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The spin Hamiltonian parameters (SHPs) and the local structures for impurity W5+ in the Zn3(PO4)2ZnO nanopowders doped with WO3 under different concentrations are theoretically investigated using the perturbation calculations of these parameters. The exponential functions of the related quantities (cubic field parameter Dq, covalency factor N, relative tetragonal compression ratio τ and core polarisation constant κ) of concentration x with totally four adjustable coefficients a, b, c and d are adopted to fit the concentration dependences of the experimental d-d transition bands and SHPs. The impurity W5+ centres demonstrate moderate tetragonal compression ratios τ (∼3.1%) due to the Jahn–Teller effect. With the increase of WO3 concentration, Dq and N show moderately decreasing rules, while τ and κ exhibit slightly and moderately increasing tendencies with x, respectively. The mechanisms of the above concentration dependences of these quantities are analysed from the modifications of the local crystal-field strength and electron cloud density around the impurity W5+ with the variation of x. Present theoretical studies would be useful to the exploration of the structural properties and optical applications for WO3 doped Zn3(PO4)2ZnO nanopowders. [ABSTRACT FROM AUTHOR]

The local structures and electron paramagnetic resonance (EPR) parameters for Cu2+in 59B2O3–10K2O–(30−x)ZnO–xBaO–1CuO (BKZBC) glasses are theoretically investigated with distinct modifier BaO concentrationsx(= 0, 6, 12, 18, 24 and 30 mol %). Theclusters are found to undergo the relative tetragonal elongations of about 13.5 and 5.0% at zero and higher BaO concentrations. The concentration dependences of the measured d–d transition bands,gfactors andA//are suitably reproduced from the Fourier type functions or sign functions of the relevant quantities withxby using only six adjustable parameters. The features of the EPR parameters and the local structures of Cu2+are analysed in a consistent way by considering the differences in the local ligand field strength and electronic cloud admixtures around Cu2+under addition of Ba2+with the highest ionicity and polarisability. The present theoretical studies would be helpful to the researches on the structures, optical and EPR properties for the similar potassium barium zinc borate glasses containing copper with variation concentration of modifier BaO. [ABSTRACT FROM PUBLISHER]

The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2− electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba2+-O2− bonds. The present studies would be helpful to understand local structures and the influences on the optical properties of RPPZ glasses containing copper dopants. [ABSTRACT FROM AUTHOR]

Thegfactors and local structures for Cu2+in the ZnX (X = O, S and Se) nanocrystals at room temperature are theoretically investigated by the perturbation calculations for a tetragonally distorted tetrahedral 3d9cluster in a consistent way, and the isotropicgfactor is predicted for the ZnS:Cu2+nanocrystals at room temperature. The bond angles θ between the four equivalent Cu2+−X2−bonds and the C4axis are found to be about 1.26°, 1.24° and 1.07°, respectively, larger in the ZnO, ZnS and ZnSe nanocrystals than that (θ0≈ 54.74°) for an ideal tetrahedron, inducing tetragonally compressed tetrahedra. The declining tendency (ZnO > ZnS > ZnSe) of the tetragonal angular distortion Δθ (= θ − θ0) can be ascribed to the decreasing strength of the dynamic Jahn–Teller effect via the vibration interactions of the [CuX4]6−groups due to the weakening Cu2+−X2−bonding. The isotropicgfactors are attributable to the appropriate Δθ due to the dynamic Jahn–Teller effect and the internal stress. The slightly increasing (ZnO < ZnS < ZnSe)gfactors can be illustrated by the declining cubic field parameterDq, angular distortion Δθ and covalency factorNof the systems. [ABSTRACT FROM PUBLISHER]