Diploma - Max Planck Institute for Solid State Research

More documents

Recommendations

Info

$diffraction from single powder grains - Max Planck Institute for Solid ...$

30 4 EuRh 2 Si 2 – semi-localized electrons Figure 4.5: (a) charge isosurface and extended lattice configuration of EuRh 2 Si 2 : an (arbitrarily-selected) isosurface of the converged charge density is plotted with respect to the lattice denoting the bonding between the Rh and Si layers; (b) + (c): difference between the converged total charge density and the “atomic” charge densities to estimate the charge transfer inside the unit cell, positive (negative) isocharge depicts inflow (outflow) of electrons with respect to the start configuration
4.1 Overview – properties and classification 31 Figure 4.6: cleavage behaviour: (a) interlayer distances as a function of doubled c-lattice constant; increasing strain pulls apart mainly Eu and Si-Rh-Si structures, whereas the distances inside the Si-Rh-Si compound remain approximately constant; if the strain is too strong (a c ≈ 28 Å), the crystal breaks into two parts revealing one Eu and one Si terminated surface (the maroon marked graph depicts the maximum distance of next-neighbour Eu-Si layers); the inset magnifies the small region of elastic deformation; (fplo 9.07.41, LDA, 4f 7 unpolarized open core | force minimization) (b) a slab geometry for a z < 28 Å; (c) a slab for a z > 28 Å, the calculations shown are marked in (a) several isocharge surfaces. Recognizing that the charge density between the Eu layer and the Si-Rh-Si part is localized around the compounds, not in between, points to ionic character. Contrariwise, the localization of charge between two neighbouring atoms for Si-Rh / Si-Rh is an aspect for rather covalent bonds. Both aspects are supported by the total charge density distribution in fig. 4.5a, because the iso-charge level shown reveals no connection between the Eu layer and the Si- Rh-Si part. Whether the covalent or the ionic bond is stronger, cannot be answered generally, but since the covalent one is directional in contrast to the undirectional ionic bond, we can expect that shear strain will force to break up the ionic bonds first and hence the cleave will reveal Si and Eu termination. However, one should be careful, because this is a suggestive interpretation of (differences in) charge density. In addition, using only the corresponding Wyckoff positions (e.g. only Eu, leaving all other positions empty) for the atomic charge densities neglects the possible formation of bonds during the convergence (e.g. metallic bonding for Eu, since the distance between two atoms is not small enough). In principle, one could use the start density before the iteration process, but due to the special compressed orbital basis set, the configuration is as well not equal to the atomic configuration. Further investigations should be undertaken to clarify this issue. All in all, this method is computationally inexpensive since only the converged charge density has to be extracted in real space.
Page 1 and 2: - Photoemission on EuRh 2 Si 2 - di
Page 3: Abstract A thorough knowledge of co
Page 7: vii Nomenclature AF APW ARPES BO BZ
Page 10 and 11: 2 1 Introduction conflicting limits
Page 12 and 13: 4 2 Theoretical foundation fore the
Page 14 and 15: 6 2 Theoretical foundation system a
Page 16 and 17: 8 2 Theoretical foundation such a s
Page 18 and 19: 10 2 Theoretical foundation Figure
Page 20 and 21: 12 2 Theoretical foundation Figure
Page 22 and 23: 14 2 Theoretical foundation Fi
Page 25 and 26: 17 3 Experimental foundations 3.1 P
Page 27 and 28: 3.2 General setup 19 Figure 3.2: ch
Page 29 and 30: 3.4 SLS: SIS-HRPES 21 1 3 ARPES the
Page 31 and 32: 23 4 EuRh 2 Si 2 - semi-localized e
Page 33 and 34: 4.1 Overview - properties and class
Page 37: 4.1 Overview - properties and class
Page 49 and 50: 4.2 Hybridization: localized versus
Page 61 and 62: 4.3 Perspective: quasi-linear dispe
Page 63: 4.3 Perspective: quasi-linear dispe
Page 66 and 67: 58 5 Summary to the f-d interaction
Page 68 and 69: 60 Bibliography [13] B. Kramer. A P
Page 70 and 71: 62 Bibliography [44] T. M. Rice and
Page 72 and 73: 64 Bibliography [75] Hari C. Manoha
Page 75: List of Tables 67 List of Tables 2.
Page 79: Erklärung Hiermit versichere ich,

Diploma - Max Planck Institute for Solid State Research

Create successful ePaper yourself

Delete template?

Save as template?