Atlas of putative minima and low-lying energy networks of water clusters n = 3–25

Abstract

We report a database consisting of the putative minima and ∼3.2 × 106 local minima lying within 5 kcal/mol from the putative minima for water clusters of sizes n = 3–25 using an improved version of the Monte Carlo temperature basin paving (MCTBP) global optimization procedure in conjunction with the ab initio based, flexible, polarizable Thole-Type Model (TTM2.1-F, version 2.1) interaction potential for water. Several of the low-lying structures, as well as low-lying penta-coordinated water networks obtained with the TTM2.1-F potential, were further refined at the Møller-Plesset second order perturbation (MP2)/aug-cc-pVTZ level of theory. In total, we have identified 3 138 303 networks corresponding to local minima of the clusters n = 3–25, whose Cartesian coordinates and relative energies can be obtained from the webpage https://sites.uw.edu/wdbase/. Networks containing penta-coordinated water molecules start to appear at n = 11 and, quite surprisingly, are energetically close (within 1–3 kcal/mol) to the putative minima, a fact that has been confirmed from the MP2 calculations. This large database of water cluster minima spanning quite dissimilar hydrogen bonding networks is expected to influence the development and assessment of the accuracy of interaction potentials for water as well as lower scaling electronic structure methods (such as different density functionals). Furthermore, it can also be used in conjunction with data science approaches (including but not limited to neural networks and machine and deep learning) to understand the properties of water, nature’s most important substance.

Infrared spectroscopy of neutral water clusters at finite temperature: Evidence for a noncyclic pentamer

“…S3. Both calculations indicate that the most stable structure of the water trimer, tetramer, and pentamer are cyclic, whereas that of the hexamer is noncyclic, consistent with previously well-established threshold of 3D water structures instigating at hexamer (34)(35)(36). Vibrational frequencies for these neutral water clusters were also calculated using harmonic model at the MP2 level.…”

“…quantum-tunneling-induced hydrogen-bond breaking in the neutral prism hexamer was investigated (31). Along with significant advances in theoretical calculations (32)(33)(34)(35)(36), these studies provided great insights into the hydrogen bonding structures and dynamics of neutral water clusters.…”

“…As pointed out by Clary (3), water molecules in liquid are held together by an ever-changing network of hydrogen bonds, which are 3D in nature. From previous studies, it is known that the water trimer, tetramer, and pentamer all have cyclic minimumenergy structures with all oxygen atoms in a two-dimensional (2D) plane, while the water hexamer has noncylic 3D structures (34)(35)(36). Clearly there are two important issues: when does the 2D-to-3D structural change occur in neutral water clusters and how is this structural change manifested in the OH stretching spectra?…”

How many water molecules are needed to solvate one?

“…16 Many experimental and theoretical investigations have been undertaken to describe the intermolecular interactions of these systems, going from small quasi-planar (with reference to the oxygen atoms) clusters to larger ones. [17][18][19][20] On the theoretical side, this has led to construction of accurate potential energy surfaces (PES), 21,22 search of geometric and energy minima in a very complicated energy landscape, and spectroscopic calculations. 23,24 For instance, the structural characteristics of water clusters beyond the transition between "all-surface" and "interior" ones have been studied.…”

A two state model study of photo‐detachment dynamics driven by an optimally designed polychromatic field: A simulated annealing based optimisation

“…We have also achieved ∼38% of dissociation probability by application of our optimally designed pulse. These pulses are designed by simulated annealing (SA) technique which is an algorithm based on stochastic principles [7–10]. A very significant advantage of using stochastic optimiser is that it helps us to reach to the global solution instead of getting stuck in a local one.…”