calculated. The results show that the Cn cluster binding energy, and therefore, the stability of the cluster structure increase monotonically with cluster size n. The cluster energy gap varies in a non-monotonic manner with cluster size, and its range of values indicates that the clusters behave as semiconductors. According to the partial density of states of the carbon atoms, the energy of the s state falls with increasing cluster size, whereas the energy of the p state rises.