Theoretical Study On The Local Structures And Spectral Properties Of D~n(n Is Odd) Ions

In view of the rapid development of science and technology,explorstion of functional materials are becoming more and more important and urgent.Doping is one of the most important methods for the enahncement of the properties in these materials.Among various dopants,transition-metal ions are often doped in functional materials due to their rich optical and magnetic properties arising from the abundant electronic levels of the unfilled d shells.For the doped materials,the above optical and magnetic propeties usually strongly depend upon the local structures around the transition-metal impurities,which can be efficiently anlyzed by means of some spectroscopic methods.Electron paramagnetic resonance（EPR）is a powerful technique to study the local structural properties and electornic states of transition-metal ions in crystals and compounds.In this dissertation,the representative and important d^1,3,5,7,9 ions among the transition-metal groups are systematically studied from the perturbation formulas of the spin Hamiltonian parameters（SHPs）,and the information of local structures for these impurities are obtained on the basis of satisfactory interpretation for the experimental EPR spectra of these ions in some functional materials.And the relationship between the local structures of these dⁿ ions and the optical and magnetict properties of the materials as well as the related physical mechanisms are discussed in a uniforma way.The main research content can be illustrated as follows.（1）d¹ systems—3d¹(V⁴⁺),4d¹(Mo⁵⁺)and 5d¹(W⁵⁺).Ⅰ.The defect structures and SHPs for V⁴⁺in lead halo borate（xPbX₂-（30-x）PbO-68B₂O₃,X=F,Cl,Br and x=5,10,15,20 and 25 mol%）glass composites containing 2 mol%of V₂O₅ dopant are theoretically studied by applying the perturbation formulas of the SHPs for tetragonally compressed octahedral 3d¹ clusters.The related parameters are simulated with the corresponding Fourier type content functions.The distinct deviations of these quantities from the relevant simulated Fourier type content functions at 5 mol%of Pb Cl₂ and Pb Br₂ are reasonably explained from the modifications of compactness and electronic cloud distributions around V⁴⁺at this content.This is supported by the previous analysis on the content variations of ionic conductivity of the systems.Ⅱ.Theoretical study is perfomred for Mo⁵⁺doped x MoO₃（100-x）[P₂O₅·CaO]（0.3≤x≤50 mol%）glass systems through the perturbation formulas of g factors and hyperfine structure constants of tetragonally compressed octahedron 4d¹ clusters.Based on the local structure model,the EPR experimental results are reasonably explained.Due to the Jahn-Teller effect,the obtained model parameters are suitably explained at different concentration.Ⅲ.EPR g factors and defect structures for W⁵⁺in lead bismuth arsenate glasses（40–x）Pb O-15Bi₂O₃-45As₂O_3-x WO₃（PBA,x=1～6 mol%）are theoretically investigated from the g formulas for tetragonally compressed octahedral 5d¹ clusters.The d-d transition bands（including the minimal at 4 mol%）for varying concentrations are satisfactorily reproduced from the Fourier type concentration function of x.The distinct extrema of the spectral parameters（i.e.,the maxima of g factors and the minimum of Dq）and the relevant quantities（i.e.,the maxima ofρand the minimum of N）at 4 mol%are illustrated as the most intense local structural modifications and electronic cloud distributions around the impurity W⁵⁺arising from the variation of WO₃ doping concentration.（2）d³ systems—3d³(Cr³⁺).