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 (H 2 O) n , n=8, 12, 16, and 20 clusters. (H 2 O) 8 is found to have, in agreement with previous studies, low-energy cubic structures of D 2d and S 4 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 (H 2 O) 12 is confirmed by means of MP2 calculations