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According to the high‐order perturbation formulae of 3d5(Mn2+) and 3d9(Cu2+) ions in octahedron, the local structures and electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants A) for Cu2+ and Mn2+ in CdO are theoretically studied in a consistent way. Due to the Jahn–Teller effect, both the substituted sites of Cu2+ and Mn2+ show the tetragonally elongated distortion with different elongation τ. Meanwhile, the crystal field and covalency around doped Cu2+ and Mn2+ are obtained, which can account for the electronic properties in doped CdO. In order to make further investigation of the potential optical and electrical properties, the band structure and density of states (DOS) of pure and transition metal ions (TMs) doped CdO are comparably calculated through density functional theory (DFT). The results show that the band gap of Mn2+‐ and Cu2+‐doped CdO can be effectively reduced, due to the improved covalency between the central ions and ligand ions. [ABSTRACT FROM AUTHOR]

The mixed‐metal pillar‐layered metal–organic frameworks of Zn(bdc)(DABCO)0.5, Zn0.5Cu0.5(bdc)(DABCO)0.5 and Cu(bdc)(DABCO)0.5 (bdc = 1,4‐benzenedicarboxylate, DABCO = 1,4‐diazabicyclo[2.2.2]octane) are investigated for their local structures and gas adsorption properties. According to the obtained electron paramagnetic resonance (EPR) spectra, the distorted structures around Cu2+ are proposed to be tetragonally and orthorhombically elongated [CuO4N] with the well fitted high‐order perturbation formulae of the EPR parameters. Due to the doped Cu2+, the adsorption isotherms of industrially relevant gases (CO2, CO, CH4 and N2) and lower alkanes (CH4, C2H6, C3H8, C4H10 and C5H12) are different, especially at different temperatures. By combining the structural properties and adsorption isotherms, a comprehensive study suggests that the ZnDABCO series can be a controllable tool in gas storage and separation. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) have been well-known and extensively researched due to the high storage /good selectivity for gas molecules. Herein, the structures and electron paramagnetic resonance (EPR) spectra for dicopper paddle wheel MOF compound (Cu2(µ2-O2CCH3)4 with various gas molecule are theoretically investigated by density functional theory (DFT) calculations. The adsorption energies and isotherms (including pure gas molecules and the mixed ones) are calculated for the gas molecules interacting with the unsaturated Cu2(µ2-O2CCH3)4. Both quantities exhibit the roughly consistent orders (e.g. H2S > NH3 > CO2 > CO > H2O > N2 > NO > H2 for isotherms and H2S > NH3 > N2 > CO2 > NO > H2O > H2 > CO for adsorption energies), possibly suggesting that this material may act as a potential adsorbent of these gas molecules. The catalytic property of Cu2(µ2-O2CCH3)4 for oxidation of CO and NO into non-toxic molecules and splitting of H2O into H2 and O2 in the solvent condition are uniformly discussed. Simulation of Grand Canonical Monte Carlo (GCMC) in MS 8.0 and calculations in Langmuir model reveal that Cu2(µ2-O2CCH3)4 has good selectivity for CH4 in natural gas (CH4/CO2/N2) and SO2 in fog (SO2/NO/NO2/H2O/O2), which would exhibit potential environmentally friendly applications. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) technology had been adopted to analyze the structures and properties of Cu2+ and VO2+ in Biochar (BG1 and BG2), but the local structural properties have not been clarified up to now. In present work, three possible structures (orthorhombically, rhombically and tetragonally elongated octahedra) are proposed for Cu2+ in BG1 and BG2 samples, and the former seems most reasonable in view of the best agreement between the theoretical EPR parameters based on the perturbation formulae and the experimental data. As for the VO2+ center, unlike the previous assignment of the tetragonally elongated [VO 5 ]6− cluster based on the simple formulae of EPR parameters, presently proposed tetragonally compressed [VO 6 ]8− cluster and the high order perturbation formulae of the EPR parameters yields good agreement with the observed values. This point is also supported by the d-d optical absorption 2B 1g →2B 2g for tetragonally compressed octahedral 3 d1 systems. • Local structure of amorphous biochar is investigated for Cu2+ and V4+. • Based on the analysis of experimental work, several improved discussions are completed. • High concentration of O in biochar may induce strong distortion along C 4 axis. • Cu2+ and VO2− in BG1 and BG2 form orthorhombically elongated octahedra and tetragonally compressed octahedra, respectively. [ABSTRACT FROM AUTHOR]

