Supercooled Low-Entropy Water Clusters (original) (raw)
Related papers
Long-lived water clusters in hydrophobic solvents investigated by standard NMR techniques
Scientific Reports, 2019
Unusual physical characteristics of water can be easier explained and understood if properties of water clusters are revealed. Experimental investigation of water clusters has been reported by highly specialized equipment and/or harsh experimental conditions and has not determined the properties and the formation processes. In the current work, we used standard 1H-NMR as a versatile and facile tool to quantitatively investigate water clusters in the liquid phase under ambient conditions. This approach allows collection of data regarding the formation, long lifetime, stability, and physical properties of water clusters, as a cubic octamer in the liquid phase.
Formation of Water Clusters in a Hydrophobic Solvent
Angewandte Chemie International Edition, 2003
Water is of fundamental importance for all forms of life and plays an important role in many biological and chemical processes. The exploration of the structural and binding properties of small water complexes provides a key to the understanding of bulk water in its liquid and solid phases. As a result, considerable attention has been given to the theoretical and experimental study of small water complexes.
The Journal of Physical Chemistry Letters, 2020
The hydrophilic/hydrophobic interactions of water are important in biological and chemical self-assembly phenomena. Water clusters in hydrophobic environments exhibit a unique morphology. Their process of formation and nonpolar properties have been extensively studied, but no direct experimental evidence has been available until now. This study provides spectroscopic evidence for the transformation of water to nonpolar configuration via clustering. Although individual water molecules form hydrogen bonds with the hydroxyl protons of n-hexanol when codissolved in a nonpolar solvent (toluene-d 8), the water clusters are comprised solely of hydrogen bonds between water molecules and do not form hydrogen bonds with the hydroxyl protons of n-hexanol. This behavior indicates that the water clusters are nonpolar rather than polar. This study reports the first example of nonpolar water configuration produced via a liquid-state clustering. This property is a common and important interfacial phenomenon of water in chemistry, biology, materials science, geology, and meteorology.
Physical Chemistry Chemical Physics, 2004
Clustering of water molecules in partially miscible aqueous solutions (with immiscibility gap) was studied by Monte Carlo (MC) simulations. Liquid-liquid coexistence curves were determined by MC simulations in the Gibbs ensemble. Water cluster size distributions were studied in the organic-rich one-phase region. At the coexistence curve we observe the broadest distribution of cluster sizes in agreement with the Fisher droplet model. There are no percolating water clusters in aqueous mixtures of solutions of hydrophobic particles in the studied concentration range. In contrast, in an aqueous solution of hydrophilic solutes crossing the coexistence curve approximately coincides with the 3D percolation threshold of water. An infinite water cluster (percolating cluster or droplet of the second phase) appears in an aqueous solution, when the average number of water-water H-bonds per molecule exceeds ca. 1.6.
The Journal of Chemical Physics, 1999
Energetics, structural features, polarity, and melting transitions in water clusters containing up to eight molecules were studied using ab initio methods and empirical force field models. Our quantum approach was based on density functional theory performed at the generalized gradient approximation level. For the specific case of ͑H 2 O͒ 6 , we selected five conformers of similar energy with different geometries and dipolar moments. For these cases, the cyclic arrangement was found to be the only nonpolar aggregate. For ͑H 2 O͒ 8 , the most stable structures corresponded to nonpolar, cubic-like, D 2d and S 4 conformers. Higher energy aggregates exhibit a large spectrum in their polarities. The static polarizability was found to be proportional to the size of the aggregates and presents a weak dependence with the number of hydrogen bonds. In order to examine the influence of thermal fluctuations on the aggregates, we have performed a series of classical molecular dynamics experiments from low temperature up to the melting transition using two different effective pseudopotentials: the TIP4P and MCY models. Minimum energy structures for both classical potentials were found to reproduce reasonably well the results obtained using ab initio methods. Isomerization and phase transitions were monitored by following changes in dipole moments, number of hydrogen bonds and Lindemann's parameter. For ͑H 2 O͒ 6 and ͑H 2 O͒ 8 , the melting transitions were found at T m Ϸ50 and 160 K, respectively; for both aggregates, we observed premelting transitions between well differentiated conformers as well.
Structure and some properties of small water clusters
Journal of Structural Chemistry, 1994
The energies and structures of many small water clusters (H20)n (n = 8-26) are calculated using the atom-atom potential functions suggested earlier. For each n, several stable configurations were found that differ in the number of H-bonds and in the topology of the graphs formed by such bonds. The clusters in which the molecules lie at the vertices of convex polyhedra have the lowest-energy but other configurations may have close or even lower energies. For the most stable clusters, the energy dependence on n is close to linear. At 300 K, the mean energies of the clusters behave similarly. Monte-Carlo simulations showed that the clusters undergo pseudomelting at approximately 200 K.
Water clusters: Untangling the mysteries of the liquid, one molecule at a time
Proceedings of the National Academy of Sciences, 2001
Extensive terahertz laser vibration-rotation-tunneling spectra and mid-IR laser spectra have been compiled for several isotopomers of small (dimer through hexamer) water clusters. These data, in conjunction with new theoretical advances, quantify the structures, force fields, dipole moments, and hydrogen bond rearrangement dynamics in these clusters. This new information permits us to systematically untangle the intricacies associated with cooperative hydrogen bonding and promises to lead to a more complete molecular description of the liquid and solid phases of water, including an accurate universal force field.
Proton nuclear magnetic resonance ( 1 H NMR) experiments have been performed to measure the spin-lattice, T 1 , and spin-spin, T 2 , relaxation times of the three functional groups in water/methanol mixtures at different methanol molar fractions (X MeOH ) 0, 0.04, 0.1, 0.24, 0.5, 1) as a function of temperature in the range 205 K < T < 295 K. The measured relaxation times in the mixtures, at all the methanol molar fractions, are faster than those of pure water and methanol because of strong interactions, resulting in a complex hydrogen bonding dynamics that determines their thermodynamic properties. In particular, we observe how the interplay between hydrophobicity and hydrophilicity changes with temperature and influences the peculiar thermal behavior of the NMR relaxation times of the solution. The obtained results are interpreted in terms of the existence of stable water-methanol clusters at high temperature whereas, upon cooling to low temperature, clusters of single species are present in the mixture.
Hydrophobic meddling in small water clusters
Theoretical Chemistry Accounts, 2013
What would be the effects on the nature of hydrogen bonds, on the energies, and on the overall structural possibilities of replacing some hydrogen atoms by small hydrophobic groups in small water networks? Aiming at investigating this question, we performed an exhaustive search of the conformational space of the (Methanol) 2 (Water) 3 representative model system, characterized the results, and made key comparative analysis with pentameric pure water clusters. The potential energy surface yielded a global minimum structural motif consisting of several puckered ring-like cyclic isomers very close in energy to each other. They are followed by other structural motifs, which, contrary to conventional belief, would also contribute to the properties of a macroscopic sample of this composition. We found that the C-HÁÁÁO interactions play a subordinate structural role and preferably accommodate to the established O-HÁÁÁO based structures. In comparison with the pure (H 2 O) 5 case, we showed that (1) the same basic structural motifs and in a similar hierarchy energy order are obtained, but with a richer structural isomerism;