arXiv subjects
Publications and source records attributed to Chang Q Sun.
Unlike conventional thought, the H-O bond is flexible, instead, and sensitive to perturbation. This exercise empowers the electron and phonon spectroscopies with the Tight-binding approach, enabling a referential database to synchronically quantize the relaxation and flexibility of these identities for substances involving the H-O bond during phonon spectroscopy.
As the extremely-sized nanocrystals and nanopores, an adatom M and atomic vacancy V exhibit extraordinary capability of catalysis with however little knowledge about the catalyst-reactant interfacial bonding dynamics. With the aid of DFT calculations, we examined the dehydrogenization of a single CH4 molecule catalyzed using the Rh(111,100), W(110), Ru(0001) surfaces, and monolayer graphene, with and without M or V. It is uncovered in the following three components: (i) catalyst polarization due to atomic under- or hetero-coordination raises the valence band of the catalyst by bond contraction and atomistic dipolar MP and vacancy dipolar V formation; (ii) reactant bond elongation by the interplay of the MP-V = H attraction and MP-V = C repulsion with the = denoting the negative pole of the MP-V; and (iii) reactant conversion, i.e., the scale of H-C elongation, the catalyst valence-band shift, the adsorption energy, and the catalytic activity are proportional to the charge quantity of the MP-V whose local electric field matters.
NaCl solvation turns the fS portion molecules into the hydrating supersolid phase by ionic polarization and leaves the rest fO portion ordinary. Polarization shortens and stiffens the HO bond and does the O:H nonbond contrastingly in the supersolid. Water absorbs energy by HO cooling contraction in the quasisolid phase during the transition from Liquid to Quasisolid and then Ice The solution R drops with the fO loss till zero corresponding to 10 water molecules that saturates the solvation per solute at least. The polarization-weakening of the O H nonbonds lowers the TN to 253 K or below of the supersolid phase.
The segmental specific heat ratio of the couple hydrogen bond defines not only the phase of Vapor, Liquid, Ice I and XI phase with a quasisolid phase that shows the negative thermal extensibility but uniquely the slope of density of water ice in different phases. Ice floats because H-O contracts less than O:H expands in the QS phase at cooling.
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.
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.
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.
Atomic undercoordination, charge injection, mechanical and thermal activation mediate the properties of a material intrinsically by bond relaxation from one equilibrium to another while the phonon spectrometrics probes the ever-unexpected information of the binding energy density, atomic cohesive energy, single bond force constant, crystal elastic modulus, Debye temperature and the abundance-length-stiffness transition of bonds under perturbation.
Atomic undercoordination fascinates defects, surfaces, and nanostructures in electronic binding energy, lattice oscillation frequency, elasticity and plasticity (IHPR), thermal stability, photon emisibility, reactivity, dielectrics, super-hydrophobicity, spin-resolved topological edge and monolayer high-TC superconductivity, etc., through local bond contraction, quantum entrapment and polarization.
A combination of the temporally and spatially resolved phonon spectroscopy has enabled calibration of hydrogen bond transition from the vibration mode of heavy water to the core/shelled nanodroplet and the subnanosized ionic hydration shell 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 of HO (DO as a probe) bond contraction, O:H elongation, and electron polarization. The bond transition stems the solution viscosity, surface stress, and slows down the molecular dynamics. The skin reflection further hinders phonon energy dissipation and thus lengthens the phonon lifetime of the nanodroplet.
This work reviews the progress in STM/S, XPS, NEXFAS, SFG, DPS, ultrafast UPS and FTIR observations and quantum theory calculations on the bond/electron/phonon correlation in the supersolid phase derived by molecular undercoordination (confinement) and aqueous charge injection.
Charge injection in terms of anions, cations, electrons, lone pairs, protons, and molecular dipoles by acid,base, salt and organic molecular solvation mediates the O:HO bonding network and properties of the solution through O:H formation, HH fragillization, O:=:O compression, electrostatic polarization, H2O dipolar shielding, and solute/solute interaction
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.
We resolved the hydrogen bond transition from the mode of ordinary water to its hydration in terms of its phonon stiffness (vibration frequency shift), order of fluctuation (line width), and number fraction (phonon abundance) upon chage injection by solvation.
Unlike other unusual materials whose bonds contract under compression, the O:H nonbond undergoes contraction and the H-O bond elongation towards O:H and H-O length symmetry in water and ice. The energy drop of the H-O bond dictates the melting point Tm depression of ice. Once the pressure is relieved, the O:H-O bond fully recovers its initial state, resulting in Regelation.
Complementing STM/S, U/XPS, and APECS, BOLS-NEP theory enabled ZPS (USA patent) distils atomistic, dynamic, local, and quantitative information of bond relaxation and associated energetics, localization, quantum entrapment, and polarization of electrons associated with adatoms, point defects, terrace edges, monolayer skins, nanocrystals, impurities, and interfaces. Distilled entitles dominate ubiquitously and will propel the ill-coordination Chemistry and Physics.
Numerical reproduction of measurements, experimental evidence for skin super-solidity and hydrogen-bond memory clarified that Mpemba paradox integrates the heat emission-conduction-dissipation dynamics in the source-path-drain cycle system.
Hydrogen-bond forms a pair of asymmetric, coupled, H-bridged oscillators with ultra-short-range interactions and memory. hydrogen bond cooperative relaxation and the associated binding electron entrapment and nonbonding electron polarization discriminate water and ice from other usual materials in the physical anomalies. As a strongly correlated fluctuating system, water prefers the statistically mean of tetrahedrally-coordinated structure with a supersolid skin that is elastic, polarized, ice like, hydrophobic, with 3/4 density.