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Atoms with even fewer neighbors perform both atomic like and bulk like associated with shorter and stronger interatomic bonds. The bond contraction raises the local charge and energy density and the bond strength gain deepens the local potential well and entraps the core electrons. The locally and densely entrapped core electrons in turn polarize the valence electrons. The subjective valence electron polarization occurs to those atoms with unpaired lone electrons in the s orbitals such as Rh, Au, Ag, Cu and the unpaired 4f145d46s2 (5d56s1 seems to be stable) electrons of the W adatoms and Mo(4d55s1) as well. However, the Co(3d74s2) with fully-occupied s electrons and the Re(5d56s2) with semi-occupied d electrons exhibit entrapment dominance. The undercoordination resolved valence electron entrapment or polarization laid foundations for the extraordinary catalytic ability of the excessively undercoordinated atoms and the dispersed single atom.

Physical perturbation mediates material’s properties by relaxing the interatomic bonding and electron configuration in various bands. Phonon spectroscopy probes bond relaxation or bond tranformation from one equilibrium to another under perturbation and electron spectroscopy fingerprints bond-relaxation induced electronic configuration, which have important impact to chemistry, physics, and material engineer and science. However, extracting information from the phonon spectroscopic measurements and gaining consistent insight into the physics behind observations are still infancy compared to crystallography and surface morphology because of lacking basic regulations. Conventional decomposition of spectral peaks or empirical simulation of spectral evolution under perturbation provide limited information with freely adjustable parameters and debating mechanisms. The featured multifield phonon spectrometrics aims to extracting atomistic, local, and quantitative information on the bonding and nonbonding dynamics and their correlation to performance of a variety of substances under external perturbations.

Electron binding energy shift directly features the change of bond energy with coordination environments and chemical conditions, from which one can evaluate the local and quantitative information on the local bond length, bond energy, core charge entrapment and valence electron polarization. Bonds and electrons associated with undercoordinated adams, point defects, skins, and nanostructures follows the BOLS-NEP notion but bonds associated with the hetero-coordinated and the tetrahedrally-coordinated impurities and interfaces may subject to bond nature alteration and the local electrons may subject to entrapment or polarization.

Decomposition of the XPS profiles into components of sublayers derives information on the local bond length, bond energy, atomic cohesive energy, binding energy density, and the energy levels Eν(0) of an isolated atom and its shift with the coordination environment. The Eν(0) and Eν(12) remain constant and the atomic CN varies only with the layer order and surface registry, regardless of the skin chemical constituent. Atomic undercoordination induced bond contraction drives relaxation and reconstruction of the surface of a crystal.

A physical perturbation mediates intrinsically the performance of a substance through relaxing the length and energy of the chemical bonds and associated electrons in various energy bands. From the perspective of Fourier transformation, one can formulate the bond oscillation frequency ∆ω (z, d, E, μ) for a variety of materials by perturbing the Hamiltonian. Reproduction of the excited ∆ω by a perturbation xi such as bond-order-imperfection, electric polarization, compression, tension, and thermal activation turns out information on the bond length d(xi), bond energy E(xi), single-bond force-constant, binding energy density, mode cohesive energy, Debye temperature, elastic modulus, etc., complementing the electron spectrometrics. Exercises proved the immense power of the phonon spectrometrics in revealing the nature behind the lattice vibration in terms of multifield single-bond oscillation dynamics in liquid and solid phases.

Like adatoms, monoatomic chain ends, and atomic clusters with even less-coordinated atoms demonstrate extraordinary properties due to dominance of stronger quantum entrapment and polarization. Consistency between quantum calculations and XPS/STS observations resolves the origin of the unusual performance of such even undercoordinated atoms. A combination of the XPS and AES, called APECS, refines the energy shifts of both the core band and the valence band with derived information of the screening effect and charge transport during reaction.

