Structure and Stability of Water Clusters (H₂O)_n, n = 8−20:  An Ab Initio Investigation

Abstract

Extensive ab initio calculations have been performed using the 6-31G(d,p) and 6-311++G(2d,2p) basis sets for several possible structures of water clusters (H 2 O) n , n ) 8-20. It is found that the most stable geometries arise from a fusion of tetrameric or pentameric rings. As a result, (H 2 O) n , n ) 8, 12, 16, and 20, are found to be cuboids, while (H 2 O) 10 and (H 2 O) 15 are fused pentameric structures. For the other water clusters (n ) 9, 11, 13, 14, and 17-19) under investigation, the most stable geometries can be thought of as arising from either the cuboid or the fused pentamers or a combination thereof. The stability of some of the clusters, namely, n ) 8-16, has also been studied using density functional theory. An attempt has been made to estimate the basis set superposition error and zero-point energy correction for such clusters at the HartreeFock (HF) level using the 6-311++G(2d,2p) basis set. To ensure that a minimum on the potential-energy surface has been located, frequency calculations have been carried out at the HF level using the 6-31G(d,p) and 6-311++G(2d,2p) basis sets for some of the clusters. Molecular electrostatic potential topography mapping has been employed for understanding the reactivity as well as the binding patterns of some of the structurally interesting clusters.

Brønsted basicity of the air–water interface

“…3). We find that these results depend little on the various close-lying energy minima or the anharmonicity of low-frequency vibrations in W n ·OH − clusters (47). Because ΔG 3°= −43 kcal mol −1 , it is quite plausible that an OH − located near the interface would induce barrierless PT.…”

Simulating Water with the Self-Consistent-Charge Density Functional Tight Binding Method: From Molecular Clusters to the Liquid State

“…If those structures were minimized again with ab initio methods, most of them eventually converged to the same small ensemble of minimum energy conformations identified in the original ab initio calculations. 31 In other words, it appears that the surface of the SCCDFTB calculation may be discontinuous and thus many artificial minimum energy states showed up. This result might be attributed to the tabulated parameters in the SCCDFTB method which were designed to speed up the speed of computations.…”

From Simple Rings to One‐Dimensional Channels with Calix[8]arenes, Water Clusters, and Alkali Metal Ions.

“…Thus, reaction of 4-tert-butylcalix [8] 27 Here, the square is stabilized by two hydrogen bond interactions (O16-O9; 2.715(2) Å ) with two THF molecules, each water molecule in fact being oriented in such a way that one hydrogen atom bridges to the neighboring water molecule whereas the second hydrogen atom points outward from the square. 27,28 Further water molecules (O17 and symmetry equivalents) are linked to oxygen atoms of the calixarene ligand and are shielded by H bonding to THF ligands (O12) arranged around the sandwich structure. Other heavily disordered THF and water molecules are found in the structure.…”

“…Such a structure for (H 2 O) 10 has not been described before in the literature, but a similar one has been predicted as one possible, but not the most stable, structure in ab initio studies. [28][29][30][31][32][33][34] Reaction O11 O10 Na2 Na1 Figure 1. The asymmetric unit of 1 (H atoms and non-coordinating solvent omitted for clarity).…”