Complex Borides RERu4B4 (RE = Ce,Pr, Nd,Sm) – Bonding Peculiarities and Magnetic Properties

The rare earth borides RERu₄B₄ (RE = Ce, Pr, Nd, Sm) were synthesized from the elements by arc‐melting and their crystal structures were studied on the basis of X‐ray powder and single‐crystal diffraction: LuRu₄B₄ type, I4₁/acd, a = 747.47(8), c = 1506.4(3) pm, wR₂ = 0.0579, 362 F² values for CeRu₄B₄, a = 751.3(2), c = 1507.1(5) pm, wR₂ = 0.0724, 471 F² values for PrRu₄B₄, a = 751.0(2), c = 1506.9(6) pm, wR₂ = 0.0598, 384 F² values for NdRu₄B₄, and a = 749.1(1), c = 1506.0(3) pm, wR₂ = 0.0759, 413 F² values for SmRu₄B₄, with 18 variables per refinement. Striking structural motifs of the RERu₄B₄ structures are Ru₄ tetrahedra and B₂ dumbbells with Ru–Ru and B–B distances of 271 and 180 pm in CeRu₄B₄. The intermediate valence of cerium leads to shorter Ce–Ru distances of 292 pm. CeRu₄B₄ behaves like a Pauli paramagnet with a small room temperature susceptibility of 1.5 × 10^–4 emu · mol^–1. Chemical bonding analyses shows substantial Ru–B and B–B bonding within the [Ru₄B₄] substructure.     

(A19N7)[In4]2 (A = Ca,Sr) and (Ca4N)[In2]: Synthesis,Crystal Structures,Physical Properties,and Chemical Bonding

Single phase powders of (A₁₉N₇)[In₄]₂ (A = Ca, Sr) and (Ca₄N)[In₂] were prepared by reaction of melt beads of the metallic components with nitrogen. The crystal structure of (Ca₁₉N₇)[In₄]₂ was refined based on neutron and X‐ray powder diffraction data. The crystal structure of (Sr₁₉N₇)[In₄]₂ was solved from the X‐ray powder pattern. The structure refinements in combination with results from chemical analyses ascertain the compositions. The compounds (A₁₉N₇)[In₄]₂ (A = Ca, Sr) are isotypes of (Ca₁₉N₇)[Ag₄]₂; (Ca₁₉N₇)[In₄]₂ is probably identical to the earlier reported (Ca_18.5N₇)[In₄]₂. The crystal structure of the isotypes (A₁₉N₇)[In₄]₂ (A = Ca, Sr; cubic, , Ca: a = 1471.65(3) pm; Sr: a = 1561.0(1) pm) contains isolated [In₄] tetrahedra embedded in a framework of edge‐ and vertex‐sharing (A₆N) octahedra. Six of these octahedra are condensed by edge‐sharing around one central A²⁺ ion to form “superoctahedra” (A₁₉N₆) which are connected three‐dimensionally via further octahedra by corner‐sharing. The crystal structure of (Ca₄N)[In₂] (tetragonal, I4₁/amd, a = 491.14(4) pm, c = 2907.7(3) pm) consists of alternating layers of perovskite type slabs of vertex‐sharing octahedra (Ca₂Ca_4/2N) and parallel arranged infinite zigzag chains equation/tex2gif-stack-1.gif[In₂]. In the sense of Zintl‐type counting the compounds (A²⁺)₁₉(N^3?)₇[(In^2.125?)₄]₂ present an electron excess, (Ca²⁺)₄(N^3?)[(In^2.5?)₂] is electron deficient. Metallic properties are supported by electrical resistivity and magnetic susceptibility measurements. The analysis of the electronic structures gives evidence for the existence of homoatomic interactions In–In and significant heteroatomic metal–metal interactions Ca–In which favor the deviations of the title compounds from the (8 – N) rule.     

