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Understanding the nature of H-bonding interactions is essential to modern sciences, such as biology, chemistry, and physics. Using density functional theory calculations, herein, we have identified two unique H-bonding types existing in a single sheet of a mixed water–hydroxyl phase on close-packed metal surfaces, in sharp contrast to conventional H-bonds in liquid water and water ices. Interestingly, the shallow H-bonds show reduced electrostatic and Pauli repulsion interactions, with an electrostatic polar character resulted from complete σ resonances, whereas the deep H-bonds exhibit enhanced electrostatic and Pauli repulsion interactions, with an electrostatic dipolar feature originated from hybrid orbital interactions. A trade-off-like cooperativity law of the two types of H-bonds was discovered, that is, strengthening in the internal bonds (dO–H) leads to weakening in the external bonds (dO:H) or vice versa. However, the shallow H-bonds exhibit a non-linear cooperativity, whereas the deep H-bonds show a linear cooperativity. We also identified an oxygen backbone cooperativity rule that strengthening the adsorbate–metal interactions has a net effect in analogy to reducing the O–O repulsion within the adlayer. Furthermore, we have discovered several universality classes in geometrical, vibrational, and electronic spaces for the two H-bonding types. Although shared by electronic universality classes, the two contrasting H-bonding types are featured by divergent trends with significant overlapping, where competitive variations in the electrostatic and Pauli repulsion strengths are basic rules for the cooperative H-bonding types. The knowledge of the unconventional H-bonding types expands our current understanding of H-bonding interactions in liquid water and water ices and points to the importance of H-bonding manipulation at electronic levels. These findings not only shed new light on probing the fundamental nature of H-bonds in general but also have insightful implications for resolving the cooperative H-bonding nature of interfacial water, liquid water, water ices, and aqueous solutions. Published version This work was supported by Na- tional Natural Science Foundation of China under Contract No. 21875024.

It has been a long pursuit to discriminate the ionic roles of mono- and di-valent salt solutions in modulating the hydrogen bonding network and solution properties. We attended this issue by examining the effect of concentrated YX 2 (Y[dbnd]Mg, Ca, Sr; X[dbnd]Cl, Br) solvation on O:H–O bonds transition from the mode of ordinary water to hydration in terms of the number fraction f YX2 (C) and the segmental O:H–O bond phonon stiffness shift Δω(C) with C being the solute concentration. The invariant df Y (C) / dC at C ≤

Understanding the performance of individual ions in salt solutions and the consequence of ionic hydration on hydrogen bonding network distortion, surface stress, and solution viscosity remains great challenge. We show herein findings pertained to alkali halide YX solutions using differential phonon spectroscopy (X = Cl, Br, I; Y = Li, Na, K, Rb, Cs): (i) an ion occupies eccentrically the tetrahedrally-coordinated interstitial of water to form a (±:4H2O:6H2O) hydration cell without bonding to H2O molecules; (ii) ionic polarization shortens and stiffens the H-O bond while does the O:H nonbond contrastingly; (iii) the screening of the hydrating water dipoles limits the cation hydration cell to be size invariant while the inter-anion repulsion reduces its hydration volume by weakening the anionic long-range electric field when the ionic separation shrinks; and (iv) the polarization of cation and anion dictates respectively the linear and the nonlinear part of Jones-Dale’s viscosity and surface stress. Findings would provide profound impact to the understanding and deep engineering of water, ice, and aqueous solutions.

Freezing-thawing cycling of salt solutions is ubiquitously important to fields varying from biochemistry to agriculture, climate, and geological engineering. However, understanding the dynamics of energy exchange and freezing-temperature TN shift during phase transition of the concentrated solutions remains elusive despite intensive investigations since the discovery of Homeister series in 1888. Here we address this issue by focusing on the performance of the hydrogen bond (O:H O) in the fraction fS molecules of the hydrating supersolid phase and in the remaining fraction fO molecules of the pristine phase during NaCl solution ice formation. The supersolid formation is related to the effect of ionic polarization that shortens and stiffens the H O bond, while lengthening and weakening the O:H non-bonding interactions in the hydration cells. The supersolid phase is gel-like, less dense, viscoelastic, and mechanically and thermally stable. We demonstrate that the polarization-weakening of the O:H non-bonding interactions of the supersolid phase reduces the TN of the solution and that the H O cooling contraction in the quasisolid (QS) phase of the pristine water absorbs energy during the Liquid-QS-Ice transition of solution. At fS = 1, neither TN nor energy absorption is resolved within the range of 273 ± 20 K. The least saturation number of molecules is 10 per pair of Na+ and Cl− ions. These findings shall help to develop solutions with tunable TN for practical applications and to understand the mechanism of energy exchange during phase transition in the temperature and time domains.

Deep engineering of liquid water by charge and impurity injection, charged support, current flow, hydrophobic confinement, or applying a directional field has becoming increasingly important to the mankind toward overcoming energy and environment crisis. One can mediate the processes or temperatures of molecular evaporation for clean water harvesting, H O bond dissociation for H2 fuel generation, solidification for living-organism cryopreservation, structure stiffening for bioengineering, etc., with mechanisms being still puzzling. We show that the framework of “hydrogen bonding and electronic dynamics” has substantiated the progress in the fundamental issues and the aimed engineering. The segmental disparity of the coupled hydrogen bond (O:H O or HB with “:” being lone pair of oxygen) resolves their specific-heat curves and turns out a quasisolid phase (QS, bound at −15 and 4 °C). Electrification shows dual functionality that not only aligns, orders, polarizes water molecules but also stretches the O:H O bond. The O:H O segmental cooperative relaxation and polarization shift the QS boundary through Einstein's relation, ΔΘDx ∝ Δωx, resulting in a gel-like, viscoelastic, and stable supersolid phase with raised melting point Tm and lowered temperatures for vaporization TV and ice nucleation TN. The supersolidity and electro structure ordering provide additional forces to reinforce Armstrong's water bridge. QS dispersion and the secondary effect of electrification such as compression define the TN for Dufour's electro-freezing. The TV depression, surface stress disruption, and electrostatic attraction raise Asakawa's molecular evaporability. Composition of opposite, compatible fields eases the H O dissociation and soil wetting. Progress evidences not only the essentiality of the coupled O:H O bond theory but also the feasibility of engineering water and solutions by programmed electrification.

