Water and water-like liquids: relationships between structure, entropy and mobility

Abstract

Liquids with very diverse underlying interactions share the thermodynamic and transport anomalies of water, including metalloids, ionic melts and mesoscopic fluids. The generic feature that characterises such water-like liquids is a density-driven shift in the nature of local order in the condensed phases. The key semiquantitative relationships between structural order, thermodynamics and transport that are necessary in order to map out the consequences of this common qualitative feature for liquid-state properties and phase transformations of such systems are reviewed here. The application of these ideas to understand and model tetrahedral liquids, especially water, is discussed and possible extensions to other complex fluids are considered.

Triplet Correlations Dominate the Transition from Simple to Tetrahedral Liquids

“…Experimental tools such as confocal video microscopy can be used to directly compute triplet correlation functions for colloidal fluids from which entropic changes associated with self-assembly can be obtained. While this study focuses on the connections between structural correlations and excess entropy, the implications of enhancing triplet correlations for dynamics can be explored using mode-coupling theory [54] or excess entropy scaling of dynamical properties [10,55]. The results of this study should therefore be of relevance to experimentalists and theoreticians working on simple and complex fluids, soft materials, and self-assembly of colloids and nanoparticles.…”

“…They show a density-driven shift from four-coordinate, local order at low densities to random, close-packing arrangements at high densities. Depending on the degree of energetic preference for local tetrahedral order, they display several differences in comparison to simple liquids, including density and related response function anomalies, negative volume changes on melting, crystalline polymorphism, and polyamorphism [10,[14][15][16][17][18]. Our motivation here is to understand the competition between pair and triplet correlations that underlies the transformation of a simple liquid into a complex, tetrahedral liquid, using the multiparticle correlation expansion for the entropy to translate the information on pair and triplet correlations into thermodynamic signatures associated with liquid state behavior and phase transformations [19][20][21][22][23][24].…”

“…Here we address the changing relationships between structural correlations and thermodynamics that underlie the transformation of a simple liquid into a complex, tetrahedral liquid dominated by triplet correlations, driven by a systematic variation of the degree of anisotropy of the interparticle interactions. Tetrahedral fluids are among the simplest of complex fluids and include a number of important systems, such as water, ionic melts (SiO 2 ,BeF 2 ), covalently bonded liquids (C, Si), metalloids (Ge, Sn), and dispersions of patchy colloids [4][5][6][7][8][9][10][11][12][13]. They show a density-driven shift from four-coordinate, local order at low densities to random, close-packing arrangements at high densities.…”

Simple liquids’ quasiuniversality and the hard-sphere paradigm

“…The van der Waals picture is not able to predict which systems are quasiuniversal and which are not. It is not surprising that complex liquids like water violate quasiuniversality [12,20], [153][154][155][156][157]. But even some simple liquid models (i.e.…”

Communication: Local structure-mobility relationships of confined fluids reverse upon supercooling

“…[17][18][19][20][21][22][23][24][25][26][27] To wit, it has been shown that single-particle diffusivities, relaxation times, and viscosities along structurally invariant (i.e., isotropic) dimensions of simple confined fluids can be predicted based on knowledge of how dynamic properties of the bulk fluid relate to static quantities including excess entropy s ex (relative to the ideal gas) and fractional available space exp{c (1) } (or insertion probability p 0 ), which characterize short-range static correlations and particle packings, respectively.…”