Search for Low Energy Structures of Water Clusters (H₂O)_n, n = 20−22, 48, 123, and 293

Abstract

A search for low energy structures of water clusters was performed with a combination of three computational tools: (a) temperature-dependent classical trajectories; (b) hydrogen network improvement; (c) rigid body diffusion Monte Carlo calculation on a smoothed potential energy surface. For the sizes of our main interest, n ) 48, 123, and 293, input configurations included spheroid structures cut from crystalline ice, and amorphous structures. For n ) 48, tube and sandwich minima were explored as well. The lowest energy configurations found were characterized by compact three-dimensional shapes. In the case of n ) 48 and 123, crystallinity was lost in the course of the optimization; for these sizes, one finds four-, five-, and six-membered rings of water molecules, On the other hand, the lowest energy structure found for n ) 293 includes a crystal core, dominated by six-membered rings, and an amorphous surface.

Experimental nanocalorimetry of protonated and deprotonated water clusters

“…This result was confirmed by vibrational IR spectroscopy experiments on pure water and Na-doped clusters [10,13], which suggest an onset of crystallization at about 275 water molecules [13]. Computer simulations support the assumption of amorphous-tocrystalline transition occurring above 200 molecules [14]. On the other hand, 21-molecule water clusters and sizes slightly above are likely to form more or less deformed cage structure; thus, a transition from cage to amorphous structures is expected to occur somewhere between 21 and 275 molecules.…”

Infrared Spectra and Hydrogen‐Bonded Network Structures of Large Protonated Water Clusters H+(H2O)n (n=20–200)

“…For example, the lowest-energy structures of (H 2 O) n (n 9 1000) on the empirical potentialenergy surface have been reported, and these studies suggested that crystal cores are formed in the size region of a few hundred water molecules or more. [2][3][4]22] We show clear spectroscopic signatures for the abundance of the interior (4-coord) water. Furthermore, the fact that IR spectral patterns approach those of supercooled water and ice with increasing cluster size suggests formation of more ordered H-bonded network structures.…”

Understanding the structure and hydrogen bonding network of (H2O)32and (H2O)33: an improved Monte Carlo temperature basin paving (MCTBP) method and quantum theory of atoms in molecules (QTAIM) analysis

“…15 In the DSI method as applied by Kazimirski and Buch, 51 all the oxygen-oxygen pair distances are calculated and sorted in ascending or descending order to get a vector of n(n À 1)/2 distances for n number of oxygen atoms from both structures. Then, the distance between these two vectors gives the DSI value.…”

“…50 Kazimirski and Buch used a molecular dynamics simulation and MC method on large water clusters. 51 One of the well-known MC optimization techniques, basin hopping, was rst applied to water clusters by Wales et al on (H 2 O) n , n # 21. 52 Kabrede did vibrational modes analysis in the basin hopping technique using TIP4P potential for water cluster optimization.…”