Phonon spectrometrics examination of the effect of pressure, temperature, molecular undercoordination, and charge injection by acid, base, and salt solvation establishes the regulations for the hydrogen bonding and electronic dynamics and the properties of the deionized water and aqueous solutions. Consistency between theory and measurements confirms the essentiality of the quasisolid phase of negative thermal expansion due to O:H–O segmental specific heat disparity, and the supersolid phase due to electrostatic polarization by ions injection or molecular undercoordination. Lewis acid and base solvation creates the H↔H anti–HB due to the excessive protons and the O:⇔:O super–HB because of the excessive lone pairs, respectively. The multifield mediation of the HB network results in anomalies of water ice and aqueous solutions such as ice friction, ice floating, regelation, superheating and supercooling, warm water speedy cooling, and critical conditions for phase transition. Extending the knowledge towards the deep engineering of liquid water would be promising.

The presence of the nonbonding XH tension constrains and the presence of the anti or super hydrogen bond fosters the explosion in aqueous alkali and molten alkali halides; the combination of the coupled hydrogen bond and the repulsive anti or super hydrogen bond not only stabilzes the structure but also stores energy of the energetic molecular assemblies by shortening all covalent bonds., Comment: 4 figure, 3500 works

The inter oxygen repulsion opposes compression minimizing the compressibility. Polarization enlarges the bandgap and the dielectric permittivity of water ice by raising the nonbonding states above the Fermi energy. Progress evidences the efficiency and essentiality of the coupled hydrogen bonding and electronic dynamics in revealing the core physics and chemistry of water ice, which could extend to other molecular crystals such as energetic materials., Comment: 15 k words, 118 refs, 17 figures

Density functional computation revealed that in YOH solvation (Y = Li, Na, and K), the Y+ cation locates eccentrically at the interstitial hollow site to form the Y+·4H2O unit, and the hydroxyl adds an excessive electron lone pair ":" to form a OH-·H2O unit where the hydroxide stays in the the center. The surrounding four oriented H2O neighbors interact with the Y+ through Y+ ↔ H+ repulsion and Y+:O2- attraction, causing the Y+ eccentric dislocation by some 0.80 A. The ":" turns one O:H-O bond into the O: ⇔ :O super hydrogen bond by altering H2O·4H2O into HO-·4H2O. The repulsive Y+ ↔ H+ enlarges its separation and the attractive Y+:O shortens itself, showing the anisotropic polarization of the Y+ cation. The anisotropic Y+ polarizability, O: ⇔ :O compressibility, and the H-O bond contraction of the solute OH- distorts the solute bonding network and disperses the O:H-O segmental phonon frequencies, as confirmed spectroscopically.

Solvation of aldehydes and formic acids has an important impact to health care because these additives can damage DNA and denature proteins causing cancers with the mechanism behind remaining great challenge. From the perspective of solvent hydrogen bond (O:HO or HB with “:” being the electron lone pair of oxygen) transition from the mode of the ordinary water to the hydrating states, we examined the solvation bonding dynamics and the solute capabilities of O:HO bond and surface stress transition using differential Raman spectroscopy and contact angle detection. Results suggest that besides the short-range O:H van der Waals (vdW) bond, the H ↔ H and O: ⇔ :O repulsive intermolecular interactions, and the molecular dipolar polarization play important roles in disrupting the solution network and surface stress. Observations may infer the manner of DNA fragmentation by aldehyde and formic acid disruption. Accepted version

A localized, metastable, 5775-type defect is uncovered in the double-layer ice with and without Au(1 1 1) support from density functional theory calculations. Without destroying the total number conservation of the hydrogen bonds in the hexagonal ice, the defect only dislocates the molecules by 0.08 A associated with a 3.27% difference of the interaction energy. The high energy barrier, low quantum tunneling and thermal transporting probabilities hindered the transformation from the 6666 to the 5775 structures. This finding indicates that the defected ice is stable, and it tends to form during the ice growth instead of post-grown process.

Raman phonon differential spectrometrics (DPS) and contact angle measurements resolved that solvation of the NaX (X = HSO4, NO3, ClO4, SCN) complex salts stiffens the H O stretching phonon from 3200 to ~ 3500 cm− 1 and softens the O:H nonbond phonon from 180 to ~ 70 cm− 1 with rising of solution surface stress. The solute capability of bond transition in terms of the fraction coefficient, follows the relation, fNaX(C) ∝ 1-exp(− C/C0) towards saturation, with C being the solute concentration and C0 the decay constant. Observations evidence that: (i) the solute ionic field electrification aligns, stretches, and polarizes its neighboring H2O molecules, which shortens the H O bond but lengthens the O:H nonbond via O O Coulomb repulsion; (ii) the effect of X− electrification on the O:H O bond relaxation varies with solute type and solute concentration. Exercises not only verify the essentiality of solvent O:H O bond cooperative relaxation and polarization but also demonstrate the power of DPS that resolves processes occurred upon solvation.

Solvation of acid, base, and salt is ubiquitously important to all subject areas in chemistry, health care and life science. However, fine resolution of the solvation dynamics, solute-solvent molecular interactions, and solute capability of transforming the hydrogen bond (O:H O, or HB) and surface stress remain great challenge. Incorporating the notion of O:H O bond cooperativity with a strategy of differential phonon spectroscopy (DPS) has enabled resolution on the fraction and stiffness of the solvent HB from the mode of water to the hydration shells upon NaOH, NaI and HI solvation. Results show that Na+ and I+ ionic polarization shortens the H O bond and stiffens its phonon from 3200 to 3500 cm− 1 in the hydration shells. The H+ in the HI solution forms a H ↔ H anti-HB that disrupts the solution network and surface stress. The excessive electron lone pairs of OH– form the O : ⇔ : O super-HB that compresses the network, sharing the same effect of mechanical compression shifting the H O phonon from above 3100 cm− 1 to its below; the solute H O bond performs the same to the H O dangling bond at surface featured at 3610 cm− 1. The fraction coefficients or phonon abundance transition, fH = 0, fHO ∝ C, and fx ∝ 1-exp(− C/C0) (x = Na+ and I− and C the solute concentration) towards saturation, feature the solute capability of HB transformation. Practice not only confirms the essentiality of the H ↔ H anti-HB point fragilization, the O : ⇔ : O super-HB point compression, and the ionic polarization to the performance of the respective HI, NaOH, and NaI solutions, but also demonstrate the power of the DPS that enables fine-resolution of solvation dynamics and solute capabilities.

