Free energy surface of ST2 water near the liquid-liquid phase transition

Poole, Peter H.; Bowles, Richard K.; Saika‐Voivod, Ivan; Sciortino, Francesco

doi:10.1063/1.4775738

Cited by 132 publications

(142 citation statements)

References 29 publications

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“…Here, the liquid-liquid critical point (LLCP) scenario hypothesizes the existence of a second critical point in the metastable supercooled phase [179][180][181][182][183][184], below which liquid water would phase separate into two different liquids, low-density liquid (LDL) and high-density liquid (HDL) (the scenario has been intensely debated over the last years [185], but recent results seem to have confirmed it [183,184]). Also glassy water has been found to exist in different states, called low-density (LDA), high-density (HDA) and very high-density (VHDA) [186] amorphous ices, which can interconvert with each other by the application of pressure.…”

Section: Local Structural Ordering and Thermodynamic Anomalies Of Watermentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

107

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Nucleation is an activated process in which the system has to overcome a free energy barrier in order for a first-order phase transition between the metastable and the stable phases to take place. In the liquid-to-solid transition the process occurs between phases of different symmetry, and it is thus inherently a multi-dimensional process, in which all symmetries are broken at the transition. In this Focus Article, we consider some recent studies which highlight the multi-dimensional nature of the nucleation process. Even for a single-component system, the formation of solid crystals from the metastable melt involves fluctuations of two (or more) order parameters, often associated with the decoupling of positional and orientational symmetry breaking. In other words, we need at least two order parameters to describe the free-energy of a system including its liquid and crystalline states. This decoupling occurs naturally for asymmetric particles or directional interactions, focusing here on the case of water, but we will show that it also affects spherically symmetric interacting particles, such as the hard-sphere system. We will show how the treatment of nucleation as a multi-dimensional process has shed new light on the process of polymorph selection, on the effect of external fields on the nucleation process, and on glass-forming ability.

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Section: Local Structural Ordering and Thermodynamic Anomalies Of Watermentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

107

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“…However, none of the LLTs reported so far is free from criticisms (20,21), mainly because these LLTs take place under experimentally difficult conditions [e.g., at high temperature and pressure (14,15,(17)(18)(19)] or in a supercooled state below the melting point (1-3, 5-7, 9, 10), where the transition is inevitably contaminated by microcrystal formation. The latter is not limited to experiments but arises in numerical simulations, often causing many controversies [LLT (22)(23)(24)(25) vs. crystallization (26)(27)(28)]. For ST2 water, however, this issue has recently been settled by an extensive simulation study by Palmer et al (4).…”

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confidence: 99%

Microscopic identification of the order parameter governing liquid–liquid transition in a molecular liquid

Murata

Tanaka

2015

Proc. Natl. Acad. Sci. U.S.A.

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A liquid-liquid transition (LLT) in a single-component substance is an unconventional phase transition from one liquid to another. LLT has recently attracted considerable attention because of its fundamental importance in our understanding of the liquid state. To access the order parameter governing LLT from a microscopic viewpoint, here we follow the structural evolution during the LLT of an organic molecular liquid, triphenyl phosphite (TPP), by timeresolved small-and wide-angle X-ray scattering measurements. We find that locally favored clusters, whose characteristic size is a few nanometers, are spontaneously formed and their number density monotonically increases during LLT. This strongly suggests that the order parameter of LLT is the number density of locally favored structures and of nonconserved nature. We also show that the locally favored structures are distinct from the crystal structure and these two types of orderings compete with each other. Thus, our study not only experimentally identifies the structural order parameter governing LLT, but also may settle a longstanding debate on the nature of the transition in TPP, i.e., whether the transition is LLT or merely microcrystal formation.liquid-liquid transition | order parameter | X-ray scattering | locally favored structure | transition kinetics L iquid-liquid transition (LLT) is an intriguing phenomenon in which a liquid transforms into another one via a first-order transition. This means that there can be more than two liquid states for a single-component substance. Despite its counterintuitive nature, there have recently been many pieces of experimental and numerical evidence for the existence of LLT, for various liquids such as water (1-5), aqueous solutions (6-8), triphenyl phosphite (9-12), l-butanol (13), phosphorus (14), silicon (15, 16), germanium (17), and Y 2 O 3 -Al 2 O 3 (18,19). This suggests that the LLT may be rather universally observed for various types of liquids. However, none of the LLTs reported so far is free from criticisms (20, 21), mainly because these LLTs take place under experimentally difficult conditions [e.g., at high temperature and pressure (14,15,(17)(18)(19)] or in a supercooled state below the melting point (1-3, 5-7, 9, 10), where the transition is inevitably contaminated by microcrystal formation. The latter is not limited to experiments but arises in numerical simulations, often causing many controversies vs. crystallization (26-28)]. For ST2 water, however, this issue has recently been settled by an extensive simulation study by Palmer et al. (4).One of the hottest and long-standing debates is on the nature of the transition found in a molecular liquid, triphenyl phosphite (TPP), by Kivelson and his coworkers (29). The transition is very easy to access experimentally, because it takes place at ambient pressure and at a temperature range between 230 and 210 K and the transformation speed is slow enough to follow the kinetics. Since the finding of this transition (29, 30), many researchers thus have been inte...

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“…Although some recent works question the existence of a LLPT in ST2 water, 30,31 most recent computational works robustly demonstrate that ST2 water exhibits a metastable LLPT at low temperature. [32][33][34][35][36] In addition, the possibility of a LLPT has been seen in computer simulations of many other pure fluids. [37][38][39][40][41][42][43][44] More importantly, technical questions regarding equilibration raised in Refs.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced transformations in computer simulations of glassy water

Chiu

Starr

Giovambattista

2013

The Journal of Chemical Physics

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Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and highdensity amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-induced LDA-to-HDA, (ii) decompression-induced HDA-to-LDA, and (iii) compression-induced hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a lowdensity and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative pressures, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high pressure to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water. © 2013 AIP Publishing LLC.

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Free energy surface of ST2 water near the liquid-liquid phase transition

Cited by 132 publications

References 29 publications

Crystal nucleation as the ordering of multiple order parameters

Crystal nucleation as the ordering of multiple order parameters

Microscopic identification of the order parameter governing liquid–liquid transition in a molecular liquid

Pressure-induced transformations in computer simulations of glassy water

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