1
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Affiliation(s)
- Hajime Tanaka
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan
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2
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Walton F, Bolling J, Farrell A, MacEwen J, Syme CD, Jiménez MG, Senn HM, Wilson C, Cinque G, Wynne K. Polyamorphism Mirrors Polymorphism in the Liquid-Liquid Transition of a Molecular Liquid. J Am Chem Soc 2020; 142:7591-7597. [PMID: 32249557 PMCID: PMC7181258 DOI: 10.1021/jacs.0c01712] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
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Liquid–liquid
transitions between two amorphous phases in
a single-component liquid have courted controversy. All known examples
of liquid–liquid transitions in molecular liquids have been
observed in the supercooled state, suggesting an intimate connection
with vitrification and locally favored structures inhibiting crystallization.
However, there is precious little information about the local molecular
packing in supercooled liquids, meaning that the order parameter of
the transition is still unknown. Here, we investigate the liquid–liquid
transition in triphenyl phosphite and show that it is caused by the
competition between liquid structures that mirror two crystal polymorphs.
The liquid–liquid transition is found to be between a geometrically
frustrated liquid and a dynamically frustrated glass. These results
indicate a general link between polymorphism and polyamorphism and
will lead to a much greater understanding of the physical basis of
liquid–liquid transitions and allow the systematic discovery
of other examples.
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Affiliation(s)
- Finlay Walton
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
| | - John Bolling
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Andrew Farrell
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Jamie MacEwen
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
| | | | | | - Hans M Senn
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Claire Wilson
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
| | - Gianfelice Cinque
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE, U.K
| | - Klaas Wynne
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
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3
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Role of hydrodynamics in liquid-liquid transition of a single-component substance. Proc Natl Acad Sci U S A 2020; 117:4471-4479. [PMID: 32051252 DOI: 10.1073/pnas.1911544117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Liquid-liquid transition (LLT) is an unconventional transition between two liquid states in a single-component system. This phenomenon has recently attracted considerable attention not only because of its counterintuitive nature but also since it is crucial for our fundamental understanding of the liquid state. However, its physical understanding has remained elusive, particularly of the critical dynamics and phase-ordering kinetics. So far, the hydrodynamic degree of freedom, which is the most intrinsic kinetic feature of liquids, has been neglected in its theoretical description. Here we develop a Ginzburg-Landau-type kinetic theory of LLT taking it into account, based on a two-order parameter model. We examine slow critical fluctuations of the nonconserved order parameter coupled to the hydrodynamic degree of freedom in equilibrium. We also study the nonequilibrium process of LLT. We show both analytically and numerically that domain growth becomes faster (slower), depending upon the density decrease (increase) upon the transition, as a consequence of hydrodynamic flow induced by the density change. The coupling between nonconserved order parameter and hydrodynamic interaction results in anomalous domain growth in both nucleation-growth-type and spinodal-decomposition-type LLT. Our study highlights the characteristic features of hydrodynamic fluctuations and phase ordering during LLT under complex interplay among conserved and nonconserved order parameters and the hydrodynamic transport intrinsic to the liquid state.
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4
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Walton F, Wynne K. Using optical tweezing to control phase separation and nucleation near a liquid-liquid critical point. SOFT MATTER 2019; 15:8279-8289. [PMID: 31603454 DOI: 10.1039/c9sm01297d] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
About 20 years ago, it was shown that lasers can nucleate crystals in super-saturated solutions and might even be able to select the polymorph that crystallises. However, no theoretical model was found explaining the results and progress was slowed down. Here we show that laser-induced nucleation may be understood in terms of the harnessing of concentration fluctuations near a liquid-liquid critical point using optical tweezing in a process called laser-induced phase separation (LIPS) and LIPS and nucleation (LIPSaN). A theoretical model is presented based on the regular solution model with an added term representing optical tweezing while the dynamics are modelled using a Kramers diffusion equation, and the roles of heat diffusion and thermophoresis are evaluated. LIPS and LIPSaN experiments were carried out on a range of liquid mixtures and the results compared to theory.