The interaction between an adsorbed CO molecule and the unsaturated coordinated Co2+ center in the metal–organic framework (MOF) PCN‐224 is investigated by analyzing the electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) and the adsorption energies at various temperatures. Six‐ and five‐coordinated octahedral models (four planar N with two and one axial CO molecules, respectively) are constructed to simulate the local structures of the Co2+ centers at different temperatures. Because of the Jahn–Teller effect of the Co2+ centers, the C2–Co–N4 and C–Co–N4 combinations undergo different tetragonal elongation distortions along the C4 axis, characterized by the relative elongation ΔZ and displacement ΔZ′ of Co2+ at different temperatures. Given the agreement between the calculated and experimental EPR parameters, as well as the adsorption properties, the six‐ and five‐coordinated models are regarded as suitable for low‐ and high‐temperature systems, respectively. These studies may be helpful to understand the properties of similar MOFs with adsorbed molecules under the effect of ambient temperature. [ABSTRACT FROM AUTHOR]

The local angular distortions Δθ are theoretically studied for the various Ni3+ centers in LiAlyCo1-yO2 at different Al concentrations (y = 0, 0.1, 0.5, and 0.8) based on the perturbation calculations of electron paramagnetic resonance g factors for a trigonally distorted octahedral 3d7 cluster with low spin (S = 1/2). Due to the Jahn-Teller effect, the [NiO6]9- clusters are found to experience the local angular distortions (Δθ ≈ 5°-9°) along the C3 axis. The variation trend of Δθ with y is in accordance with that of anisotropy (Δg = g|| - g⊥). As the substitutions can weaken bond strengths between transition metal and oxygen and the structural stability plays an important role in cathode performances, detailed investigations on the structural properties of the cathode materials LiAlyCo1-yO2 can be practically helpful to understand the performances of these materials. The oxy-redox properties of LiAlyCo1-yO2 systems are comprehensible in the framework of Ni3+/Ni4+ couples, and the trigonally compressed octahedral [NiO6]9- clusters are applicable to the clarification of the electrochemical properties of lithium nickel oxide batteries. It appears that LiAl0.8Co0.2O2 with the largest Al concentration may correspond to the smallest distortion among the mixing systems. [ABSTRACT FROM AUTHOR]

This work presents a systematic density functional theory (DFT) study for geometrical and electronic structures, g factors and UV–vis spectra of three Cu(II) coordination polymers (CPs) [Cu(XL)(NO 3 ) 2 ] n (1), {[Cu(XL)(4,4′-bpy)(NO 3 ) 2 ]∙CH 3 CN} n (2) and {[Cu(XL) 3 ](NO 3 ) 2 ·3.5H 2 O} n (3) based on the ligand N,N′-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole) (XL) with the linker triazole coordinated with copper to construct the CPs. For three CPs with distinct ligands, the optimized molecular structures with PBE0 hybrid functional and the 6-311g basis set agree well with the corresponding XRD data. Meanwhile, the electronic properties are also analyzed for all the systems. The calculated g factors are found sensitive to the (Hartree-Fock) HF character due to the significant hybridization between copper and ligand orbitals. The calculated UV–visible spectra reveal that the main electronic transitions for CP 1 contain d-d and CT transitions, while those for CPs 2 and 3 largely belong to CT ones. The present CPs seem difficult to adsorb small molecules, e.g., CP 1 with H 2 O and NO 2 exhibit unfavorable adsorption and deformation structures near the Cu 2+ site. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance parameters and local structures for V 4 + in xV 2 O 5 -(100 − x)[0.8NaPO 3 -0.2ZnO] glasses are theoretically investigated by using the perturbation formulas for tetragonally compressed octahedral 3d 1 clusters. Polynomial, custom and power law functions are applied to describe the concentration variations of covalency factor N , relatively tetragonal compression ratio ρ, core polarization constant κ and reduction factor H . The concentration dependences of the measured electron paramagnetic resonance parameters are suitably reproduced, and the PL functions are found to be the optimal with the lowest mean absolute percentage deviation from the experimental data. The [VO 6 ] 8 − clusters exhibit moderately decreasing N , rapidly increasing ρ, slightly decreasing κ and moderately increasing H with x. The calculated decreasing local optical basicity Λ loc also supports the declining trend of covalency factor. The theoretical study of the microscopic mechanisms for the concentration dependences of the relevant quantities are discussed in view of the impurity local behaviors with x due to mixed alkali effect. [ABSTRACT FROM AUTHOR]