A set of analytical strategies has enabled atomistic, local, dynamic, and quantitative information on the bonding and electronic energetics induced by atomic under- and hetero-coordination. With the aids of the ZPS, one can purify the energy states with high precision without needing decomposition of the spectral peaks. APECS and NEXAS probe simultaneously the shifts of a core and the valence energy bands with provision of the screening and recharging information. Quantitative information includes the bond length, bond energy, core level shift, core charge entrapment and valence electron polarization, atomic cohesive energy, and binding energy density. Such a collection of information is fundamentally crucial to designing and synthesizing functional materials.

A combination of the hetero- and under-coordination forms a promising means of mediating the bonding and electronic dynamics and properties of a substance as the hetero- and under-coordination enhance each other on the charge entrapment and polarization. However, at a critical size, polarization may compensate or override quantum entrapment because of the polarization screens and splits the interatomic potentials.

VLLED has enabled quantification of the four-stage Cu3O2 pairing-tetrahedra formation in the Cu(001) surface transiting from O− to O2− with production of the missing rows, Cu-O-Cu chains, oppositely paired Cup crossing the missing rows. The surface stress turns from tensile in the O− derived first phase to the O2− derived second phase. The phase transition dynamics is beyond the scope of computations from the perspective of total energy minimization or structural optimization. Annealing relaxes the Cu3O2 bond geometry, the SPB, and the valence states accordingly while heating at a dull-red color de-hybridizes the sp orbits of oxygen, desorption will occur at higher temperatures.

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.

Hetero-coordinated bond formation changes the local bond strength and charge distribution. Polarization dominance reduces the CL and makes the alloy a donor-like catalyst with weakened interface mechanical strength; entrapment dominance does it contrastingly. The ZPS offers such a unique yet straightforward means that diagnosis the interface bonding and electronic dynamics in alloys, compounds, impurities, and interfaces for devising functional substance.

Oxide tetrahedral bond formation with orbital occupation by the shared bonding and nonbonding electron pairs determine uniquely the bond geometry, valence density of states, and the surface potential barrier. Parameterization of all involved parameters as a function of the bond angle and length and the origin of the SPB not only simplified the calculations but also importantly ensured the solution approaching true situations.

O-Cu(001) chemisorption derives the Cu3O2 pairing-tetrahedronand the Cup:O2−:CuP chains lined along the missing-raw edges, which roughen the SPB and the surface morphology. At the dipole site, The origin of the SPB moves \(\sqrt {2}z_{0}\) outwardly with \(\sqrt {2}\lambda_{0}\) saturation degree, at the atomic vacancy site, the SPB is characterized by \(z_{0} /\sqrt 2\) and \(\lambda_{0} /\sqrt 2\), with z0 and λ0 being the references for clean Cu(001) surface. Connecting the Bragg diffraction peaks results in the first and the second two-dimensional Brillouin zones with the 〈11〉 direction deformation corresponding to a 0.22 A dislocation of the Cup towards the MR. Matching the theoretical Brillouin zones derived the electronic effective mass of \(m_{1}^{*}\) = 1.10, and \(m_{2}^{*}\) = 1.14 at the boundaries.

VLEED offers such a unique tool that collects information of bond geometry, valence density-of states (DOS), and SPB outside the second atomic layer with high sensitivity and reliability. Based on the principle of Fourier transformation, VLEED calculation derives consistent information obtained with electron spectroscopy, crystallography, and morphology on an atomic scale.

The OH− and the H2O2 possess each two excessive pairs of electron lone pairs “:” that form an O:⇔:O super−HB upon solvation. The O:⇔:O compression shortens the O:H nonbond and stiffens its phonon but relaxes the H–O bond oppositely. The H–O bond elongation emits energy to heat up the solution. Bond-order-deficiency shortens the solute H–O bond and stiffens its phonon to 3550 cm−1 for H2O2 and 3610 cm−1 for OH−. However, the O:⇔:O compression annihilates the weak cationic polarization. The H2O2 is less than the OH− capable of transiting the solvent H–O bonds and surface stress. The linear fraction coefficient f(C) suggests that the OH− be less sensitive to other solutes. The resultant of solvent exothermic H–O elongation by O:⇔:O compression and the solute endothermic H–O contraction by bond order deficiency heats up the solutions. Observations evidence not only the significance of the inter-lone-pair interaction but also the universality of the bond order-length-strength (BOLS) correlation to aqueous solutions.