Crystal Structure and Properties of Some Filled and Unfilled Skutterudites: GdFe4P12, SmFe4P12, NdFe4As12, Eu0.54Co4Sb12, Fe0.5Ni0.5P3, CoP3, and NiP3

The new cubic compound Fe_0.5Ni_0.5P₃ (a = 775.29(5) pm) as well as the known compounds CoP₃ and NiP₃ were synthesized from the elemental components using tin as a flux. Their skutterudite (CoAs₃) type structures were refined from single‐crystal X‐ray data. The new compound GdFe₄P₁₂ was prepared by reaction of an alloy Gd_1/3Fe_2/3 with phosphorus in a tin flux. Its cubic “filled” skutterudite (LaFe₄P₁₂ type) structure was refined from single‐crystal X‐ray data: a = 779.49(4) pm, R = 0.019 for 304 structure factors and 11 variable parameters. SmFe₄P₁₂ shows Van Vleck paramagnetism while GdFe₄P₁₂ is a soft ferromagnet with a Curie temperature of T_C = 22(5) K. Both are metallic conductors. The new isotypic polyarsenide NdFe₄As₁₂ (a = 830.9(1) pm) was obtained by reacting NdAs₂ with iron and arsenic in the presence of a NaCl/KCl flux. The new isotypic polyantimonide Eu_0.54(1)Co₄Sb₁₂ (a = 909.41(8) pm) was prepared by reaction of EuSb₂ with cobalt and antimony. Its structure was refined from single‐crystal X‐ray data to a residual of 0.024 (137 F values, 12 variables). A comparison of the Fe–P and P–P bond lengths in the compounds AFe₄P₁₂, where the A atoms (A = Ce, Eu, Gd, Th) have differing valencies, suggests that the Fermi level cuts through Fe–P bonding and P–P antibonding bands.     

Synthesis,Crystal Structure,Magnetic Property,and Electronic Structure of Ba2YbInSe5

A new barium ytterbium indium selenide, Ba₂YbInSe₅, was obtained by conventional high temperature solid state reaction. The compound crystallizes in the noncentrosymmetric space group Cmc2₁ of the orthorhombic system. The structure contains infinite one‐dimensional anionic chains ¹_∞[YbInSe₅]^4–, which are built from YbSe₆ octahedra and InSe₄ tetrahedra and separated by Ba²⁺ cation. The magnetic measurement indicates that the compound is paramagnetic. In addition, the calculated bandgap is 0.29 eV.     

Structure property relationships in the ATi2O4 (A=Na, Ca) family of reduced titanates

Reduced titanates in the ATi₂O₄ (A=Li, Mg) spinel family exhibit a variety of interesting electronic and magnetic properties, most notably superconductivity in the mixed-valence spinel, Li_1+xTi_2−xO₄. The sodium and calcium analogs, NaTi₂O₄ and CaTi₂O₄, each differ in structure, the main features of which are double rutile-type chains composed of edge-sharing TiO₆ octahedra. We report for the first time, the properties and band structures of these two materials. XANES spectroscopy at the Ti K-edge was used to probe the titanium valence. The absorption edge position and the pre-edge spectral features observed in the XANES data confirm the assignment of Ti³⁺ in CaTi₂O₄ and mixed-valence Ti³⁺/Ti⁴⁺ in NaTi₂O₄. Temperature-dependent resistivity and magnetic susceptibility studies are consistent with the classification of both NaTi₂O₄ and CaTi₂O₄ as small band-gap semiconductors, although changes in the high-temperature magnetic susceptibility of CaTi₂O₄ suggest a possible insulator-metal transition near 700 K. Band structure calculations agree with the observed electronic properties of these materials and indicate that while Ti-Ti bonding is of minimal importance in NaTi₂O₄, the titanium atoms in CaTi₂O₄ are weakly dimerized at room temperature.     

