Thermodynamic determination of fragility in liquids and a fragile-to-strong liquid transition in water

Ito, Kaori; Moynihan, Cornelius T.; Angell, C. Austen

doi:10.1038/19042

Cited by 731 publications

(702 citation statements)

References 34 publications

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“…This result was also subsequently confirmed qualitatively by an extensive molecular dynamics (MD) simulation (12). In a series of experiments using both neutron scattering and NMR spectroscopies, a fragile-to-strong dynamic cross-over (FSC) (13) and the Stokes-Einstein relation violation (SEV) (14) at and below the cross-over were observed (11). The FSC marks a transition from a Vogel-Fulcher-Tamman (VFT) to an Arrhenius behavior in dynamical parameters such as the average translational relaxation time and the inverse self-diffusion coefficient (11).…”

mentioning

confidence: 56%

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Mallamace

Broccio

Corsaro

et al. 2007

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

277

301

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By confining water in a nanoporous structure so narrow that the liquid could not freeze, it is possible to study properties of this previously undescribed system well below its homogeneous nucleation temperature T H ‫؍‬ 231 K. Using this trick, we were able to study, by means of a Fourier transform infrared spectroscopy, vibrational spectra (HOH bending and OH-stretching modes) of deeply supercooled water in the temperature range 183 < T < 273 K. We observed, upon decreasing temperature, the building up of a new population of hydrogen-bonded oscillators centered around 3,120 cm ؊1 , the contribution of which progressively dominates the spectra as one enters into the deeply supercooled regime. We determined that the fractional weight of this spectral component reaches 50% just at the temperature, T L Ϸ 225 K, where the confined water shows a fragile-to-strong dynamic cross-over phenomenon dynamic cross-over in water ͉ dynamic transitions in water ͉ Fourier transform infrared spectroscopy ͉ low-density liquid water ͉ Widom line in water W ater plays a fundamental and ubiquitous role on Earth and in all aspects of life phenomena. Understanding its properties is of paramount importance to mankind, and thus water is the most studied molecular system in science and technology. However, despite intense scrutiny over the years, scientists are still far from reaching a coherent understanding of all its unusual properties (1-3). Instead of behaving like other simple molecular liquids, many thermodynamic response functions of water, such as the isothermal compressibility, isobaric heat capacity, and thermal expansion coefficient, display counterintuitive trends as temperature is lowered. In particular, extrapolated from their values at moderately supercooled states, these functions all appear to diverge at a singular temperature around T S ϭ 228 K. Over the years, many plausible explanations for these strange behaviors have been proposed, starting from the two-state and the clathrate models (1-3). Three hypotheses are of active interest: (i) the stability limit (4), (ii) the percolation (5), and (iii) liquid-liquid (LL) critical point (6). The third approach has received support from various theoretical studies (7-9). However, in all three approaches, the main role is played by the local hydrogen-bond (HB) interaction pattern surrounding a typical water molecule in liquid state that governs the overall structure and dynamics (1) of water. Some of our recent experimental results (10, 11) on water confined in nanoporous structures as a function of temperature and pressure showed that the theoretical approach based on existence of the LL critical point is able to describe coherently many strange properties of water. By using the neutronscattering technique, we obtained evidence of the LL critical point (the second critical point predicted by the theory to be at T C ϳ 220 K and P C ϳ 1 kbar) located at T C ϭ 200 K and P C ϭ 1.5 kbar (10). This result was also subsequently confirmed qualitatively by an extensive molecular dynam...

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mentioning

confidence: 56%

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Mallamace

Broccio

Corsaro

et al. 2007

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

277

301

View full text Add to dashboard Cite

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“…Unlike other network forming materials [26], water behaves as a non-Arrhenius liquid in the experimentally accessible window [16,27,28]. Based on analogies with other network forming liquids and with the thermodynamic properties of the amorphous forms of water, it has been suggested that, at ambient pressure, liquid water should show a dynamic crossover from non-Arrhenius behavior at high T to Arrhenius behavior at low T [24,[29][30][31][32][33]. Using Adam-Gibbs theory [34], the dynamic crossover in water was related to the C max P line [22,35].…”

Section: The Widom Linementioning

confidence: 99%

The puzzling unsolved mysteries of liquid water: Some recent progress

Stanley

Kumar

et al. 2007

Physica A: Statistical Mechanics and its Applications

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Water is perhaps the most ubiquitous, and the most essential, of any molecule on earth. Indeed, it defies the imagination of even the most creative science fiction writer to picture what life would be like without water. Despite decades of research, however, water's puzzling properties are not understood and 63 anomalies that distinguish water from other liquids remain unsolved. We introduce some of these unsolved mysteries, and demonstrate recent progress in solving them. We present evidence from experiments and computer simulations supporting the hypothesis that water displays a special transition point (which is not unlike the ''tipping point'' immortalized by Malcolm Gladwell). The general idea is that when the liquid is near this ''tipping point,'' it suddenly separates into two distinct liquid phases. This concept of a new critical point is finding application to other liquids as well as water, such as silicon and silica. We also discuss related puzzles, such as the mysterious behavior of water near a protein. r

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“…These values correspond to 1.37 and 1.39 C p l / C p g ratios for the KMWPO and RbMWPO glasses, respectively. A number of studies showed that such a large increase of C p Ј is a characteristic feature of a fragile liquid, 17,19,20,25 indicating that the KMWPO and RbMWPO phosphates are relatively fragile liquids. Recently, a correlation between the dynamic and thermodynamic fragilities has been reexamined for a number of glass formers.…”

Section: A Heat Capacitymentioning

confidence: 99%

“…[13][14][15][16] On the other hand, heat capacity studies may provide, among others, some information on fragility, structural relaxation, and aging effects in glasses. [17][18][19][20] A particularly suitable technique for studies of glass transitions is modulated differential scanning calorimetry ͑MDSC͒ since it gives information on both real and imaginary parts of heat capacity. 17,21 In this paper two phosphate glasses of the composition corresponding to crystalline K 2 MgWO 2 ͑PO 4 ͒ 2 and Rb 2 MgWO 2 ͑PO 4 ͒ 2 have been studied since these phosphates exhibit interesting properties.…”

Section: Introductionmentioning

confidence: 99%

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

Mączka

Hanuza

Baran

et al. 2006

The Journal of Chemical Physics

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The authors report the results of temperature-dependent Brillouin scattering from both transverse and longitudinal acoustic waves, heat capacity studies as well as room temperature Raman scattering studies on M 2 O-MgO-WO 3 -P 2 O 5 glasses ͑M=K,Rb͒. These results were used to obtain information about structure and various properties of the studied glasses such as fragility, elastic moduli, ratio of photoelastic constants, and elastic anharmonicity. They have found that both glasses have similar properties but replacement of K + ions by Rb + ions in the glass network leads to decrease of elastic parameters and P 44 photoelastic constant due to increase of fragility. Based on Brillouin spectroscopy they show that a linear correlation between longitudinal and shear elastic moduli holds over a large temperature range. This result supports the literature data that the Cauchy-type relation represents a general rule for amorphous solids. An analysis of the Boson peak revealed that the form of the frequency distribution of the excess density of states is in agreement with the Euclidean random matrix theory. The reason of the observed shift of the maximum frequency of the Boson peak when K + ions are substituted for Rb + ions is also briefly discussed.

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Thermodynamic determination of fragility in liquids and a fragile-to-strong liquid transition in water

Cited by 731 publications

References 34 publications

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Evidence of the existence of the low-density liquid phase in supercooled, confined water

The puzzling unsolved mysteries of liquid water: Some recent progress

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

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