Skins of water and ice perform anomalously in capacities of hydrophobicity, lubricity, mass density, thermal stability, viscoelasticity, and phonon frequency with yet little knowledge about the mechanism behind these anomalies. We present the recent progress in this regard from the perspective of molecular undercoordination induced O:H-O bond segmental cooperative relaxation and nonbonding electron polarization. The skin molecular undercoordination shortens the intramolecular H-O covalent bond spontaneously from 1.0 to 0.84 Ǻ, while the Coulomb repulsion between oxygen anions lengthens the intermolecular O:H nonbond from 1.70 to 2.71 Ǻ associated with strong polarization. The O:H-O resultant elongation depresses the mass density to 0.75 g/cm 3 ; the polarization results the skin high stress, hydrophobicity, lubricity, viscoelasticity; the H-O contraction shifts its stretching vibration frequency from the bulk value of 3150 to 3450 cm -1 at skin and to 3650 cm -1 of vapor; the O:H elongation shifts its stretching mode from 210 of bulk to 180 cm -1 at skin. Therefore, molecular undercoordination induced O:H-O bond relaxation and the associated polarization govern the performance of molecules at the skins of water and ice.

Although the alcohol–water mixtures are ubiquitously important to beverage and pharmacy industries, it remains yet puzzling how the alcohols interact with water molecules and how the alcohol molecules functionalize the hydrogen bond network of liquid water and body fluid. We show spectrometrically that alcohol hydration softens both the H–O bond and the O:H nonbond through hydrogen bond cooperative relaxation and associated charge polarization. Observations suggested that each of the dangling hydroxide group :O:H− (interacts with :O or –H+) and the dangling methyl group C–H+ (with –H+ or :O) is equally capable of interacting with H2O molecules in the form of O:↔:O point compressor, H+↔H+ point breaker, and O:H–O hydrogen bond at the alcohol–water interface without charge sharing or new bond formation. The alcohol–water O:H–O formation enables the solubility and hydrophilicity of the alcohol; the H+↔H+ breaker embrittles the hydration network; the O:↔:O compression shortens the O:H nonbond and lengthens the H–O bond. H–O softening is associated with heat emission and depression of solution melting temperature; the O:H nonbond softening (due to polarization) lowers the critical temperatures for freezing. Copyright © 2016 John Wiley & Sons, Ltd.

We show phonon spectrometrically that the unprecedented H 2 O: ↔ :O:H – compression resolves the performance of the base solution networks with “:” being the electron lone pair of oxygen. At hydration, LiOH, NaOH, KOH molecules dissolve each into a :O:H – hydroxide and cations of Li + , Na + , and K + , respectively. The cations serve as charge centers to polarize the neighboring water molecules and raise the solution skin stress (or surface tension). The :O:H – tetrahedron adds, however, three lone pairs and one bonded H + proton to the solution matrix, turning the initially 2N lone pairs into 2N + 3 and the 2N bonded H + into 2N + 1 with an additional O 2– anion. This hydration process breaks the conservation of the 2N lone pairs and protons with two extra lone pairs that only can form a H 2 O: ↔ :O:H – super hydrogen bond (super-HB) with strong repulsivity. In addition to the H O bond of the :O:H – featured at 3610 cm − 1 , the internal H 2 O: ↔ :O:H – compression has an identical effect of mechanical compression, shortening the O:H nonbonds and stiffening their phonons from below 200 cm − 1 to the above. Meanwhile, compression lengthens the network H O bonds and softens their phonons from above 3150 cm − 1 to below. The network H O bonds elongation decreases their energy from ~ 4.0 to ~ 2.7 eV at hydration, which heats the solution as one often observes. The H 2 O: ↔ :O:H – super-HB compressor and the alkali cation polarizor form the keys to the base hydration networks and the properties.

A combination of the differential Raman spectrometrics and contact-angle measurements has enabled resolution of the hydrogen bond (HB, O:H O) relaxation and molecular dynamics in the NaX hydration shells. Observations suggest that the aqueous ions create each an electric field to form the hydration shells through O:H O bond elongation and polarization. The ionic polarization shares the same, and even stronger, effect of molecular undercoordination that shortens the H O bond and stiffen its phonon, and meanwhile, the O O Coulomb repulsivity lengthen and soften the O:H nonbond with an association of polarization. O:H O bond electrification raises not only the structure order of molecules and the viscosity in the hydration shells but also the skin stress and thermal stability of the solution. Exercises not only deepen our insight into the salt solute-solvent interaction involved in the Hofmeister series in terms of O:H O bond electrification but also provide a powerful means quantifying the dynamic, local, molecular-site-resolved information regarding the O:H O bond cooperativity in aqueous solutions.

Water skin is the toughest of ever known with a mechanism that remains unclear. We show phonon spectrometrically that molecular undercoordination induced hydrogen bond (O:H O) relaxation and nonbonding electron polarization furnished the skin with the supersolid nature – less dense, elastic, thermally more stable than the bulk. Heating from 5 to 95 °C stiffens the skin H O phonon (or bond stiffness) from 3443 cm− 1 by 0.38%, and the bulk phonon from 3239 cm− 1 by 1.48%, but softens the H O dangling bonds from 3604 cm− 1 by − 0.40%. Heating also changes the respective molecular structural order and phonon abundance by − 8.4/− 19.7%, 4.9/− 2.6%, and 13.0/137.0%. Observations also evidenced that both heating and molecular undercoordination have the same effect on O:H O bond relaxation but opposite on polarization, which improves our understanding of the anomalous skin of liquid water.