The defect structures for Co 2+ in ZnO microwires, thin films and bulks are theoretically investigated by analyzing the electron paramagnetic resonance (EPR) parameters (zero-field splitting D, g factors g // and g ⊥ and hyperfine structure constants A // and A ⊥ ) for trigonally distorted tetrahedral 3d 7 clusters in a consistent way. The impurities Co 2+ are found to suffer the displacements (≈0.046, 0.044 and 0.045 Å) away from the ligand triangles along the C 3 axis in ZnO microwires, thin films and bulks, respectively, which considerably reduce the trigonal distortions of the Zn 2+ sites in the hosts. Apart from the contributions from the conventional crystal-field (CF) mechanism, those from the charge-transfer (CT) mechanism are important and should be included in the EPR analysis. The defect structures and spectral properties of the three ZnO:Co 2+ systems are discussed. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR)gfactors and local structures for Ni3+in LiAlyCo1–yO2as the cathode materials for lithium-ion batteries are theoretically investigated at various Al concentrationsy(= 0.1, 0.5, 0.8 and 1.0). The [NiO6]9–clusters are subject to the tetragonal elongation distortions along theC4axis owing to the Jahn–Teller effect and the different degrees of distortions are characterised by the slightly increasing relative elongation ratioρ(and also crystal-field strength and covalency) withy. In pure LiAlO2(y = 1.0), the [NiO6]9–cluster exhibits the largestρ(≈1.4%) and an additional relative variation ratioτ(≈1.4%) of the planar bond lengths, responsible for the perpendicularganisotropyδg= (gx–gy). The number of impurity Ni3+centres increases from one aty = 0 and 1.0 to two aty = 0.1 and 0.8 and reaches the maximum four aty = 0.5, in accordance with the increasing degree of disorder of the systems. The distinct impurity centres for the sameymay be accompanied by the comparable energies of the ground and near excited states, similar to ‘resonant states’ with slightly different local elongation distortions and tetragonal level splittings. The present studies will be helpful to understand the relationships between local structures and performances of LiAlyCo1–yO2type cathode materials. [ABSTRACT FROM PUBLISHER]

The electron paramagnetic resonance parameters (EPR) and local structure properties of the Cu2+ center in xCaF 2 –20TeO 2 -(79-x)Na 2 B 4 O 7 -CuO glasses are theoretically studied based on the high-order perturbation formulae of a 3d9 ion in a tetragonally elongated octahedron. Determined from the best fitted piecewise linear function (the reverse point at 40 mol%), the corresponding overall varying tendencies and fluctuations of local distortions, EPR parameters and optical properties are reproduced, which can be ascribed to the generated non-bridging oxygen's. The microscopic mechanisms of the above concentration dependences for these quantities are illustrated from the transformation of BO 3 and TeO 3 units. Meanwhile, the electronic properties are obtained through the covalence parameters N and the decrease optical basicity, which both mean the decreasing covalency of the whole glass systems and strong ionicity around Cu2+. [ABSTRACT FROM AUTHOR]

The local distortions and electron paramagnetic resonance (EPR) parameters for Cu 2+ in 40MgO–(10−x)PbF 2 –50SiO 2 –xCuO (MPSC) glasses are theoretically studied at various impurity CuO concentrations x (= 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 mol %) in a consistent way. Due to the Jahn-Teller effect, the [CuO 6 ] 10− clusters are found to experience the moderate tetragonal elongation distortions (characterized by the moderate relative tetragonal elongation ratios ρ ≈ 3%) along C 4 axis. With only five adjusted coefficients a 1 , a 2 , b 1 , b 2 and ω , the relevant model parameters ( Dq , k , ρ, κ and H ) are described by the Fourier type functions, which suitably reproduce the corresponding overall varying tendencies and fluctuations of the measured d–d transition bands and EPR parameters with x. The microscopic mechanisms of the varying rules of the relevant quantities with x are discussed in view of the whole decreasing ability of Si 4+ to accept electrons and the reverse tendencies due to partial Cu 2+ reduced to Cu + at x ≥ 0.7 mol %. The monotonically increasing tendency of the calculated optical basicity reveals decreasing covalency of the whole glass systems with x. [ABSTRACT FROM AUTHOR]

