Density Depletion and Enhanced Fluctuations in Water near Hydrophobic Solutes: Identifying the Underlying Physics

Coe, Mary Kathryn; Evans, Robert; Wilding, Nigel B.

doi:10.1103/physrevlett.128.045501

Cited by 24 publications

(18 citation statements)

References 43 publications

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“…As a perspective, recent theoretical studies proposed that more complex behaviors could arise when increasing the solute size: Hande et al [49] . proposed that the length‐scale cross‐over predicted by the LCW theory does not take place for large alcohols, while Coe et al [50] . showed that vapor bubbles formed at the interface between water and extended hydrophobic surfaces have a prominent effect on hydration free energies.…”

Section: Figurementioning

confidence: 99%

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

et al. 2022

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Hydration free energies are dictated by a subtle balance of hydrophobic and hydrophilic interactions. We present here a spectroscopic approach, which gives direct access to the two main contributions: Using THz-spectroscopy to probe the frequency range of the intermolecular stretch (150-200 cm À 1 ) and the hindered rotations (450-600 cm À 1 ), the local contributions due to cavity formation and hydrophilic interactions can be traced back. We show that via THz calorimetry these fingerprints can be correlated 1 : 1 with the group specific solvation entropy and enthalpy. This allows to deduce separately the hydrophobic (i.e. cavity formation) and hydrophilic contributions to thermodynamics, as shown for hydrated alcohols as a case study. Accompanying molecular dynamics simulations quantitatively support our experimental results. In the future our approach will allow to dissect hydration contributions in inhomogeneous mixtures and under non-equilibrium conditions.

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Section: Figurementioning

confidence: 99%

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

et al. 2022

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“…So far, this assumption could not be directly tested experimentally, and our approach makes it possible to do so, as we have shown here for small alcohols. As a perspective, recent theoretical studies proposed that more complex behaviors could arise when increasing the solute size: Hande et al [49] proposed that the length-scale cross-over predicted by the LCW theory does not take place for large alcohols, while Coe et al [50] showed that vapor bubbles formed at the interface between water and extended hydrophobic surfaces have a prominent effect on hydration free energies. These new findings call for further refinement of our theoretical understanding, and THz calorimetry will be a valuable tool to confirm and possibly improve these models.…”

mentioning

confidence: 99%

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

et al. 2022

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Hydration free energies are dictated by a subtle balance of hydrophobic and hydrophilic interactions. We present here a spectroscopic approach, which gives direct access to the two main contributions: Using THz‐spectroscopy to probe the frequency range of the intermolecular stretch (150–200 cm−1) and the hindered rotations (450–600 cm−1), the local contributions due to cavity formation and hydrophilic interactions can be traced back. We show that via THz calorimetry these fingerprints can be correlated 1 : 1 with the group specific solvation entropy and enthalpy. This allows to deduce separately the hydrophobic (i.e. cavity formation) and hydrophilic contributions to thermodynamics, as shown for hydrated alcohols as a case study. Accompanying molecular dynamics simulations quantitatively support our experimental results. In the future our approach will allow to dissect hydration contributions in inhomogeneous mixtures and under non‐equilibrium conditions.

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“…( 5) turns into − κ 2 ∫ drρ(r)rr, where the integral is the matrix of second spatial moments of the density profile. The alternative form − κ 2 〈∑ i r i r i 〉 is obtained upon expressing the density profile as the average of ρðrÞ and carrying out the integral over r. Collecting all terms and dividing by κ 2 we obtain the sum rule (5) for the case of an interacting system inside of a harmonic trap as: R drdr 0 ρðrÞρðr 0 Þhðr; r 0 Þrr 0 ¼ R drρðrÞðk B Tκ À1 1 À rrÞ.…”

Section: Resultsmentioning

confidence: 99%

“…However, much of modern condensed matter physics is focused on seemingly entirely different physical behavior, namely that of fluctuating, disordered, spatially random, yet strongly interacting systems that possess a large number of degrees of freedom. Recent examples include active particles that display freezing 3 and wetting 4 , hydrophobicity rationalized as critical drying 5 , the structure of two-dimensional colloidal liquids 6 and that of fluid interfaces 7,8 .…”

mentioning

confidence: 99%

Variance of fluctuations from Noether invariance

Hermann

Schmidt

2022

Commun Phys

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The strength of fluctuations, as measured by their variance, is paramount in the quantitative description of a large class of physical systems, ranging from simple and complex liquids to active fluids and solids. Fluctuations originate from the irregular motion of thermal degrees of freedom and statistical mechanics facilitates their description. Here we demonstrate that fluctuations are constrained by the inherent symmetries of the given system. For particle-based classical many-body systems, Noether invariance at second order in the symmetry parameter leads to exact sum rules. These identities interrelate the global force variance with the mean potential energy curvature. Noether invariance is restored by an exact balance between these distinct mechanisms. The sum rules provide a practical guide for assessing and constructing theories, for ensuring self-consistency in simulation work, and for providing a systematic pathway to the theoretical quantification of fluctuations.

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Density Depletion and Enhanced Fluctuations in Water near Hydrophobic Solutes: Identifying the Underlying Physics

Cited by 24 publications

References 43 publications

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

Variance of fluctuations from Noether invariance

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