Water dissolves salt into ions and then hydrates the ions to form an aqueous solution. Hydration of ions deforms the hydrogen bonding network and triggers the solution with what the pure water never shows such as conductivity, molecular diffusivity, thermal stability, surface stress, solubility, and viscosity, having enormous impact to many branches in biochemistry, chemistry, physics, and energy and environmental industry sectors. However, regulations for the solute-solute-solvent interactions are still open for exploration. From the perspective of the screened ionic polarization and O:H-O bond relaxation, this treatise features the recent progress and a perspective in understanding the hydration dynamics of Hofmeister ions in the typical YI, NaX, ZX2, and NaT salt solutions (Y = Li, Na, K, Rb, Cs; X = F, Cl, Br, I; Z = Mg, Ca, Ba, Sr; T = ClO4, NO3, HSO4, SCN). Phonon spectrometric analysis turned out the f(C) number fraction of bonds transition from the mode of deionized water to the hydrating. The linear f(C) ∝ C form features the invariant hydration volume of small cations that are fully-screened by their hydration H2O dipoles. The nonlinear f(C) ∝ 1 - exp.(-C/C0) form describes that the number insufficiency of the ordered hydrating H2O dipoles partially screens the anions. Molecular anions show stronger yet shorter electric field of dipoles. The screened ionic polarization, inter-solute interaction, and O:H-O bond transition unify the solution conductivity, surface stress, viscosity, and critical energies for phase transition. Accepted version

Charge injection in terms of lone pairs ‘:’, protons, and ions upon acid and base solvation mediates the hydrogen bonding network and properties of Lewis solutions, and is ubiquitously important in many subject areas of Chemical Physics. This work features the recent progress and future trends in this aspect with a focus on the solute–solvent interactions and hydrogen bond (O:H–O or HB) transition from the vibration mode of ordinary water to the hydrating states. A combination of the O:H–O bond cooperativity notion, differential phonon spectrometrics, calorimetric detection, and quantum computations clarified the solute capabilities of O:H–O bond transition in HX and YOH (X = Cl, Br, I and Y = Li, Na, K) solutions. The H+ and the lone pair do not stay alone to move or shuttle freely between adjacent H2O molecules, but they are attached to a H2O molecule to form (H3O+ and OH−)·4H2O tetrahedral motifs, which transits an O:H–O bond into the H↔H anti-HB point breaker in acidic solutions and into the O:⇔:O super-HB compressor and polarizer in basic solutions, respectively. H↔H disrupts the solvent network and surface stress, having the same effect of liquid heating on HB bond relaxation and thermal fluctuation on surface stress. The O:⇔:O compression lengthens and weakens the solute H–O bond, which heats up the solution during solvation. The H–O bonds due to H3O+ contract by 3% and due to OH− shrink by 10%. The Y+ and X− ions perform in the same manner as they do in salt solutions to form hydration shells through electrostatic polarization and hydrating H2O dipolar screen shielding. Focusing more on the O:H–O bond transition would be even more promising and revealing than on the manner and mobility of lone pair and proton transportation.

A combination of the spatially- and temporally-resolved phonon spectroscopies has enabled calibration of hydrogen bond transition from the vibration mode of heavy water to the core-shell structured nanodroplets and to the ionic hydration shells of salt solutions in terms of phonon abundance-lifetime-stiffness. It is uncovered that charge injection by salt solvation and skin formation by molecular undercoordination (often called confinement) share the same supersolidity characterized by H–O (D–O as a probe) bond contraction, O:H nonbond elongation, and polarization. Such a process of bond transition stems the solution viscosity, surface stress, and slowing down of the molecular dynamics and diffusivity. The nanodroplet skin reflection further hinders phonon energy dissipation associated with longer D–O phonon lifetime. Financial support received from National Natural Science Foundation of China (Nos. 11872052(YL); 21875024(CQ)), the Science Challenge Project (No. TZ2016001) of China is acknowledged.

Water dissolves salt into ions and then hydrates the ions in an aqueous solution. Hydration of ions deforms the hydrogen bonding network and triggers the solution with what the pure water never shows such as conductivity, molecular diffusivity, thermal stability, surface stress, solubility, and viscosity, having enormous impact to many branches in biochemistry, chemistry, physics, and energy and environmental industry sectors. However, regulations for the solute-solute-solvent interactions are still open for exploration. From the perspective of the screened ionic polarization and O:H–O bond relaxation, this chapter is focused on understanding the hydration dynamics of Hofmeister ions in the typical YI, NaX, ZX2, and NaT salt solutions (Y = Li, Na, K, Rb, Cs; X = F, Cl, Br, I; Z = Mg, Ca, Ba, Sr; T = ClO4, NO3, HSO4, SCN). Phonon spectrometric analysis turned out the f(C) fraction of bond transition from the mode of deionized water to the hydrating. The linear f(C) ∝ C form features the invariant hydration volume of small cations that are fully-screened by their hydration H2O dipoles. The nonlinear f(C) ∝ 1 − exp(−C/C0) form describes that the number insufficiency of the ordered hydrating H2O diploes partially screens the anions. Molecular anions show stronger yet shorter electric field of dipoles. The screened ionic polarization, inter-solute interaction, and O:H–O bond transition unify the solution conductivity, surface stress, viscosity, and critical energies for phase transition.

An incorporation of the hydrogen bond cooperativity theory to the DPS strategy and surface stress (contact angle) detection could resolve the solvation bonding and nonbonding dynamics and solute capabilities. The enabled information includes bond length and stiffness transition, electron polarization, and the fraction of bonds transformed from the mode of ordinary water to the hydration shells. A combination of the DPS and the ultrafast IR spectroscopy would be more revealing towards solute-solvent and solute-solute molecular interactions, solute capabilities, and solution properties. The DPS is focused on the solvation O:H–O segmental cooperative bonding dynamics and the ultrafast IR on molecular motion dynamics by measuring phonon relaxation time.