Ⅰ.The SHPs（i.e.ZFSs and g factors）and local structures of the two Cr³⁺centers I and II in KCl single crystals at room temperature are theoretically investigated from the perturbation calculations for a rhombically distorted octahedral 3d³ cluster.The impurity systems are attributed to the doped Cr（CN）₆^3?groups into KCl replacing the host KCl₆^5?ones,associated with two nearest neighbor potassium vacancies V_K in[011]and[0 1 1]axes in center I and one nearest neighbor V_K along[0 11]and another next-nearest neighbor V_K along[100]axis in center II,respectively.Ⅱ.The SHPs and the local structure for Cr³⁺in K₂Pd Cl₄ single crystal are theoretically investigated from the perturbation calculations of the SHPs for an orthorhombically distorted octahedral 3d³ cluster.The impurity Cr³⁺is found not to occupy the conventional square planar Pd²⁺site but to locate at the octahedral K⁺site,associated with the relative axial compression ratioρ（≈11.1%）and the relative planar bond length variation ratioτ（≈11.7%）.（3）d⁵ systems—3d⁵(Mn²⁺)and 4d⁵(Ru³⁺).Ⅰ.The SHPs and the local structures for Mn²⁺in[Zn（en）₃]（NO₃）₂ single crystal are theoretically investigated from the perturbation calculations of the SHPs for a trigonally distorted octahedral 3d⁵ cluster.The trigonal Mn²⁺center is found to undergo the moderate angular variations Δβ of 4.5?with respect to the host Zn²⁺site due to size mismatch.The signs and magnitudes of the trigonal distortion angleδβ（≈–0.3°）related to an ideal octahedron and the local angular variation Δβ（=β–β_H）related to the host bond angle β_H are suitably illustrated by those of the axial distortion degree（ADD）and the angular variation degree（AVD）,respectively.Ⅱ.The local structures and SHPs for the Ru（en）₃³⁺cluster in the ethylenediamine complexes are theoretically studied from the perturbation formulas of SHPs for trigonally distorted octahedral 4d⁵ clusters with the low spin S=1/2 of strong field case.The local impurity-ligand bonding angle related to the C₃ axis suffers a negative variationΔβ（≈–1.85°）with respect to the host β_H in[Ru（en）₃]Cl₃·4H₂O at 4 K.（4）d⁷ systems—3d⁷(Co²⁺)and 4d⁷(Pd³⁺).Ⅰ.The SHPs and defect structure for LiMgPO₄ doped with 0.1%Co²⁺at 4.2 K are theoretically investigated from the perturbation formulas of the SHPs for a rhombically distorted octahedral 3d⁷ cluster.The impurity Co²⁺on host Mg²⁺site is found to suffer the local rhombic compression distortion due to the size mismatch,characterized by the larger relative axial compression ratioρ（≈0.76%）and the planar angular variationΔφ（≈6.64°）related to the host oxygen octahedron.Ⅱ.Using the SHPs perturbation formulas of the tetragonally elongated octahedral4d⁷ cluster with a very strong field,the theoretical study of the SHPs and the superhyperfine parameters of Cl^–ligand is assigned for the cyanide complex[Pd（CN）₄Cl₂]^3–in Na Cl and KCl single crystals.The EPR experimental results are suitably explained,and the related properties of impurity-ligand orbital mixing（covalence）and s-p orbital hybridization of ligand Cl^–were systematically analyzed.（5）d⁹ systems—3d⁹(Cu²⁺).Ⅰ.The local structures and SHPs（g factors and hyperfine structure constants）for the Cu（en）₃²⁺clusters in ethylenediamine complexes are theoretically studied from the perturbation formulas of these parameters for tetragonally elongated octahedral 3d⁹clusters.Cu²⁺centers I and II may experience the slight relative elongationsΔZ by about0.005 and 0.007?in Zn（en）₃（NO₃）₂ polycrystalline powder at 4.2K and room temperature,respectively,along the C₄ axis because of the Jahn-Teller effect.Ⅱ.From the perturbation formulas of g factors for an orthorhombically compressed octahedral 3d⁹ group,g factors and local structures for the[Cu（en）₃]²⁺groups in Cu（en）₃SO₄ and Cu（en）₃Cu（CN）₃ powders are theoretically investigated.The local structure of Cu²⁺in Cu（en）₃Cu（CN）₃ is evaluated by analyzing the experimental g factors and found to exhibit moderate axial compressionΔZ（≈0.018?）and planar bond length variationΔR（≈0.015?）related to an ideal octahedron owing to the Jahn-Teller effect.