Order Parameter of the Liquid–Liquid Transition in a Molecular Liquid

Mosses, Joanna; Syme, Christopher D.; Wynne, Klaas

doi:10.1021/jz5022763

Cited by 28 publications

(39 citation statements)

References 35 publications

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“…Similar situations are often seen in other candidates of LLTs, such as l-butanol [LLT (13) (6, 7) vs. microcrystallization (8,28,47,48)]. For TPP, however, some pieces of experimental evidence supportive of the LLT scenario rather than the microcrystallization scenario have recently been reported (11,12).We propose a two-order-parameter (TOP) model of a liquid to explain LLT (20,49). The main point of this model is that it is necessary to consider the spatiotemporal hierarchical nature of a liquid to understand LLT.…”

supporting

confidence: 58%

“…Similar situations are often seen in other candidates of LLTs, such as l-butanol [LLT (13) vs. microcrystallization (40)(41)(42)(43)], confined water [LLT (5) vs. other phenomena (44)(45)(46)], and aqueous solutions [LLT (6, 7) vs. microcrystallization (8,28,47,48)]. For TPP, however, some pieces of experimental evidence supportive of the LLT scenario rather than the microcrystallization scenario have recently been reported (11,12).…”

supporting

confidence: 52%

“…refractive index (or, density) (9,10,29,30), and the polarity associated with local molecular ordering (12) has been suggested for LLT in TPP. There have been structural studies on LLT by X-ray and neutron scattering measurements, focusing on local liquid structures at an inter-and intramolecular scale (36,38,(52)(53)(54) and mesoscopic structures (34,55).…”

mentioning

confidence: 99%

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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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supporting

confidence: 58%

supporting

confidence: 52%

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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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“…Thus, further study is necessary to address this problem. Nevertheless, combining other pieces of experimental evidence, 17,46,47 we conclude that the phenomenon is most reasonably explained by the LLT scenario.…”

Section: Discussionmentioning

confidence: 52%

Time-Resolved Light Scattering Study on the Kinetics of the Liquid–Liquid Transition in Triphenyl Phosphite

2015

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There is experimental evidence suggesting the existence of a liquid-liquid transition (LLT) in a single-component liquid. However, none of this evidence is free from controversy, including the case of a molecular liquid, triphenyl phosphite, which we study here. Furthermore, the kinetics of LLT has been largely unexplored. Here we study the phase-transition dynamics of triphenyl phosphite in a supercooled liquid state by means of time-resolved polarized and depolarized small-angle light scattering to clarify whether the transition is a liquid-liquid transition (LLT) or merely nanocrystal formation. A part of this study was recently reported in another of our papers [Shimizu, R.; Kobayashi, M.; Tanaka, H. Phys. Rev. Lett. 2014, 112, 125702]. A detailed analysis of our experimental results of light scattering and the comparison with heat evolution during LLT have revealed the following facts. The polarized scattering from domains has a finite (nonzero) intensity in the low-wavenumber limit, and the time evolution of its average intensity is almost proportional to the square of the heat-releasing rate. The depolarized scattering intensity monotonically increases in the process of LLT during isothermal annealing above the spinodal temperature TSD but exhibits a peak below TSD. On the basis of these results, we suggest that the primary process is LLT, whose order parameter is of a nonconserved nature, but accompanies nanocrystal formation. In the NG-type LLT, the sharp interface between liquid II droplets and the liquid I matrix promotes nanocrystal formation there, whereas much less nanocrystal formation is induced in the SD-type LLT due to the lack of such sharp interfaces.

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“…In the experiments, the samples were quenched and held at a selected temperature. 35,36 Microscopy Microscopy was carried out using an Olympus BX53 light microscope that features modular units for phasecontrast and fluorescence microscopy, and a custom unit allowing for simultaneous laser irradiation and microscopy. The laser used was a 785-nm diode laser (Thorlabs Ltd.) producing a maximum power incident on the sample of 200 mW with an elliptical mode with a mean beam radius (at half height) of 2.4 µm when using a 10´ objective.…”

Section: Methodsmentioning

confidence: 99%

Control over phase separation and nucleation using a laser-tweezing potential

Walton

Wynne

2018

Nature Chem

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Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallisation engineering by varying physicochemical parameters, controlling which polymorph crystallises or whether a molecule crystallises or forms an amorphous precipitate is still a black art. Although there are now numerous examples of control using laserinduced nucleation, a physical understanding is absent and preventing progress. Here we show that the proximity of a liquid-liquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation through a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter.The nucleation of new phases such as crystals from solution is of enormous technological importance but poorly understood. Although the vast majority of pharmaceutical products and most fine and speciality chemical products are made in crystalline form, industrial crystallisation has changed little in the past 350 years and suffers from an embarrassing lack of control with sometimes unexpected and severe financial consequences.1 Therefore, a deeper understanding of and control over (crystal) nucleation is of great importance.Two decades ago, it was shown that nanosecond pulsed lasers can nucleate crystals in a supersaturated solution through a non-photochemical process.2 Most significantly, it was shown that the crystal polymorph could be selected by the polarisation state of the laser.3 Subsequent work has shown that laser pulses can induce nucleation of various crystals, 4,5 liquid crystals, 6,7 and bubbles. 8 It was initially suggested that the Kerr effect was responsible for laser-induced nucleation 2 but subsequent work has shown that the data are inconsistent with it. 9 Most disconcertingly, the reproducibility of polarisation-control over polymorph selection has been questioned while pulsedlaser induced nucleation appears to require impurity particles.10 However, a laser-induced nucleation experiment using CW lasers did reliably show polarisation-control over polymorph selection.11 Thus, it is fair to say that a physical understanding of these phenomena is still sorely lacking.In a supersaturated solution, the crystal is the thermodynamically most stable state but is difficult to access in the absence of heterogeneous nucleation sites. In the simplest case, random fluctuations lead to the formation of a critical nucleus and ultimately a macroscopic crystal. As suggested by Frenkel for proteins 12 and more generally in non-classical nucleation theories, 13-15 the concentration fluctuations leading to nucleation may well be enhanced by...

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Order Parameter of the Liquid–Liquid Transition in a Molecular Liquid

Cited by 28 publications

References 35 publications

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

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

Time-Resolved Light Scattering Study on the Kinetics of the Liquid–Liquid Transition in Triphenyl Phosphite

Control over phase separation and nucleation using a laser-tweezing potential

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