材料期刊网

EXPLORATION FOR APPLICATION OF EET IN METALLIC BIOMATERIALS RESEARCH

Y.P.Lu1 , 2) R.F.Zhu1) , T.Q.Lei2) , Q.S.Ma3)and M.S.Li1) 1) College of Materials Science and Engineering , Shandong University of Technology , Jinan 250061 , China2) Harbin Institute of Technology , Harbin 150001 , China 3) Qingrui Oralimplant Center , Shandong Provincial Hospital , Jinan 250021 , China

金属学报(英文版)

Theelectron densitiesonsomeplaneofinvolved cellsin αTitanium and Ti Al , Ti 6 Al 4 V and Au Pd Ptalloys werecalculated through EET. Theresultsshow thatthereexist planes withsimilarelectron density amongα Ti,Ti Al,Ti Vand Au Pd Pt unitcells, which veri fiedtosomeextentthe validity ofthe application of EETand atomic boundary condition inTFDtheoryin biomaterials.

关键词: biomaterial , null , null

Studies on the local structure of the tetragonal Er3+ center in CaO

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The local structure of the tetragonal Er3+ center in CaO is theoretically studied by using the perturbation formulas of the g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixtures of various states are taken into account. Based on the investigations, this center is suggested to be the impurity Er3+ substituting the host Ca2+ site, associated with a Ca2+ vacancy V-Ca in the [100] (C-4) axis due to charge compensation. By studying the g factors of the tetragonal center, impurity Er3+ is expected to undergo an off-center displacement Delta Z( approximate to 0.2 A) towards the V-Ca along the C-4 axis because of the electrostatic attraction. The calculated g factors based on the displacement Delta Z show reasonable agreement with the observed values.

关键词: defect structures;electron paramagnetic resonance (EPR);crystal-field;and spin hamiltonians;Er3+;CaO;electron-spin-resonance;superposition-model;insulator coatings;magnesium-oxide;vanadium alloys;single-crystals;calcium oxide;parameters;blankets;ions

Defect structure of Co2+ center in rhombohedral BaTiO3

Optical Materials

The spin-Hamiltonian parameters (g factor g(parallel to), gi(perpendicular to) and hyperfine structure constants A(parallel to), A(perpendicular to)) of Co2+ ion in rhombohedral BaTiO3 crystal are calculated from the perturbation formulas based on the cluster approach for the spin-Hamiltonian parameters of 3d(7) ion in trigonal octahedral site. The calculations are related to the trigonal field parameters and hence to the defect structure of Co2+ center. From the calculations, it is found that in order to reach a good fit between calculations and experiments, the off-center displacement of Co2+ ion in oxygen octahedron of BaTiO3 is much smaller than that of the host Ti4+ ion it replaces. This point is similar to the case of Fe3+ ion in BaTiO3 obtained in the previous studies by analyzing EPR zero-field splitting from the superposition model. (c) 2005 Elsevier B.V. All rights reserved.

关键词: defect structure;electron paramagnetic resonance;crystal and ligand;field;photorefractive material;Co2+;BaTiO3;electron-paramagnetic-resonance;atomic screening constants;photorefractive properties;superposition model;scf functions;dependence;position;distance;fields;sites

Theoretical investigations of the defect structure and the g factors of a tetragonal Ni3+ center in PbTiO3

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The defect structure and the anisotropic g factors of a tetragonal Ni3+ center in PbTiO3 are theoretically investigated from improved perturbation formulas of the g factors for a 3d(7) ion with low spin S = 1/2 in tetragonally elongated octahedra, established in this work. Based on the studies, the distance between the impurity Ni3+ and the center of the oxygen octahedron is found to be about 0.14 A, which is smaller than that (approximate to 0.3 angstrom) for the host Ti4+ site due to the inward shift (approximate to 0.16 angstrom) towards the center of the oxygen octahedron. The theoretical g factors based on the above defect structure agree well with the observed values.

关键词: defect structures;electron paramagnetic resonance;crystal-fields and;spin Hamiltonian;Ni3+;PbTiO3;electron-paramagnetic-resonance;atomic screening constants;superposition model;epr parameters;lead titanate;scf functions;ions;crystals;cr3+;nanopowders

Theoretical investigations of the local structure and the g factors for the tetragonal Ru3+ center in PbTiO3

Radiation Effects and Defects in Solids

The local structure and the g factors for the tetragonal Ru3+ center in PbTiO3 are theoretically studied from the perturbation formulas of the g factors for a 4d(5) ion in tetragonally distorted octahedra. From the studies, the distance between the impurity Ru3+ and the center of the oxygen octahedron is found to be about 0.283 angstrom, which is smaller than that (approximate to 0.3 angstrom) for the host Ti4+ site. It appears that the impurity may not occupy exactly the host Ti4+ site but suffer a slight inward shift toward the center of the oxygen octahedron. The calculated g factors based on the above local structure show good agreement with the experimental values.

