Examining the Cubic, Fused Cubic, and Cage Structures of (H2O)n for n = 8, 9, 12, 16, 20, and 21: Do Fused Cubic Structures Form?

Abstract

The structures and stabilization energies (SE) of water clusters, (HzO),, with n = 8, 9, 12, 16, 20, and 21, were calculated by applying the intermediate neglect of differential overlap self-consistent field restricted Hartree-Fock method (INDO SCF RHF) after proper parametrization. These cluster structures include the neutral cubic forms for 8 and 9 mers, fused cubic 12, 16, 20, and 21 mers and cage structures for 16, 20, and 21 mers. In addition, the structure and SE values of the protonated fused cubic 20 and 21 mer clusters were calculated and compared with those of the cage structures. A closer examination of the fused cubic and the cage structures combined with the experimental evidence suggests that the fused structures are not likely to form. The present study also explains the observed magic numbers in experiments.

Computational studies of the stability of the (H2O)100 nanodrop

“…Structures for cage-based clusters with 15-22, 28 and 30 molecules were taken from Refs [4,7,[17][18][19][20] (Fig. 2).…”

“…Cage-based clusters, like the low energy structures for the clusters with 21 and 28 molecules [5][6][7][8], consist of a 3-coordinated cage that may enclose a number of molecules Hbonded to the surrounding cage. Quantum-chemical calculations most often predict more dense structures [2,3].…”

Energetic and fragmentation stability of water clusters (H2O)n, n=2–30

“…Structures composed in this way are more energetic favorable than the other motifs for water clusters of these sizes. The structures of the lowest-energy isomers of water clusters (H 2 O) 8,10,12,15,18 can be thought of ring-stacking structures with two 4-sides rings, two 5-sides rings, three 4-sides rings, three 5-sides rings, and three 6-sides rings, respectively [8][9][10][11][12][13]39]. It is interesting to note that water heptamer and nonamer [5][6][7][8] can be viewed as removing or inserting a water monomer into a cubic octamer isomer, respectively.…”

“…For larger water clusters (H 2 O) n , n > 10, studies using empirical potentials [32][33][34][35][36], semi-empirical calculations [37], as well as ab initio calculations [8][9][10][11][12][13]20,23] have been reported. Due to the existence of many local minima on the potential energy surface which grow rapidly with increasing cluster size, it is very difficult to locate the global minima geometries for these clusters.…”

Water Clusters in Gas Phases Studied by Liquid Ionization Mass Spectrometry

“…13), 15) The clathrate structure has been suggested experimentally and a distorted dodecahydron has been suggested by theoretical calculation. 15), 17) Results of calculation have been reported recently for a variety of water clusters 5), 16) and cluster ions.…”