Synthesis, electronic transport and magnetic properties of Zr1−xYxNiSn, (x=0-0.25) solid solutions

The crystal structure of the Zr_1−xY_xNiSn half-Heusler solid solutions is synthesized and their crystal structure is determined. Electrical resistivity and thermoelectric Seebeck coefficient are measured in the 80-380 K temperature range, whereas magnetic susceptibility is measured at 290 K. It is established that substitution of Zr host atoms by Y in the ZrNiSn intermetallic semiconductor is equivalent to doping by acceptor impurities. Self-consistent ab initio calculations, based on the full potential local orbital (FPLO) minimum basis method, are performed to investigate the electronic and thermoelectric properties of these alloys. Spin polarized within the framework of the coherent potential approximation (CPA) are included.     

CeAgAs2 — a New Derivative of the HfCuSi2 Type of Structure: Synthesis,Crystal Structure and Magnetic Properties

Single crystals of CeAgAs₂ have been obtained by chemical transport reactions starting from a pre‐reacted powder sample. The crystal structure was solved using X‐ray diffraction (space group Pmca, No. 57, a = 5.7586(4) Å, b = 5.7852(4) Å, c = 21.066(3) Å, Z = 8) and refined to a residual of R(F) = 0.029 for 46 refined parameters and 1020 reflections. The structure of CeAgAs₂ represents a new distorted and ordered variant of the HfCuSi₂ type. The characteristic feature of this structure are infinite cis‐trans chains of As atoms with As—As distances of 2.563(1) Å and 2.601(1) Å. CeAgAs₂ is paramagnetic (μ_eff = 2.37 μ_B, θ = —10.5(2) K), with antiferromagnetic ordering at 5.5(2) K and exhibits a metamagnetic transition starting at 4.6 kOe and T = 1.8 K.     

Preparation,Crystal Structure,and Physical Properties of the Rare-Earth Metal Palladium Silicides LnPdSi (Ln = La,Ce, Pr) and the a-ThSi2 Type Compounds LaPd0.787(2)Si1.213(2) and CePd0.758(5)Si1.242(5)

Darstellung, Kristallstruktur und physikalische Eigenschaften der Seltenerdmetall-Palladium-Silicide LnPdSi (Ln = La, Ce, Pr) und die Verbindungen LaPd_0,787(2)Si_1,213(2) und CePd_0,758(5)Si_1,242(5) mit a-ThSi₂-Struktur Die äquiatomaren Seltenerdmetall-Palladium-Silicide LnPdSi (Ln = La, Ce, Pr) kristallisieren mit einem neuen monoklinen Strukturtyp, welcher aus Einkristall-Röntgen-Diffraktometerdaten von PrPdSi bestimmt worden ist: P2₁/c, a = 1079,1(5) pm, b = 584,1(2) pm, c = 786,7(2) pm, β = 92,00(2)°, Z = 8. Die Palladium- und Siliciumatome bilden ein dreidimensional-unendliches Netzwerk, in dem die Palladiumatome drei Siliciumnachbarn haben, während ein Teil der Siliciumatome vier Palladium- und der andere Teil ein Silicium- und zwei Palladiumnachbarn hat. Die Abstände Pd–Si (zwischen 242,8 und 255,3 pm) und Si–Si (233,0 pm) sind ähnlich wie die entsprechender Zweielektronen-Bindungen. Die Praseodymatome haben zwölf Silicium- und Palladiumnachbarn. Ein Pr–Pr-Abstand ist überraschend kurz mit 347,5 pm. LaPdSi ist ein metallischer Leiter und Pauli-paramagnetisch, während CePdSi und PrPdSi Curie-Weiss-Verhalten zeigen mit magnetischen Momenten, wie sie für Ce⁺³ und Pr⁺³ erwartet werden und ferro- oder ferrimagnetischer Ordnung unterhalb von 7 K. Die Verbindungen LaPd_0,787(2)Si_1,213(2) und CePd_0,758(5)Si_1,242(5) kristallisieren mit α-ThSi₂-Struktur. Ihre Zusammensetzung wurde durch Strukturverfeinerungen aus Einkristall-Diffraktometerdaten bestimmt.     