4d 1 (Mo 5+ ) and 5d 1 (W 5+ ) impurities doped into nonlinear optical crystals KTiOPO 4 (KTP) can occupy the inequivalent Ti1 and Ti2 sites and exhibit orthorhombically compressed octahedral n d 1 ( n = 4, 5) centres arising from the Jahn–Teller effect. Closely relevant to the electronic levels as well as optical and magnetic properties of these materials, the above local distortions can be suitably reflected by the anisotropic electron paramagnetic resonance (EPR) signals with the paramagnetic n d 1 probes. This work stresses on the theoretical studies of the EPR parameters ( g factors g x , g y , g z and hyperfine structure constants A x , A y , A z ) and local distortions for the above n d 1 impurity centres in a consistent way. The local distortions are characterised by the relative axial compression ratios ρ (≈0.040, 0.032 and 0.031) and the relative planar bond length variation ratios τ (≈0.030, 0.015 and 0.012) for Mo 5+ centre I and W 5+ centres II and III, respectively, which are larger than those of host Ti1 and Ti2 sites. [ABSTRACT FROM AUTHOR]

The defect structures and spin Hamiltonian parameters (SHPs) for three Rh 2+ centres (denoted C 1 in KTiOAsO 4 and C 2 and C 3 in KTiOPO 4 ) are theoretically investigated by utilising the perturbation formulae for a 4d 7 ion under orthorhombically (D 2 h ) elongated octahedra. The defect structures are characterized by the axial elongation ratios of 4.91%, 4.93% and 4.90% along the Z axis and the planar bond length variation ratios of 0.05%, 0.01% and 0.04% for centres C 1 , C 2 and C 3 , respectively, owing to the Jahn–Teller effect. The nearly identical moderate axial elongation ratios and the slightly different tiny planar bond length variation ratios may suitably account for the comparable moderate axial g anisotropies ∆ g (≈0.6087, 0.6124 and 0.6067) and the slightly dissimilar tiny perpendicular g anisotropies δ g (≈0.0649, 0.0097 and 0.0509) of the three centres, respectively. All centres demonstrate similar strong crystal-field interactions and moderate covalence arising from the comparable short impurity-ligand distances. [ABSTRACT FROM AUTHOR]

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (gfactors, hyperfine structure constants and zero-field splittings) for Cu2+, Mn2+and Fe3+in ZnWO4are theoretically studied based on the perturbation calculations for rhombically elongated octahedral 3d9and 3d5complexes. The impurity centres on Zn2+sites undergo the local elongations of 0.01, 0.002 and 0.013 Å along the C2axis and the planar bond angle variations of 8.1°, 8.0° and 8.6° for Cu2+, Mn2+and Fe3+, respectively, due to the Jahn–Teller effect and size and charge mismatch. In contrast to the host Zn2+site with obvious axial elongation (∼0.31 Å) and perpendicular (angular) rhombic distortion, all the impurity centres demonstrate more regular octahedral due to the above local lattice distortions. The copper centre exhibits significant Jahn–Teller reductions for the spin-orbit coupling and orbital angular momentum interactions, characterised by the Jahn–Teller reduction factorJ(≈0.29 ≪ 1). The calculated EPR parameters agree well with the experimental results. The local structures of the impurity centres are analysed in view of the corresponding lattice distortions. [ABSTRACT FROM AUTHOR]

The defect structure and the spin Hamiltonian parameters ( g factors g || , g ⊥ , the hyperfine structure constants A || and A ⊥ of Cu 2+ and the superhyperfine parameters A || ′ and A ⊥ ′ of Ga 3+ ) for LaSrGa 0.995 Cu 0.005 O 4 crystal are systematically investigated on the basis of the perturbation calculations for these quantities of a tetragonally elongated octahedral 3d 9 complex. Arising from the Jahn–Teller effect, the impurity Cu 2+ center indicates the slightly larger relative tetragonal elongation ratio (≈4.0(1)%) than that (≈3.40(4)%) of the host Ga 3+ site. The computed values of the spin Hamiltonian parameters agree well with the measured results. To the best of our knowledge, the superhyperfine parameters of Ga 3+ are theoretically studied for the first time. The unusual superhyperfine anisotropy ( A || ′< A ⊥ ′) for the present Ga 3+ ligand with respect to the conventional rule ( A || ′> A ⊥ ′) for the common anion ligands is ascribed to the opposite signs of the anisotropic terms for the [CuGa 4 ] 14+ cluster. The present studies reveal significant Cu 2+ –O 2− orbital hybridization and local tetragonal elongation around Cu 2+ , reflecting, to a certain extent, similar behaviors of the CuO 2 planes in oxide cuprates high T c superconductors. [ABSTRACT FROM AUTHOR]

