| 1. |
- Olovsson, Weine, et al.
(författare)
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Core-level shifts in complex metallic systems from first principle
- 2006
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 243:11, s. 2447-2464
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Tidskriftsartikel (refereegranskat)abstract
- We show that core-level binding energy shifts (CLS) can be reliably calculated within density functional theory. The scheme includes both the initial (electron energy eigenvalue) as well as final state (relaxation due to core-hole screening) effects in the same framework. The results include CLS as a function of composition in substitutional random bulk and surface alloys. Sensitivity of the CLS to the local chemical environment in the bulk and at the surface is demonstrated. A possibility to use the CLS for structural determination is discussed. Finally, an extension of the model is made for Auger kinetic energy shift calculations.
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| 2. |
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| 3. |
- Abrikosov, Igor, 1965-, et al.
(författare)
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Local environment effects in random metallic alloys
- 2005. - 1
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Ingår i: The Science of Complex Alloy Phases. - USA : TMS. - 087339593X - 9780873395939 ; , s. 87-108
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This book is published in honor of the 2005 Hume-Rothery Award Recipient, Uichiro Mizutani. It emphasizes both theoretical and experimental aspects of electronic, structural, and thermodynamic properties of complex alloy phases. Leading experts provide an assessment of our current understanding of the structural properties of complex materials, including quasicrystalline and amorphous alloys. Special emphasis is placed on our understanding of why nature is able to stabilize complex atomic arrangements and on recent results related to structurally complex alloy phases. These topics, in the spirit of the work carried out by U. Mizutani, constitute the main theme of the book
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| 4. |
- Alling, Björn, 1980-, et al.
(författare)
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Comparison of thermodynamic properties of cubic Cr 1-x Al x N and Ti 1-x Al x N from first-principles calculations
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 102:044314
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the stability of the cubic phase of Cr1−xAlxN at high AlN content, first principles calculations of magnetic properties, lattice parameters, electronic structure, and mixing enthalpies of the system were performed. The mixing enthalpy was calculated on a fine concentration mesh to make possible the accurate determination of its second concentration derivative. The results are compared to calculations performed for the related compound Ti1−xAlxN and with experiments. The mixing enthalpy is discussed in the context of isostructural spinodal decomposition. It is shown that the magnetism is the key to understand the difference between the Cr- and Ti-containing systems. Cr1−xAlxN turns out to be more stable against spinodal decomposition than Ti1−xAlxN, especially for AlN-rich samples which are of interest in cutting tools applications.
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| 5. |
- Marten, Tobias, 1979-, et al.
(författare)
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Ab initio study of disorder broadening of core photoemission spectra in random Cu-Pd and Ag-Pd alloys
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 72:5
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Tidskriftsartikel (refereegranskat)abstract
- A first-principles study of the effect of local environment on the electronic structure of random face-centered cubic Ag-Pd and Cu-Pd alloys is presented. The core-level shift for each atom in the equiatomic alloys is calculated and compared to experimental data. It is shown how the initial-state and final-state distributions contribute to the total broadening. We find that the initial-state and the final-state contributions together increase the broadening for the investigated core levels in Cu and Ag, whereas they cancel each other to a large degree for Pd. We also demonstrated how local lattice relaxations influence the binding energy shift. We find that relaxation does not influence the average shift, though it is able to affect the broadening of the simulated x-ray photoelectron spectroscopy spectra. © 2005 The American Physical Society.
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| 6. |
- Marten, Tobias, 1979-, et al.
(författare)
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Double-segregation effect in AgxPd1-x/Ru(0001) thin film nanostructures
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : APS. - 1098-0121 .- 1550-235X. ; 77:12
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Tidskriftsartikel (refereegranskat)abstract
- We study the structural properties of ultrathin AgxPd1-x films on top of a Ru(0001) substrate. Effective interatomic interactions, obtained from first-principles calculations, have been used in Monte Carlo simulations to derive the distribution of the alloy components in a four-monolayer (4-ML) Ag-Pd film. Though Ag-Pd alloys show complete solubility in the bulk, the thin film geometry leads to a pronounced segregation between Ag and Pd atoms with a strong preference of Ag atoms toward the surface and Pd atoms toward the interface. The theoretical prediction of this double-segregation effect is strongly supported by photoelectron spectroscopy experiments carried out for 4-ML thin films. We also show, in an additional experiment, that even in the case where initially 1 ML Ag is buried under 6 ML Pd, the whole Ag ML segregates to the surface.
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| 7. |
- Marten, Tobias, 1979-
(författare)
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Theoretical Considerations of Local Environment Effects in Alloys
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is devoted to a theoretical study of local environment effects in alloys. A fundamental property of a disordered system is that all chemically equivalent atoms are different due to their different chemical environments, in contrast to an ideal periodic solid where all the atoms that occupy equivalent positions in the crystal have exactly the same physical properties. The local environment effects have been largely ignored in earlier theories of disordered systems, that is the system has been treated as a whole and average properties have been derived. Moreover, inhomogeneous systems, such as surfaces and interfaces, induce local environment effects that are not necessarily present in the bulk.The importance and presence of local environment effects are illustrated by calculating observable physical properties in various systems. In particular, by employing the complete screening picture the effects of local environments on the core-level binding energy shifts as well as Auger shifts in random alloys are in- vestigated. This so-called disorder broadening effect has recently been observed experimentally. It is shown that there are different contributions to the disorder broadening that vary with the local chemical environment. Furthermore, the influ- ence of inhomogeneous lattice distortions on the disorder broadening of the core- level photoemission spectra are considered for systems with large size-mismatch between the alloy components.The effects of local chemical environments on physical properties in magnetic systems are illuminated. A noticeable variation in the electronic structure, local magnetic moments and exchange parameters at different sites is obtained. This reflects the sensitivity to different chemical environments and it is shown to be of qualitative importance in the vicinity of magnetic instability.The local environment effects due to the presence of surfaces and interfaces are also considered. The effect is explicitly studied by considering the concentration profile of a thin Ag-Pd film deposited on a Ru substrate. Two computational approaches are utilized to calculate the relative composition in each layer of the thin film as a function of temperature in a theoretically consistent way. It is shown that, opposed to the situation in the bulk, where a complete solubility between Ag and Pd takes place, a non-uniform distribution of the alloy components across the film is observed.In another study it is investigated whether the presence of TiN interfaces changes the dynamical and thermodynamic stability of B1 SiN. Phonon calcula- tions show that TiN interfaces have a stabilization effect on the lattice dynamics. On the other hand, calculations of the Si vacancy formation energy show that the structures are unstable with respect to composition variations.
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