Liquid-liquid transition in ST2 water

Yang, Ling; Palmer, Jeremy C.; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

doi:10.1063/1.4769126

Cited by 159 publications

(195 citation statements)

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“…24,29,39,40,43,72, and 91. The present results were based on isobaric heating simulations starting from LDA and HDA at pressures in the range −500 ≤ P ≤ 1700 MPa.…”

Section: Summary and Discussionmentioning

confidence: 99%

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Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

Chiu

Starr

Giovambattista

2014

The Journal of Chemical Physics

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Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDAto-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T "phase diagram" for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related, both being associated with the limit of kinetic stability of LDA (HDA).

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“…24,29,39,40,43,72, and 91. The present results were based on isobaric heating simulations starting from LDA and HDA at pressures in the range −500 ≤ P ≤ 1700 MPa.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…However, the density values and structure of LDA and HDA are better predicted by the SPC/E model than by the ST2 model. 38 The main qualitative difference between these models is that equilibrium MD simulations indicate the existence of a LLPT in ST2 water 24,[39][40][41][42][43][44][45] (see, however, Refs. [46][47][48][49].…”

Section: Introductionmentioning

confidence: 99%

Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

Chiu

Starr

Giovambattista

2014

The Journal of Chemical Physics

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“…We note that bulk crystallization of all-atom water models is rather unusual in MD simulations, 35,81,82 but high-pressure crystallization to an ice VII-like structure has been previously reported for the ST2 model. 35,83 We confirm that the crystal formed is ice VII by evaluating the structure factor S(q). Fig.…”

Section: Crystallization Of Hda To Ice VIImentioning

confidence: 99%

“…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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“…1,2,4-18 Different thermodynamic consistent scenarios have been proposed [19][20][21][22] leading to intense discussions which extend up to present days. [23][24][25][26][27][28] The first thermodynamic scenario coherently accounting for the observed density, compressibility, and specific heat anomalies of water was proposed in 1982 by Robin Speedy. 29 In this very elegant piece of work, Speedy focused on the limit of stability of the liquid phase -which in mean-field coincides with the gas-liquid spinodal line -a line emanating from the gas-liquid critical point.…”

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confidence: 99%