The Studies of Geometrical Microstructure of Tetragonal Co2+-VO Centers in KNbO3 and KTaO3 Crystals from EPR Data

2002 ◽  
Vol 57 (12) ◽  
pp. 925-928 ◽  
Author(s):  
Wen-Chen Zheng ◽  
Shao-Yi Wu
Keyword(s):  
Oxygen Vacancy ◽  
Shell Model ◽  
Crystal Field ◽  
Theoretical Studies ◽  
Cluster Approach ◽  
Model Simulations ◽  
Cluster Calculations ◽  
Experimental Values ◽  
Octahedral Crystal Field ◽  
Perovskite Type

From the perturbation formulas for the EPR ɡ factors g|| and g⊥ of a 3d7 ion in tetragonal octahedral crystal field based on a cluster approach, the geometrical microstructures of tetragonal Co2+-VO centers in KNbO3 and KTaO3 crystals are obtained by fitting the calculated g|| and g⊥ to the observed values. It is found that the Co2+ ion in Co2+-VO centers is displaced away from the oxygen vacancy VO by 0.3 Å in KNbO3 and by 0.29 Å in KTaO3. These results are comparable with those of Fe3+-VO centers in ABO3 perovskite-type crystals obtained fromboth the shell-model simulations and the embedded-cluster calculations, and from theoretical studies of EPR data. The experimental values of g|| and g⊥ for the tetragonal Co2+-VO centers in both crystals are also explained reasonably.

Theoretical Studies of the g Factors for Co2+ in MgO and CaO Crystals

2001 ◽  
Vol 56 (3-4) ◽  
pp. 249-252 ◽  
Author(s):  
Shao-Yi Wu ◽  
Wen-Chen Zheng
Keyword(s):  
Configuration Interaction ◽  
Optical Spectra ◽  
Theoretical Studies ◽  
Cluster Approach ◽  
Experimental Values ◽  
Good Agreement ◽  
G Factors

Abstract This paper presents a cluster approach to the calculation of the g factors for 3d7 ions in cubic oc­ tahedral crystals, in which the parameters related to the configuration interaction and the covalency reduction effects are obtained from optical spectra of the studied crystals, and so no adjustable parameters are applied. From the approach, the g factors for MgO:Co2+ and CaO:Co2+ are cal­culated. The calculated results show good agreement with the observed values. The experimental values of g 4.333 for CaO:Co2+ are also explained.

THEORETICAL STUDIES ON THE GYROMAGNETIC FACTORS FORFe3+INZnX(X=O,S,Se,Te)

2010 ◽  
Vol 24 (17) ◽  
pp. 1891-1898 ◽  
Author(s):  
XUE-FENG WANG ◽  
SHAO-YI WU ◽  
PEI XU ◽  
LI-LI LI
Keyword(s):  
Experimental Data ◽  
Charge Transfer ◽  
Crystal Field ◽  
Reasonable Agreement ◽  
Model Parameters ◽  
Theoretical Studies ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Cluster Approach ◽  
Perturbation Formula

The gyromagnetic factors for Fe3+in ZnX ( X = O , S , Se , Te ) are theoretically studied from the perturbation formula of the g-factor for a 3d5ion in tetrahedra based on inclusion of both the crystal-field and the charge-transfer contributions. The related model parameters in the calculations are determined from the cluster approach in a uniform way. The g-shift Δg (= g-gs, where gs≈ 2.0023 is the spin-only value) from the charge-transfer contributions is opposite (positive) in sign and much larger in magnitude as compared with that from the crystal-field ones. The importance of the charge-transfer contributions increases rapidly with increasing the covalency and the spin-orbit coupling coefficient of the ligand and thus exhibits the order of O2-< S2-< Se2-< Te2-. The calculated g-factors by considering both the crystal-field and charge-transfer contributions show reasonable agreement with the experimental data for all the Fe3+centers in ZnX .

