Pd₄Br₄Te₃ was prepared from Pd, Te, and PdBr₂ at 700 K. Its structure was determined by single-crystal X-ray diffraction to be triclinic, P, Pearson symbol aP22; a=842.5(2), b=845.0(3), c=864.8(3) pm; α=82.55(3), β=73.36(2), γ=88.80(2)°; Z=2. The Br and Te atoms are arranged according to the motif of cubic closest-packed spheres in which every 15th position is vacant; the Pd atoms occupy 8/15 of the octahedral voids. The symmetry relations with the packing of spheres are derived. Prominent structural units are hollow cuboctahedral [(PdBrTe)₆] units, the Pd atoms are positioned near the centers of the square faces of the Br₆Te₆ cuboctahedra; the cuboctahedra and double-octahedral Pd₂Br₄Te₆ units are connected to strands by sharing triangular Te₃ faces. The strands are condensed by common Br atoms into layered assemblies. Conspicuously close TeTe contacts in the Te₃ triangles indicate attractive TeTe interactions. The valence puzzle is resolved by the formula Pd(+II)₄Br(−I)₄Te(−4/3)₃. Positive TeTe Mulliken orbital populations and the PdK, BrK, and TeL_III XANES spectra of Pd₄Br₄Te₃ referenced to the spectra of PdBr₂, K₂PdBr₆, PdTe, and PdTe₂ are in accord with attractive TeTe interactions. The measured semiconducting and diamagnetic properties are compatible with the derived picture of chemical bonding in Pd₄Br₄Te₃.

Pd₄Br₄Te₃ wurde aus Pd, Te und PdBr₂ bei 700 K hergestellt. Nach der Strukturanalyse mittels Einkristall-Röntgenbeugung kristallisiert es triklin, P, Pearson-Symbol aP22; a=842,5(2), b=845,0(3), c=864,8(3) pm; α=82,55(3), β=73,36(2), γ=88,80(2)°; Z=2. Die Br- und Te-Atome sind nach dem Muster einer kubisch-dichtesten Kugelpackung angeordnet, in der jede 15-te Position unbesetzt ist; die Pd-Atome besetzen 8/15 der Oktaderlücken. Die Symmetriebeziehungen zur Kugelpackung werden hergeleitet. Im Zentrum unbesetzte, kuboktaedrische [(PdBrTe)₆]-Baugruppen sind mit Pd₂Br₄Te₆-Doppeloktaedern über gemeinsame dreieckige Te₃-Flächen zu Strängen verknüpft, die ihrerseits über gemeinsame Br-Atome zu Schichten angeordnet sind. Auffällig kurze TeTe-Kontakte in den Te₃-Dreiecken deuten auf attraktive TeTe-Wechselwirkungen hin. Die zunächst rätselhafte Valenzsituation wird durch die Formulierung Pd(+II)₄Br(−I)₄Te(−4/3)₃ gedeutet. Positive TeTe-Mulliken-Orbital-Populationen und die PdK-, BrK- und TeL_III-XANES-Spektren von Pd₄Br₄Te₃ im Vergleich zu den Spektren von PdBr₂, K₂PdBr₆, PdTe und PdTe₂ bestätigen die attraktiven TeTe-Wechselwirkungen. Die gemessenen halbleitenden und diamagnetischen Eigenschaften von Pd₄Br₄Te₃ passen zu dem abgeleiteten Bindungsmodell.

The crystal structure, its variation within the homogeneity range and some physical properties of the new zinc-rich, partly disordered phase Ir_7+7δZn_97−11δ (0.31≤δ≤0.58) are reported. The structures of three phases with distinct composition were determined by means of single crystal X-ray diffraction. Ir_7+7δZn_97−11δ exhibits a significant homogeneity range, adopts a complex γ-brass related cubic structure (cF403–406), is stable up to 1201(2) K, and transforms sluggishly below 1048(4) K into a phase with 394 atoms in the monoclinic primitive unit cell. It is a diamagnetic, moderate metallic conductor. Six distinguishable clusters consisting of 22–29 atoms comprise the structure. The clusters are situated about the 16 high symmetry points of the cubic F lattice. The structure can be subdivided into two partial structures, one with constant composition IrZn₅ and 192 atoms per unit cell and a second being significantly richer in zinc with variable composition and 211–214 atoms per unit cell. The meandering triply periodic minimal surface of two interpenetrating diamond-like nets separates the compositionally variable from its complementary invariant part. The phase width is coupled with substitutional and positional disorder. A comprehensive analysis of composition-dependent site occupancy factors reveals a linear correlation between the various types of disorder which can be conclusively interpreted in terms of an incoherent intergrowth of distinctive partial structures in variable proportions on a length scale comparable to the size of the approximately 2 nm large unit cell. On the basis of the structural findings we derive the structure chemically meaningful formula Ir_7+7δZn_97−11δ which quantitatively accounts for the interrelation between substitutional and positional disorder and provides a measure for the homogeneity range in structural terms.

