**7. Conclusion**

be realized in appropriate experimental conditions. Besides, the experimental angle (~30°) is close to the weighted average (~29°) of *α* = 51.5, 17.4, and 18.7° in **Table 2**, which have been

Any novel approach, including the CEE model, can be truly evaluated by a benefit from its practical application. By an example of the graphite based materials, the chapter has shown how a confluence of the XPS and DFT data can provide additional information on chemical behavior, local

treatment can be useful in the field of surface engineering as well, because just a deep knowledge on chemical behavior of a sample can disclose the mechanism and dynamics of its wear performance, thus facilitating the development of advanced materials. The valence band of chemically bound atoms is insensitive to a photoelectron, whose energy it uses for the CEE transition. Then, in the case of the multicomponent materials, agreement or disagreement between energy losses in the XPS spectra of some atoms can be a descriptor of the presence or absence of chemical bonding between these atoms in a sample [17, 19, 22]. Moreover, the state of any component can be traced through change or invariability of the satellites in its XPS spectra, obtained in the course of external influence, thus revealing a wear performance of the material. In case of a "simple" material, the reliable structural data can be used as starting conditions for the appropriate DFT run, which gives comprehensive information on a sample at the atomic level [16, 18]. Extensive

use and practice of the XPS and DFT techniques make the CEE analysis easily accessible.

CEE control in a coordinated XPS and DFT study is characterized by the following obvious,

• Comparison of fine XPS spectra with the calculated CEE transitions can provide the local geometry and bond types in a sample from conventional DFT facilities. The occurrence and consequence of bonding between atoms can be also determined, because the core-level excitation of an atom is accompanied by CEE satellites of the next one only within the

• The multiple CEE controls (around different XPS peaks) facilitate the data interpretation, while individual sets of the core-level energies improve studying of the multicomponent

• Hydrogen tracing by the XPS, as a specific CEE satellite above the core-level energy of the other sample component, is possible without a contradiction with XPS principles.

• The CEE control is available for samples of any conductivity, because the photoelectron energy losses are linked up to the XPS peak regardless its apparent core-level energy.

• The valence band structure in the XPS spectra differs from that obtained by the nondestructive and theoretical methods. The CEE event is nondestructive as well, because the valence band absorbs only a part of the photoelectron energy for a CEE transition, omitting

molecule and of the other atoms in a sample. A similar

found for the most probable unit cells #2, #6, and #9, respectively.

**6. Outlook**

160 Advanced Surface Engineering Research

geometry and state of the embedded Br<sup>2</sup>

verified, and hidden resources.

integrated valence band.

a destructive force of the incident X-ray impact.

materials.

Primary collecting of the extra data by a routine technique is always desirable. This chapter highlights a rational model that gives a chance to realize this desire using the conventional XPS and DFT outputs. The model is based on following statements.

