Temperature dependent anomalous fluctuations in water: shift of ≈1 kbar between experiment and classical force field simulations

Pathak, Harshad; Späh, Alexander; Amann‐Winkel, Katrin; Perakis, Fivos; Kim, Kyung Hwan; Nilsson, Anders

doi:10.1080/00268976.2019.1649486

Cited by 8 publications

(15 citation statements)

References 54 publications

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“…In addition, the LLCP scenario provides a natural framework to understand the anomalous behavior of binary aqueous solutions [23]. We also note that the LLCP scenario is strongly supported by computer simulations of many classical water models where a LLCP is found at low temperatures [9,[24][25][26][27][28][29][30].…”

Section: Introductionsupporting

confidence: 53%

Nuclear quantum effects on the thermodynamic response functions of a polymorphic waterlike monatomic liquid

Liu

Sun

Eltareb

et al. 2020

Phys. Rev. Research

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Water and hydrogen are examples of substances proposed to exhibit a liquid-liquid critical point (LLCP) at conditions where nuclear quantum effects are relevant. The LLCP is usually accompanied by lines of maxima in density ρ and thermodynamic response functions, such as isothermal compressibility κ T and isobaric heat capacity C P , in the supercritical region of the P-T plane. In the case of water, the ρand κ T-maxima lines can be accessed in experiments, while, instead, the LLCP has not been observed due to rapid crystallization. In this work, we study the nuclear quantum effects on a monatomic liquid that exhibits waterlike anomalous properties and a LLCP. By performing path-integral Monte Carlo simulations with different values of the Planck's constant h, we are able to explore how the location of the LLCP in the P-T plane and, in particular, the maxima lines in the supercritical region, shift as the system evolves from classical, h = 0, to quantum, h > 0. We find that as the quantum nature of the liquid (as quantified by h) increases and the atoms in the liquid become more delocalized, the LLCP shifts towards higher pressures and lower temperatures while the LLCP volume remains constant. Similar shifts (towards higher pressures and lower temperatures) are found in the case of the C P-and κ T-maxima lines. Instead, the ρ-maxima line extends towards higher temperatures and expands over a wider pressure interval as the liquid becomes more quantum. It follows that the nuclear quantum effects on the location of the LLCP may be estimated from the shift in C P-and κ T-maxima lines but not on measurements of the ρ-maxima line. Interestingly, nuclear quantum effects considerably alter the slope of the liquid-liquid coexistence line and C P-maxima line in the P-T plane while the slope of the κ T-maxima line along the Widom line is barely affected. We discuss briefly the implications of our results to the case of H 2 O/D 2 O.

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Section: Introductionsupporting

confidence: 53%

Nuclear quantum effects on the thermodynamic response functions of a polymorphic waterlike monatomic liquid

Liu

Sun

Eltareb

et al. 2020

Phys. Rev. Research

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“…The observed steep rise in C p at T < 235 K means a rapid increase in entropy fluctuations. We also see a rapid change in κ T and S 1 position with respect to temperature at T < 235 K, which is correlated with tetrahedrality ( 16 ). We have the following relation between κ T and C p :

where ρ is the liquid density.…”

Section: Discussionmentioning

confidence: 68%

“…Such a hypothesis is consistent with the observation that the liquid is rapidly undergoing a structural change at the Widom line, becoming dominated by tetrahedral structures, as observed in the X-ray scattering data ( 13 , 14 ). However, although the TIP4P/2005 model has some qualitative features resembling the anomalies of water, the values of maxima in C p ( 47 ), as well as κ T , ξ, and dS 1 /dT ( 16 ) at the Widom line are largely underestimated. Therefore, estimation of the fragile-to-strong transition using the TIP4P/2005 model would be far from quantitative and further experiments are necessary.…”

Section: Discussionmentioning

confidence: 99%

“…7 are only

0.8 1.4

apart, which means that we might be close to an LLCP) of water. Previous studies have compared the experimental data to various molecular simulation models for water, locating the LLCP of real water at 600–1,000 bar ( 13 , 16 , 28 , 41 , 42 ).…”

Section: Discussionmentioning

confidence: 99%

“…Other experiments using sound velocity in stretched liquid water ( 15 ) also predict a maxima in κ T and C p . Based on a combination of MD simulations and temperature-dependent structure factor measurements, a consistency was derived with which α P may also exhibit a minimum at 229 K ( 16 ). If all thermodynamic response functions showed evidence of a Widom line with maxima or minima, this would validate the LLCP scenario, more so if they were in close proximity in temperature.…”

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confidence: 99%

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Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry

Pathak

Späh

Esmaeildoost

et al. 2021

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

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Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid–liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.

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Multiple insights call for revision of modern thermodynamic models to account for structural fluctuations in water

2022

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Modern thermodynamic models incorporate the concept of association (hydrogen bonding) and they can describe very satisfactorily many properties of water containing mixtures. They have not been successful in representing water's anomalous properties and this work provides a possible explanation. We have analyzed and interpreted recent experimental data, molecular simulation results, and two‐state theory approaches and compared against the predictions from thermodynamic models. We show that the dominance of the tetrahedral structure implemented in modern thermodynamic models may be the reason for their failure for describing water systems. While this study does not prove the two‐state theories for water, it indicates that a high level of tetrahedral structure of water is not in agreement with water's anomalous properties when used in thermodynamic models.

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Temperature dependent anomalous fluctuations in water: shift of ≈1 kbar between experiment and classical force field simulations

Cited by 8 publications

References 54 publications

Nuclear quantum effects on the thermodynamic response functions of a polymorphic waterlike monatomic liquid

Nuclear quantum effects on the thermodynamic response functions of a polymorphic waterlike monatomic liquid

Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry

Multiple insights call for revision of modern thermodynamic models to account for structural fluctuations in water

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