THEORETICAL-STUDY OF SMALL WATER CLUSTERS - LOW-ENERGY FUSED CUBIC STRUCTURES FOR (H2O)N, N=8, 12, 16, AND 20

Force field calculations employing the TIP4P potential are used to optimize several structures of the (H2O)n, n = 8, 12, 16, and 20 clusters. (H2O)8 is found to have, in agreement with previous studies, low-energy cubic structures of D2d and S4 symmetry. The lowest-energy forms of the larger clusters are found to have fused cubic structures rather than cagelike or networked structures. The stability of the fused cubic structures of (H2O)12 is confirmed by means of MP2 calculations.