Studies on the Local Structure and the Spin Hamiltonian Parameters for Co2+ in CaTiO3

2008 ◽  
Vol 278 ◽  
pp. 55-62 ◽  
Author(s):  
Guang Duo Lu ◽  
Shao Yi Wu ◽  
Hua Ming Zhang ◽  
Li Hua Wei
Keyword(s):  
Local Structure ◽  
Lattice Distortion ◽  
Impurity Center ◽  
Orthorhombic Symmetry ◽  
Spin Hamiltonian ◽  
Orthorhombic Distortion ◽  
Local Lattice Distortion ◽  
Local Lattice ◽  
Crystal Field Parameters ◽  
Hamiltonian Parameters

The local structure and the spin Hamiltonian parameters g factors gi (i =x, y and z) and the hyperfine structure constants Ai for Co2+ in orthorhombic CaTiO3 are theoretically investigated from diagonalization of 6 × 6 energy matrix within the 4T1 ground state for a 3d7 ion in orthorhombic symmetry. In the calculations, the contributions from the admixtures of various J states (J=1/2, 3/2, 5/2), the ligand orbitals and spin-orbit coupling and the fourth-order orthorhombic field parameter, which were usually neglected in the previous works, are taken into account. The crystal-field parameters are determined from the superposition model in consideration of the suitable lattice distortion due to the charge and size mismatching substitution of Ti4+ by Co2+. Based on the studies, the bond lengths R1 and R2 in the xy plane are estimated to suffer the relative alternation R ≈ 5.4%, yielding more significant orthorhombic distortion in the impurity center as compared with that for the host Ti4+ site in pure crystal. The calculation results based on the above local lattice distortion show reasonable agreement with the observed values. The various contributions to the spin Hamiltonian parameters are discussed. Present studies may theoretically verify that the impurity Co2+ occupies the 6-fold coordinated Ti4+ site rather than the 12-fold coordinated Ca2+ site, associated with the enhanced orthorhombic distortion due to the mismatching substitution.

Theoretical Study of the Local Lattice Distortion at the Trigonal Cr3+ Center in BiI3

2006 ◽  
Vol 61 (1-2) ◽  
pp. 78-82 ◽  
Author(s):  
Shao-Yi Wu ◽  
Xiu-Ying Gao ◽  
Hui-Ning Dong
Keyword(s):  
Lattice Distortion ◽  
Theoretical Study ◽  
Impurity Center ◽  
Cluster Approach ◽  
Pure Crystal ◽  
Local Lattice Distortion ◽  
Trigonal Symmetry ◽  
Local Lattice ◽  
Epr Parameters ◽  
Local Angle

The local lattice distortion at the trigonal Cr3+ center in BiI3 is theoretically studied by the perturbation formulas of the EPR parameters for a 3d3 ion in trigonal symmetry, based on the cluster approach. In these formulas the contributions from the s-orbitals of the ligands, which were often ignored, are taken into account. It is found that the local angle β (between the direction of the impurityligand bonding R and the C3 axis) in the impurity center is smaller than the host angle βH in the pure crystal. The calculated EPR parameters are improved compared to those in absence of the ligand s-orbital contributions. The local lattice distortion obtained in this work is discussed.

INVESTIGATIONS OF THE SPIN HAMILTONIAN PARAMETERS AND THE LOCAL STRUCTURE FOR THE RHOMBICCu2+CENTER IN RUTILE

2010 ◽  
Vol 24 (22) ◽  
pp. 2357-2364 ◽  
Author(s):  
HUA-MING ZHANG ◽  
SHAO-YI WU ◽  
PEI XU ◽  
LI-LI LI
Keyword(s):  
Local Structure ◽  
Impurity Center ◽  
Angular Distortion ◽  
Spin Hamiltonian ◽  
Rhombic Distortion ◽  
Calculation Results ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Structure Constants ◽  
Hamiltonian Parameters

The spin Hamiltonian parameters (the anisotropic g factors and the hyperfine structure constants) and the local structure for the rhombic Cu2+center in rutile ( TiO2) are theoretically investigated using the formulas of these parameters for a 3d9ion in rhombically elongated octahedra. From the studies, the planar impurity-ligand bond angle is found to be about 5.8° larger than that for the host Ti4+site due to the Jahn–Teller effect via bending the planar Cu2+– O2-bonds, which yields much smaller rhombic distortion in the impurity center. The theoretical spin Hamiltonian parameters based on the above local angular distortion show good agreement with the experimental data, and the improvement of the calculation results are also achieved as compared with those of the previous works.

Theoretical investigations on the spin Hamiltonian parameters and the local structure for Rh2+ in rutile

2010 ◽  
Vol 88 (1) ◽  
pp. 49-53 ◽  
Author(s):  
S. X. Zhang ◽  
S. Y. Wu ◽  
P. Xu ◽  
L. L. Li
Keyword(s):  
Local Structure ◽  
Impurity Center ◽  
Angular Distortion ◽  
Spin Hamiltonian ◽  
Theoretical Investigations ◽  
Rhombic Distortion ◽  
Ligand Orbital ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Hamiltonian Parameters

The spin Hamiltonian parameters, the g factors gi (i = x, y, z) and the hyperfine structure constants Ai, and the local structure for Rh2+ in rutile (TiO2) are theoretically investigated from the perturbation formulas of these parameters for a 4d7 ion under rhombically elongated octahedra. In view of the covalency, the ligand orbital and spin-orbit coupling contributions are taken into account from the cluster approach. The planar bond angle in the impurity center is found to be 7.5° larger than that of the host Ti4+ site because of the Jahn–Teller effect via bending of the planar Rh2+-O2– bonds, leading to much smaller rhombic distortion. The theoretical spin Hamiltonian parameters based on the above Jahn–Teller angular distortion show reasonable agreement with the experimental data.

