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2 Theory: Bond-Electron-Energy Correlation
2.4 Valence Band and Nonbonding States
2.4.1 Complexity of the Valence DOS
Valence electrons perform quite differently from electrons in the core bands of a
specific constituent element. Valence electrons are mixture of all involved elements
in the solid, which respond to the chemical environment directly at functioning. The
behavior of valence electrons is much more complicated because of the delocalization, polarization, and charge redistribution among constituent elements in reaction.
Besides the undercoordination effect featured by BOLS-NEP notion, atomic heterocoordination due to formation of alloys, compounds, dopants, impurities, interfaces,
or glasses also results in the densification, localization, entrapment, and polarization of the valence electrons because of the bond nature alteration. Both under- and
hetero-coordination change the valence band substantially and irregularly.
In addition to polarization and localization of the conduction electrons by the
densely entrapped core electrons, such as the zigzag-edge of graphene [16] and the
Rh adatoms [35], presence of the nonbonding lone pairs and the lone pair-induced
dipoles upon reaction with F, O, and N play a role of significance [3, 4, 15].
2.4.2 Tetrahedral-Bonding Mediated Valence DOS
Figure 2.6 illustrates the residual DOS of metals and semiconductors resulting from
involvement of N, O, and F [4]. The sp
3 -orbit hybridization produces four directional
Fig. 2.6 Differential valence DOS of metals (upper) and semiconductors (lower) mediated by N,
O, and F addition with four excessive DOS features: bonding pairs (E F ), nonbonding lone pairs
(E F ). The DOS features in the vicinity of the
E F are crucial to the performance of a compound. Reprinted with permission from [4]. Copyright
2006 Elsevier
2 Theory: Bond-Electron-Energy Correlation
2.4 Valence Band and Nonbonding States
2.4.1 Complexity of the Valence DOS
Valence electrons perform quite differently from electrons in the core bands of a
specific constituent element. Valence electrons are mixture of all involved elements
in the solid, which respond to the chemical environment directly at functioning. The
behavior of valence electrons is much more complicated because of the delocalization, polarization, and charge redistribution among constituent elements in reaction.
Besides the undercoordination effect featured by BOLS-NEP notion, atomic heterocoordination due to formation of alloys, compounds, dopants, impurities, interfaces,
or glasses also results in the densification, localization, entrapment, and polarization of the valence electrons because of the bond nature alteration. Both under- and
hetero-coordination change the valence band substantially and irregularly.
In addition to polarization and localization of the conduction electrons by the
densely entrapped core electrons, such as the zigzag-edge of graphene [16] and the
Rh adatoms [35], presence of the nonbonding lone pairs and the lone pair-induced
dipoles upon reaction with F, O, and N play a role of significance [3, 4, 15].
2.4.2 Tetrahedral-Bonding Mediated Valence DOS
Figure 2.6 illustrates the residual DOS of metals and semiconductors resulting from
involvement of N, O, and F [4]. The sp
3 -orbit hybridization produces four directional
Fig. 2.6 Differential valence DOS of metals (upper) and semiconductors (lower) mediated by N,
O, and F addition with four excessive DOS features: bonding pairs (E F ), nonbonding lone pairs
(
E F are crucial to the performance of a compound. Reprinted with permission from [4]. Copyright
2006 Elsevier