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5
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Bachler J, Handle PH, Giovambattista N, Loerting T. Glass polymorphism and liquid-liquid phase transition in aqueous solutions: experiments and computer simulations. Phys Chem Chem Phys 2019; 21:23238-23268. [PMID: 31556899 DOI: 10.1039/c9cp02953b] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One of the most intriguing anomalies of water is its ability to exist as distinct amorphous ice forms (glass polymorphism or polyamorphism). This resonates well with the possible first-order liquid-liquid phase transition (LLPT) in the supercooled state, where ice is the stable phase. In this Perspective, we review experiments and computer simulations that search for LLPT and polyamorphism in aqueous solutions containing salts and alcohols. Most studies on ionic solutes are devoted to NaCl and LiCl; studies on alcohols have mainly focused on glycerol. Less attention has been paid to protein solutions and hydrophobic solutes, even though they reveal promising avenues. While all solutions show polyamorphism and an LLPT only in dilute, sub-eutectic mixtures, there are differences regarding the nature of the transition. Isocompositional transitions for varying mole fractions are observed in alcohol but not in ionic solutions. This is because water can surround alcohol molecules either in a low- or high-density configuration whereas for ionic solutes, the water ion hydration shell is forced into high-density structures. Consequently, the polyamorphic transition and the LLPT are prevented near the ions, but take place in patches of water within the solutions. We highlight discrepancies and different interpretations within the experimental community as well as the key challenges that need consideration when comparing experiments and simulations. We point out where reinterpretation of past studies helps to draw a unified, consistent picture. In addition to the literature review, we provide original experimental results. A list of eleven open questions that need further consideration is identified.
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Affiliation(s)
- Johannes Bachler
- Institute of Physical Chemistry, University of Innsbruck, A-6020 Innsbruck, Austria.
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6
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Liu X, Liu S, Chen E, Peng L, Yu Y. First-Order Liquid-Liquid Transition without Density Discontinuity in Molten Sodium Acetate Trihydrate and Its Influence on Crystallization. J Phys Chem Lett 2019; 10:4285-4290. [PMID: 31318570 DOI: 10.1021/acs.jpclett.9b01101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Liquid-liquid transition (LLT) refers to the phase transition among thermodynamically distinct liquid states with identical composition in analogy to the polymorphic transition in solid. The growing awareness of its significance to understanding the nature of liquid also provokes curiosity about its potential impact on crystallization. Here, we report a first-order liquid-liquid transition above liquidus temperature in the melt of sodium acetate trihydrate using nuclear magnetic resonance, differential scanning calorimetry, and high-precision density measurements, which show negligible change in density associated with the observed LLT. Further, the kinetics and products of crystallization are significantly influenced by LLT, providing a new way for the controlling crystallization pathway and realizing crystal polymorph selection.
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Affiliation(s)
- Xun Liu
- School of Materials Science and Engineering and State Key Lab for Materials Processing and Die and Mold Technology , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
| | - Shiyu Liu
- School of Materials Science and Engineering and State Key Lab for Materials Processing and Die and Mold Technology , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
| | - Enyi Chen
- School of Materials Science and Engineering and State Key Lab for Materials Processing and Die and Mold Technology , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
| | - Liang Peng
- School of Materials Science and Engineering and State Key Lab for Materials Processing and Die and Mold Technology , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
| | - Yao Yu
- School of Materials Science and Engineering and State Key Lab for Materials Processing and Die and Mold Technology , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
- Wuhan National High Magnetic Field Center , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
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7
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Link between molecular mobility and order parameter during liquid-liquid transition of a molecular liquid. Proc Natl Acad Sci U S A 2019; 116:7176-7185. [PMID: 30944219 DOI: 10.1073/pnas.1822016116] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Liquid-liquid transition (LLT) is the transformation of one liquid to another via first-order phase transition. For example, LLT in a molecular liquid, triphenyl phosphite, is macroscopically the transformation from liquid I in a supercooled state to liquid II in a glassy state. Reflecting the transformation from the liquid to glassy state, the LLT is accompanied by considerable slowing down of overall molecular dynamics, but little is known about how this proceeds at a molecular level coupled with the evolution of the order parameter. We report such information by performing time-resolved simultaneous measurements of dielectric spectroscopy and phase contrast microscopy/Raman spectroscopy by using a dielectric cell with transparent electrodes. We find that the temporal change in molecular mobility crucially depends on whether LLT is nucleation growth type occurring in the metastable state or SD type occurring in the unstable state. Furthermore, our results suggest that the molecular mobility is controlled by the local order parameter: more specifically, the local activation energy of molecular rotation is controlled by the local fraction of locally favored structures formed in the liquid. Our study sheds light on the temporal change in the molecular dynamics during LLT and its link to the order parameter evolution.