Supersolidity of ice, which was proposed in 2013 and intensively verified since then [C. Q. Sun et al., Density, Elasticity, and Stability Anomalies of Water Molecules with Fewer than Four Neighbors, J. Phys. Chem. Lett., 2013, 4, 2565-2570; C. Q. Sun et al., Density and phonon-stiffness anomalies of water and ice in the full temperature range, J. Phys. Chem. Lett., 2013, 4, 3238-3244], refers to the water molecules being polarized by molecular undercoordination, which is associated with the skin of bulk ice, nanobubbles, and nanodroplets (often called confinement), or by the electrostatic field of ions in salt solutions [X. Zhang et al., Mediating relaxation and polarization of hydrogen-bonds in water by NaCl salting and heating, Phys. Chem. Chem. Phys., 2014, 16(45), 24666-24671; C. Q. Sun et al., (H, Li)Br and LiOH solvation bonding dynamics: molecular nonbond interactions and solute extraordinary capabilities, J. Phys. Chem. B, 2018, 122(3), 1228-1238]. From the perspective of hydrogen bond (O:H-O or HB with ":" representing the lone pairs on O2-) cooperative relaxation and polarization, this review features the recent progress and recommends future trends in understanding the bond-electron-phonon correlation in the supersolid phase. Supersolidity is characterized by a shorter and stiffer H-O bond, longer and softer O:H nonbond, deeper O 1s energy band, and longer photoelectron and phonon lifetimes. The supersolid phase is less dense, viscoelastic, and mechanically and thermally more stable. Furthermore, O:H-O bond cooperative relaxation offsets the boundaries of structural phases and increases the melting point while lowering the freezing temperature of ice, which is known as supercooling and superheating. Accepted version

A systematic phonon spectrometric examination revealed that the H C phonon (2966 cm−1) undergoes blueshift under both compression and heating, but the C N (921 cm−1) and the N O (1403 cm−1) bonds undergo regular thermal redshift and compression blueshift in the Nitromethene (CH3NO2) assembly that is a solid under compression and a liquid under heating. An extension of the Gruneisen parameters integrates the phonon frequency shift to the intrinsic compressibility, thermal expansibility, specific heat, equilibrium bond length, atomic cohesive energy, and bonding energy density of the single bond which represents all of its sorts contributing to the spectral peak shift. The coupled hydrogen bond (HB, N (O):H–C), performs the same as the O:H–O of liquid water and ice I does in responding to heating. Results suggested that the combination of the N (O):H-C tension and the O:⇔:N repulsion stabilize the crystal structure and store energy, as they do in the cyclo-N5−:[4H3O+; 3H3O+ + 2NH4+] complexes.

The solute–solvent interaction of salts has a striking impact on various biological and industrial processes but its mechanism remains yet mysterious despite intensive studies since 1888 when Franz Hofmeister established the salt series. A combination of confocal Raman spectroscopy and contact angle measurements has enabled us to resolve the hydrogen bond relaxation (O:H―O, HB) and the associated charge polarization dynamics at different molecular site because of alkali halides hydration. Results show consistently that salt hydration softens the O:H phonon but stiffens H―O phonon cooperatively. The extent of HB relaxation and polarization is proportional to the electronegativity difference and ionic radius, following the order of Hofmeister series: X (R/η) = I (2.2/2.5) > Br (1.96/2.8) > Cl (1.81/3.0) > F (1.33/4.0) ≈ 0 for anions, and Y(R/η) = Na (0.98/0.9) > K (1.33/0.8) > Rb (1.49/0.8) > Cs (1.65/0.8) for cations. Observations suggest that ions create each an electric field that aligns, stretches, and polarizes water molecules, which relaxes the O:H―O bond cooperatively, depresses the molecular dynamics, and enhances the hydration shell viscosity and the skin stress. Exercises also demonstrate that Raman spectroscopy performs as a powerful tool for probing the molecular-site-resolved HB network relaxation dynamics in terms of phonon stiffness, molecular fluctuation dynamics, and phonon abundance transition under external stimulus. Copyright © 2016 John Wiley & Sons, Ltd.

This presentation features recent progress in understanding the phase diagram of water and ice from the perspective of hydrogen bond (O:H–O) cooperative relaxation with focus on how the segmental length and the containing angle of the O:H–O bond change with mechanical compression and thermal excitation. By interplaying theoretical predictions, numerical computations, and phonon spectrometrics, we firstly examined the relaxation dynamics of O:H–O bond segmental length and phonon stiffness of: i) liquid water at 300 K and ice at 80 K as a function of pressure, ii) liquid water cooling from 350 K to 80 K under the ambient pressure, iii) mechanical freezing of the ambient water under compression up to 1.83 GPa, and, iv) liquid water heating from 253 to 753 K under 30 MPa pressure. Observations allow us to classify the TC(P) phase boundaries of water and ice into four types according to their slopes and then formulate them in terms of hydrogen bond relaxation in segmental length and containing angle. Observations reinforce the essentiality and effectiveness of hydrogen bond notion in dictating the unusual behavior of water and ice and clarify the bonding dynamics during phase transition, which is beyond the scope of classical thermodynamics.