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.

The excessive number of H+ or “:” and their asymmetrical distribution determines the performance of their surrounding water molecules in a way different from that of ordinary water. The naked lone pairs and protons are equally capable of interacting with the solvent H2O molecules to form O:H vdW bond, O:⇔:O super–HB or H↔H anti-HB without charge sharing or new bond forming. Solvation examination of alcohols, aldehydes, formic acids, and sugars reveals that O:H–O formation enables the solubility and hydrophilicity of alcohol; the H↔H anti-HB formation and interface structure distortion disrupt the hydration network and surface stress. The O:H phonon redshift depresses the freezing point of sugar solution of anti-icing.

Solvation is a process of aqueous charge injection in the forms of H+, electrons, electron lone pairs, cations, anions, or molecular dipoles with long- and short-range interaction. A solute interacts with its neighboring H2O molecules through the O:H vdW, O:⇔:O super-HB compression, H↔H anti-HB fragilization, ionic or dipolar polarization with screen shielding, and solute-solute interaction and their combinations. The hydration H2O dipoles tend to be aligned oppositely along the electric field screen in turn the electric fields of the solute. The ionic size, charge quantity, and the numbers and spatial distribution of H+ and “:” determine the form of solute-solvent interaction. A solute may be sensitive or not to interference of other solutes depending on the solute size and its extent of screening. The intermolecular nonbond and intramolecular bond cooperative relaxation determines the performance of a solution in terms of surface stress, solution viscosity, energy absorption-emission-dissipation at solvation, solvation temperature, thermal stability, critical pressures and pressures 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.

Solvation dissolves the HX into an H+ and an X−. The H+ bonds to a H2O to form a firm H3O+ and a H↔H anti − HB point breaker. The H–O bond due H3O+ is 3% shorter and the associated O:H nonbond is 60% longer than normal. The H↔H compression shortens its nearest O:H nonbond by 11% and lengthens the H–O by 4%. The X− point polarizer shortens the H–O bond and stiffens its phonon but relax the O:H nonbond oppositely in the supersolid hydration shell. The X− solute capability of bond transition follows the I > Br > Cl order in the form of fx(C) ∝ 1 − exp(−C/C0) towards saturation because of the involvement of the X−↔X− interaction that weakens the hydration-shell electric field at higher concentrations. However, the H+ neither hops or tunnels freely nor polarize its neighbors, fH(C) = 0. The H↔H has the same effect of heating on the surface stress and solution viscosity disruption.

Sixty basic rules govern the O:H–O bond relaxation and electron polarization and their consequences on detectable properties of water and ice such as the phonon frequencies, O 1s binding energy shift, crystal geometry, H–O phonon lifetime, mass density, elasticity, hydrophobicity, fluidity, lubricity, supersolidity, quasisolidity, viscosity, skin stress, skin solubility, molecular dynamics, degree of fluctuation, thermal stability and their interdependence.

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.

Lagrangian solution of oscillator dynamics transforms the observed H–O bond and O:H nonbond lengths and their characteristic phonon frequencies (d x, ω x) into their respective force constants and cohesive energies (k x, E x), which results in mapping of the potential paths for the O:H–O bond cooperative relaxation under stimulus. Results show that molecular undercoordination not only reduces its size (d H) 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 (d L) 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 310 K, and the O:H energy loss lowers the freezing temperature of a 1.4 nm sized droplet from the bulk value 258 to 202 K. However, compression does the opposite to molecular undercoordination on bond relaxation but the same on polarization.

A solute forms a hydration shell by clustering water molecular dipoles surrounding it, which elongates the O:H–O bond in the shell and stiffens its H–O phonon and softens the O:H–O nonbond phonon by different extents. Polarization dominance of salt solutions raises the H–O phonon lifetime, molecular structural order, skin stress, solution viscosity, and thermal stability. Quantum fragmentsation of acid solutions weakens molecular structural order, skin stress, and the reflectivity of Raman photon and the transmittance of IR photons. The difference in electronegativity, electronic structure, and ionic size between H+ and other alkali metals could be origin.