Studies of the Spin Hamiltonian Parameters and the Local Structure of Tetragonal Zr3+ Centers in Orthophosphate MPO4 (M = Sc, Lu, Y) Crystals

2006 ◽  
Vol 61 (12) ◽  
pp. 688-690 ◽  
Author(s):  
Gui-Qiang Qu ◽  
Wang Fang ◽  
Wen-Chen Zhenga
Keyword(s):  
Lattice Relaxation ◽  
Structural Data ◽  
Tetragonal Symmetry ◽  
Spin Hamiltonian ◽  
Local Lattice ◽  
Structure Constants ◽  
Experimental Values ◽  
Crystal Field Parameters ◽  
Hamiltonian Parameters ◽  
Zircon Type

The spin Hamiltonian parameters (g factors g||, g⊥ and hyperfine structure constants A||, A⊥) of Zr3+ on the tetragonal M3+ (M = Sc, Lu, Y) sites of zircon-type orthophosphate MPO4 crystals are calculated by high-order perturbation formulas of d1 ions in tetragonal symmetry. The crystal-field parameters are estimated by the superposition model and reasonable local structural data of impurity centers. The results show good agreement with the experimental values. It appears that in the case of size mismatch, the explanation of the spin Hamiltonian parameters of a paramagnetic impurity in crystals should take the impurity-induced local lattice relaxation into account.

Local Lattice Distortion and Chemical Short Range Order in High Entropy Alloys

2020 ◽  
Author(s):  
Yuan-Yuan Tan ◽  
Ming-Yao Su ◽  
Zhou-Can Xie ◽  
Zhong-Jun Chen ◽  
Yu Gong ◽  
...  
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Lattice Distortion ◽  
Range Order ◽  
High Entropy Alloys ◽  
Local Lattice Distortion ◽  
High Entropy ◽  
Local Lattice

scholarly journals Element-resolved local lattice distortion in complex concentrated alloys: An observable signature of electronic effects

2021 ◽  
pp. 117135
Author(s):  
Hyun Seok Oh ◽  
Khorgolkhuu Odbadrakh ◽  
Yuji Ikeda ◽  
Sai Mu ◽  
Fritz Körmann ◽  
...  
Keyword(s):  
Lattice Distortion ◽  
Electronic Effects ◽  
Local Lattice Distortion ◽  
Local Lattice

scholarly journals Lattice Distortion and Phase Stability of Pd-Doped NiCoFeCr Solid-Solution Alloys

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 900 ◽  
Author(s):  
Fuxiang Zhang ◽  
Yang Tong ◽  
Ke Jin ◽  
Hongbin Bei ◽  
William Weber ◽  
...  
Keyword(s):  
Long Range ◽  
Lattice Distortion ◽  
Maximum Pressure ◽  
Local Lattice Distortion ◽  
X Ray ◽  
High Entropy ◽  
Local Lattice ◽  
Pd Doping ◽  
Fcc Phase ◽  
The Stability

In the present study, we have revealed that (NiCoFeCr)100−xPdx (x= 1, 3, 5, 20 atom%) high-entropy alloys (HEAs) have both local- and long-range lattice distortions by utilizing X-ray total scattering, X-ray diffraction, and extended X-ray absorption fine structure methods. The local lattice distortion determined by the lattice constant difference between the local and average structures was found to be proportional to the Pd content. A small amount of Pd-doping (1 atom%) yields long-range lattice distortion, which is demonstrated by a larger (200) lattice plane spacing than the expected value from an average structure, however, the degree of long-range lattice distortion is not sensitive to the Pd concentration. The structural stability of these distorted HEAs under high-pressure was also examined. The experimental results indicate that doping with a small amount of Pd significantly enhances the stability of the fcc phase by increasing the fcc-to-hcp transformation pressure from ~13.0 GPa in NiCoFeCr to 20–26 GPa in the Pd-doped HEAs and NiCoFeCrPd maintains its fcc lattice up to 74 GPa, the maximum pressure that the current experiments have reached.

Investigation of the Spin Hamiltonian Parameters of Yb3+ in CaWO4 Crystal

2004 ◽  
Vol 59 (12) ◽  
pp. 943-946 ◽  
Author(s):  
Hui-Ning Dong ◽  
Shao-Yi Wu
Keyword(s):  
Hyperfine Structure ◽  
Local Structure ◽  
Reasonable Agreement ◽  
Second Order ◽  
Order Perturbation ◽  
Superposition Model ◽  
Spin Hamiltonian ◽  
Structure Constants ◽  
Hamiltonian Parameters ◽  
G Factors

In this paper, the spin Hamiltonian parameters g factors g∥ and g⊥ of Yb3+ and hyperfine structure constants A∥ and A⊥ of 171Yb3+ and 173Yb3+ in CaWO4 crystal are calculated from the two-order perturbation formulae. In these formulae, the contributions of the covalence effects, the admixture between J =7/2 and J =5/2 states as well as the second-order perturbation are included. The needed crystal parameters are obtained from the superposition model and the local structure of the studied system. The calculated results are in reasonable agreement with the observed values. The results are discussed.

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