15.1 Decoding Methodology
303
15.1.4 Criteria for Model Justification
Criteria for the optimal z 0 (E) profiles, and correspondingly, the optimal bond geometry are essential. In convention, it is expected that the z 0 (E) approaches a constant.
This is acceptable for pure metal surfaces with homogeneous energy states and small
ion core corrugations but it is no longer true for a system with chemisorbed oxygen.
The z 0 (E) profile should be in any form showing joint features of topography and
valence DOS other than traditional constant or monotonically energy dependence.
With respect to both the conventional wisdom and the features of the new SPB showing humps due to electron excitation, the criteria for selecting the z 0 (E) curves were
set as follows:
• The number of solutions of z 0 (E) is finite;
• z 0 is as small as possible; and
• The fewest extra features appear on the z 0 (E) curve.
The z 0 -scanning and z 0 -optimizing methods are much more revealing than calculations by adjusting independently all parameters. These methods have enabled
the best models and the match between the STM/S images and the VLEED refined
contour plots, which reveals information on the electronic spatial distribution and
variation of the valence DOS in the VLEED energy window.
15.2 Code Validation
15.2.1 Clean Cu(001)
Two identifies determine the VLEED fine-structure features. One is the surface lattice
geometry subjecting to reconstruction and relaxation; the other is the SPB describing the behavior of surface electrons in both real and energy domains. Usually,
presumption is made that the lattice geometry is already known and then one can
explore the SPB parameters. In order to verify the validity of the multiple diffraction code, scattering from a Cu(001) clean surface was first calculated by using the
one-dimensional SPB approximation and the monotonic damping functions with the
known lattice structure. The conventional wisdom for clean metal surface is adequate
to obtain qualitative agreement between theory and measurement [5].
VLEED fine-structure features are very sensitive to the elastic ReV(z, z 0 , λ)
potential. A minimal difference of the parameters from earlier work is due to the
multiple diffraction effects that are fully included in the multi-atom and multiple
diffraction code [6].
A total of nine SPB parameters were divided into two groups. The orthogonaloptimization of the L 25 (5
6 )-(γ, δ, η, β, z 1 , V 0 ) group and the L 9 (3
4 )-(z 0 , λ, α) group
were conducted to gain the best fit. The following describes the calculation procedures
[10]:
303
15.1.4 Criteria for Model Justification
Criteria for the optimal z 0 (E) profiles, and correspondingly, the optimal bond geometry are essential. In convention, it is expected that the z 0 (E) approaches a constant.
This is acceptable for pure metal surfaces with homogeneous energy states and small
ion core corrugations but it is no longer true for a system with chemisorbed oxygen.
The z 0 (E) profile should be in any form showing joint features of topography and
valence DOS other than traditional constant or monotonically energy dependence.
With respect to both the conventional wisdom and the features of the new SPB showing humps due to electron excitation, the criteria for selecting the z 0 (E) curves were
set as follows:
• The number of solutions of z 0 (E) is finite;
• z 0 is as small as possible; and
• The fewest extra features appear on the z 0 (E) curve.
The z 0 -scanning and z 0 -optimizing methods are much more revealing than calculations by adjusting independently all parameters. These methods have enabled
the best models and the match between the STM/S images and the VLEED refined
contour plots, which reveals information on the electronic spatial distribution and
variation of the valence DOS in the VLEED energy window.
15.2 Code Validation
15.2.1 Clean Cu(001)
Two identifies determine the VLEED fine-structure features. One is the surface lattice
geometry subjecting to reconstruction and relaxation; the other is the SPB describing the behavior of surface electrons in both real and energy domains. Usually,
presumption is made that the lattice geometry is already known and then one can
explore the SPB parameters. In order to verify the validity of the multiple diffraction code, scattering from a Cu(001) clean surface was first calculated by using the
one-dimensional SPB approximation and the monotonic damping functions with the
known lattice structure. The conventional wisdom for clean metal surface is adequate
to obtain qualitative agreement between theory and measurement [5].
VLEED fine-structure features are very sensitive to the elastic ReV(z, z 0 , λ)
potential. A minimal difference of the parameters from earlier work is due to the
multiple diffraction effects that are fully included in the multi-atom and multiple
diffraction code [6].
A total of nine SPB parameters were divided into two groups. The orthogonaloptimization of the L 25 (5
6 )-(γ, δ, η, β, z 1 , V 0 ) group and the L 9 (3
4 )-(z 0 , λ, α) group
were conducted to gain the best fit. The following describes the calculation procedures
[10]: