Bond Valence Sum Research Articles

Hexa-μ-acetato-chlorido-(μ-N,2-dioxodo-benzene-1-carboximidato)-μ3-oxido-tetra-iron(III)-water (1/1) and hexa-μ-acetato-(μ-N,2-dioxodo-benzene-1-carboximidato)fluorido-μ3-oxido-tri-pyridine-tetra-iron(III)-pyridine-water (1/1/0.24).

The title compounds, [Fe4(C2H3O2)6(C7H4O3)FO(C5H5N)3]·C5H5N·0.24H2O (1-F) and [Fe4(C2H3O2)6(C7H4O3)ClO(C5H5N)3]·H2O (1-Cl) were synthesized using a self-assembly reaction in methanol and pyridine with stoichiometric addition of salicyl-hydroxamic acid (H3shi), acetic acid (HOAc), and the appropriate ferric halide salt. The compounds crystallize as solvates, where 1-F has one pyridine mol-ecule that is disordered about a twofold axis and one water mol-ecule with an occupancy of 0.24 (2); and 1-Cl has one water mol-ecule that is disordered over two sites with occupancies of 0.71 (1) and 0.29 (1). The space groups for each analog differ as 1-F crystallizes in Fdd2 while 1-Cl crystallizes in P21. The difference in packing is due to changes in the inter-molecular inter-actions involving the different halides. The two mol-ecules are mostly isostructural, differing only by the torsion of the pyrine ligands and slight orientation changes in the acetate ligands. All of the iron(III) ions are in six-coordinate octa-hedral ligand field geometries but each one exhibits a unique coordination environment with various numbers of O (four to six) and N (nought to two) atom donors. Bond-valence sums confirm each iron is trivalent. The hydroximate ligand is bound to three iron(III) ions using a fused chelate motif similar to those in metallacrown compounds.

Aluminum to germanium inversion in mullite‐type RAlGeO5: Characterization of a rare phenomenon for R = Y, Sm–Lu

AbstractMullite‐type RMn2O5 (R = Y, rare‐earth element) ceramics are of ongoing research attentions because of their interesting crystal‐chemical, physical, and thermal properties. We report a detailed structural, spectroscopic and thermal analysis of the series of mullite‐type RAlGeO5 (R = Y, Sm‐Lu) phases. Polycrystalline samples are prepared by solid‐state synthesis methods. Each sample is characterized by X‐ray powder diffraction followed by Rietveld refinements, showing that they are isotypic and crystallize in the space group Pbam. The change of the metric parameters is explained in term of the lanthanide contraction effect. A rare inversion of Al/Ge between octahedral and pyramidal sites have been observed for these mullite‐type so called O10 compounds, and the inversion parameter found to be between 0.22(1) and 0.30(1) for different R‐cations. The <Al/Ge–O> bond distances and their bond valence sums (BVSs) support the respective inversions. Density functional theory (DFT) calculated phonon density of states (PDOS) and electronic band structures are compared for the vibrational and electronic band gap features respectively. Analysis of UV/Vis absorption spectra using both derivation of absorption spectra fitting (DASF) and Tauc's methods demonstrates that each of the RAlGeO5 O10 compounds is high bandgap semiconductor, possessing direct transition between 4.1(1) and 5.4(1) eV. Both Raman and Fourier transform infrared spectra show clear red shift (quasi‐harmonic) of the vibrational wavenumbers with respect to the ionic radii of the R‐cations. Selective Raman bands at higher wavenumber region further complement the inversion of Al/Ge between two coordination sites. The higher decomposition temperature of the RAlGeO5 compounds, compared to those of RMn2O5 phases, is explained in terms of higher bond strength of Al/Ge‐O than those of Mn‐O. Irrespective to the inversion between Al‐ and Ge‐sites, the decomposition temperature also depends on the type of R‐cation in RAlGeO5.

Behavior of Li-ion on the surface of Ti3C2–T (T = O, S, Se, F, Cl, Br) MXene: Diffusion barrier and conductive pathways

After obtaining Ti3C2 MXene structures terminated with O, S, Se, F, Cl, and Br, we calculate the energy barrier for Li-ion diffusion on the surface of each MXene, being the first to report on the Li-ion diffusivity in Cl and Br terminated Ti3C2. We find that the Ti3C2Cl2 MXene has the lowest diffusion barrier, substituting the Ti3C2S2 reported in the literature so far. In addition, a study on the adsorption energies indicates that the top binding position is the most stable adsorption position for the Li-ion. Furthermore, it is shown that the adsorption energy depends on the electronegativity of the termination atoms, as well as the distance between the terminations, the Li, and the surface Ti-atoms. Finally, we show that the bond valence sum method provides an indication of the transition state of the Li-ion and can serve as a comparison tool for the diffusion barriers of different structures.

Accelerated Design of Battery Materials Interfaces by Embedded‐Atom‐Inspired Bond Valence Sum Forcefields

To achieve higher energy density in safer energy storage systems, a transition to ceramic all‐solid‐state batteries is widely expected. Their performance and cycle‐life is largely controlled by processes at buried interfaces. While experimental operando probing of interfacial processes is under development, first‐principle computational methods are challenged by the complexity of the multiphase models and long simulation periods required to capture slow degradation processes. Thus, simpler empirical reactive forcefields have the potential to substantially accelerate the design and optimization of all‐solid‐state batteries, provided that parameters are available for a wide range of relevant atom types. The energy‐scaled bond valence‐based softBV forcefield has successfully enabled the design of new solid electrolytes or insertion‐type electrode materials and analyses of ion transport processes therein. As a two‐body forcefield, it enables fast simulations for complex structures over long periods, but inevitably shares the tendency of two‐body forcefields to maximize coordination numbers if free volume facilitates a reorganization of the atoms, which makes them less suitable for studying interfacial processes. Herein, this vulnerability of two‐body forcefields is overcome in a computationally efficient way by introducing an embedded‐atom‐method‐inspired bond‐valence‐sum‐based new class of transferable forcefields and its effective use for modeling of surfaces and interfaces is demonstrated.

Structure Elucidation of Complex Endotaxially Intergrown Lanthanum Barium Oxonitridosilicate Oxides by Combination of Microfocused Synchrotron Radiation and Transmission Electron Microscopy.

Single‐crystalline domains in intergrown microcrystalline material of the new compounds Ba22.5+x La55−x [Si129N240−x O x ]O3:Ce3+ and Ba25.5+x La77−x [Si170N312−x O9+x ]O4:Ce3+ were identified by transmission electron microscopy (TEM). Precise diffraction data from these domains were collected with microfocused synchrotron radiation so that crystal structure elucidation of the complex disordered networks became possible. They are composed of two different interconnected slabs of which one is similar in both compounds, which explains their notorious intergrowth. The distribution of Ba and La is indicated by the analysis of bond‐valence sums and by comparison with isostructural Sr28.5+x La75−x [Si170N312−x O9+x ]O4. Ce3+ doping leads to yellow luminescence. This is a showcase that highlights the discovery and accurate characterization of new compounds relevant for luminescence applications from heterogeneous microcrystalline samples by exploiting the capability of the combination of TEM and diffraction using the latest focusing techniques for synchrotron radiation.

Site-Selective Oxygen Vacancy Formation Derived from the Characteristic Crystal Structures of Sn–Nb Complex Oxides

Divalent tin oxides have attracted considerable attention as novel p-type oxide semiconductors, which are essential for realizing future oxide electronic devices. Recently, p-type Sn2Nb2O7 and SnNb2O6 were developed; however, an enhanced hole mobility by reducing defect concentrations is required for practical use. In this work, we investigated the correlation between the formation of oxygen vacancy (VO··), which may reduce the hole-generation efficiency and hole mobility, and the crystal structure in Sn–Nb complex oxides. Extended X-ray absorption fine structure spectroscopy and a Rietveld analysis of X-ray diffraction data revealed the preferential formation of VO·· at the O site bonded to the Sn ions in both the tin niobates. Moreover, a larger amount of VO·· around the Sn ions was found in the p-type Sn2Nb2O7 than in the p-type SnNb2O6, indicating the effect of VO·· on the low hole-generation efficiency. To elucidate the dependence of the formation of VO·· on the crystal structure, we evaluated the Sn–O bond strength based on the bond valence sum and Debye temperature. The differences in the bond strengths of the two Sn–Nb complex oxides are correlated through the steric hindrance of Sn2+ with an asymmetric electron density distribution. This suggests the importance of the material design with a focus on the local structure around the Sn ions to prevent the formation of VO·· in p-type Sn2+ oxides.

Self-assembled organic-inorganic hybrids: Synthesis, structural, third-order nonlinear optical properties and Hirshfeld surface analysis of bis(1,2,3,4-tetrahydroisoquinolin-2-ium) hexahalostannate(IV)

Two organic-inorganic hybrids viz., bis(1,2,3,4-tetrahydroisoquinolin-2-ium) hexachlorostannate(IV) (1) and bis(1,2,3,4-tetrahydroisoquinolin-2-ium) hexabromostannate(IV) (2) were synthesized and confirmed by single-crystal X-ray diffraction analysis. The optical properties of the compounds were studied by diffuse reflectance and photoluminescence spectral studies. The thermal behaviour of the compounds was determined by thermo gravimetric (TG) and differential thermal analysis (DTA) concerning the temperature. The significant third-order nonlinear optical response shown by the compounds is disclosed by the Z-scan studies. The surface morphology and the elemental composition of the compounds were studied by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses. Bond valence sum (BVS) calculation confirmed the formal oxidation state of tin to be +4. Check continuous symmetry measure (CSM) calculation on SnX62− (X=Cl, Br) yields a value significantly near to the perfect octahedral geometry of the anions. The intermolecular interactions and their quantity contributions in the crystal packing were studied by Hirshfeld analysis and fingerprint plots.

Mode Crystallography Analysis through the Structural Phase Transition and Magnetic Critical Behavior of the Lacunar Spinel GaMo4Se8.

In the lacunar spinels, with the formula AB4X8, transition-metal ions form tightly bound B4 clusters resulting in exotic physical properties such as the stabilization of Néel-type skyrmion lattices, which hold great promise for energy-efficient switching devices. These properties are governed by the symmetry of these compounds with distortion of the parent noncentrosymmetric F4̅3m space group to the polar R3m, with recent observation of a coexisting Imm2 low-temperature phase. In this study, through powder neutron diffraction, we further confirm that a metastable Imm2 coexists with the R3m phase in GaMo4Se8 and we present its structure. By applying the mode crystallography approach to the distortions together with anisotropic microstrain broadening analysis, we postulate that the formation origin of the minority Imm2 phase stems from the high compressive stress observed in the R3m phase. Bond valence sum analysis also suggests a change in electronic configuration in the transition to Imm2 which could have implications on the electrical properties of the compound. We further establish the nature of the magnetic phase transition using critical exponent analysis obtained from single-crystal magnetization measurements which shows a mixture of tricritical mean-field and 3D Heisenberg behavior [β = 0.22(4), γ = 1.19(1), and δ = 6.42(1)]. Magnetoentropic mapping performed on a single crystal reveals the signature of a positive entropy region near the magnetic phase transition which corresponds to the skyrmion phase field observed in a polycrystalline sample.

Effect of Mo substitution on the structure and electrical properties of Gd2Ru2O7 pyrochlore

Polycrystalline samples of Gd2Ru2-xMoxO7 were prepared by the molten salt method. Rietveld refinement showed that a lattice parameter increases as the Mo content increases. Bond-valence sum model analysis (BVS) shows high stability in the structure. An increase in XPS valence band (VB) intensity at zero eV is observed as the Mo content increases. Theoretical calculations within the local density approximation, considering Hubbard U, reveal that the Gd2Ru2O7 compound is a semiconductor with activation energy (Ea) of 0.089 eV. DOS analysis shows that the main contributions are the Ru4d and O 2p states. Good correspondence is observed between the VB measure and the DOS calculated. Electrical resistivity measurements at low temperatures show that the Gd2Ru2O7 compound is a semiconductor with an Ea of 0.098 eV and decreases with Mo content. We suggest two conduction mechanisms; ionic conduction occurs via oxygen vacancy or interstitial migration and electronic conduction via variable-range hopping.

Antiferromagnetic Order and Spin-Canting Transition in the Corrugated Square Net Compound Cu3(TeO4)(SO4)·H2O.

Strongly correlated electrons in layered perovskite structures have been the birthplace of high-temperature superconductivity, spin liquids, and quantum criticality. Specifically, the cuprate materials with layered structures made of corner-sharing square-planar CuO4 units have been intensely studied due to their Mott insulating ground state, which leads to high-temperature superconductivity upon doping. Identifying new compounds with similar lattice and electronic structures has become a challenge in solid-state chemistry. Here, we report the hydrothermal crystal growth of a new copper tellurite sulfate, Cu3(TeO4)(SO4)·H2O, a promising alternative to layered perovskites. The orthorhombic phase (space group Pnma) is made of corrugated layers of corner-sharing CuO4 square-planar units that are edge-shared with TeO4 units. The layers are linked by slabs of corner-sharing CuO4 and SO4. Using both the bond valence sum analysis and magnetization data, we find purely Cu2+ ions within the layers but a mixed valence of Cu2+/Cu+ between the layers. Cu3(TeO4)(SO4)·H2O undergoes an antiferromagnetic transition at TN = 67 K marked by a peak in the magnetic susceptibility. Upon further cooling, a spin-canting transition occurs at T* = 12 K, evidenced by a kink in the heat capacity. The spin-canting transition is explained on the basis of a J1-J2 model of magnetic interactions, which is consistent with the slightly different in-plane superexchange paths. We present Cu3(TeO4)(SO4)·H2O as a promising platform for the future doping and strain experiments that could tune the Mott insulating ground state into superconducting or spin liquid states.

Addressing the High-Voltage Structural and Electrochemical Instability of Ni-Containing Layered Transition Metal (TM) Oxide Cathodes by "Blocking" the "TM-Migration" Pathway in the Lattice.

"Layered"/"cation-ordered"/O3-type Li-TM-oxides (TM: transition metal) suffer from structural instability due to "TM migration" from the TM layer to the Li layer upon Li removal (viz., "cation disordering"). This phenomenon gets exacerbated upon excessive Li removal, with Ni ions being particularly prone to migration. When used as cathode material in Li-ion batteries, the "TM migration" and associated structural changes cause rapid impedance buildup and capacity fade, thus limiting the cell voltages to ≤4.3 V for stable operation and lowering the usable Li-storage capacity (concomitantly, energy density). Looking closely at the "TM migration" pathway, one realizes that the tetrahedral site (t-site) of the Li layer forms an intermediate site. Accordingly, the present work explores a new idea concerning suppression of "Ni migration" by "blocking" the intermediate crystallographic site (viz., the t-site) with a dopant, which is the most stable at that site. In this regard, density functional theory (DFT)-based simulations indicate that the concerned t-site is energetically the most preferred and stable site for d10 Zn2+. Detailed analysis of crystallographic data (including bond valence sum) obtained with the as-prepared Zn-doped Li-NMC supports the same. Furthermore, the simulations also predict that Zn doping is likely to suppress "Ni migration" upon Li removal. Supporting these predictions, galvanostatic delithiation/lithiation studies with Zn-doped and undoped Li-NMCs demonstrate significantly improved cyclic stability, near-complete suppression of "cation mixing", and negligible buildup of impedance (as well as potential hysteresis) for the former, even upon being subjected to long-term cycling using a high upper cut-off potential of 4.7 V (vs Li/Li+). Accordingly, such subtle tuning of the composition and structure, in the light of electronic configuration of the dopant and specific crystallographic site occupancy, is likely to pave the way toward the development of Ni-containing stable high voltage O3-type Li-TM-oxide cathodes for the next-generation Li-ion batteries.