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (anisotropic g factors and the hyperfine structure constants) for the two Pt centers in ZnWO are theoretically investigated by utilizing the perturbation formulas of these parameters for a 5 d ion under rhombically elongated and compressed octahedra. The elongated (and compressed) centers are ascribed to the [PtO] clusters on Zn site suffering the axial elongation of 0.01 Å (and compression of 0.02 Å) along Z axis and the planar bond angle variations of 7.4° (and 7.8°), respectively, due to the Jahn-Teller effect. The above local lattice deformations may considerably cancel the original large axial elongation (~0.31 Å) and perpendicular rhombic angular distortion of the host [ZnO] cluster and yield more regular [PtO] clusters in the impurity centers. The calculated EPR parameters based on the above lattice deformations show good agreement with the experimental data, and the local structures of the impurity centers are discussed. [ABSTRACT FROM AUTHOR]

By establishing the perturbation formulas of the spin Hamiltonian parameters (anisotropic g factors and hyperfine structure constants) for a rhombically compressed 4d7 cluster, the EPR spectra and local structure are theoretically investigated for Rh2+:ZnWO4. Due to the Jahn-Teller effect, the impurity center shows slight axial compression of about 0.002 nm along the Z-axis and the perpendicular angular variation of about 6° for the planar impurity-ligand bonds. These lattice deformations transform the significant elongation (by about 0.031 nm) of host Zn2+ site into slight compression in the impurity center. The local distortion of the Jahn-Teller nature is discussed. [ABSTRACT FROM AUTHOR]

The anisotropic g factors and local structure for the rhombic Fe + center in NaF are theoretically studied using the perturbation formulas of the g factors for a rhombically distorted octahedral 3d 7 cluster. The impurity Fe + is found not to occupy exactly the host Na + site in NaF but to experience the off-center displacement of about 0.28 Å along [1 1 0] axis due to size mismatch substitution. The calculated g factors based on the above impurity displacement show reasonable agreement with the experimental data. The local structure of the Fe + center is discussed. [ABSTRACT FROM AUTHOR]

Copper(II) chloride anionic coordination complexes with different imidazole‐derived ligands due to the potential cytotoxic activity play the important role in protein. By investigating the experimental electron paramagnetic resonance (EPR) and ultraviolet–visible (UV–vis) spectra of [CuCl(C6H10N2)4]Cl, [CuCl(C6H10N2)4]Cl, [CuCl2(C4H6N2)4], and [Cu2Cl2(C5H8N2)6]Cl2·2H2O, the local structure of the corresponding Cu2+ centers and the role of different ligands are obtained. Based on the well‐agreed EPR parameters and the d‐d transitions (10Dq), the four Cu2+ centers show tetragonal and orthorhombic distortion, corresponding to the different anisotropies of EPR signals. In addition, the general rules of governing the impact of methanol in imidazolylalkyl derivatives are also discussed, especially the influence on the local environment (symmetry, distortion, covalency, and crystal field) of above four copper(II) chloride anionic coordination complexes. Therefore, the obtained results in this study will be beneficial to provide a theoretical basis for the experimental design of desired copper‐containing imidazolyl alkyl derivatives. [ABSTRACT FROM AUTHOR]

Based on the perturbation formulas of the spin Hamiltonian parameters (i.e., g factors and hyperfine structure constants A), the electron paramagnetic resonance (EPR) spectra (labeled as: signals a, b and c) are comprehensively investigated, from which the local environments of three different doped Ag2+ sites can be obtained and are characterized by coordinated and electronic structures. Meanwhile, the adsorption properties of CO, CO 2 and O 2 , as well as the catalytic behaviors of CO, are simultaneously verified, which are conducted by comparing the adsorption energy ∆ H , the reaction barrier ∆E of pure and the Ag doped CeO 2 surface (111). In addition, the micro-mechanism and role of doped Ag2+ in CeO 2 are explored from the interactions between the central Ag2+ and ligand oxygen ions, which are represented as covalence factor N and partial density of states (PDOS). [Display omitted] • Signals a, b and c for CeO 2 :Ag2+ is calculated by perturbation formulas. • Increase ∆H reflects positive role of doped Ag2+ for adsorbing CO molecule. • Doped Ag2+ reduce the activation energy for the oxidation process of CO. [ABSTRACT FROM AUTHOR]