A sequential of concepts developed in last decade has enabled a resolution to multiple anomalies of water ice and its low-dimensionality, particularly. Developed concepts include the coupled hydrogen bond oscillator pair, segmental specific heat, three-body coupling potentials, quasisolidity, and supersolidity. Resolved anomalies include ice buoyancy, ice slipperiness, water skin toughness, supercooling and superheating at the nanoscale, etc. Evidence shows consistently that molecular undercoordination shortens the HO bond and stiffens its phonon while undercoordination does the OH nonbond contrastingly associated with strong lone pair polarization, which endows the low-dimensional water ice with supersolidity. The supersolid phase is hydrophobic, less dense, viscoelastic, thermally more diffusive and stable, having longer electron and phonon lifetime. The equal number of lone pairs and protons reserves the configuration and orientation of the coupled hydrogen bond bonds and restricts molecular rotation and proton hopping, which entitles water the simplest, ordered, tetrahedrally-coordinated, fluctuating molecular crystal covered with a supersolid skin. The hydrogen bond segmental cooperativity and specific-heat disparity form the soul dictating the extraordinary adaptivity, reactivity, recoverability, sensitivity of water ice when subjecting to physical perturbation. It is recommended that the premise of hydrogen bonding and electronic dynamics would deepen the insight into the core physics and chemistry of water ice., 11.7 k words, 13 figures,115 refs. Chinese Physics B 2020

From the perspective of O:H-O bond cooperativity, we analyzed the solute capability of transiting the O:H-O bond from the mode of ordinary water to the hydration state and its consequence on the solution viscosity and surface stress. Phonon spectrometric results suggest that glycine and its N-methyl derivatives strongly affect the surrounding solvent molecules through H ↔ H repulsion and dipolar polarization. The H ↔ H interproton repulsion disrupts the surface stress, and the polarization enhances the solution viscosity.

Aqueous charge injection in forms of electrons, protons, lone pairs, ions, and molecular dipoles by solvation is ubiquitously important to our health and life. Pursuing fine-resolution detection and consistent insight into solvation dynamics and solute capabilities has become an increasingly active subject. This treatise shows that charge injection by solvation mediates the O:H–O bonding network and properties of a solution through O:H formation, H↔H frag-ilization, O:⇐⇒:O compression, electrostatic polarization, H 2 O dipo-lar shielding, solute–solute interaction, and undercoordinated H–O bond contraction. A combination of the hydrogen bond (O:H–O or HB with ‘:’ being the electron lone pairs of oxygen) cooperativity notion and the differential phonon spectrometrics (DPS) has enabled quantitative information on the following: (i) the number fraction and phonon stiffness of HBs transiting from the mode of ordinary water to hydration; (ii) solute–solvent and solute–solute molecular nonbond interactions; and (iii) interdependence of skin stress, solution viscosity, molecular diffusivity, solvation thermodynamics, and critical pressures and temperatures for phase transitions. An examination of solvation dynamics has clarified the following: (i) the excessive protons create the H↔H or anti-HB point breaker to disrupt the acidic solution network and surface stress. (ii) The excessive lone pairs generate the O:⇐⇒:O or super–HB point compressor to shorten the O:H nonbond but lengthen the H–O bond in H 2 O 2 and basic solutions; yet, bond-order-deficiency shortens and stiffens the H–O bond due H 2 O 2 and OH − solutes. (iii) Ions serve each as a charge center that aligns, clusters, stretches, and polarizes their neighboring HBs to form hydration shells. (iv) Solvation of alcohols, aldehydes, complex salts, carboxylic and formic acids, glycine, and sugars distorts the solute–solvent interface structures with the involvement of the anti-HB or the super-HB. Extending the knowledge and strategies to catalysis, solution–protein, drug–cell, liquid–solid, colloid–matrix interactions and molecular crystals would be even more fascinating and rewarding.

The resultant energy of solvent H–O bond exothermic elongation by O:⇔:O repulsion, featured at 150% the O:H cohesive energy of 0.095 eV that caps the energy dissipating by molecular motion, thermal fluctuation, diffusion, and even evaporation. Therefore, the intramolecular H–O bond relaxation dictates the OH − solvation bonding thermodynamics and the performance of basic solutions. Accepted version

We examined O:H-O bond relaxation under compression,heating,molecular undercoordination and claimed a universal resolution to the best-known mysteries of water ice such as ice foating, ice slipperiness, relegation and warm water cools faster. progress shows that O:H-O bond segmental disparity and O-O repulsivity form the soul dictating the extraordinary adaptivity, cooperativity, recoverability, and sensitivity of water and ice., Comment: 42 k words, 411 Refs, 65 figures, 10 tables

Relaxation of the hydrogen bond (O:H–O) between oxygen ions of undercoordinated molecules fascinates the behavior of water nanodroplets and nanobubbles. However, probing such potentials remains yet far from reality. Here we show that the Lagrangian solution (Huang et al. J. Phys. Chem. B 2013, 117, 13639) transforms the observed H–O bond (x = H) and O:H nonbond (x = L) lengths and their characteristic phonon frequencies (dx, ωx) (Sun et al. J. Phys. Chem. Lett. 2013, 4, 2565) into their respective force constants and cohesive energies (kx, Ex), which results in mapping of the potential paths for the O:H–O bond relaxing with (H2O)N cluster size. Results show that molecular undercoordination not only reduces its size (H–O length dH) with enhanced H–O energy from the bulk value of 3.97 to 5.10 eV for a H2O monomer but also enlarges their separation (O:H distance dL) with O:H energy reduction from 95 to 35 meV for a dimer. The H–O energy gain raises the melting point of water skin from the bulk value 273 to 3...

It has long been puzzling that water nanodroplet undergoes simultaneously “supercooling” at freezing and “superheating” at melting. Recent progress [Sun et al., J Phys Chem Lett 2013, 4: 2565; ibid, 4: 3238] enables us to resolve this anomaly from the perspective of hydrogen bond (O:H-O) specific-heat disparity. A superposition of the specific-heat x(T) curves for the H-O bond (x = H) and the O:H nonbond (x = L) defines two intersecting temperatures that form boundaries of the quasi-solid phase between ice and liquid water. Molecular undercoordination (with fewer than four nearest neighbours in the bulk) stretches the H(T) curve by raising the Debye temperature DH through H-O bond shortening and phonon stiffening. The H(T) stretching is coupled with the L(T) depressing because of the Coulomb repulsion between electron pairs on oxygen ions. The extent of dispersion varies with the size of a droplet that prefers a core-shell structure configuration – the bulk interior and the skin. Understandings may open an effective way of dealing with the thermodynamic behaviour of water droplets and bubbles from the perspective of O:H-O bond cooperativity. Accepted version