Synthesis,Crystal Structure Determination and Fe/Rh Site Preference in the New Ternary Boride FeRh6B3

Single crystals of FeRh₆B₃ were synthesized by arc‐melting the elements in a water‐cooled copper crucible under an argon atmosphere. The new silver‐like compound, structurally characterized by single‐crystal X‐ray analysis, crystallizes in the hexagonal Th₇Fe₃ structure type (space group P6₃mc, no. 186, Z = 2; a = 7.4135(6) Å, c = 4.7168(6) Å, R₁ = 0.040, wR₂ = 0.083 for all 376 reflections and 21 parameters). The structure consists of layers of boron‐centered trigonal prisms of rhodium/iron atoms and one‐dimensional strings of face‐sharing octahedral Rh₆ clusters.     

Preparation,Crystal Structure,Physical Properties,and Electronic Band Structure of TlTaS3

TlTaS₃ was prepared by applying a sequence of two melting processes with mixtures of Tl₂S, Ta, and S having different molar metal to sulphur ratios. TlTaS₃ crystallises in space group Pnma with a = 9.228(3)Å, b = 3.5030(6)Å, c = 14.209(3)Å, V = 459.3(2)ų, Z = 4. The structure is closely related to the NH₄CdCl₃‐type. Characteristic features of the structure are chains of edge‐sharing [Ta(+5)S₄S_2/2]₂ double octahedra running along [010]. These columns are linked by Tl⁺ ions. The Tl⁺ ion is surrounded by eight S^2— anions to form a distorted bi‐capped trigonal prism. The Tl⁺ ions are shifted from the centre of the trigonal prism toward one of the rectangular faces. This is discussed in context with other isostructural compounds. TlTaS₃ is a semiconductor. The electronic structure is discussed on the base of band structure calculations performed within the framework of density functional theory.     

Fe/Cr超晶格的电子结构和磁性质

应用密度泛函全势线性缀加平面波(FLAPW)方法研究了Fem/Crn (m=3, 4; n=1, 3, 4)超晶格的电子结构和磁性质. 结果表明, Fe3/Cr1和Fe3/Cr3体系的基态中, Fe层间存在铁磁耦合; 而Fe4/Cr4体系基态中, 存在反铁磁耦合; Cr层的磁矩方向交替变化, 交界面上的Fe和Cr间存在反铁磁耦合.     

Halogenide der Seltenerdmetalle Ln4X5Z. Teil 3: Das Chlorid La4Cl5B4 – Präparation,Struktur und Verwandtschaft zu La4Br5B4, La4I5B4

Rare Earth Halides Ln₄X₅Z. Part 3: The Chloride La₄Cl₅B₄ – Preparation, Structure, and Relation to La₄Br₅B₄, La₄I₅B₄ La₄Cl₅B₄ is synthesized by reaction of LaCl₃, La metal and boron in sealed Ta containers at 1050 °C < T < 1350 °C. It crystallizes in the monoclinic space group C2/m with a = 16.484(3) Å, b = 4.263(1) Å, c = 9.276(2) Å and β = 120.06(3)°. Ce₄Cl₅B₄ is isotypic, a = 16.391(3) Å, b = 4.251(1) Å, c = 9.180(2) Å and β = 120.20(3)°. The La atoms form strings of trans-edge shared La octahedra, and the B atoms inside the strings form B₄-rhomboids, which are condensed to chains via opposite corners. The Cl atoms interconnect the channels according to La₂La_4/2Clⁱ⁻ⁱ_6/2Cl^i−a_2/2Cl^a−i_2/2. The crystal structures of the bromide and the iodide are comparabel, however, the interconnection of the strings is different in the three structure types, as 14 Cl, 13 Br and 12 I atoms surround the La₆ octahedra.     