• Local structure of Ti3+ in CFCYBPT glasses are investigated. • Five coordinated [TiO 5 ]7‒ is more suitable than six coordinated [TiO 6 ]9‒ in view of better fitting results. • Fitting E 2 with the experimental data, inflection point at x (= 0.58 mol%) is acceptable. • The microscopic mechanisms of the variation rules of the relevant quantities are explained related with NBO. • Conventional and local optical basicities are studied to represent local environment of Ti3+ in CFCYBPT glasses. Local structure and g factors for (20-x)CaF 2 -10CaO-5Y 2 O 3 -10B 2 O 3 -55P 2 O 5 : x TiO 2 (x = 0.2, 0.4, 0.6, 0.8 and 1.0 mol%) glasses are theoretically studied by using the perturbation formulae for a tetragonally elongated octahedral 3d1 cluster. Six coordinated [TiO 6 ]9‒ and five coordinated [TiO 5 ]7‒ clusters are evaluated in view of the Jahn-Teller effect and the charge compensation of impurity Ti3+ for host Ti4+. d -d transition bands of E 2 (2B 2g →2A 1g) and E 3 (2B 2g →2B 1g) of the [TiO 5 ]7‒ cluster is obtained with the piecewise linear fitting function of x. The microscopic mechanisms of the varying rules of relevant quantities g // , E 2 and N with x are related with NBO. The role of various TiO 2 concentrations in local structure and optical spectra is also comprehensively studied from the local optical basicity Λ loc , which can represent the local environment and covalency of the Ti3+ center. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters ( g factors g // , g ⊥ , hyperfine structure constants A // , A ⊥ and superhyperfine parameters A z ′ , A x ′ and A y ′ ) and defect structures for Ag 2+ in NaF and CsCdF 3 crystals are theoretically studied using the improved perturbation formulas of these quantities for a 4d 9 ion in a tetragonally elongated octahedron. The contributions from both the crystal-field and charge transfer mechanisms are taken into account, and the relevant model parameters are quantitatively obtained from the cluster approach in a consistent way. The impurity centers are found to undergo the relative tetragonal elongations of about 9.4% and 8.2% for Ag 2+ in NaF and CsCdF 3 , respectively, along the C 4 axis due to the Jahn–Teller effect. By employing the few adjustable parameters, the calculated spin Hamiltonian parameters based on the above uniform formulas and the local tetragonal elongation distortions agree well with the experimental data. Despite dominant ionicity of the hosts, the charge transfer contributions are actually important to the spin Hamiltonian parameters (e.g., about 20% for the g -shifts) due to strong covalency of impurity Ag 2+ . [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters ( g factors and hyperfine structure constants) are theoretically studied for the two interstitial Cu 2+ centers I and II in the ZnO nanocrystals from the perturbation formulas of these parameters for a tetragonally elongated octahedral 3d 9 cluster. The ligand spin–orbit coupling and orbital contributions are involved from the cluster approach in view of moderate covalency. The two Cu 2+ centers demonstrate slight tetragonal elongation distortions (denoted by the relative elongation parameters ρ ≈ 3.4% and 3.2% for centers I and II, respectively) due to the Jahn–Teller effect. The calculated spin Hamiltonian parameters and three optical transition bands are in good agreement with the observed values. The differences in EPR and optical spectra for both centers can be ascribed to the weaker covalency (higher N ), stronger tetragonal elongation distortion (larger ρ ) and slightly larger core polarization constant κ as well as almost identical crystal-fields (nearly the same Dq ) for center I as compared to center II. The above delicate discrepancies in spectroscopic behaviors may be attributed to the tiny differences in local structures and electronic states for Cu 2+ at dissimilar parts of the ZnO nanocrystals. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters (zero-field splittingD,gfactors and hyperfine structure constants) are theoretically studied for Mn2+in the ZnS nanocrystals and bulks from the perturbation formulae of these quantities for trigonal and cubic tetrahedral 3d5clusters, respectively. The trigonal Mn2+centre in the ZnS nanocrystals is attributed to the impurity–ligand bond angle related to the C3axis about 0.39° larger than that (≈109.47°) of an ideal tetrahedron. Almost the samegfactors and hyperfine structure constants for the nanocrystals and bulks can be ascribed to similar crystal-field environments (i.e. comparable cubic field parametersDq), nearly the same covalency (i.e. the equal covalency factorsN) and the Mn2+3d–3s orbital admixture (i.e. the identical core polarisation constants κ) in both systems. The ligand orbital and spin–orbit coupling contributions are found to be important and should be included in the electron paramagnetic resonance analysis in view of significant covalency. [ABSTRACT FROM AUTHOR]

• High order perturbation method is applied to study experimental EPR spectra. • Local environment and stability of glasses can be modified by halides. • Halides' electronegativities affect application in optical devices. • Optical basicities Λ th exhibit increase acidity and support above results. Local structure and the effect of halide on MX∙M 2 O∙B 2 O 3 (M = Pb, Ba; X = F, Cl, Br) glasses doped with Cu2+ and VO2+ are investigated by means of the perturbation calculations of the spin Hamiltonian parameters (SHPs). Based on the fitted EPR results, [CuO 6 ]10− and [VO 6 ]8− clusters prefer to suffer the tetragonal elongation and compression distortions, respectively. Compare the ionic radius of Cu2+ with V4+ and Pb2+ with Ba2+ in MX∙M 2 O∙B 2 O 3 , the glasses with larger ionic radius of metal may induce larger tetragonal distortions and larger g anisotropies. The d-d transition bands show whole opposite trends for 3d9 and 3d1 impurities with the similar fluctuations due to the increase of non-bridging oxygen. The d-d transition bands and g factorsare are also analyzed from the electronegativities of incorporated halides. The values of basicities Λ th of BCBBV are found larger than PCPBC and PbX-PbO-B 2 O 3 glasses due to stronger ionicity of Ba than Pb. [ABSTRACT FROM AUTHOR]

The EPR g factors for the oxygenated and nonoxygenated BaCuO 2+ x are theoretically studied from the perturbation formulas of the g factors for an orthorhombically elongated octahedral 3d 9 complex based on the cluster approach. The relative axial elongation ratios (≈1% and 0.6%) along c axis and the relative planar bond length variations (≈6.9% and 8.9%) are found for the oxygenated and nonoxygenated systems, respectively. The above local orthorhombic distortions of the Jahn–Teller nature around Cu 2+ can suitably account for the axial and perpendicular anisotropies of the observed g factors. The present studies can be useful to understand the influences of this parasitic phase BaCuO 2+ x on the EPR behaviours and superconductivity of the R 123 high T c superconductors. [ABSTRACT FROM AUTHOR]

A comprehensively theoretical study of structural properties and thermostability is performed to investigate the role of ligands in Metal Organic Frameworks (MOFs). By fitting the experimental EPR spectra, the high order perturbation formulae of a 3 d9 ion in four Cu-MOFs with ligands btm, bte, btp and btb are adopted for orthorhombically and tetragonally elongated octahedral [CuO 2 N 4 ]12− groups so as to reveal the local environment around central Cu2+, including the detail structure information and local electromagnetic properties. Since the application of MOFs are normally limited by the unsatisfied thermostability, the molecule dynamic (MD) calculation based on density functional theory (DFT) is performed to clarify the influence on the stability of MOFs from the different ligands. Based on the above investigations, the mechanism of ligands substitution in MOFs can be comprehensively understood, which would be useful for designing and synthesizing novel MOFs. • EPR parameters of different ligans coordinated MOFs are studied. • M 2 (and M 3) and M 1 (and M 4) show orthorhombical and tetragonal elongation. • M 1 is the best one when considering the local environment of Cu2+. • Ligands substitution can modify the structure distortion of the active sites. [ABSTRACT FROM AUTHOR]

