Space Group F4 Research Articles

Material Design and Discovery in Full-Heusler Compounds: A Comprehensive First-Principles Analysis of XMg2Hg, XMgHg2, and X2MgHg (X = Sc, Li)

This study conducts a comprehensive first-principles analysis of the structural, mechanical, phonon dispersion, and electronic properties of XMg2Hg, XMgHg2, and X2MgHg (X = Sc and Li) compounds. Using energy-volume curves, cohesive and formation energy, and phonon dispersion analyses, we confirm the stability of these compounds. Our calculations reveal that Li2MgHg and ScMg2Hg are more stable in the cubic structure with space group F4¯3m (216), whereas other compounds are stable in the Fm3¯m (225) structure. Phonon dispersion calculations indicate dynamical stability for all compounds except Li2MgHg in the Fm3¯m structure and Sc2MgHg and LiMg2Hg in the cubic structure with space group F4¯3m (216). Mechanical stability is confirmed through the calculation of elastic constants, with Sc-based compounds showing higher bulk modulus, shear modulus, and Young's modulus compared to Li-based compounds. Electronic properties, analyzed through density of states and band structure calculations, confirm the metallic nature of these compounds, with significant contributions from Mg atoms at the Fermi energy. The study also identifies distinct electronic features such as flat electron bands and a Dirac point at the Gamma point for ScMgHg2​. Pressure-dependent studies indicate these materials are normal metals without topological phase transitions.

Elucidation of annealing effects on austenite–martensite and magnetic phase transitions in Mn2Ni1.6Sn0.4 ribbons synthesized from bulk alloys prepared by RF induction melting

We investigate the consequences of annealing on the structure, microstructure, magnetic, and electrical transport of Mn2Ni1.6Sn0.4 ribbons. The 40–60 μm thick ribbons were formed by melt spinning of the bulk ingot synthesized by RF induction melting. Ribbons were annealed at 600 °C for 12 hrs and the other at 800 °C for 2 hrs in vacuum. All ribbons crystallize into a cubic symmetry (space group F4¯3m). The orthorhombic phase appears as the secondary one. In ribbons annealed at 600 °C, the crystallite size decreases from ∼ 47 nm to ∼ 29 nm, and annealing at 800 °C doubles the crystallite size to ∼ 96 nm. The least amount of microstrains (17x10−4) in the as-synthesized ribbon is consistent with the occurrence of the superlattice peaks (111) and (200). Lower intensities of the superlattice peaks in 600 °C and 800 °C ribbons are consistent with higher microstrains (25x10−4 and 24x10−4). Hence, a higher degree of Ni-Mn ordering improves magnetic properties in annealed samples. The as-synthesized ribbon has an austenite-phase Curie temperature of TCA∼303K, which enhances to TCA∼320K and TCA∼310K after annealing at 600 °C and 800 °C. The ribbon annealed at 600 °C has the highest saturation moment. All the ribbons show the exchange-bias (EB) effect, and the most pronounced effect is seen in the 800 °C annealed ribbon. Microstructure uniformization and relative strengths of the Ni-Mn and Mn-Mn interactions improve the magnetics. Near TC, MT=M0TC-Tβ is satisfied (β = 0.31, 0.36, and 0.37, for as-synthesized, 600 °C and 800 °C annealed ribbons). The low-temperature spontaneous magnetization obeys the Bloch law MT=M01-AT32, with a deviation in 600 °C annealed ribbon due to spin freezing. The ρ-T has been fitted in the different temperature ranges using the various combinations in ρT=ρ0+AphT+BsdTα. At T < 85 K, the resistivity of the as-synthesized ribbon follows ρT=ρ0+BsdTα, with α≈1.47, while for the 600 °C annealed ribbon, α≈1.49. The exponent α∼1.5 supports the existence of the spin glass state in the lower temperature region of as-synthesized and 600 °C annealed ribbons. In the high-temperature range, the linear ρ-T behavior is described by ρT=ρ0+AphT and consistent with the electron–phonon scattering.

Complex magnetic interactions and critical behavior analysis in quaternary CoFeV0.8Mn0.2Si Heusler alloy

We investigate the magnetic behavior and critical exponents of quaternary CoFeV0.8Mn0.2Si Heusler alloy to understand the interactions across the Curie temperature (TC). The Rietveld refinement of the x-ray diffraction pattern with the space group F4¯3m confirms a single-phase cubic Y-type crystal structure. The magnetic susceptibility χ(T) data show a ferromagnetic nature with a second-order phase transition from paramagnetic to ferromagnetic at 446±1 K. The saturation magnetization at 5 K is found to be 2.2 μB/f.u., which is close to the Slater–Pauling rule and indicates its half-metallic nature. The values of asymptotic critical exponents (β, γ, and δ) and the TC are extracted through detailed analytical analysis including the modified Arrott plot, the Kouvel–Fisher (K–F) method, and the Widom scaling relation. Interestingly, the estimated values of β=0.369 and γ=1.445 closely approximate the theoretical values of the 3D Heisenberg model across the TC and validate the second-order thermodynamic phase transition. The obtained exponents lead to the collapse of renormalized isotherms, represented by the relationship between the magnetization (m) and the applied magnetic field (h), into two distinct branches above and below the TC, which validates the reliability of the analysis. Furthermore, these exponents suggest that the spin interaction follows a decay pattern of J(r)∼r−4.99, indicating a short-range magnetic ordering, akin to the itinerant-electron 3D Heisenberg model.

Crystal structures of the alkali aluminoboracites A 4B4Al3O12Cl (A = Li, Na)

Single crystals of alkali aluminoboracites, A 4B4Al3O12Cl (A = Li, Na), were grown using the self-flux method, and their isotypic cubic crystal structures were determined by single-crystal X-ray diffraction. Na4B4Al3O12Cl is the first reported sodium boracite, and its lattice parameter [13.5904 (1) Å] is the largest among the boracites consisting of a cation–oxygen framework reported so far. For both crystals, structure models refined in the cubic space group F\overline{4}3c, which assume that all cubic octant subcells in the unit cell are equivalent, converged with R1 factors of ∼0.03. However, the presence of weak hhl reflections with odd h and l values indicates that refinements in the space group F23, which presume a checkerboard-like ordering of two types of subcells with slightly different atomic positions, are more appropriate.

Superconductivity in the amorphous phase of the half-Heusler TiNiSn alloy

Amorphous TiNiSn films were prepared at T≈4.2K and resistance R(T) and thermopower S(T) have been investigated. R(T) shows that the sample is superconducting and the transition temperature Tc increases with increasing annealing temperature, being the maximum Tc3=4.19K. The electron–phonon coupling estimated from S(T) results is very close to the value calculated using McMillan equation for the superconducting transition Tc, indicating that amorphous TiNiSn is an intermediate electron–phonon coupled superconductor. After annealing up to T=850K, the amorphous sample crystallizes at TK≈785K. The atomic structure and high stability of the amorphous phase can be explained in the framework of electronically stabilized Hume–Rothery phases, where hybridization from Ti-d and Ni-d electrons plays an important role. The crystallized sample shows a well-ordered half-Heusler crystalline phase, space group F4¯3m, with a TiNiSn atomic order in the unit cell instead of the common NiTiSn type.

CuGa5S8’in Elektronik Davranışı ve Mekaniksel Karakteri

In this theoretical study, it is presented that the electronic behavior and mechanical characteristics of CuGa5S8 compound having face centered cubic structure with space group F4 ̅3m and space number 216. All calculations based on density functional theory (DFT) were performed by Generalized Gradient Approximation (GGA). It is understood from the observed electronic band structure of this system that it has semiconducting behavior close to zero-band gap. Also, the high similarity between spin-up and spin-down states indicates that the magnetic nature of this compound may be paramagnetic. Furthermore, the elastic constants were calculated by the stress-strain method, and then, the mechanical stability of this system was determined. Finally, these constants were used to predict some important mechanical properties of the mentioned system.

High-temperature behavior and structural studies on Ca14Al10Zn6O35

Abstract Single-crystals of Ca14Al10Zn6O35 suitable for structural investigations were grown from slow cooling of a melt with the same chemical composition in the range between 1300 and 1000 °C. Diffraction experiments performed at ambient temperature yielded the following crystallographic data: space group F23, a = 14.8468 (6) Å, V = 3272.6 (2) Å3, Z = 4. Structure determination and subsequent least‐squares refinements resulted in a residual of R(|F|) = 1.49% for 753 independent observed reflections and 55 parameters. The chiral structure is based on a tetrahedral framework of corner sharing (Zn,Al)O4-tetrahedra. Zn–Al-distributions among the four crystallographically independent T-sites have been studied. A detailed topological analysis based on natural tiles is presented. Actually, the net can be constructed from a total of four different cages (tiles). The largest cavities (face symbol: [316. 616]) have volumes of about 680 Å3 and host [AlO6][Ca14O36] heteropolyhedral clusters consisting of a central [AlO6] – octahedron surrounded by [CaO6]- and [CaO7]-groups. The calcium cations provide linkage to the tetrahedral framework, in other words, the [AlO6]-unit in the barycenter of the cluster is not directly connected to the framework. Furthermore, thermal expansion has been studied in the interval between 25 and 790 °C using in-situ high‐temperature single‐crystal diffraction. No indications for a structural phase transition were observed. From the evolution of the lattice parameters the thermal expansion tensor has been obtained. The response of the structure to variable temperature has been discussed.

Structural and optical properties of Fe doped InSb bulk systems

Infrared detectors are of extensive interest due to minimum atmospheric absorption and are mainly developed in the narrow wavelength region (08–12 μm) III-V group compounds. Indium Antimonide (InSb) is a narrow bandgap semiconductor for a vital purpose. We report here the structural and optical studies of the Fe concentration variation in In1-xFexSb (x = 0.00, 0.05, 0.10 and 0.20) bulk systems. Rietveld refinement of the X-ray diffraction pattern for x = 0.00 reveals the single-phase having space group F4¯3m with Face centred cubic structure. The crystallite size observed from the Debye Scherrer formula decreased with the increase in Fe concentration. The optical studies are examined by FTIR absorption spectroscopy. The energy bandgap evaluated for doped samples is 0.14 eV. The doping of Fe in the InSb bulk system reduces the optical energy bandgap.

Structural, Electronic and Magnetic Properties of Mn2Co1-xVxZ (Z = Ga, Al) Heusler Alloys: An Insight from DFT Study

Structural, electronic, and magnetic properties of Mn2Co1-xVxZ (Z = Ga, Al, x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys were theoretically investigated for the case of L21 (space group Fm3¯m), L21b (L21 structure with partial disordering between Co and Mn atoms) and XA (space group F4¯3m) structures. It was found that the XA structure is more stable at low V concentrations, while the L21 structure is energetically favorable at high V concentrations. A transition from L21 to XA ordering occurs near x = 0.5, which qualitatively agrees with the experimental results. Comparison of the energies of the L21b and XA structures leads to the fact that the phase transition between these structures occurs at x = 0.25, which is in excellent agreement with the experimental data. The lattice parameters linearly change as x grows. For the L21 structure, a slight decrease in the lattice constant a was observed, while for the XA structure, an increase in a was found. The experimentally observed nonlinear behavior of the lattice parameters with a change in the V content is most likely a manifestation of the presence of a mixture of phases. Almost complete compensation of the magnetic moment was achieved for the Mn2Co1-xVxZ alloy (Z = Ga, Al) at x = 0.5 for XA ordering. In the case of the L21 ordering, it is necessary to consider a partial disorder of atoms in the Mn and Co sublattices in order to achieve compensation of the magnetic moment.

Tm4IrIn and Lu4PtIn – In4 tetrahedra embedded in RE 22 polyhedra

Abstract The rare earth-rich indides Tm4IrIn and Lu4PtIn were synthesized by reaction of the elements in sealed tantalum ampules in an induction furnace. Tm4IrIn (a = 1340.77(4) pm) and Lu4PtIn (a = 1338.0(1) pm) crystallize with the Gd4RhIn-type structure, space group F 4 ‾ 3 m $F\overline{4}3m$ . The Lu4PtIn structure was refined from single crystal X-ray diffractometer data: wR = 0.0524, 517 F 2 values and 20 variables. The striking crystal chemical motif is the fcc packing of In4 tetrahedra with 318 pm In–In. The Lu4PtIn structure is closely related to the structures of Lu13Ni6In, Lu14Pd3In3 and Lu20Ir5In3 which all show icosahedral indium coordination and different condensation patterns that build up the indium substructure that consists of a dumbbell in Lu14Pd3In3 and a triangle in Lu20Ir5In3. The results of magnetic susceptibility measurements indicate Curie-Weiss paramagnetism for Tm4IrIn (7.76(1) µB per thulium atom) without magnetic ordering down to 2.5 K. Lu4PtIn is Pauli-paramagnetic.

Ba33Zn22Al8O67 with a Framework of ([O(Zn/Al)4]/Ba)(Zn/AlO4)4 Motifs.

Single crystals of a new oxide, Ba33Zn22Al8O67 (melting point = 1452 K), were grown in a melt-solidified sample prepared by heating a compact of a BaCO3, ZnO, and Al2O3 mixed powder in a dry airflow. Ba33Zn22Al8O67 can be handled in dry air, but it decomposes into carbonates, hydroxides, and hydrates in humid air. Single-crystal X-ray structure analysis clarified that Ba33Zn22Al8O67 crystallizes in a cubic cell (a = 16.3328 (3) Å, space group F23) having a three-dimensional Zn/AlO4 framework in which {([OZn4]/Ba)(Zn/AlO4)4} motifs are connected to each other by bridging Zn/AlO4 tetrahedra. A Ba atom or a [OZn4] cluster is statistically situated at the center of the motif with a probability of 0.5. Motifs of another type, {([O(Zn/Al)4])(Zn/AlO4)4}, are isolated from the Zn/AlO4 framework. These motifs, {([OZn4]/Ba)(Zn/AlO4)4} and {([O(Zn/Al)4])(Zn/AlO4)4}, are alternatingly arranged along the a axis like a checkered cube, and Ba atoms are situated between the motifs. A linear thermal expansion coefficient of 10.4 × 10–6 K–1 was measured in an Ar gas flow at 301–873 K for a sintered Ba33Zn22Al8O67 polycrystalline sample with a relative density of 73%. A relative permittivity of 31 and a temperature coefficient of 15 ppm K–1 at 301 K were obtained for another sintered sample (relative density = 70%) in a dry airflow. The electrical conductivity at 1073 K and the activation energy for conduction at 923–1073 K measured for the sintered samples in dry and wet airflows were 6.2 × 10–7 S cm–1 and 0.65 eV and 2.9 × 10–6 S cm–1 and 0.59 eV, respectively.

