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.

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.

Local Lattice Distortion near Co2+ in SrLaAlO4 Crystal

2001 ◽  
Vol 56 (8) ◽  
pp. 557-560 ◽  
Author(s):  
Shao-Yi Wu ◽  
Wen-Chen Zheng
Keyword(s):  
Ionic Radius ◽  
Lattice Distortion ◽  
Tetragonal Distortion ◽  
Host Crystal ◽  
Local Lattice Distortion ◽  
Oxygen Octahedron ◽  
Local Distortion ◽  
Local Lattice ◽  
Epr Parameters ◽  
Metal Ligand

Abstract The local tetragonal distortion in the vicinity of substitutional Co2+ impurities in SrLaAlO4 crystal is studied by fitting the calculated EPR parameters g\\, g⟂, A\\ and A⟂ to the observed values. The result shows that the local distortion is mainly due to the elongation of metal-ligand distance R± perpendicular to the C4 axis. This point is consistent with the expectation based on the consideration of ionic radius sum. This smaller tetragonal distortion of the oxygen octahedron surrounding the Co2+ impurity than that in the host crystal is supported by the result obtained in Cr3+-doped SrLaAlO4 crystal. -P a cs: 61.70Rj; 76.30Fc; 71.70Ch

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.

The phase transition in superconductors - I. Nucleation

1952 ◽  
Vol 214 (1118) ◽  
pp. 392-412 ◽  
Keyword(s):  
Surface Tension ◽  
Room Temperature ◽  
Lattice Distortion ◽  
Impurity Content ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Local Lattice Distortion ◽  
Surface Conditions ◽  
Local Lattice ◽  
Crystal Boundaries

A detailed study of ‘supercooling' in tin rods has confirmed the hypothesis that this is caused by the difficulty of forming a nucleus of the superconducting phase. The experiments show that when nucleation does occur it only happens at certain flaws in the metal, which have been proved to lie at the surface and to be between 10 -4 and 10 -3 cm in size. These flaws do not appear to be necessarily associated with surface conditions, impurity content, or crystal boundaries. Any handling of the specimen affects them, but simply warming it to room temperature often does not, in which case the supercooling observed in separate experiments is reproducible. The degree of supercooling ϕ l defined as ( H 2 c - H 2 l )/ H 2 c , where H l is the field at which nucleation is first possible, varies in magnitude from flaw to flaw (0⋅8 is the largest value found), but it always depends on temperature in the same way, rising as T → T c , The supercooling can sometimes be increased by applying a high field to the specimen beforehand, indicating that some of the flaws can be temporarily destroyed by such treatment. The behaviour of the flaws can be accounted for if they are assumed to be domains where the interphase surface tension has become negative, perhaps as the result of local lattice distortion produced by dislocations. Using a simple model based on this picture the magnitude and temperature dependence of ϕ l have been explained quantitatively in terms of the characteristic flaw size and the positive surface tension in the undistorted metal (as estimated from work on the intermediate state). Slight superheating (up to 1⋅5% of H c ) has also been observed.

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