Structural and Spectroscopic Studies of NaCuCr2(PO4)3: A Noncentrosymmetric Phosphate Belonging to the α-CrPO4-Type Compounds

An electron and joint neutron and X-ray diffraction study of the synthetic copper/chromium phosphate NaCuCr2(PO4)3 (NaCuP) is reported. A noncentrosymmetric Imm2 space group belonging to the well-known α-CrPO4 type is observed contrary to what is reported in NaMCr2(PO4)3 (M = Co and Ni) phosphates. The structural model is validated by bond valence sum analysis and charge-distribution (CHARDI) calculations and supported by complementary infrared and Raman spectroscopy investigations. Both Raman spectroscopy and theoretical study by deformation density approach further suggest the presence of Cu2+ (3d9) and Cr2+ (3d4) Jahn-Teller polaron effects as a key factor to the centro Imma to noncentrosymmetric Imm2 phase change.

Synthesis, structure, and properties of new Dion-Jacobson compounds A’LnNaNb3O10 (A’ = Cs, Rb, H; Ln = Nd, Pr)

A new series of Dion-Jacobson layered perovskite compounds A’LnNaNb3O10 (A’ = Cs, Rb, H; Ln = Nd, Pr) was synthesized for the first time. Phase and chemical purity of compounds were proved using XRD, SEM, and EDX. Compounds RbNdNaNb3O10, RbPrNaNb3O10, CsNdNaNb3O10 and CsPrNaNb3O10 were synthesized using solid-state reaction, whereas HNdNaNb3O10, HPrNaNb3O10 were obtained by ion-exchange reaction. Crystal structures of solid-state reaction products were refined using the Rietveld method. The plausibility of obtained crystal structures was studied using the bond valence sum (BVS) method. The thermal behavior of compounds was established using DTA. Ion-exchange products were found to be metastable hydrates. The presence of the crystallization water was confirmed by DTA and IR spectroscopy. Optical band gap, electronegativity, valence band (EVB), and conduction band (ECB) potentials of obtained compounds were calculated from diffuse reflectance spectroscopy data. A previously proposed correlation between band gap and structural distortions was confirmed.

Novel Dy3+-doped Ge4+-substituted apatite-type phosphors, Ca9La(PO4)5[(Si1-xGexO4)]F2:Dy3+: Synthesis, structure, crystal chemical features, and luminescent properties

The series of novel phosphors Ca9La(PO4)5 [(Si1-xGexO4)]F2:0.15Dy3+ with x = 0, 0.25, 0.50, 0.75 and 1 (CLPS1-xGxF:0.15Dy3+) with apatite-type structure (space group P63/m) has been synthesized. The crystal structure and electronic structure have been studied by powder X-ray diffraction (PXRD) in combination with the atomic-scale density functional theory (DFT) calculations. A combination of Raman, nuclear magnetic resonance (29Si NMR) spectroscopy and the evolution of Dy3+ ions photoluminescent properties was used to characterize the local crystal structure features. Based on the variation of the [SiO4] by [GeO4] tetrahedral substitutions in the apatite-type structure, the difference in the thermal stability and decay curves of CLPS1-xGxF:0.15Dy3+ phosphors were referred to crystal chemical stability of as-prepared compounds, which is also confirmed by the values of polyhedral distortion, bond valence sum (BVS) and DFT calculations. The present study provides new insights the synthetic methodology and fundamental characterizations into the design of new phosphors combined with theoretical methods.