An incorporation of the hydrogen bond (O:H O or HB) cooperativity notion, contact angle detection, and the differential phonon spectrometrics (DPS) has enabled us to gain refined information on the HCl, KCl and KOH solvation resolved solute-solvent molecular interactions and the solution surface stresses. Results show that ionic polarization stiffens the solvent H O bond phonon from 3200 to 3480 cm −1 in the hydration shells. The HO − in alkaline solution, however, shares not only the same H O phonon redshift of compressed water from 3200 to −1 but also the dangling bonds of H 2 O surface featured at 3610 cm −1 . Salt and alkaline solvation enhances the solution surface stress by K + and Cl − ionic polarization. The excessive H + proton in acid solution forms a H↔H anti-HB that depresses the solution surface stress, instead. The solute capability of transforming the fraction of the O:H O bonds of the solvent matrix is featured by: f H = 0 and f x ∝ 1-exp(-C/C 0 ) (x = HO − , K + and Cl − ) towards saturation. Exercises not only confirm the presence of the H↔H anti-HB point fragilization, the O:⇔:O super-HB point compression, and ionic polarization dominating the performance of the respective HCl, KOH, and KCl solutions, but also demonstrate the power of the DPS that enables high resolution of solute-solute-solvent interactions and correlation between HB relaxation and solution surface stress.

Water nanobubbles manifest fascinatingly higher mechanical strength, higher thermal stability, and longer lifetime than macroscopic bubbles; thus, they provide an important impact in applications in the biomedical and chemical industries. However, a detailed understanding of the mechanism behind these mysteries of nanobubbles remains a challenge. Consistency between quantum computations and Raman spectrometric measurements confirmed our predictions that a nanobubble skin shares the same supersolidity with molecular clusters, skins of bulk water, and water droplets because of molecular undercoordination (fewer than four nearest molecular neighbors). Molecular undercoordination (coordination number Zcluster < Zsurface < Zbubble < Zbulk = 4) shortens/extends the H–O/O:H bond and stiffens/softens its corresponding stretching phonons, whose frequency shift is proportional to the square root of the cohesive energy and inversely proportional to the segmental length. The strongly polarized O:H–O bond slows the mo...

A combination of the Lagrangian mechanics of oscillators vibration, molecular dynamics decomposition of volume evolution, and Raman spectroscopy of phonon relaxation has enabled us to resolve the asymmetric, local, and short-range potentials pertaining to the hydrogen bond (O:H-O) in compressed ice. Results show that both oxygen atoms in the O:H-O bond shift initially outwardly with respect to the coordination origin (H), lengthening the O-O distance by 0.0136 nm from 0.2597 to 0.2733 nm by Coulomb repulsion between electron pairs on adjacent oxygen atoms. Both oxygen atoms then move toward right along the O:H-O bond by different amounts upon being compressed, approaching identical length of 0.11 nm. The van der Waals potential VL(r) for the O:H noncovalent bond reaches a valley at -0.25 eV, and the lowest exchange VH(r) for the H-O polar-covalent bond is valued at -3.97 eV.

Coulomb repulsion between the bonding electron pair in the H-O covalent bond (denoted by "-") and the nonbonding electron pair of O (":") and the specific-heat disparity between the O:H and the H-O segments of the entire hydrogen bond (O:H-O) are shown to determine the O:H-O bond angle-length-stiffness relaxation dynamics and the density anomalies of water and ice. The bonding part with relatively lower specific-heat is more easily activated by cooling, which serves as the "master" and contracts, while forcing the "slave" with higher specific-heat to elongate (via Coulomb repulsion) by different amounts. In the liquid and solid phases, the O:H van der Waals bond serves as the master and becomes significantly shorter and stiffer while the H-O bond becomes slightly longer and softer (phonon frequency is a measure of bond stiffness), resulting in an O:H-O cooling contraction and the seemingly "regular" process of cooling densification. In the water-ice transition phase, the master and the slave swap roles, thus resulting in an O:H-O elongation and volume expansion during freezing. In ice, the O--O distance is longer than it is in water, resulting in a lower density, so that ice floats.

Goldschmidt-Pauling contraction of the H-O polar-covalent bond elongates and polarizes the other noncovalent part of the hydrogen bond (O:H-O), that is, the O:H van der Waals bond, significantly, through the Coulomb repulsion between the electron pairs of adjacent oxygen (O-O). This process enlarges and stiffens those H2O molecules having fewer than four neighbors such as molecular clusters, hydration shells, and the surface skins of water and ice. The shortening of the H-O bond raises the local density of bonding electrons, which in turn polarizes the lone pairs of electrons on oxygen. The stiffening of the shortened H-O bond increases the magnitude of the O1s binding energy shift, causes the blue shift of the H-O phonon frequencies, and elevates the melting point of molecular clusters and ultrathin films of water, which gives rise to their elastic, hydrophobic, highly-polarized, ice-like, and low-density behavior at room temperature.

Phonon spectrometrics and contact-angle measurements revealed the essentiality of anti-HB (hydrogen bond), super-HB, and electrified-HB representing molecular interactions in the Lewis acid, base, and adduct (salt) solutions, respectively. Hydronium creation (H3O tetrahedron with one lone pair) in acid solution results in the H↔H anti-HB that breaks the O:H–O bond network, diluting blood flow for instance; hydroxide (OH tetrahedron with three lone pairs) leads to the O:↔:O super-HB that serves as a point compressor to the hydration network, releasing heat by softening the H–O bond at hydrating. Salt ions create each an electric field that aligns, clusters, polarizes, and stretches water molecular dipoles in a supersolid hydration-shell manner. The electrification-induced phonon relaxation disperses the quasisolid phase boundary outwardly and hence lowers the freezing temperature and raises the melting point. O:H–O bond electrification also raise the viscosity, skin stress, H–O phonon lifetime, but depresses the order of fluctuation and the coefficient of molecular rotation and self-diffusion in the hydration shells. The extent of electrification is molecular site, solute concentration and type dependent, following the Hofmeister series.

