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| 2. |
- Gunnarsson, O., et al.
(författare)
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Information from photoemission spectral weights and shapes
- 2001
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier. - 0368-2048 .- 1873-2526. ; 117-118, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Photoemission line shapes can be used to extract important information about ground-state and low-energy properties. This is illustrated for the electron–phonon interaction in C60 molecules, the occupancy and hybridization of the 4f-level in Ce compounds, the effect of the Cu–O network on core-level photoemission in cuprates and the properties of one-dimensional conductors.
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| 3. |
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| 4. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Chemical shifts for monovalent, divalent and trivalent Cu compounds
- 1992
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 4:3, s. 895-909
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Tidskriftsartikel (refereegranskat)abstract
- The authors study the chemical shift of the Cu 2p core level for Cu 2O, CuO and NaCuO2, where Cu is formally monovalent, divalent and trivalent, respectively. They find that the binding energy increases with the valence, as expected, although the variation in the number of 3d electrons is small and the trivalent Cu atom is found to have a smaller net positive charge than the monovalent or divalent Cu. The origin of the calculated chemical shifts is analysed and the relation with the chemical valence is discussed.
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| 5. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Core level chemical shifts and line shapes for systems with different valencies and Cu-O networks
- 2000
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Ingår i: International Journal of Modern Physics B. - : World Scientific. - 0217-9792 .- 1793-6578. ; 14:32, s. 3791-3830
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the Cu-2p core level photoemission spectrum of a variety of cuprates, mainly focusing on the chemical shift and the shape of the leading peak. The spectra are calculated using the Anderson impurity model and we obtain a very good agreement with the experimental data. We find that the shape of the leading peak depends crucially on the structure of the Cu-O network. The main peak turns out to be quite narrow if the network consists of Cu-O-Cu bond angels of the order of 90°. On the other hand, if the Cu-O atoms are arranged with bond angles of approximately 180°, the main peak becomes substantially broader and contains a rather complicated structure. However, in some cases it is not sufficient only to consider the Cu-O network because interactions with other atoms are also important. In the model compounds Cu2O, CuO and NaCuO2, where Cu is formally monovalent, divalent and trivalent, respectively, we find that the number of 3d electrons is rather similar. Nevertheless, the binding energy increases with the valence as expected from chemical intuition. The spectra exhibit a large variation in the strength of the d9-like satellite and in the width of the main line. We, furthermore, study the chemical shift of three inequivalent Cu atoms in YBa2Cu3O6.5, and compare the results with the model compounds, which suggests that the different Cu atoms in YBa2Cu3O6.5 have formal valences of approximately one, two and three. These findings are analyzed and related to the formal valence.
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| 6. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Cu 2p chemical shifts for YBa2Cu3O6.5 : Valence of the Cu atoms
- 1992
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 45:13, s. 7559-7562
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Tidskriftsartikel (refereegranskat)abstract
- We study the chemical shift of three different Cu atoms in YBa2Cu3O6.5, and compare the results with the formally mono-, di-, and trivalent model compounds Cu2O, CuO, and NaCuO2. We find similar chemical shifts between Cu in the empty chains, Cu in the planes, and Cu in the intact chains as between the Cu atoms in the model compounds. This suggests that the different Cu atoms in YBa2Cu3O6.5 have formal valences of approximately 1,2, and 3. © 1992 The American Physical Society.
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| 7. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Cuprate Core-Level Line Shapes for Different Cu-O Networks
- 1999
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 82:17, s. 3528-3531
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the Cu core-level photoemission spectra in the Anderson impurity model for cuprates with different Cu-O networks, dimensionalities (zero, one, two, and three) and Cu valencies (two and three). We focus on the shape of the leading peak and obtain very good agreement with the experimental data. We show how the shape of the spectrum is related to the valence electronic structure and the Cu-O network but also that other atoms can play a role.
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| 8. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Shape of the Cu 2p core level photoemission spectrum for monovalent, divalent and trivalent Cu compounds
- 1992
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 4:11, s. 2801-2816
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Tidskriftsartikel (refereegranskat)abstract
- We calculate the shape of the 2p core level photoemission spectrum for Cu2O, CuO and NaCuO2, where Cu is formally mono-, di- and trivalent, respectively. Although the number of 3d electrons is similar in the three compounds, there is a large variation in the strength of the d9-like satellite and in the width of the main line. We relate the differences between Cu2O and CuO to the difference in the valence, while for NaCuO2 the detailed form of the hopping matrix elements is also found to be important. © 1992 IOP Publishing Ltd.
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| 9. |
- Koitzsch, A., et al.
(författare)
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Core-hole screening response in two-dimensional cuprates : A high-resolution x-ray photoemission study
- 2002
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 66:2
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the core level photoemission spectra of the two-dimensional cuprates Sr2CuO2Cl2, Sr2CuO2Br2, Ca2CuO2Cl2, Bi2Sr2CaCu2O8+δ, and Nd2CuO4, with particular focus on the screening response to core-hole creation in the Cu−2p3/2 level. The influence of the apex positions on the shape of the so-called main line is investigated, and found to be weak. Additionally, an Anderson impurity model was used to fit the shape of the main lines, obtaining good agreement with the data from Nd2CuO4. For the other compounds, while the energy spread of the two screening channels (local and nonlocal) is well reproduced, the theory underestimates the width of the nonlocally screened feature. The shapes of the main lines are discussed in detail.
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| 10. |
- Aryasetiawan, F., et al.
(författare)
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Calculations of Hubbard U from first-principles
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : The American Physical Society. - 1098-0121 .- 1550-235X. ; 74:12, s. Article number 125106-
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Tidskriftsartikel (refereegranskat)abstract
- The Hubbard U of the 3d transition metal series as well as SrVO3, YTiO3, Ce, and Gd has been estimated using a recently proposed scheme based on the random-phase approximation. The values obtained are generally in good accord with the values often used in model calculations but for some cases the estimated values are somewhat smaller than those used in the literature. We have also calculated the frequency-dependent U for some of the materials. The strong frequency dependence of U in some of the cases considered in this paper suggests that the static value of U may not be the most appropriate one to use in model calculations. We have also made comparison with the constrained local density approximation (LDA) method and found some discrepancies in a number of cases. We emphasize that our scheme and the constrained local density approximation LDA method theoretically ought to give similar results and the discrepancies may be attributed to technical difficulties in performing calculations based on currently implemented constrained LDA schemes.
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