Evidence for Local Structural Distortion and Mixed States of Fe in <i>β</i>-NaFeO<sub>2</sub>: A Bond Valence Sum Analysis

We have analyzed the crystal structure, interatomic distances and bond valence sums in β-phase of sodium ferrite based on neutron diffraction measurement at room temperature. The Rietveld analysis performed using Pna21 space group obtains smaller lattice constants compared to the previous reports. This discrepancy is attributed to the sodium deficiency. We notice that the Na-O bonds are shortened, while Fe-O bonds are elongated. The calculated bond valence sum around the sodium and the iron ions are 1.08 and 2.64, respectively. This indicates the presence of Fe2+-Fe3+ mixed valence state.

Structural Characterization of Cerium‐encapsulated Preyssler‐type Phosphotungstate: Additional Evidence of Ce(III) in the Cavity

AbstractSingle‐crystal X‐ray structure analysis revealed the precise structure of a Ce‐encapsulated Preyssler‐type phosphotungstate which was first synthesized by Pope et al. Antonio et al. reported that encapsulated Ce has a 3+ oxidation state and is redox‐inactive, which is unlike other Ce‐containing phosphotungstates. Therefore, precise structural analysis about Ce position is needed. The encapsulated Ce was located in one of the side cavities, and was coordinated to one H2O molecule. The position of Ce was similar to that of Y3+ and Eu3+ in similar compounds. This result, together with the bond valence sum calculation, provides additional evidence that the oxidation state of the redox‐inactive Ce in the Preyssler‐type compound is 3+.

Structure and Microwave Dielectric Properties of Gillespite-Type ACuSi4O10 (A = Ca, Sr, Ba) Ceramics and Quantitative Prediction of the Q × f Value via Machine Learning.

Structure and dielectric properties of gillespite-type ceramics ACuSi4O10 (A = Ca, Sr, Ba) were investigated by crystal structure refinement, far-infrared reflectivity spectroscopy, and microwave dielectric measurements. A series of (CaxSr1-x)CuSi4O10 (0 < x < 1) ceramics with relative permittivities of 5.70-5.82, Q × f values of 20391-48794 GHz (@ ∼ 13.5 GHz), and τf of -46.3 to -38.9 ppm/°C were synthesized. By Ca2+ substitution for Sr2+ at the A-site, the rigid double-layered copper silicate framework remains stable, resulting in the nearly unchanged relative permittivity, while the [(Ca,Sr)O8] dodecahedron undergoes shrinkage and distortion, which is correlated to the changes in the Q × f and τf values. The normalized bond valence sums indicate that almost all ions are rattling, weakening the bond strengths and enlarging the molecular dielectric polarizability. The fitting of far-infrared reflectivity spectra reveals that the local structure changes suppress the intermediate and low-frequency vibrational modes significantly and improves the contribution from electronic polarization to permittivity. Symmetry breaking of the [(Ca,Sr)O8] dodecahedron conforms to the elevated restoring forces acting on the ions and improves the τf value. The large span in Q × f value may have intricate correlations to local structure changes and defects. Machine learning methods were introduced to explore the decisive structural factors for the Q × f value. A Q × f value prediction model correlated with the A-O2 bond length and the variance of A-O bond lengths was established. The Q × f values of isostructural (BaySr1-y)CuSi4O10 ceramics were predicted and verified by experiments.