• Borate-based glasses with different alkaline earth oxides are studied. • EPR analysis reveal the tetragonally elongated distortion around Cu2+. • High-period alkaline earth oxide composited lead to large distortion. • Alkaline earth oxide sufficiently modify the optical properties of glasses. • Mechanism is discussed by local optical basicity, FTIR spectra and NBO. According to the experimental EPR, optical absorption and FTIR spectra of 10MO-(30‒x) ZnO-60B 2 O 3 -xCuO (M=Mg, Ca, and Sr) glasses, the local structure of Cu2+ center and the role of different alkaline earth oxides (MgO, CaO, SrO) are obtained from high order perturbation formulae. Based on the well fitted spin-Hamiltonian parameters, the clusters [CuO 6 ]10‒ in different alkaline earth oxides glasses all are found to suffer the tetragonally elongated distortion (D 4h) and the different composite ingredients of alkaline earth (M=Mg, Ca, and Sr) can strengthen the distortion. In addition, based on the reasonably calculated spin-Hamiltonian parameters, the paramagnetic susceptibility (χ) of MZBC, CZBC, and SZBC glasses is also calculated. As a remarkable feature of glass, the local optical basicity Λ loc is obtained from the reasonably obtained local environment (e.g., occupation, coordination number, local symmetry, the strength of crystal fields) of 10MO-(30‒x) ZnO-60B 2 O 3 -xCuO glasses. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters (SHPs) (i.e., g factors, hyperfine structure constants and superhyperfine parameters) are theoretically investigated for the irradiation induced Rh 2+ and Rh 0 centres in NH 4 Cl by use of the perturbation calculations. The tetragonally compressed Rh 2+ centre in the form of [RhCl 4 (H 2 O) 2 ] 2 ‾ group originates from interstitial Rh 2+ (reduced from original Rh 3+ of doped RhCl 3 by capturing one electron during gamma irradiation) associated with two adjacent axial NH 4 + cations substituted by two H 2 O molecules due to charge compensation. The orthorhombically compressed Rh 0 centre in the form of [RhCl 4 (H 2 O) 2 ] 4 ‾ group arises from interstitial Rh 0 (reduced from Rh 3+ by capturing three electrons during gamma irradiation) with two adjacent axial NH 4 + replaced by two H 2 O molecules as charge compensators and the planar Rh 0 -Cl‾ bond length variation of about 0.042 Ǻ along [011] and [ 0 1 ¯ 1 ] axes due to the Jahn-Teller effect. The calculated SHPs are in good agreement with the observed values. The EPR spectra and local structures are discussed for both centres. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) parameters and defect structures for Cu 2+ in alkaline earth zinc borate glasses 10RO + 30ZnO + 60B 2 O 3 (RZB, where R = Mg, Ca and Sr) are quantitatively investigated from the consistent analysis of these parameters for a tetragonally elongated octahedral 3d 9 complex. The studied [CuO 6 ] 10− complexes are found to undergo the relative tetragonal elongation ratios of about 5.8%, 4.5% and 8.6% in MgZB, CaZB and SrZB glasses, respectively, due to the Jahn-Teller effect. The increasing tendencies (MgZB < CaZB < SrZB) of g // is attributed to the decreasing (MgZB > CaZB > SrZB) cubic field parameter Dq and increasing orbital reduction factor k , while the increasing magnitudes of hyperfine structure constants are illustrated by the increases of the reduction factor H arising from the tetragonal elongation distortions. The defect structures and the properties of the EPR parameters are discussed. [ABSTRACT FROM AUTHOR]

The improved perturbation formulas of the spin Hamiltonian parameters (zero-field splittingDandgfactors) for a 3d5ion in trigonally distorted tetrahedra are constructed from the cluster approach by including both the crystal-field and charge-transfer contributions. These formulas are applied to the studies of the local structures and the electron paramagnetic resonance (EPR) spectra for Fe3+in CdX (X = S, Se, Te). The impurity Fe3+is found not to occupy exactly the host Cd2+sites but to experience the small outward shifts 0.014 and 0.006 Å away from the ligand triangles along the C3axis in CdS and CdSe, respectively. The charge-transfer contributions to the spin Hamiltonian parameters are important and increase significantly with increasing atomic number of the ligand (i.e., S2−< Se2−< Te2−) arising from the decreases of charge-transfer energy levels and the increases of ligand spin–orbit coupling coefficients. The results are discussed. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters ( g factors and hyperfine structure constants) and local structures are theoretically studied for the tetragonal Cu 2+ centers in the ZnX (X=O and S) nanocrystals from the perturbation formulas of these parameters for a 3d 9 ion in tetragonally distorted tetrahedra. The ligand orbital and spin–orbit coupling contributions are considered in view of strong covalency. Due to the Jahn–Teller effect, the local Cu 2+ ‒X 2− bond angles between the four equivalent impurity-ligand bonds and the four-fold axis are found to be about 2.47° and 1.68° larger than that (≈54.74°) for an ideal tetrahedron. This induces tetragonally compressed [CuX 4 ] 6− clusters on tetrahedral substitutional Zn 2+ sites, different from the assignments (i.e., Cu 2+ on tetragonally elongated octahedral and tetrahedral substitutional sites in the ZnO and ZnS nanocrystals, respectively) in the previous works. The calculated g factors for both systems and the parallel component of the hyperfine structure constants for the ZnS:Cu 2+ nanocrystals based on the above local angular distortions are in good agreement with the observed values. The validity of the present assignments for the local structures of the Cu 2+ centers is analyzed. [ABSTRACT FROM AUTHOR]