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8
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Reichenbach J, Wynne K. Frustration vs Prenucleation: Understanding the Surprising Stability of Supersaturated Sodium Thiosulfate Solutions. J Phys Chem B 2018; 122:7590-7596. [DOI: 10.1021/acs.jpcb.8b04112] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
| | - Klaas Wynne
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K
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9
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Zhao G, Wang H, Hu DM, Ding MC, Zhao XG, Yan JL. Anomalous phase behavior of first-order fluid-liquid phase transition in phosphorus. J Chem Phys 2018; 147:204501. [PMID: 29195280 DOI: 10.1063/1.4999009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Although the existence of liquid-liquid phase transition has become more and more convincing, whether it will terminate at a critical point and what is the order parameter are still open. To explore these questions, we revisit the fluid-liquid phase transition (FLPT) in phosphorus (P) and study its phase behavior by performing extensive first-principles molecular dynamics simulations. The FLPT observed in experiments is well reproduced, and a fluid-liquid critical point (FLCP) at T = 3000 ∼ 3500 K, P = 1.5-2.0 Kbar is found. With decreasing temperature from the FLCP along the transition line, the density difference (Δρ) between two coexisting phases first increases from zero and then anomalously decreases; however, the entropy difference (ΔS) continuously increases from zero. These features suggest that an order parameter containing contributions from both the density and the entropy is needed to describe the FLPT in P, and at least at low temperatures, the entropy, instead of the density, governs the FLPT.
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Affiliation(s)
- G Zhao
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - H Wang
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - D M Hu
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - M C Ding
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - X G Zhao
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - J L Yan
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
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10
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Walton F, Wynne K. Control over phase separation and nucleation using a laser-tweezing potential. Nat Chem 2018; 10:506-510. [DOI: 10.1038/s41557-018-0009-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 01/23/2018] [Indexed: 11/09/2022]
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11
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Frustration of crystallisation by a liquid-crystal phase. Sci Rep 2017; 7:42439. [PMID: 28209972 PMCID: PMC5314399 DOI: 10.1038/srep42439] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/10/2017] [Indexed: 12/26/2022] Open
Abstract
Frustration of crystallisation by locally favoured structures is critically important in linking the phenomena of supercooling, glass formation, and liquid-liquid transitions. Here we show that the putative liquid-liquid transition in n-butanol is in fact caused by geometric frustration associated with an isotropic to rippled lamellar liquid-crystal transition. Liquid-crystal phases are generally regarded as being “in between” the liquid and the crystalline state. In contrast, the liquid-crystal phase in supercooled n-butanol is found to inhibit transformation to the crystal. The observed frustrated phase is a template for similar ordering in other liquids and likely to play an important role in supercooling and liquid-liquid transitions in many other molecular liquids.
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12
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Murata KI, Tanaka H. Impact of surface roughness on liquid-liquid transition. SCIENCE ADVANCES 2017; 3:e1602209. [PMID: 28232957 PMCID: PMC5315451 DOI: 10.1126/sciadv.1602209] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 01/10/2017] [Indexed: 06/06/2023]
Abstract
Liquid-liquid transition (LLT) in single-component liquids is one of the most mysterious phenomena in condensed matter. So far, this problem has attracted attention mainly from the fundamental viewpoint. We report the first experimental study on an impact of surface nanostructuring on LLT by using a surface treatment called rubbing, which is the key technology for the production of liquid crystal displays. We find that this rubbing treatment has a significant impact on the kinetics of LLT of an isotropic molecular liquid, triphenyl phosphite. For a liquid confined between rubbed surfaces, surface-induced barrierless formation of the liquid II phase is observed even in a metastable state, where there should be a barrier for nucleation of the liquid II phase in bulk. Thus, surface rubbing of substrates not only changes the ordering behavior but also significantly accelerates the kinetics. This spatiotemporal pattern modulation of LLT can be explained by a wedge-filling transition and the resulting drastic reduction of the nucleation barrier. However, this effect completely disappears in the unstable (spinodal) regime, indicating the absence of the activation barrier even for bulk LLT. This confirms the presence of nucleation-growth- and spinodal decomposition-type LLT, supporting the conclusion that LLT is truly a first-order transition with criticality. Our finding also opens up a new way to control the kinetics of LLT of a liquid confined in a solid cell by structuring its surface on a mesoscopic length scale, which may contribute to making LLT useful for microfluidics and other industrial applications.