As an often overlooked degree of freedom, molecular undercoordination shortens the H–O polar-covalent bond and stiffens its phonon but lengthens and softens the O:H nonbond more significantly through the Coulomb repulsion between the electron pairs of adjacent oxygen. This process shrinks those H2O molecules having fewer-than-four neighbors such as molecular clusters, hydration shells, and the surface skin 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 forming anchored dipoles pointing outwardly. The stiffening of the shortened H–O bond increases the magnitude of the O 1s binding energy shift, causes the blueshift 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, ice-like, frictionless, and low-density behavior irrespective of temperature.

Phonon spectrometric mapping of the O:H–O bond relaxation dynamics across the phase diagram along the following paths confirmed the reality of the O:H–O cooperativity mechanism: (i) liquid water at 300 K and ice at 80 K as a function of pressure, (ii) liquid water cooling from 350 to 80 K under the ambient pressure, (iii) mechanical freezing of the ambient water under compression up to 4.0 GPa, and, (iv) liquid water heating from 253 to 753 K under 30 MPa pressure. Observations classify the TC(P) phase boundaries of water and ice into four types according to their slopes. O:H compression dictates the positively-sloped such as Vapor/Liquid boundaries; the H–O elongation dictates the negatively-sloped such as VII/VIII boundaries, while O:H–O frozen dictates the XI/Ic constant TC boundary and the symmetrical relaxation governs the X/(VII, VIII) constant PC boundaries.

A combination of the electrification-induced quasisolidity and the undercoordination-induced skin supersolidity laid foundations for the water floating bridge, electrofreezing and electromelting of liquid water. Both electrification and molecular undercoordination disperse the quasisolid phase boundaries, which not only depresses the freezing temperature and molecular dynamics but also raises the melting point, H–O phonon lifetime, skin stress, and viscosity. The extent of quasisolidity is charge quantity and sign dependent. Aqueous solutions weaken the field of capacitors or charged particles, so aqueous solutions destabilize the floating bridge and wet faster soil particles.

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.

Consistency in experimental observations, numerical calculations, and theoretical predictions revealed that skins of 25 °C water and −(15-20) °C ice share the same attribute of supersolidity characterized by the identical H–O vibration frequency of 3450 cm−1. Molecular undercoordination and inter-electron-pair repulsion shortens the H–O bond and lengthen the O:H nonbond, leading to a dual process of nonbonding electron polarization. This relaxation-polarization process enhances the dipole moment, elasticity, viscosity, thermal stability of these skins with 25 % density loss, which is responsible for the hydrophobicity and toughness of water skin and the superfluidity in a microchannel.

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.

Solute ionic electrification of the O:H–O bond modulates significantly the critical pressures, temperatures, and gelation times for transiting aqueous solution into solid by dispersing the boundaries of the quasisolid phase. High-pressure in situ Raman spectrometrics revealed that transiting NaX solutions into ice VI and then into ice VII phase requires higher excessive pressures at 298 K temperature. The ΔPC varies in the order of Hofmeister series: X = I > Br > Cl > F ~ 0. Meanwhile, salting st​iffens the ωH and elongates the dOO throughout the course of compressure when transiting phase VII to phase X at even higher pressure. Recovering the electrification-shortened H–O bond needs excessive energy for the same sequence of phase transitions. Concentration dependence of the NaI solution indicates a different mechanism from that of solution type but it is similar to heating on the Liquid-VI-VII phase transition dynamics.

TDS features and work function change coincidently demonstrate four-stage bond forming kinetics and associated valence charge relaxation. The four stages include the following: (1) O1− formation, (2) O1− transition O2− with sp-orbit hybridization, (3) tetrahedron relaxation, and (4) dipole annihilation upon oxygen overdosing.