Nanobody-aided crystallization of the transcription regulator PaaR2 from Escherichia coli O157:H7.

paaR2-paaA2-parE2 is a three-component toxin-antitoxin module found in prophage CP-993P of Escherichia coli O157:H7. Transcription regulation of this module occurs via the 123-amino-acid regulator PaaR2, which forms a large oligomeric structure. Despite appearing to be well folded, PaaR2 withstands crystallization, as does its N-terminal DNA-binding domain. Native mass spectrometry was used to screen for nanobodies that form a unique complex and stabilize the octameric structure of PaaR2. One such nanobody, Nb33, allowed crystallization of the protein. The resulting crystals belong to space group F432, with unit-cell parameter a = 317 Å, diffract to 4.0 Å resolution and are likely to contain four PaaR2 monomers and four nanobody monomers in the asymmetric unit. Crystals of two truncates containing the N-terminal helix-turn-helix domain also interact with Nb33, and the corresponding co-crystals diffracted to 1.6 and 1.75 Å resolution.

Revisiting the cubic crystal structures of Sr4Nb2O9 and Sr5Nb2O10

We have synthesized polycrystalline and single crystal samples of Sr4Nb2O9 and Sr5Nb2O10 and revisited the crystal structure of the high-temperature cubic phase. By careful analysis of single-crystal X-ray diffraction (SXRD), powder synchrotron X-ray diffraction (Syn-PXRD) and powder neutron diffraction (PND) data, we arrive at a structure model in space group F4¯3m (#216), a subgroup of the reported Fm3¯m (#225) model. The F4¯3m model gives a better fit to the diffraction data, especially the PND data. We observed an interstitial oxide ion (O3) on the 48h site near the typical perovskite 24e site (O1), which gives a Td Nb–O symmetry rather than an Oh one as found in the Fm3¯m model. The temperature-dependent conductivities of Sr4Nb2O9 and Sr5Nb2O10 in dried O2 were studied using impedance spectroscopy. The activation energies of Sr4Nb2O9 and Sr5Nb2O10 were estimated to be 1.18(1) eV and 1.17(4) eV, respectively. This disordered crystallographic arrangement of the O1 and O3 anions is likely a key structural factor behind oxide ionic migration in Sr4Nb2O9 and Sr5Nb2O10.

A partly disordered 2 × 2 × 2 – superstructure of γ-brass related phase in Mn–Ni–Zn system

Abstract The T phase in the Mn–Ni–Zn system was obtained as a product of high-temperature solid-state syntheses from the loaded composition of MnxNi2−xZn11 (x = 0.2–1.5)/MnxNi15.38−xZn84.62 (x = 1.54–11.54). The crystal structure of the T phase has been explored by means of X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The structures were solved in the face-centered cubic space group F 4 ‾ 3 m $F&amp;#x203e;{4}3m$ (216) and contain 409–410 atoms/unit cell. The lattice constants were found to be a = 18.1727(2) and 18.1954(1) Å for crystals C1 and C2, respectively. The crystal structure denoted the T phase is a (2aγ)3-superstructure of the ordinary cubic γ-brass-type phase. The phase is isostructural to (Fe, Ni)Zn6.5. A “cluster” description has been used to visualize the crystal structure of the title phase. The structures have been constructed by the five distinct clusters and they are situated about the high symmetry sites of the face-centered cubic lattice. The T phase is stabilized at a valance electron concentration of 1.78, which is slightly higher than those expected for typical γ-brass Hume‐Rothery compounds.

Crystal electric field effects and heavy-fermion behavior in cubic PrCu2Au3 compound

We report the crystal structure as well as the magnetic, electronic and transport properties of PrCu2Au3 which crystallizes in the MgCu4Sn-type structure with the cubic space group F4¯3m (No. 216). In this structure, the Pr3+ ion sits on a lattice site with the cubic Td symmetry which dictates the crystal electric field (CEF) splitting of the Hund’s 3H4 ground multiplet into four levels. The sample has been investigated by measurements of temperature dependences of specific heat, Cp(T), electrical resistivity, ρ(T), magnetic susceptibility, χ(T), isothermal magnetization, M(B,T), thermal conductivity, κT(T) and thermoelectric power, S(T). χ(T) follows a Curie-Weiss behavior above 100 K with an effective magnetic moment, μeff = 3.3 μB/Pr which is comparable to a calculated value of 3.58 μB/Pr for a free Pr3+ ion and a Weiss temperature, θCW = 15.70 K indicating a dominant ferromagnetic interaction. From the analysis of M(B,T) and the 4f-electron derived specific heat (C4f(T)) results, the CEF ground state is a Γ5 magnetic triplet and the CEF energy scheme is presented. The Sommerfeld coefficient, γ estimated from the low-temperature C4f(T) is 304 mJ/(mol K2) indicating a mass enhancement of the conduction electrons at low temperatures. Further analysis of the heavy fermion properties based on the Sommerfeld-Wilson ratio supports the formation of a heavy fermion state in PrCu2Au3. However, the absence of an enhancement in S/T at low temperatures possibly suggests a weak correlation between the conduction electrons and the 4f-electrons at the Fermi energy. The thermal transport properties suggest that PrCu2Au3 is likely a compensated metal.

Overexpression, Purification, and Preliminary Crystallographic Analysis of the Archaeosine Synthase GAT‐QueC

Archaeosine (G+) is a highly modified nucleosides found exclusively at position‐15 in the dihydrouridine loops (D‐loop) of archaeal tRNAs where it contributes to tRNA structural stability. In a late step in G+ biosynthesis, the precursor nucleoside 7‐cyano‐7‐deazaguanine (preQ0) is inserted into tRNA by the enzyme tRNA‐guanine transglycosylase (arcTGT) before conversion to G+ by archaeosine synthases that vary among archaeal phyla: ArcS in Euryarchaeota, and QueF‐like or GAT‐QueC in Chrenoarchaeota. GAT‐QueC is a two‐domain enzyme harboring an N‐terminal glutamine amidotransferase (GAT) domain, and a C‐terminal domain homologous to QueC, the enzyme that produces preQ0. Consistent with its 2‐domain structure, GAT‐QueC functions in vivo as both a preQ0 synthase and an amidinotransferase, generating G+‐modified tRNA. However, it remains unknown whether the GAT domain acts on preQ0 before or after its insertion into tRNA by arcTGT. Here we describe overexpression, purification and preliminary biochemical and crystallographic characterization of GAT‐QueC from Sulfolobus tokodaii (StGAT‐QueC). Analytical gel filtration chromatography and electrophoretic mobility shift analysis reveal that StGAT‐QueC is a monomeric protein with molecular weight of 55 kDa and no affinity for tRNA, suggesting that the enzyme acts on free preQ0, not preQ0‐modified tRNA. High throughput crystallization of the apoenzyme (and in the presence of preQ0) using the vapor diffusion method yielded crystals that grew in 21 days from solutions containing methyl pentanediol and sodium acetate, and diffracted to 5.8 Å without cryo protection. The crystals belong to cubic space group F23, exhibit unit cell length=292 Å and contain 4 protein molecules per asymmetric unit.Support or Funding InformationNIGMS grant GM110588 and GM132254 to M.A.S., and The California Metabolic Research Foundation (SDSU).

Structural characterization of the Pseudomonas aeruginosa dehydrogenase AtuB involved in citronellol and geraniol catabolism

Pseudomonas aeruginosa can metabolize acyclic monoterpenoids (such as citronellol and geraniol) as the only carbon and energy sources. A total of seven proteins (AtuA, AtuB, AtuCF, AtuD, AtuE, AtuG, AtuH) have been identified in Pseudomonas aeruginosa as participating in the acyclic terpene utilization pathway. AtuB is a dehydrogenase enzyme responsible for citronellol and geraniol catabolism in the acyclic terpene utilization (Atu) pathway, although its structure and function have not been characterized to date. Here we report the crystal structure of AtuB from Pseudomonas aeruginosa PAO1 (PaAtuB) to 1.8 Å resolution. PaAtuB crystallizes in the space group F222 with a single monomer in the asymmetric unit. Analytical ultracentrifugation data shows that PaAtuB forms a stable tetramer in solution, which is consistent with the structure. Structural analysis confirms that AtuB belongs to the short-chain dehydrogenase/reductase (SDR) family. AtuB is predicted to bind NADP(H) from the crystal structure, which is confirmed by MicroScale Thermophoresis analysis that shows PaAtuB binds NADP(H) with a Kd value of 258 μM. This work provides a starting point to explore potential biotechnology and pharmaceutical applications of AtuB.

Combinatorial Tuning of Structural and Optoelectronic Properties in CuxZn1−xS

Summary P-type transparent conductors (TCs) are important enabling materials for optoelectronics and photovoltaics, but their performance still lags behind n-type counterparts. Recently, semiconductor CuxZn1−xS has demonstrated potential as a p-type TC, but it remains unclear how properties vary with composition. Here, we investigate CuxZn1−xS across the entire alloy space (0 ≤ x ≤ 1) using combinatorial sputtering and high-throughput characterization. First, we find a metastable wurtzite alloy at an intermediate composition between cubic endpoint compounds, contrasting with solid solutions or cubic composites (ZnS:CuyS) from the literature. Second, structural transformations correlate with shifts in hole conductivity and absorption; specifically, conductivity increases at the wurtzite phase transformation (x ≈ 0.19). Third, conductivity and optical transparency are optimized within a "TC regime" of 0.10

Counter‐Anion‐Regulated Mixed‐Valency of Cobalt(II/III) Centers in a Metallosupramolecular Framework

A diamagnetic AuI 4 CoIII 2 hexanuclear complex, [Au4 Co2 (dppe)2 (l-nmc)4 ]2+ ([1L -nmc ]2+ ; dppe=1,2-bis(diphenylphosphino)ethane, l-H2 nmc=N-methyl-l-cysteine), was newly synthesized by the reaction of [Co(l-nmc)2 ]- with [Au2 Cl2 (dppe)] and crystallized with different inorganic anions (X=ClO4 - , NO3 - , Cl- , SO4 2- ) to produce ionic solids ([1L -nmc ]Xn ). Single-crystal X-ray analysis revealed that all the solids crystallize in the chiral space group F432 with a face-centered-cubic lattice structure consisting of supramolecular octahedra of complex cations. The paramagnetic nature of all the solids was evidenced by magnetic susceptibility measurements, showing the variation of the oxidation states of two cobalt centers in [1L -nmc ]n+ from CoII 1.00 CoIII 1.00 for X=ClO4 - or NO3 - to CoII 0.67 CoIII 1.33 for X=Cl- , via CoII 0.83 CoIII 1.17 for X=SO4 2- . The difference in the CoII/III mixed-valences was explained by the difference in sizes and charges of counter anions accommodated in lattice interstices with a fixed volume.

Synthesis, electrical transport, magnetic properties and electronic structure of Ti1-xScxCoSb semiconducting solid solution

The effect of Sc doping on the electric transport, magnetic properties and electronic structure of the half-Heusler TiCoSb semiconductor was studied. Samples of the Ti1-xScxCoSb solid solution (0.005 ≤ x ≤ 0.15) were synthesized by arc-melting, annealed at 1070 K and examined by X-ray powder diffraction and scanning electron microscopy with energy-dispersive X-ray analysis. All alloys of the solid solution crystallize in the MgAgAs structure type (space group F4¯3m) and stability range reaches the Ti0.85Sc0.15CoSb composition. Electrical resistivity and Seebeck coefficient were measured in the 80–380 K temperature range. It was found that doping TiCoSb by Sc atoms results in transition from semiconducting behavior to metallic. Increasing of Sc acceptor impurity in the Ti1-xScxCoSb solid solution changes the Seebeck coefficient from negative to positive values. The mechanisms of electrical conductivity of the Ti1-xScxCoSb solid solution were analyzed and compared with the results of the electronic band structure calculations.