关键词: defect structures;electron paramagnetic resonance;crystal-fields and;spin Hamiltonian;Ru3+;PbTiO3;electron-paramagnetic-resonance;atomic screening constants;spin-resonance;lead titanate;scf functions;crystals;ions;cr3+;nanopowders;epr

Local structure of the trigonal defect center for Cr3+ ions in KMgF3 crystals

Radiation Effects and Defects in Solids

The zero-field splitting D, the anisotropic g-factors g(parallel to), Delta g(= g(parallel to) - g(perpendicular to)) and the first excited state splitting Delta(E-2) for the trigonal Cr3+-V-K center in KMgF3:Cr3+ crystals have been studied from Macfarlane's high-order perturbation formulas. From the studies, the local structure of the trigonal center is obtained. The local lattice distortions (i.e., the displacement directions of the ions in the center) are consistent with the expectation based on the electrostatic interaction.

关键词: electron paramagnetic resonance;optical spectrum;local crystalline;structure;crystal-field theory;Cr3+;KMgF3;electron-paramagnetic-res;fe3+

Theoretical study of the local lattice distortion at the trigonal Cr3+ center in BiI3

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The local lattice distortion at the trigonal Cr3+ center in BiI3 is theoretically studied by the perturbation formulas of the EPR parameters for a 3d(3) 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 beta (between the direction of the impurity-ligand bonding R and the C-3 axis) in the impurity center is smaller than the host angle beta(H) 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.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Cr3+;BiI3;electron-paramagnetic-resonance;atomic screening constants;indirect;band bottom;secondary-emission;scf functions;crystals;excitons;ions;recombination;parameters

EPR parameters and local lattice structure study of trigonal Fe3+ center in CSMgCl3 crystal

Chemical Physics

The EPR parameters and local lattice structure study of trigonal Fe3+ center in CSMgCl3 crystal has been performed on the basis of the complete energy matrices for a d(5) configuration ion in a trigonal ligand field. It is indicated that the local lattice structure around a trigonal Fe3+ center has an elongation distortion along the crystalline c-axis, and the elongation magnitude of trigonal Fe3+ center is larger than that of the host Mg2+ ion. This may be ascribed to the fact that Fe2+ ion which exists in the as-grown CSMgCl3 crystal substitutes for Mg2+ ion. The Fe2+ ion whose radius is larger than that of host Mg2+ ion pushes the chlorine ligands upwards and downwards, respectively. Finally, the Fe2+ ion is changed into Fe3+ ion by X-ray irradiation. Simultaneously, for the trigonal Fe3+ center in the crystal, the local lattice structure parameters, R = 2.535 angstrom and theta = 50.314 degrees, are determined from our calculation, and EPR parameters b(2)(0), b(4)(0), and b(4)(3) also get a satisfactory explanation. (c) 2006 Elsevier B.V. All rights reserved.

关键词: EPR parameters;local lattice structure;complete energy matrices method;electron-paramagnetic-resonance;temperature-dependence;cross-relaxation;single-crystal;rate constants;ions;pairs;mn;co

Optical absorption and EPR study of the octahedral Fe3+ center in yttrium aluminum garnet

Physical Review B

The optical-absorption and EPR spectra of octahedral Fe3+ center in yttrium aluminum garnet have been studied by diagonalizing the complete energy matrices for a d(5) configuration ion in a trigonal ligand field. It is shown that the local lattice structure around an octahedrally coordinated Fe3+ center has an expansion distortion. The expansion distortion may be attributed to the fact that the radius of Fe3+ ion is larger than that of Al3+ ion, and the Fe3+ ion will push the oxygen ligands outwards. Simultaneously, the local lattice structure distortion parameters Delta R=0.0907 A and Delta theta=1.940 degrees for the octahedral Fe3+ center in the crystal are determined. From optical spectra calculation, we confirm that two strong sharp transitions at 407 and 415 nm, which are apparent in the optical absorption spectra for lightly doped YAG:Fe3+ system, should be ascribed to the tetrahedral Fe3+ center. This is also in accord with the conclusion of Rotman [J. Appl. Phys. 66, 3207 (1989)].

关键词: electron-paramagnetic-resonance;crystals;field;ion;parameters;impurities;fe-3+

Defect structure of the tetragonal Cu2+ center in PbTiO3 : Cu2+ crystal

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

defect structure of the tetragonal Cu2+ center in PbTiO3: Cu2+ crystal is studied by analyzing the EPR g factors and hyperfine structure constants. From the study, we suggest that an oxygen vacancy occurs in the nearest-neighbors site of Cu2+ due to charge compensation, and that the off center displacement of Cu2+ is smaller than that of the replaced host ion Ti4+. The reasonableness of the defect structure is discussed.

关键词: defect structure;electron paramagnetic resonance;crystal-field theory;Cu2+;PbTiO3;electron-paramagnetic-resonance;superposition model;single-crystals;batio3;ions;ni