Compressed Distortion Research Articles

Theoretical study of local lattice structure of Mn 2+ in perovskite fluorides A 2MF 4 (A=K, Rb; M=Mg, Zn, Cd) series

A theoretical method for investigating the inter-relation between the molecular structure and electronic structure has been established on the basis of the 252×252 complete energy matrices for a 3d 5 configuration ion in a tetragonal ligand field. By means of this method, which is independent of the X-ray diffraction, the local structure of the paramagnetic Mn 2+ ion in perovskite fluorides A 2MF 4 (A=K, Rb; M=Zn, Mg, Cd) are determined directly by analyzing the EPR spectrum of octahedral Mn 2+ center in A 2MF 4 crystals and the optical absorption spectrum of the (MnF 6) 4− cluster. It is shown that, comparing with the octahedral cubic structure, the local micro-structure in the vicinity of Mn 2+ displays an elongated distortion when b 2 0 > 0 and a compressed distortion when b 2 0 < 0 , and Δ R vs. 1 0 4 b 2 0 as well as Δ R vs. 1 0 4 b 4 0 in the distortion region is, respectively, approximately linear. Simultaneously, the theoretical zero-field-splitting parameters b 2 0 , b 4 0 and b 4 4 are in good agreement with the experimental values.

Theoretical investigation of electron paramagnetic resonance parameters and lattice distortion in α-Al2O3 crystal doped with V3+ ions

The electron paramagnetic resonance parameters D, g ∥ and g ⊥ for V3+ ions in α-Al2O3 crystals are calculated on the basis of the complete diagonalization method and the superposition model. In the calculation, the contributions of the variation of the cation–ligand bond lengths and bond angles are taken into consideration. The calculated results agree well with the experimental data. Our investigation shows that the local structure around the V3+ ions possesses a compressed trigonal distortion above the O2−-triangle and an elongated trigonal distortion in the lower one.

EPR spectra and local lattice structure of Fe 3+ impurity ions in ferroelectric LiNbO 3

The optical absorption and EPR spectra of Fe 3+ impurity ions doped in near stoichiometric LiNbO 3 crystal are studied by diagonalizing the complete energy matrices for a d 5 configuration ion in a trigonal ligand-field. By analyzing the optical absorption and EPR spectra simultaneously, the distortion parameters Δ θ 1 = 3.42°, Δ θ 2 = −7.22° are determined for Li + substitutional position supported by ENDOR experiments. The theoretical results indicate that there exists a compressed distortion in LiNbO 3:Fe 3+ system, which may be ascribed to the fact that the radius of Fe 3+ ion is slightly smaller than that of the host ion. Meanwhile, the local structure parameters R 1 = 2.08 A, R 2 = 1.91 A, θ 1 = 47.99° and θ 2 = 62.52° for the octahedral Fe 3+ center in LiNbO 3 crystal are also determined, which are close to that of the αFe 2O 3. The calculated transition energies of octahedral Fe 3+ center in LiNbO 3 are in good agreement with those of Fe 3+ cations in other oxides due to the similar octahedral (FeO 6) 9− cluster.

Spin Hamiltonian parameters and structural disorder analysis for Cr 3+ ion in YGG crystals

A new crystalline lattice distortion model has been proposed, on the basis of it, the relations between spin Hamiltonian parameters and crystal micro structure have been established. By taking into account slight magnetic interactions, including spin–spin (SS), spin-other-orbit (SOO), and orbit–orbit (OO) interactions, the local structure of Cr 3+ ion in YGG crystal has been studied using complete diagonalization method (CDM). The studies show that the local structure in the YGG:Cr 3+ crystal is of the compressed trigonal distortion. The ligand oxygen plane moved 0.0138 nm toward Cr 3+ ion along C 3-axis. Accordingly, the SH parameters in YGG:Cr 3+ crystal are explained successfully.

EPR theoretical study of local lattice structure on Mn 2+ ion doped in calcite and differences between single crystal and fresh water snail, Pila globosa

By diagonalizing the complete energy matrices for a d 5 configuration ion in a trigonal ligand-field and considering the second-order, fourth-order EPR parameters D and ( a − F) simultaneously, the substitution position of Mn 2+ ion in the CaCO 3:Mn 2+ system has been studied by analyzing the optical absorption and EPR spectra of single crystal and the ostracum layer of operculum of fresh water snail Pila globosa. The results show that in the single crystal there is an obvious compressed distortion Δ R = −0.158 Å and Δ θ = 0.70°, and the distortion in P. globosa is Δ R = −0.107 Å and Δ θ = −0.34° ∼ −0.23°. Meanwhile the EPR parameters 10 4( a − F) = 7.02–7.29 cm −1 and 10 4 a = 6.35 cm −1 are predicted in P. globosa.

