AB-INITIO CALCULATION OF THE INITIAL- AND FINAL-STATE EFFECTS ON CORE LEVEL SHIFTS AT TRANSITION METAL SURFACES

1993 ◽  
Vol 07 (01n03) ◽  
pp. 542-545
Author(s):  
D. HENNIG ◽  
M. METHFESSEL ◽  
M. SCHEFFLER
Keyword(s):  
Transition Metal ◽  
Core Level ◽  
Level Shift ◽  
Full Potential ◽  
Initial State ◽  
Final State ◽  
State Approximation ◽  
Transition Metal Surface ◽  
Lmto Method ◽  
Level Shifts

The surface core-level shift at a transition metal surface can be calculated in two different ways using the initial-state approximation or using a more involved approach which includes screening of the photo-created core hole. Our calculated results obtained using the full-potential LMTO method for the close packed surfaces of all 4d transition metals within the initial state picture can be well explained by standard arguments.

ENHANCED SCREENING OF CORE HOLES AT TRANSITION-METAL SURFACES

1995 ◽  
Vol 02 (02) ◽  
pp. 197-201 ◽  
Author(s):  
M. METHFESSEL ◽  
D. HENNIG ◽  
M. SCHEFFLER
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Density Functional ◽  
Core Level ◽  
Level Shift ◽  
Core Hole ◽  
Initial State ◽  
Functional Theory ◽  
Level Shifts

Ab initio calculations based on density-functional theory were used to obtain surface core-level shifts for the 4d transition metals and silver in the initial-state model and in the full-impurity formulation, giving an unambiguous separation into initial state and screening terms. This shows that the screening of the core hole is substantially better at the surface than in the bulk for a transition metal. For Ag, an opposite and even larger effect is found, showing the central role of d-electron screening in the surface core-level shift of the transition metals.

Core Level Shifts and Grain Boundary Cohesion

1998 ◽  
Vol 4 (S2) ◽  
pp. 766-767
Author(s):  
D. A. Muller
Keyword(s):  
Charge Transfer ◽  
Valence Band ◽  
Core Level ◽  
Level Shift ◽  
The Core ◽  
Metallic Interfaces ◽  
Level Shifts ◽  
Electron Energy Loss ◽  
Valence Band Width

The role of core level shifts at metallic interfaces has often been ignored in electron energy loss spectroscopy (EELS) even though very small changes in bond length can lead to large core level shifts. However, the popular interpretation of core level shifts as measures of charge transfer is highly problematic. For instance, in binary alloys systems, the core level shifts can be the same sign for both atomic constituents[l]. The simple interpretation would require that both atomic species had lost or gained charge. Further, the signs of the core level shifts can be opposite to those expected from electronegativity arguments[2]. A core level shift (CLS) is still possible, even when no charge transfer occurs. As illustrated in Fig. 1, if the valence band width is increased, the position of the center of the valence band with respect to the Fermi energy will change (as the number of electrons remains unchanged).

Core Level Shifts in Transition Metal Compounds

1980 ◽  
Vol 21 (3-4) ◽  
pp. 549-552 ◽  
Author(s):  
Rolf Manne ◽  
Tor Jan Aarstad ◽  
Jiri Müller
Keyword(s):  
Transition Metal ◽  
Core Level ◽  
Transition Metal Compounds ◽  
Metal Compounds ◽  
Level Shifts

The final state shape resonance of CO on an alkali modified transition metal surface

1986 ◽  
Vol 124 (3) ◽  
pp. 237-240 ◽  
Author(s):  
W. Eberhardt ◽  
F.M. Hoffmann ◽  
R. Depaola ◽  
D. Heskett ◽  
E.W. Plummer ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Surface ◽  
Shape Resonance ◽  
Final State ◽  
Transition Metal Surface

Final State Core Level Shifts in Supported and Free Metal Particles

1988 ◽  
Vol 148 (1) ◽  
pp. 121-128 ◽  
Author(s):  
N. J. Castellani ◽  
D. B. Leroy
Keyword(s):  
Core Level ◽  
Metal Particles ◽  
Final State ◽  
Level Shifts ◽  
Free Metal

X-Ray Photoelectron Spectroscopic (XPS) Studies of Clean and Ion Beam Bombarded Sb2Te2Se and (Bi0.7Sb0.3)2Se3.0(111) Surfaces

1997 ◽  
Vol 62 (2) ◽  
pp. 199-212 ◽  
Author(s):  
Zdeněk Bastl ◽  
Ilona Spirovová ◽  
Michaela Janovská
Keyword(s):  
Surface Composition ◽  
Ion Beam ◽  
Bulk Composition ◽  
Binding Energies ◽  
Core Level ◽  
Photoelectron Spectra ◽  
Initial State ◽  
The Core ◽  
Level Shifts ◽  
Sputtering Yields

The first detailed study of photoelectron spectra of Sb2Te2Se and (Bi0.7Sb0.3)2Se3 (111) clean and sputtered surfaces is presented as part of an XPS examination of the surface chemistry of these and related materials. The core level binding energies and surface chemical composition have been determined from the XPS data. On substitution of Te by Se in Sb2Te3 leading to Sb2Te2Se the core level binding energies in Sb and Te increase by 0.3 eV while in Bi2Se3 the binding energy of core electrons does not change on replacement of Bi by Sb. The measured core level shifts are caused by changes of the initial state charge distribution and result in increase of average ionicity of bonding in the Sb2Te2Se crystal. The surface composition of Sb2Te2Se sample calculated from intensities of photoelectron spectra agrees well with the bulk composition of the crystal while (Bi0.7Sb0.3)2Se3 sample shows enrichment in Bi. The effect of argon ion bombardment on surface composition for various impact conditions has been investigated. The surface enrichment in Sb and Bi for Sb2Te2Se and (Bi0.7Sb0.3)2Se3 sample due to different atomic sputtering yields is observed. It follows from the relative intensities of photoelectron spectra measured at different detection angles that the ordered arrangement of the superficial layers sampled by the XPS method is damaged by sputtering at ion energies as low as 200 eV and doses I > 2 . 1015 ion/cm2.

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