Crystal Structure and Magnetic Properties of SrNi2–xSb2

The intermetallic phase SrNi_2–xSb₂ was synthesized by arc melting mixtures of the elements and subsequent annealing under argon, and its structure was investigated by means of both powder and single‐crystal X‐ray diffraction methods. It crystallizes with the ThCr₂Si₂ type (tI10, I4/mmm) and has a homogeneity range of x = 0.15(1)–0.28(1), which does not include the exact stoichiometric 1:2:2 composition. The crystal structure of the phase SrNi_2–xSb₂ is built from layers of edge‐sharing Ni_1–xSb₄ tetrahedra, which are separated by Sr atoms along the c direction. Magnetic measurements of SrNi_2–xSb₂ showed no superconductive transition above 1.8 K.     

Tetranuclear Complexes with {M4O4} (M = CoII,NiII) Cubane‐Like Core: Synthesis,Crystal Structure,and Magnetic Properties

Two tetranuclear clusters of formula [M₄L₄(HOMe)₄] {H₂L = (E)‐1‐[(2‐(hydroxymethyl)phenylimino)methyl]naphthalen‐2‐ol} [M = Co ( 1 ), Ni ( 2 )] were hydrothermally synthesized by reaction of M(OAc)₂ · 4H₂O with H₂L and NaOH in MeOH. X‐ray crystal structure analysis revealed that complexes 1 and 2 are isostructural. In the core of the structures, four M^II ions and four oxygen atoms occupied alternate vertices of [M₄O₄] cubane. The magnetic property measurements of 1 and 2 revealed that overall ferromagnetic M^II ··· M^II exchange interactions exist in both complexes.     

Magnetostructural correlations in the antiferromagnetic Co2−x Cux(OH)AsO4 (x=0 and 0.3) phases

The Co_2−xCu_x(OH)AsO₄ (x=0 and 0.3) compounds have been synthesized under mild hydrothermal conditions and characterized by X-ray single-crystal diffraction and spectroscopic data. The hydroxi-arsenate phases crystallize in the Pnnm orthorhombic space group with Z=4 and the unit-cell parameters are a=8.277(2) Å, b=8.559(2) Å, c=6.039(1) Å and a=8.316(1) Å, b=8.523(2) Å, c=6.047(1) Å for x=0 and 0.3, respectively. The crystal structure consists of a three-dimensional framework in which M(1)O₅-trigonal bipyramid dimers and M(2)O₆-octahedral chains (M=Co and Cu) are present. Co₂(OH)AsO₄ shows an anomalous three-dimensional antiferromagnetic ordering influenced by the magnetic field below 21 K within the presence of a ferromagnetic component below the ordering temperature. When Co²⁺ is partially substituted by Cu²⁺ions, Co_1.7Cu_0.3(OH)AsO₄, the ferromagnetic component observed in Co₂(OH)AsO₄ disappears and the antiferromagnetic order is maintained in the entire temperature range. Heat capacity measurements show an unusual magnetic field dependence of the antiferromagnetic transitions. This λ-type anomaly associated to the three-dimensional antiferromagnetic ordering grows with the magnetic field and becomes better defined as observed in the non-substituted phase. These results are attributed to the presence of the unpaired electron in the dx²−y² orbital and the absence of overlap between neighbour ions.     

Structural Properties,Mössbauer Spectra,and Magnetism of Perovskite‐Type Oxides SrFe1–xTixO3–y

Perovskite‐type phases SrFe_1–xTi_xO_3–y with 0.1 ≤ x ≤ 0.7 have been prepared from the oxides, and, in order to reach high oxygen contents and Fe^IV fractions, annealed at oxygen pressures of 60 MPa. The materials were characterised by powder x‐ray and neutron diffraction, ⁵⁷Fe Mössbauer spectroscopy, and magnetic susceptibility measurements. All samples of the series crystallise in a cubic perovskite structure and reveal considerable oxygen deficiency. The Mössbauer parameters suggest that for x = 0.1, where the Fe^IV fraction is about 90%, the itinerant electronic state of SrFeO₃ is essentially retained. In materials with larger x increasing amounts of Ti^IV and Fe^III ions lead to a stronger localisation of the σ* (Fe 3 d – O 2 p) electrons. There is no evidence for a charge disproportionation of Fe^IV in any of the materials. Magnetic susceptibility measurements show a divergence of zero‐field cooled and field‐cooled data below a temperature T_m and deviations from Curie‐Weiss behaviour above T_m. The data are indicative of spin‐glass behaviour due to disorder and competing exchange interactions.     

