2.3 BOLS-NEP-LBA Notion
33
0.0
0.5
1.0
1.5
2.0
ΔE ν (A 1 )
ΔE ν (P)
ΔE ν (i)/ΔE ν (B)
P B S 2 S 1 A 1
A 2
E ν (0)
(a)
(b)
Fig. 2.4 Atomic CN-resolved CLS. a Adatoms or defect vacancies, A i , surface layers S i on the
bulk B crystal, which create the corresponding component in the CLS spectrum b. In addition to the
main peaks of B, S 2 , S 1 , there are A i and P components being the entrapped (T) and the polarized (P)
states of the undercoordinated atoms. The energy shift of each component is proportional to the bond
energy, which follow the relationship: ν (z i )//E ν (12) = E zi /E zb = C −m
z (i = A, S 1 , S 2 ), if
the polarization effect is insignificant; otherwise, the pC −m
z
replaces the C −m
z
with p being the
polarization coefficient
Figure 2.4a Illustrates the layer-counting for a solid skin of three atomic layers
with addition of adatoms or vacancy defects. Panel (b) shows the respective CLS
component in the XPS spectrum. According to the BOLS-NEP notion, adatoms
(A i ), surface skins (S 1 , S 2 , …), bulk (B), and electron polarization (P) shift their
binding energies each by an amount in the order of: ν (A i ) > ν (S 1 ) > ν (S 2 )
> ν (B) > ν (P) with respect to the atomic E ν (0) reference. The component for
the least-coordinated adatom (z = 2) shifts most.
2.3.2.4 BOLS-LBA for Atomic Cluster and Nanocrystal
For crystals of different sizes, one has to consider the weighted sum over the outermost three atomic layers based on the LBA approach and the core-shell configuration
premise [14]. The Fourier transformation principle inspires the LBA, which indicates
that, for a given specimen, no matter whether it is a crystal, non-crystal, with or without defects, the nature and the total number of bonds remain unchanged unless phase
transition occurs. However, the length and strength of all the involved bonds will
respond to the applied stimulus in the same manner simultaneously. Therefore, one
can focus on the length and energy response of the representative bond to the external
stimulus and its effect on the CLS for the entire solid.
However, the hydrogen bond (O:H–O) in water and ice is an exception [5]. Because
of the asymmetrical, short-range interactions and the O–O Coulomb repulsion coupling, the O:H nonbond and the H–O covalent bond segment relax oppositely in
length and energy. The stronger H–O bond (4.0 eV level) dictates the CL as the
weaker O:H nonbond (0.1 eV level) contributes only 3% or less to the crystal binding
energy [23].
33
0.0
0.5
1.0
1.5
2.0
ΔE ν (A 1 )
ΔE ν (P)
ΔE ν (i)/ΔE ν (B)
P B S 2 S 1 A 1
A 2
E ν (0)
(a)
(b)
Fig. 2.4 Atomic CN-resolved CLS. a Adatoms or defect vacancies, A i , surface layers S i on the
bulk B crystal, which create the corresponding component in the CLS spectrum b. In addition to the
main peaks of B, S 2 , S 1 , there are A i and P components being the entrapped (T) and the polarized (P)
states of the undercoordinated atoms. The energy shift of each component is proportional to the bond
energy, which follow the relationship: ν (z i )//E ν (12) = E zi /E zb = C −m
z (i = A, S 1 , S 2 ), if
the polarization effect is insignificant; otherwise, the pC −m
z
replaces the C −m
z
with p being the
polarization coefficient
Figure 2.4a Illustrates the layer-counting for a solid skin of three atomic layers
with addition of adatoms or vacancy defects. Panel (b) shows the respective CLS
component in the XPS spectrum. According to the BOLS-NEP notion, adatoms
(A i ), surface skins (S 1 , S 2 , …), bulk (B), and electron polarization (P) shift their
binding energies each by an amount in the order of: ν (A i ) > ν (S 1 ) > ν (S 2 )
> ν (B) > ν (P) with respect to the atomic E ν (0) reference. The component for
the least-coordinated adatom (z = 2) shifts most.
2.3.2.4 BOLS-LBA for Atomic Cluster and Nanocrystal
For crystals of different sizes, one has to consider the weighted sum over the outermost three atomic layers based on the LBA approach and the core-shell configuration
premise [14]. The Fourier transformation principle inspires the LBA, which indicates
that, for a given specimen, no matter whether it is a crystal, non-crystal, with or without defects, the nature and the total number of bonds remain unchanged unless phase
transition occurs. However, the length and strength of all the involved bonds will
respond to the applied stimulus in the same manner simultaneously. Therefore, one
can focus on the length and energy response of the representative bond to the external
stimulus and its effect on the CLS for the entire solid.
However, the hydrogen bond (O:H–O) in water and ice is an exception [5]. Because
of the asymmetrical, short-range interactions and the O–O Coulomb repulsion coupling, the O:H nonbond and the H–O covalent bond segment relax oppositely in
length and energy. The stronger H–O bond (4.0 eV level) dictates the CL as the
weaker O:H nonbond (0.1 eV level) contributes only 3% or less to the crystal binding
energy [23].