Entrapment and Polarization

The nature, order, length, and energy of the chemical bond determine the properties of a substance. The formation, dissociation, relaxation, and vibration of the bond and non-bond, and the associated dynamics of electron densihcation, localization, entrapment, and polarization are the key of tuning the property change. The underlying mechanism and the consequences of the surface events are useful in practice ... 

Patterns of relaxation and reconstruction may change from situation to situation, the nature of the bonds and the attributes of the valence states are common. STSM/S, LEED, PES, EELS, Raman, and TDS provide comprehensive information regarding the formation, relaxation, and vibration of the bonds and nonbonds and the associated charge entrapment and polarization. 

This part aims to present a consistent understanding of the undercoordinated systems such as point defects, adatoms, flat surfaces, and nanostructures of various shapes from the perspective of atomic undercoordination that induces local bond-relaxation and charge quantum entrapment and polarization in terms of the BOLS correlation and the NEP. For simplicity, the dimensionless form of change (%) of a detectable quantity and the dimensionless form of size K (being the number of atoms lined along the radius of a sphere or across the thin film) are used unless indicated otherwise. The dimensionless approach also allows the generality of the formulation and minimizes the contribution from impurities and artifacts in measurement. Attempt is made to minimize and simplify numerical expressions with focus more on physical understanding. 

This sequential happening of bond contraction, densification, entrapment, and polarization (bonding-non-bonding electron repulsion and strong correlation) may elaborate the Strong locahzation of Anderson for systems with bond order loss [2]. 

Interface potential barrier/trap formation with charge entrapment and polarization From a dimer to considerable large bulk with skin Tunable properties that the parent bulk demonstrate (skin entrapment) ... 

Graphite monolayer skin only shows entrapment but the atomic van cay shows both entrapment and polarization—one neighbor short makes a great difference. 

All ZPS profiles show respectively a main valley corresponding to the bulk component. The peak above the valley results from polarization (P) of the otherwise valence electrons by the densely entrapped electrons (T) in the bonding and core orbits. The second peak and the second valley at the bottom edge of the bands result from the joint effects of entrapment and polarization. The locally polarized electrons screen and split the crystal potential and hence split the core band into the P and the T components, which has no effect on the bulk component. The valence LDOS of W(320) atoms exhibits apparently the CN-resolved polarization of W atom at the terrace edge, which is the same to the Au clusters in Fig. 13.3. 

All undercoordinated systems demonstrate the electronic feature of global quantum entrapment and the subjective polarization. Undercoordinated atoms of Au, Ag, Rh, and W show both entrapment and polarization, while the undercoordinated Co and Pt atoms show only entrapment. One neighbor short makes the C atom at the defect site and the ZGNR edge to be completely different from that in the flat graphite surface and in the GNR interior and AGNR edge. 

As an element of structural defects, atomic vacancies, or point defects are very important in materials and have remarkable effect on the physical properties of a material such as electrical resistance, heat capacity, and mechanical strength. A vacancy formation is associated with local strain, densification, quantum entrapment, and polarization. 

The positive Cls-level shift is associated with a reduction in work function from the bulk value of 4.6. 3 eV for the single-layer GNR [84]. The work function reduction indicates the enhancement of edge polarization and charge densification by bond contraction. The fraction of surface and edge atoms increases and the number of layer is reduced. Hence, the associated work function reduction and the Cls shift evidence the coexistence of entrapment and polarization. 

The Hamiltonian determines and correlates the properties intrinsically, and therefore, it is appropriate to consider the change of all the properties relating to the Hamiltonian rather than separate one phenomenon at a time from another. The size-induced quantum entrapment and polarization modulates the Hamiltonian, and therefore, the entire band structure of nanostructured semiconductors [1] ... 

The size-induced quantum entrapment and polarization spits the valence band of metals to generate an artihcial bandgap, which turns a metal at the nanoscale to be an insulator [27]. The artihcial bandgaps for Au [28] and Pd [29] clusters increase when the number of Au and Pd atoms is reduced in the clusters. Figure 17.2 shows the evolution of the STS spectra for Pd and Si nanowires. 

There are two kinds of surface states entrapment and polarization. The dangling bonds or surface impurities are subject to polarization, which add impurity states within the Eq of semiconductors. Termination of the dangling bonds by H adsorption could minimize the impurity states. The other is the entrapment in the relaxed surface region, which offsets the entire band strucmre down associated with Eq enlargement and the presence of band tails. 

In terms of BOLS perturbation to the Hamiltonian of an extended solid, one is able to reconcile the change of Eq, pl, pa, bandwidth, core-level shift, and the charge entrapment and polarization induced by crystal size reduction. Introducing the effect of CN imperfection in the surface skin to the convention of an extended solid evolves the entire band stmcture of a nanometric semiconductor. This approach allows one to discriminates the contribution from crystal binding from the effect of e-p coupling in determining the Eq expansion and PL blueshift. 

For a ferromagnetic nanosolid, the magnetic moment at very low temperature increases with the inverse of size compared with the bulk value due to the deepening of the intra-atomic potential well that entraps and polarizes the surface spins contributing to the angular momentum of the under coordinated atoms of a nanosohd. 

The currently described knowledge about localized charge entrapment and polarization associated with the skin of both the liquid and the solid specimen provides an electronic mechanism for the 4S. According to the BOLS-NEP notation, the small fluidic drop can be viewed as a liquid core covered with a solid-like, densely charged, and elastic sheet with pinned dipoles. The energy density, charge density, polarizability, and the trap depth are bond order dependence. 

The coupling of energy densification (solid like and high elasticity), quantum entrapment, and polarization dictates the interface 4S. 

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