The crystal structure of a rational approximant of an unprecedented dodecagonal quasicrystal is reported. The atomic arrangement of the tantalum-rich telluride Ta₉₇Te₆₀ has been determined from 30 458 symmetrically independent X-ray intensities of a crystal twinned by metric merohedry: a=2767.2(2), b=2767.2(2), c=2061.3(2) pm, space group P2₁2₁2₁, Pearson symbol oP628, 1415 variables, R(F)=0.059. A dodecagonal-shaped, vaulted Ta₁₅₁Te₇₄ cluster with maximum symmetry 6mm can be seen as a characteristic motif of the structure. Each cluster measures about 2.5 nm across and consists of nineteen concentrically condensed hexagonal antiprismatic Ta₁₃ clusters which are capped with Te atoms. The Ta₁₅₁Te₇₄ clusters can cover the plane distinctly in different ways, thereby forming a series of phases which are closely related both structurally and compositionally. In Ta₉₇Te₆₀ the buckled clusters decorate the vertices of a square tiling at a 2 nm length scale to result in corrugated lamellae [Te₃₀Ta₄₁Ta₁₅Ta₄₁Te₃₀] each about 1 nm thick. The lamellae are stacked along the c axis, corresponding to the direction of the pseudo-twelvefold axis of symmetry. Symmetry arguments are proposed that the twinning of the structure may be associated with a fine-tuning of weak interlayer Te–Te interactions which are reflected in a minimization of the deviation from the mean distance 〈d_Te–Te〉 and a doubling of the stacking vector c.

Zr₅Te₆ has been synthesized and its structure determined by means of single crystal X-ray diffraction to be trigonal, , Z=3, Pearson symbol hP33, a=1172.8(2) pm, c=707.0(1) pm. Zr₅Te₆ adopts a metal-deficient, vacancy-ordered 3a×3a×1c superstructure of the NiAs type structure. In the Zr atom layers, alternately one and two out of nine Zr atoms are missing. The less densely populated layers (7/9) consist of star-shaped Zr₇ clusters with intracluster contacts of 351.1 pm; the shortest Zr–Zr intercluster distance is 470.5 pm. In the more densely populated Zr atom layers (8/9), three quarters of the Zr atoms are arranged to pairs (326.4 pm). The distinctive distribution of the vacancies affords a topologically uniform fivefold Zr coordination (283.5–302.6 pm) for all three crystallographically inequivalent Te atoms. They are shifted towards the vacancies in the Zr atom layers. The associated corrugation of the Te atom layers is characterized by an amplitude of 28 pm. The Te–Te contacts are ≥368.1 pm. According to extended Hückel calculations, the defects in the Zr atom layers lead to a reduction in overall Zr–Te bonding interactions relative to ZrTe (NiAs). However, through the clustering the total attractive intralayer Zr–Zr interactions increase considerably, thus providing decisive stabilization of the structure. As revealed by thermal analyses, Zr₅Te₆ undergoes a reversible phase transition at 1513±5 K. On the Zr-rich side, Zr₅Te₆ coexists with ZrTe (WC), and, above 1438±5 K with the hitherto unknown ZrTe (MnP). Zr₅Te₆ exhibits temperature independent paramagnetic properties (χ_mol=0.7×10⁻³ cm³ mol⁻¹) that are typical for a metallic conductor. An abrupt increase in the magnitude of the diamagnetic susceptibility below 2.2 K in a weak magnetic field indicates a superconducting transition.

Das niedervalente Zirconiumtellurid Zr₅Te₆ wurde hergestellt. Einer Röntgenstrukturanalyse von einem meroedrisch verzwillingten Kristall zufolge kristallisiert Zr₅Te₆ trigonal in der Raumgruppe , Pearson Symbol hP33, a=1172.8(2) pm, c=707.0(1) pm. Die Struktur entspricht einer metalldefizienten 3a×3a×1c-Überstruktur des NiAs-Typs mit geordneten Leerstellen. In den Zr-Atomschichten fehlen abwechselnd eins und zwei von neun Zr-Atomen. Die weniger dicht belegten Schichten (7/9) enthalten sternförmige Zr₇-Cluster mit Intraclusterkontakten von 351.1 pm. Die kürzesten Interclusterabstände betragen 470.5 pm. In den dichter belegten Schichten sind dreiviertel der Zr-Atome im Abstand von 326.4 pm zu Paaren angeordnet. Die spezifische Verteilung der Leerstellen geht mit einer topologisch einheitlichen, fünffachen Koordination der drei kristallographisch ungleichen Te-Atome einher. Die Veschiebung der Te-Atome in Richtung der Lücken führt zu einer Wellung der Te-Atomschichten mit einer Amplitude von 28 pm und Te–Te-Kontakten ≥368.1 pm. Extended-Hückel-Rechnungen nach bedingen die Defekte in den Zr-Atomschichten verglichen mit ZrTe (NiAs) eine Verminderung heteronuklearer Bindungen, wohingegen die Zr–Zr-Wechselwirkungen innerhalb der Schicht trotz der Unterbesetzung infolge der Clusterung deutlich verstärkt sind, wodurch die Struktur entscheidend stabilisiert wird. Zr₅Te₆ durchläuft bei 1513±5 K eine reversible Phasenumwandlung. Auf der Zr-reichen Seite koexistiert es mit ZrTe (WC) und oberhalb 1438±5 K mit ZrTe (MnP). Zr₅Te₆ zeigt einen für Metalle typischen temperaturunabhängigen Paramagnetismus (χ_mol=0.7×10⁻³ cm³ mol⁻¹). Ein steiler Abfall der diamagnetischen Suszeptibilität unterhalb 2.2 K im schwachen Magnetfeld verweist auf einen Übergang in den supraleitenden Zustand.