Extra electronic outer-shell peculiarities accessible under a joint XPS and DFT study

Abstract

Electronic configuration of chemically bound atoms at the surface, including adsorbed species, or in the bulk of a solid contains a set of natural traps for energy absorption provided by valence band transitions or plasmon oscillations. The core level excitation of any origin is generally coupled with those traps, forming a multichannel route for nonradiative energy dissipation. Using an example of Pt and graphitebased materials, the study shows experimental tracing over these channels by means of elastic electron scattering and X-ray photoelectron spectroscopy. As a complement to the experimental data, calculations of the density of states provide information on chemical behavior and local geometry of the atoms in a sample.

Hidden Resources of Coordinated XPS and DFT Studies

“…(1). The calculated Pt shake-up and shake-off spectra in Figure 2 are close to each other due to strongly localized vacant states at E F and the 1D DOS at the vacuum level, respectively, and because of domination of the equal d zx , d zy , and d xy states in total DOS [30]. An agreement between experimental and simulated spectral fragments in Figure 2 implies regular involvement of the Pt DOS into CEE events, as well as similar matrix elements f(E, σ) for different partial densities of states (pDOS) in Eq.…”

“…DFT calculations have revealed that the Br 2 embedding enlarges the interlayer distance, but insignificantly affects the pDOS of the C, (F) C and F [30]. The latter conforms to chemical inertness of the pristine C 2 F cell and to low Br content in the product C 2 FBr 0.15 [62].…”

“…The difference F1s spectrum in Figure 5 exhibits a distinct structure, which conforms to shakeup transitions of the pDOS responsible for C-F bonding and which is interpreted as the C-F bond strengthening [30]. It can be the case since the Br 2 embedding weakens the interactions between carbon layers, which should be accompanied with the enrichment of the occupied DOS of C and F. Arrangement of the F atoms in a cell makes no matter for the conclusion.…”

“…The formation energy of the Bernal unit cell C 24 F 12 is by 0.008 eV higher than that of the hex C 24 F 12 cell, while pDOSs of both structures are very similar. A sizable DOS at E F accepts plasmon oscillations that can give the energy loss at 9.1 or 12.9 eV for 1 or 2 free electrons per a C 2 F fragment, respectively [30].…”

“…Fluorinated graphite serves as an intermediate of the graphene synthesis, while embedded with the alkali or halogen, exhibits high chemical stability, improves the anode activity in a fuel cell, becomes the nano-reactor or the storage nano-container of volatile compounds, and so on [27][28][29]. We have considered highly orientated pyrolytic graphite (HOPG), half-fluorinated HOPG (C 2 F), and that with the embedded Br 2 (C 2 F *0.15Br) as touchstones of the following concept [30,31]. First, inelastic electron scattering, in near-surface layer and in the bulk of a solid, follows the same regularities.…”