Synthesis,Crystal Structure,and Properties of the Sodium Molybdate Fluoride Na3MoO4F

The compound Na₃MoO₄F was synthesized by high temperature solution methods. Single‐crystal X‐ray diffraction analysis reveals that Na₃MoO₄F crystallizes in the orthorhombic space group Pnma (No. 62) with lattice constants a = 5.588(2) Å, b = 7.515(3) Å, c = 12.876(5) Å, and Z = 4. The crystal structure consists of isolated MoO₄ groups and [FNa₃]_∞ chains, which are connected by Na–O bonds to form a three‐dimensional framework. A detailed structure comparison between Na₃MoO₄F and NaMoO₃F was carried out. IR spectroscopy and bond valence sum analysis of Na₃MoO₄F indicate that the structure is reasonable. In addition, the electronic structure was investigated by the first‐principles method.     

新型电荷转移复合物(BEDT-TTF)4·H2O·Fe(C2O3)3·C6H5NO2的合成、结构与物理性质

导电性的电荷转移复合物（盐）由于其特殊的物理性质和潜在的应用前景，近年来得到广泛研究［１，２］．导电电荷转移复合物主要包括基于Ｍ（ｄｍｉｔ）２（ｄｍｉｔ＝１，３－二硫－２－硫酮－４，５－二硫醇盐）阴离子自由基［３～５］和ＢＥＤＴ－ＴＴＦ（乙二硫撑四硫...     

Synthesis,crystal structure,and physical properties of a new boride Ga2Ni21B20 with a modified Zn2Ni21B20-type structure

A ternary boride Ga₂Ni₂₁B₂₀, with modified Zn₂Ni₂₁B₂₀-type structure (space group I4/mmm, and lattice parameters a = 7.2164(1) Å, c = 14.2715(4) Å), was synthesized from the constituent elements. Single crystal diffraction data reveal Ni at 8f site splitting into 16m position with nearly half occupancy. In this structure, [Ni₆B₂₀] cages share ligand boron atoms with [Ga₂B₄Ni₉] hexa-capped square prisms, forming two dimensional layers. Layers are interconnected via Ga−Ni interactions and build up a three-dimensional framework. Quasi-two-dimensional infinite planar nets formed by intercrossed Ni atoms are embedded. Ga₂Ni₂₁B₂₀ is a metallic Pauli paramagnet, in agreement with electronic structure calculations, resulting in 8.2 states eV⁻¹ f.u⁻¹ at the Fermi level.     

Synthesis,Crystal Structure,and Magnetic Properties of a New 2D Twofold Interpenetrated Coordination Polymer [Cu(3,4‐pybz)2]n

A new coordination polymer, [Cu(3, 4‐pybz)₂]_n ( 1 ) [3,4‐Hpybz = 3‐pyridin‐4‐yl‐benzoic acid], was synthesized by hydrothermal reaction of CuCl₂ · 2H₂O and 3,4‐Hpybz, and characterized by elemental analysis, IR spectroscopy, PXRD, and single‐crystal X‐ray diffraction. The structure determination reveals that 1 exhibits a 2D twofold interpenetrated 4‐connected (4,4) network topology, these 2D layers are further enlarged to form the final 3D supramolecular edifice via aromatic π–π stacking interactions. In addition, the magnetic behavior and thermogravimetric analysis of 1 were also studied.