Superlubricity means non-sticky and frictionless when two bodies are set contacting motion. Although this occurrence has been extensively investigated since 1859 when Faraday firstly proposed a quasiliquid skin on ice, the mechanism behind the superlubricity remains debating. This chapter features a consistent understanding of the superlubricity pertaining to the slipperiness of ice, self-lubrication of dry solids, and aqueous lubricancy from the perspective of skin bond-electron-phonon adaptive relaxation. The presence of nonbonding electron polarization, atomic or molecular undercoordination, and solute ionic electrification of the hydrogen bond as an addition, ensures the superlubricity. Nonbond vibration creates soft phonons of high magnitude and low frequency with extraordinary adaptivity and recoverability of deformation. Molecular undercoordination shortens the covalent bond with local charge densification, which in turn polarizes the nonbonding electrons making them localized dipoles. The locally pinned dipoles provide force opposing contact, mimicking maglev and hovercraft.

As the basic structure element, hydrogen bond (O:H–O) is universal to all phases of water and ice irrespective geometric configuration or fluctuation order. The O:H–O bond integrates the asymmetric, coupled, short-range intermolecular and intramolecular interactions, whose segmental length and energy respond to stimulations sensitively in a “mater-slave” manner. If one segment shortens and turns to be stiffer, the other will expand and become softer. The O:H nonbond always relaxes more than the H–O bond in length. Such a manner of segmental cooperative relaxation and the associated polarization and bond angle relaxation discriminates ice and water from other substance in responding to stimuli of chemical, electrical, mechanical, thermal, and undercoordination effect, which reconcile almost all detectable properties of water and ice.

Regelation, i.e., ice melts under compression and freezes again when the pressure is relieved, remains puzzling since its discovery in 1850’s by Faraday. Here we show that hydrogen bond (O:H-O) cooperativity and its extraordinary recoverability resolve this anomaly. The H-O bond and the O:H nonbond possesses each a specific heat ηx(T/ΘDx) whose Debye temperature ΘDx is proportional to its characteristic phonon frequency ωx according to Einstein’s relationship. A superposition of the ηx(T/ΘDx) curves for the H-O bond (x = H, ωH ~ 3200 cm−1) and the O:H nonbond (x = L, ωL ~ 200 cm−1, ΘDL = 198 K) yields two intersecting temperatures that define the liquid/quasisolid/solid phase boundaries. Compression shortens the O:H nonbond and stiffens its phonon but does the opposite to the H-O bond through O-O Coulomb repulsion, which closes up the intersection temperatures and hence depress the melting temperature of quasisolid ice. Reproduction of the Tm(P) profile clarifies that the H-O bond energy EH determines the Tm with derivative of EH = 3.97 eV for bulk water and ice. Oxygen atom always finds bonding partners to retain its sp3-orbital hybridization once the O:H breaks, which ensures O:H-O bond recoverability to its original state once the pressure is relieved.

Lagrangian solution to the coupled oscillators enables mapping of the asymmetric, short-range potentials pertaining to the O:H–O bond. Both oxygen atoms in the O:H–O bond shift initially from their equilibrium (without coulomb coupling) outwardly with respect to the coordination origin (H), lengthening the O–O distance by Coulomb repulsion. Both oxygen atoms then move toward right along the O:H–O bond by different amounts upon being compressed and cooled, toward length symmetrization. The vdW potential V L(r) for the O:H non-covalent bond reaches a valley at −0.25 eV and the lowest exchange V H(r) for the H–O polar covalent bond values at −3.97 eV under compression.

Coulomb repulsion and mechanical disparity within the H-bond differentiate ice from other materials in response to compression. Compression shortens and strengthens the O:H bond and meanwhile lengthens and softens H–O bond through repulsion toward O:H and H–O length symmetry.

Molecular under-coordination effects oppositely to compression. Spontaneous H–O contraction elongates and polarizes the O:H bond significantly via interelectron-pair repulsion. Under-coordinated H2O molecules shrink in size but enlarge their separation. The shortening of the H–O bond entraps bonding electrons and raises the local density, which in turn polarizes the lone pairs of electrons on oxygen. The stiffening of the shortened H–O bond increases the magnitude of the O 1s shift, causes the blueshift of the H–O phonon frequencies, and elevates the T m of molecular clusters and ultrathin films of water, which gives rise to their supersolid phase of elastic, hydrophobic, ice-like, polarized with ultra-low-density.

Heating stores energy into water by stretching the O:H non-bond and shortening the H–O bond via a Coulomb coupling. Heating and supersolid skin elevate jointly gradients of mass density, specific heat, and thermal conductivity in the liquid, favoring heat flowing outwardly in liquid. Cooling does oppositely, like releasing a highly deformed bungee, to emit heat at a rate depending on initial storage. Convection alone raises the skin temperature without the presence of Mpemba effect. Being sensitive to the liquid volume and the temperature of the drain, Mpemba effect proceeds only in the strictly non-adiabatic source–drain interface ambient with a characteristic relaxation time that drops exponentially with the rise of the initial temperature of the source.

An extension of the Ice Rule results in the building block of an ideal tetrahedron consisting two H2O molecules and four identical O:H–O bonds. The O:H–O bond performs as a pair of asymmetric, coupled, H-bridged oscillators. Under external stimulus, one part of the O:H–O bond serves as the ‘master’ and the other as a ‘slave.’ Coulomb repulsion between electron pairs on oxygen dislocates the O atoms in the same direction under excitation along the O:H–O bond but by different amounts. The softer O:H bond relaxes always more than the stiffer H–O bond does.

The density and phonon-stiffness of water ice oscillates over the full temperature range, transiting at 277, 258, and 80 K. The segment of relatively lower specific heat contracts at cooling, which forces the other of the H-bond to elongate via Coulomb repulsion. In the liquid and solid phases, O:H bond contracts more than the H–O elongates; hence, an O:H–O cooling contraction and the seemingly ‘regular’ process of cooling densification take place. During freezing, the H–O contracts less than the O:H elongates, leading to an O:H–O elongation and volume expansion. At T < 80 K, the length and energy of both segments conserve but the O:H–O angle stretches, resulting in slight volume expansion. In ice, the O–O distance is longer than it is in water, resulting in a lower density, so that ice floats. Length contraction/elongation of the specific segment is associated with phonon-stiffening/softening.