Bis(mu-6-hydroxypicolinato)-mu-oxo-bis[dipyridinemanganese(III)] monohydrate.

The title compound, [Mn2(mu-O)(C6H3NO3)2(C5H5N)4].H2O, was isolated from the reaction of 2,6-pyridinedicarboxylic acid with [Mn12O12(CH3COO)16(H2O)4] in pyridine. The dimanganese complex has twofold symmetry; the MnIII atoms are bridged by one oxo and two amidate ligands and show compressed octahedral Jahn-Teller distortion. The molecular packing comprises a three-dimensional structure constructed by means of extensive intermolecular interactions, including three kinds of hydrogen bonds and pi-pi interactions.

Alternative spin states in synthetic analogs of biological iron-sulfur [4Fe-4S]+ clusters: further cases of variable ground states and the structure of (Et4N)3[Fe4S4(S-o-C6H4S-tert-Bu)4], containing a reduced cluster with a compressed tetragonal distortion

Alternative spin states in synthetic analogs of biological iron-sulfur [4Fe-4S]+ clusters: further cases of variable ground states and the structure of (Et4N)3[Fe4S4(S-o-C6H4S-tert-Bu)4], containing a reduced cluster with a compressed tetragonal distortion

X-ray and ESR investigation of an elongated octahedral tris-(1, 2-diaminoethane) copper (II) complex

The X-ray structure of Cu(en) 3Cl 2 · 0.75 en has been solved as a model of frozen Jahn-Teller distortions experienced by Cu(en) 2+ 3 complexes. The distorted chromophores are elongated octahedra though the crystal g values simulate a compressed distortion.

Studies on Load and Strain on the Compression of the Seat Mucosa of Complete Dentures

The fact that the compressed distortion of the seat mucosa of complete dentures (just the seat mucosa will be substituted for the seat mucosa of complete dentures in subsequent sentences) varies from an area to another is considered one of the primary factors to adhesive retention, stabilization and masticating efficiency of dentures and problems of the seat mucosa.Some researches have been already reported on the compressed distortion of the mucosa, is rather difficult to find any clinically significant values in them form the following 1) they measured just strain under a given load, whereas load itself varies regionally mucosa. 2) they have not represented accurate relationship between load and strain condition of the compressed distortion under various loads.Since the new type transducer was designed and developed by the auther, it became measure both the load and strain simultaneously in a given condition of the seat mucosa also to compare physical hardness and tension of the mucosa at different regions.The following conclusions were obtained.1) The simultaneously measured load and strain of the seat mucosa were shown in Tables -4. It was obvious that the load and strain of the seat mucosa were different regionally and they were summarized as follows.a) Both the load and strain of the seat mucosa of anterior alveolar ridge were greater than those of the seat mucosa of posterior alveolar ridge.b) In the mucosa of palate, the load in anterior region was greater than it in posterior and the strain increased with a small difference in turn in the region of middle palate, rugae and foveola palatini. And the strain in those three regions were with significance smaller than those in the palatal side of the region of premolar and in the region of posterior palatine foramen where the greatest strain was acquired from.c) When comparison was made between the load in the region of alveolar ridge and it in the region of palate, and the strain in those two regions:i) The load in anterior ridge had a tendency to be slightly smaller than it in theregion of rugae, but to be greater than it in the region of middle palate, the palatal side of the region of premolar and the region of posterior palatine foramen, and was distinctly greater than it in the region of foveola palatini.The load in posterior ridge had a tendency to be slightly greater than it in the region of rugae, although the differen between the two was little, and was obviously greater than it in the other regions, that is, middle palate, foveola palatini, palatal side of the region of premolar and posterier palatine foramen.ii) The strain in anterior ridge had a tendency to be slightly smaller than it in the region of rugae and was obviously greater than those in the region of middle palate, foveola palatini, palatal side of the region of premolar and posterior palatine foramene.The strain in posterior ridge had a tendency to be greater than it in the region of rugae and middle palate, but a tendency to be smaller than it in the region of foveola palatini and was obviously greater than those in the palatal side of the region of premolar and in the region of posterior palatine foramen. It was a trend in the aged person over 60 years, however, that difference of strain in anterior ridge, in the region of middle palate and foveola palatini became on the decrease.3) The load and strain of the seat mucosa increased with age. It was, especially, evident in the load in posterior alveolar ridge and in the region of palate. And the strain in anterior ridge and in the region of rugae remarkably increased with age.4) The load in upper alveolar ridge was significantly greater than it in lower. On the other hand, the strain in upper ridge had a tendency to be greater than it in lower, but no significant difference between the two was found.