Shell model simulations by adiabatic dynamics

1993 ◽  
Vol 5 (8) ◽  
pp. 1031-1038 ◽  
Author(s):  
P J Mitchell ◽  
D Fincham
Keyword(s):  
Shell Model ◽  
Model Simulations ◽  
Adiabatic Dynamics

INVESTIGATIONS OF ELECTRON-PARAMAGNETIC-RESONANCE PARAMETERS OF OCTAHEDRAL (CrO6)9- and (MnO6)8- CLUSTER IN MgTiO3:Cr3+, SrTiO3:Cr3+ AND SrTiO3:Mn4+ CRYSTALS

2011 ◽  
Vol 25 (21) ◽  
pp. 1779-1785
Author(s):  
MINJIE WANG ◽  
LIANXUAN ZHU ◽  
JIANLIANG DANG
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crystal Field ◽  
Valence State ◽  
Spin Orbit ◽  
Contribution Rate ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Experimental Values ◽  
Electron Paramagnetic ◽  
G Factors

The complete high-order perturbation formulas are established by both crystal-field (CF) and charge-transfer (CT) mechanisms. The EPR g factors of MgTiO 3: Cr 3+, SrTiO 3: Cr 3+ and SrTiO 3: Mn 4+ crystals are calculated from the formulas. The calculations of the EPR g factors are in agreement with the experimental values. The contribution rate of the CT mechanism (|ΔgT/ΔgF|) to EPR parameters, increases with the growth of the valence state for the 3dn ions in the crystals. For the higher valence state 3d3 ion Mn 4+ in crystals, the explanation of the EPR parameters reasonably involves both CF and CT mechanisms. The g values are also given from one-spin-orbit-parameter model and crystal-field (CF) mechanism for comparison.

scholarly journals Study of the Electric Quadrupole Moments for some Scandium Isotopes Using Shell Model Calculations with Different Interactions

2018 ◽  
Vol 15 (3) ◽  
pp. 304-309
Author(s):  
Baghdad Science Journal
Keyword(s):  
Shell Model ◽  
Theoretical Calculations ◽  
Microscopic Theory ◽  
Model Space ◽  
Electric Quadrupole ◽  
Quadrupole Moments ◽  
Core Polarization ◽  
Model Calculations ◽  
Major Shell ◽  
Experimental Values

The electric quadrupole moments for some scandium isotopes (41, 43, 44, 45, 46, 47Sc) have been calculated using the shell model in the proton-neutron formalism. Excitations out of major shell model space were taken into account through a microscopic theory which is called core polarization effectives. The set of effective charges adopted in the theoretical calculations emerging about the core polarization effect. NushellX@MSU code was used to calculate one body density matrix (OBDM). The simple harmonic oscillator potential has been used to generate the single particle matrix elements. Our theoretical calculations for the quadrupole moments used the two types of effective interactions to obtain the best interaction compared with the experimental data. The theoretical results of the quadrupole moments for some scandium isotopes performed with FPD6 interaction and Bohr-Mottelson effective charge agree with experimental values.

LATTICE DYNAMICS OF AN F-TYPE ICOSAHEDRAL QUASICRYSTAL

1993 ◽  
Vol 07 (06n07) ◽  
pp. 1487-1504 ◽  
Author(s):  
G. KASNER ◽  
H. BÖTTGER
Keyword(s):  
Lattice Dynamics ◽  
Continued Fraction ◽  
Pair Interaction ◽  
Icosahedral Quasicrystal ◽  
Cluster Approach ◽  
Vibrational States ◽  
Lennard Jones ◽  
Cluster Calculations ◽  
Face Centered ◽  
Matrix Continued Fraction

By using a matrix-continued fraction approach we calculate the density of vibrational states (DOS) of a tiling model based on the 6D face centered lattice. Parameters of the Lennard-Jones pair interaction are obtained from relaxation calculations. With a ternary decoration the tiling was found to be stable. The DOS was approximated by weighting the local DOS (LDOS) of the allowed vertex configurations by their relative frequencies in the infinite tiling. These frequencies were obtained by using extended deflation rules. Results of this approach are compared to exact finite cluster calculations and an embedded cluster approach. We find the DOS to consist of a single band (in our resolution) and a rich structure at higher frequencies.

CALCULATION OF THE CRYSTAL FIELD IN CeZn2

1996 ◽  
Vol 10 (29) ◽  
pp. 1471-1476
Author(s):  
MIRCEA ANDRECUT
Keyword(s):  
Rare Earth ◽  
Intermetallic Compound ◽  
Electric Field ◽  
Temperature Dependence ◽  
Least Squares ◽  
Crystal Field ◽  
Crystalline Electric Field ◽  
Experimental Values ◽  
Good Agreement ◽  
Rare Earth Intermetallic

The temperature dependence of the second-order crystalline electric field (CEF) parameters of rare earth intermetallic compound CeZn 2 was deduced from the least-squares nonlinear fit to the reciprocal paramagnetic susceptibility along principal crystalline axes. The results of the calculation are in good agreement with the experimental values.

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