Introduction to Ligand Field Theory

Ballhausen, C. J.; Weiner, Michael A.

doi:10.1149/1.2425758

Cited by 677 publications

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“…It was later explained that this is the outcome of the interplay of xy and x 2 − y 2 band mixing due to rotations of the RhO 6 octahedra, SOC, and sizable Coulomb interactions. 41,42 We study in more detail the d-level electronic structure and find that even the on-site energy of the Rh xy orbital is lower than the energies of the xz and yz orbitals, despite the apical elongation of the RhO 6 octahedra, which according to basic ligand-field theory should push the xy level higher in energy; 43 see Figure 2. This unexpected order of the Rh t 2g levels is the outcome of low-symmetry potentials related to the anisotropic layered structure of the extended surroundings and represents one ingredient that, in addition to the band effects discussed in refs 40−42 There are 10 alkaline-earth neighboring ions in the twodimensional square-lattice system compounds Sr 2 RhO 4 , Sr 2 IrO 4 , and Ba 2 IrO 4 (see Figure 1) and 12 in the quasi-onedimensional, chainlike compound Ca 3 CoRhO 6 (see Figure 3).…”

Section: ■ Introductionmentioning

confidence: 88%

Electronic Structure of Low-Dimensional 4d⁵ Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

et al. 2014

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The electronic structure of the low-dimensional 4d 5 oxides Sr 2 RhO 4 and Ca 3 CoRhO 6 is herein investigated by embedded-cluster quantum chemistry calculations. A negative tetragonal-like t 2g splitting is computed in Sr 2 RhO 4 and a negative trigonal-like splitting is predicted for Ca 3 CoRhO 6 , in spite of having positive tetragonal distortions in the former material and cubic oxygen octahedra in the latter. Our findings bring to the foreground the role of longerrange crystalline anisotropy in generating noncubic potentials that compete with local distortions of the ligand cage, an issue not addressed in standard textbooks on crystal-field theory. We also show that sizable t 2g 5 −t 2g 4 e g 1 couplings via spin− orbit interactions produce in Sr 2 RhO 4 ⟨ ⟩ = ⟨∑ · ⟩ l s i i i ground-state expectation values significantly larger than 1, quite similar to theoretical and experimental data for 5d 5 spin−orbit-driven oxides such as Sr 2 IrO 4 . On the other hand, in Ca 3 CoRhO 6 , the ⟨ ⟩ values are lower because of larger t 2g −e g splittings. Future X-ray magnetic circular dichroism experiments on these 4d oxides will constitute a direct test for the ⟨ ⟩ values that we predict here, the importance of many-body t 2g −e g couplings mediated by spin−orbit interactions, and the role of low-symmetry fields associated with the extended surroundings. ■ INTRODUCTIONOne of the most difficult problems in electronic structure theory is the correct description of correlated d and f electrons in solid-state compounds. Although density functional theory (DFT) provides results in reasonably good agreement with the experiment for weakly and moderately correlated electron systems, there are many materials, in particular, d-and felectron oxides, whose electronic structures cannot be properly treated within the canonical DFT framework. Extensions of DFT by dynamical mean-field theory (DMFT) led to DFT +DMFT schemes and allowed one to overcome some of the intrinsic limitations of DFT.1,2 Yet the accuracy and predictive power of the DFT+DMFT calculations is to some extent restricted by the use of parametrizations such as the on-site Coulomb repulsion U. It is therefore desirable to explore complementary techniques, e.g., wave-function-based quantum chemistry methods. While early attempts and the first encouraging results go back as early as the 1970s, with the work of Wachters, Bagus, and others, 3,4 the tremendous progress in computer technology nowadays makes possible many-body quantum chemistry calculations on larger and larger embedded clusters with remarkably good results for quantities such as the d-level splittings and intersite spin interactions; see, e.g., refs 5−34.Most of the investigations have been focused on 3d transition-metal compounds 3−24 and very recently, because of novel physics arising from strong spin−orbit coupling (SOC), on 5d oxides. 25−29 The 4d materials, on the other hand, received little attention in this context. Here we investigate with the help of ab initio quantum chemistry methods the...