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13
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The reversibility and first-order nature of liquid-liquid transition in a molecular liquid. Nat Commun 2016; 7:13438. [PMID: 27841349 PMCID: PMC5114579 DOI: 10.1038/ncomms13438] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 10/04/2016] [Indexed: 01/05/2023] Open
Abstract
Liquid–liquid transition is an intriguing phenomenon in which a liquid transforms into another liquid via the first-order transition. For molecular liquids, however, it always takes place in a supercooled liquid state metastable against crystallization, which has led to a number of serious debates concerning its origin: liquid–liquid transition versus unusual nano-crystal formation. Thus, there have so far been no single example free from such debates, to the best of our knowledge. Here we show experimental evidence that the transition is truly liquid–liquid transition and not nano-crystallization for a molecular liquid, triphenyl phosphite. We kinetically isolate the reverse liquid-liquid transition from glass transition and crystallization with a high heating rate of flash differential scanning calorimetry, and prove the reversibility and first-order nature of liquid–liquid transition. Our finding not only deepens our physical understanding of liquid–liquid transition but may also initiate a phase of its research from both fundamental and applications viewpoints. The nature of the phenomenon of so-called ‘liquid-liquid transitions' in molecular liquids is a long-standing debate. Here, the authors demonstrate the reversibility and first-order nature of the liquid-liquid transition in triphenyl phosphite via flash differential scanning calorimetry.
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14
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15
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Krivchikov AI, Andersson O. Thermal Conductivity of Triphenyl Phosphite’s Liquid, Glassy, and Glacial States. J Phys Chem B 2016; 120:2845-53. [DOI: 10.1021/acs.jpcb.6b00271] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexander I. Krivchikov
- B. Verkin Institute
for Low Temperature Physics and Engineering of NAS Ukraine, 47 Lenin Avenue, Kharkov 61103, Ukraine
| | - Ove Andersson
- Department
of Physics, Umeå University, 901 87 Umeå, Sweden
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16
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Bruijn JR, van der Loop TH, Woutersen S. Changing Hydrogen-Bond Structure during an Aqueous Liquid-Liquid Transition Investigated with Time-Resolved and Two-Dimensional Vibrational Spectroscopy. J Phys Chem Lett 2016; 7:795-799. [PMID: 26891098 DOI: 10.1021/acs.jpclett.5b02861] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigate the putative liquid-liquid phase transition in aqueous glycerol solution, using the OD-stretch mode in dilute OD/OH isotopic mixtures to probe the hydrogen-bond structure. The conversion exhibits Avrami kinetics with an exponent of n = 2.9 ± 0.1 (as opposed to n = 1.7 observed upon inducing ice nucleation and growth in the same sample), which indicates a transition from one liquid phase to another. Two-dimensional infrared (2D-IR) spectroscopy shows that the initial and final phases have different hydrogen-bond structures: the former has a single Gaussian distribution of hydrogen-bond lengths, whereas the latter has a bimodal distribution consisting of a broad distribution and a narrower, ice-like distribution. The 2D-IR spectrum of the final phase is identical to that of ice/glycerol at the same temperature. Combined with the kinetic data this suggests that the liquid-liquid transformation is immediately followed by a rapid formation of small (probably nanometer-sized) ice crystals.
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Affiliation(s)
- Jeroen R Bruijn
- Van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Tibert H van der Loop
- Van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Sander Woutersen
- Van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
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17
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Kobayashi M, Shimizu R, Tanaka H. Time-Resolved Light Scattering Study on the Kinetics of the Liquid-Liquid Transition in Triphenyl Phosphite. J Phys Chem B 2015; 119:11768-82. [PMID: 26237030 DOI: 10.1021/acs.jpcb.5b05402] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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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Affiliation(s)
- Mika Kobayashi
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo , 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Ryotaro Shimizu
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo , 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Hajime Tanaka
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo , 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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18
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Bharadwaj VS, Eagan NM, Wang NM, Liberatore MW, Maupin CM. Molecular Simulations of Fatty-Acid Methyl Esters and Representative Biodiesel Mixtures. Chemphyschem 2015; 16:2810-2817. [DOI: 10.1002/cphc.201500453] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/15/2015] [Indexed: 11/11/2022]
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19
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Murata KI, Tanaka H. Microscopic identification of the order parameter governing liquid-liquid transition in a molecular liquid. Proc Natl Acad Sci U S A 2015; 112:5956-61. [PMID: 25918385 PMCID: PMC4434750 DOI: 10.1073/pnas.1501149112] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
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 time-resolved 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 long-standing debate on the nature of the transition in TPP, i.e., whether the transition is LLT or merely microcrystal formation.
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Affiliation(s)
- Ken-ichiro Murata
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo, Tokyo 153-8505, Japan
| | - Hajime Tanaka
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo, Tokyo 153-8505, Japan
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