Metal-organic hybrids of tin(IV): Synthesis, crystal structure, third-order nonlinear optical properties and Hirshfeld surface analysis of bis(1,2,3,4-tetrahydroquinolinium) hexahalostannate(IV)

The self-assembled organic-inorganic hybrid materials such as bis(1,2,3,4-tetrahydroquinolinium) hexachlorostannate(IV) (1) and bis(1,2,3,4-tetrahydroquinolinium) hexabromostannate(IV) (2) have been synthesized for their huge applications in opto-non-linear devices. The hybrid materials (1) and (2) have been synthesized and their single crystals were grown by slow evaporation of solution technique (SEST) at room temperature. The presence of protonated NH2 group at 3396 cm–1 in both compounds are confirmed by FT-IR spectral analysis. Diffuse reflectance spectral measurements imply that the tunability of band gap is easily achieved by altering the halide ion. TG-DTA analysis reveals the thermal stability of the compounds is up to 205 °C. Bond valence sum (BVS) calculations performed on SnCl62− and SnBr62− anions (1) and (2), prove the formal oxidation state of tin in the compounds as 4+. The closed and open aperture Z-scan studies ascertained the nature of third order nonlinear optical refraction and absorption of the hybrids. The third-order nonlinear optical susceptibilities χ(3) for the two compounds (1) and (2) are found to be 1.57 × 10−7 esu and 1.46 × 10−7 esu respectively. Investigation of the intermolecular interactions and crystal packing using Hirshfeld surface analysis, derived by single-crystal XRD data, reveals the closer contacts associated with strong interactions.

Design, synthesis and physico-chemical studies of a Co(II)/Co(III) mixed-valence complex: An experimental and DFT approach

The bidentate amine, 2-picolylamine [2-(aminomethyl) pyridine: AMP], and concentrated hydrobromic acid have been used to synthesize a CoII/CoIII mixed-valence complex. Single crystals of the new compound were grown by the slow evaporation solution process at room temperature. The title compound crystallizes in the monoclinic system, space group P21/n, with a = 14.624 (5) Å, b = 10.302 (5) Å, c = 23.743(5) Å , β = 95.280(5)° and Z = 4. The crystal structure consists of three crystallographically independent bromide ions, one diprotonated AMP, one half water molecule and two crystallographically independent Cobalt(II) and Cobalt(III) ions: one has an octahedral geometry while the other is tetrahedrally coordinated. The crystal packing diagram reveals interesting non-covalent interactions involving NH···Br, OH···O and OH···Br hydrogen bonds, leading to the generation of 3D supramolecular architecture. The structural data, the BVS (Bond Valence Sum) calculations, the magnetic and the spectroscopic measurements are in agreement with a six-coordinate Cobalt(III) and four-coordinate Cobalt(II) mixed-valence complex. In this work, the experimental and theoretical study on molecular structure and vibrational spectral analysis of the new product has been reported. Theoretical calculations were performed by using density functional theory (DFT) at the B3LYP/LAN2DZ basis set levels. The electronic parameters such as frontier molecular orbitals, electrostatic potential and HOMO-LUMO energy were calculated. NLO and thermodynamic properties were studied. The theoretical values show good agreement with experimental values. Finally, thermal analysis and temperature dependent magnetic susceptibility measurements have been performed.

Synthesis, Single‐Crystal Structure, Dielectric Properties of a New Phosphate K3Bi6.5(PO4)7.5

AbstractNew potassium bismuth phosphate K3Bi6.5(PO4)7.5 has been synthesized by solid‐state reaction and characterized by single‐crystal X‐ray diffraction. This compound crystallizes in the monoclinic system, space group C2, with a = 17.637(8) Å, b = 6.9261(8) Å, c = 22.385(4)Å, β = 104.35(2)°, and Z = 4. The crystal structure model is supported by the two methods; the charge distribution (CHARDI) and bond valence sum (BVS). The crystal structure is made up of BiOn (n = 5, 6, 7, 8) polyhedra and PO4 tetrahedra sharing corners and edges to form a three‐dimensional anionic framework. The bond valence sum energy (BVSE) model of simulation shows that the potassium atoms move along [101] direction with a zigzag pathways form with an empirical activation energy of about 1.56 eV. The dielectric properties are carried out at room temperature and show high permittivity values with low dielectric loss.