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Section: ■ Introductionmentioning

confidence: 88%

Electronic Structure of Low-Dimensional 4d⁵ Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

et al. 2014

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“…3(a). These absorption bands correspond to 2 B 2g → 2 B 1g , 2 B 2g → 2 E g transitions, a characteristic of VO 2+ ions [11]. The assignment of these bands has been made on the basis of an energy level scheme for molecular orbitals of VO 2+ ion in a ligand field of C 4v symmetry [12].…”

Section: Resultsmentioning

confidence: 99%

Influence of Various Glass Compositions on Physical and Spectroscopic Properties of Cao-Pb3O4-Zno-P2O5 Glass System

Sastry¹,

Rao²

2015

IJIRSET

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ABSTRACT:A series of 20CaO-10ZnO-59.9P 2 O 5 -10Pb 3 O 4 -0.1x, (x= V 2 O 5 , Cr 2 O 3 , MnO and CuO) glasses was prepared by melt quench technique. Spectroscopic properties of the prepared glass systems were investigated using XRay diffraction, Ultra-Violet (UV) spectroscopy, Differential Scanning Calorimetry (DSC), Electron Paramagnetic Resonance (EPR -X band), Fourier Transform Infra Red (FTIR) spectroscopy and Raman spectroscopy. Present investigation is useful to study the effect of glass composition on the optical, thermal, physical properties and symmetry of the prepared glasses. Various physical properties for all the glasses were measured. X-ray diffraction of glass samples was carried to check its amorphous nature. From EPR spectra, the spin-Hamiltonian parameters were calculated and these parameters were influenced by the change in glass composition for different transition metal ions. The FTIR spectral investigations of glasses revealed characteristic vibrations of PO 4 3-units. The Raman spectra of all glass samples have displayed different spectral bands, and intensity of these bands. The results showed that the network structure of these glass samples is found to be change from glass to glass.

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“…Racha's parameter B and nephelauxetic relation (B/B free ) is a measure of bond covalency of ligand-dopant. The covalency increases when the values of B and (B/B free ) are reduced [29,[39][40][41]. For Cr 3+ ion, the value of k is 0.21 [42].…”

Section: Resultsmentioning

confidence: 99%

Structural Investigations of Cr3+ Ions Doped Alkali Lead Zinc Phosphate Glasses

Sastry¹

2015

IJIRSET

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Lead zinc phosphate glasses containing 0.1% transition metal ion Cr 3+ were prepared by melt quenching technique and their amorphous nature confirmed by X-Ray diffraction. The covalent bond nature of Cr 3+ ions with octahedral symmetry in glass network was established through Electron Paramagnetic Resonance and optical absorption spectroscopic studies. Endothermic dip for glass transition temperature (T g ) at about 410 0 C and an exothermic peak subsisted from thermal studies were obtained. De-polymerization of host glass network due to addition of alkali content to the glass matrix, has turned as a strong candidate for nonlinear optical laser applications.

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Introduction to Ligand Field Theory

Abstract: not Available.

Cited by 677 publications

References 0 publications

Electronic Structure of Low-Dimensional 4d⁵ Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

Electronic Structure of Low-Dimensional 4d⁵ Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

Influence of Various Glass Compositions on Physical and Spectroscopic Properties of Cao-Pb3O4-Zno-P2O5 Glass System

Structural Investigations of Cr3+ Ions Doped Alkali Lead Zinc Phosphate Glasses

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Introduction to Ligand Field Theory

Abstract: not Available.

Cited by 677 publications

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Electronic Structure of Low-Dimensional 4d5 Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

Electronic Structure of Low-Dimensional 4d5 Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

Influence of Various Glass Compositions on Physical and Spectroscopic Properties of Cao-Pb3O4-Zno-P2O5 Glass System

Structural Investigations of Cr3+ Ions Doped Alkali Lead Zinc Phosphate Glasses

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Electronic Structure of Low-Dimensional 4d⁵ Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

Electronic Structure of Low-Dimensional 4d⁵ Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions