Intercalates of Bi2Se3 studied in situ by time-resolved powder X-ray diffraction and neutron diffraction.

Intercalation of lithium and ammonia into the layered semiconductor Bi2Se3 proceeds via a hyperextended (by >60%) ammonia-rich intercalate, to eventually produce a layered compound with lithium amide intercalated between the bismuth selenide layers which offers scope for further chemical manipulation.

A Vacancy-Driven Intermetallic Phase: Rh3Cd5-δ (δ ∼ 0.56).

A nonstoichiometric line phase, Rh3Cd5-δ (δ ∼ 0.56), is found in close vicinity to RhCd and structurally characterized by single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy. The compound crystallizes in the cubic space group Im3m (No. 229) with lattice constant a = 6.3859(9) Å and represents a 2 × 2 × 2 superstructure of RhCd, which accommodates a vacancy concentration of nearly 6% in its crystal structure. The first-principles electronic structure calculation on a hypothetical ordered configuration of Rh3Cd5-δ reveals that Rh-Cd heteroatomic interaction plays a major role in the stability of the compound. A combination of the total energy, formation energy, and crystal orbital Hamilton population calculations on hypothetical model configurations establishes that the compound upholds an optimum vacancy concentration in the Cd2a (Cd1) site for the stability of the phase.

Ultralow Lattice Thermal Conductivity at Room Temperature in Cu4 TiSe4.

Ultralow thermal conductivity draws great attention in a variety of fields of applications such as thermoelectrics and thermal barrier coatings. Herein, the crystal structure and transport properties of Cu4 TiSe4 are reported. Cu4 TiSe4 is a unique example of a non-toxic and low-cost material that exhibits a lattice ultra-low thermal conductivity of 0.19 Wm-1 K-1 at room temperature. The main contribution to the unusually low thermal conductivity is connected with the atomic lattice and its dynamics. This ultralow value of lattice thermal conductivity (kL ) can be attributed to the presence of the localized modes of Cu, which partially hybridize with the Se atoms, which in turn leads to avoidance of crossing of acoustic phonon modes that reach the zone boundary with a reduced frequency. Like a phonon glass electron crystal, Cu4 TiSe4 could also open a route to efficient thermoelectric materials, even, with chalcogenides of relatively high electrical resistivity and a large band gap, provided that their structures offer a sublattice with lightly bound cations.

Structure and stability of γ1-AuZn2.1: a γ-brass-related complex phase in the Au-Zn System.

γ1-AuZn2.1 in the Au-Zn binary system has been synthesized and its structure analyzed by single-crystal X-ray diffraction. It crystallizes in the trigonal space group P31m (No. 157) with ∼227 atoms per unit cell and represents a \surd3a × \surd3a × c superstructure of rhombohedrally distorted γ-Au5-xZn8+y. The structure is largely tetrahedrally closed packed. The formation of γ1-AuZn2.1 can be understood within the framework of a Hume-Rothery stabilization mechanism with a valence electron concentration of 1.68 e/a (valence electrons per atom).

Atomic Ordering of Two Neighboring Transition Metals-Cu and Zn from Binary CuZn to Ternary Cu3ZnSb.

A new ternary compound Cu3ZnSb was synthesized by high temperature solid state synthesis and characterized by single crystal X-ray diffraction and energy dispersive X-ray analysis. The ternary Cu3ZnSb crystallizes in the tetragonal crystal system with the space group P4/ nmm (129), and its unit cell contains 10 atoms which are distributed over 4 independent crystallographic positions. The structure is built up with [Cu3Sb] slabs that correspond to the unit cells of Cu2Sb and planar 44 nets of Zn atoms. The planar nets of Zn atoms are interspersed between two adjacent [Cu3Sb] slabs. The structure can be viewed as alternating units of Cu2Sb and CsCl type ß'-brass (CuZn) structures in the [001]. An unusual atomic ordering of two neighboring transition metals Cu and Zn is observed and is confirmed by first principle calculations. The atomic ordering of Cu and Zn is retained from binary ß'-brass structure (CuZn) to ternary Cu3ZnSb. Total energy calculations confirmed the experimental model of Cu/Zn ordering to be the most stable in the structure of Cu3ZnSb. The calculated density of states (DOS) and crystal orbital Hamiltonian population (COHP) explain the stability and bonding characteristics in the structure of Cu3ZnSb. The implication of the persistent Cu/Zn ordering in ternary phases for materials design is emphasized.

Microporous La-metal-organic framework (MOF) with large surface area.

A microporous La-metal-organic framework (MOF) has been synthesized by the reaction of La(NO3 )3 ⋅6 H2 O with a ligand 4,4',4''-s-triazine-1,3,5-triyltri-p-aminobenzoate (TATAB) featuring three carboxylate groups. Crystal structure analysis confirms the formation of 3D MOF with hexagonal micropores, a Brunauer-Emmett-Teller (BET) surface area of 1074 m(2) g(-1) and high thermal and chemical stability. The CO2 adsorption capacities are 76.8 cm(3) g(-1) at 273 K and 34.6 cm(3) g(-1) at 293 K, a highest measured CO2 uptake for a Ln-MOFs.

AuCd4: a Hume-Rothery Phase with VEC of 1.8 and icosahedral and trigonal-prismatic clusters as building blocks.

The η phase in the Au-Cd binary system has been synthesized, and the structure has been analyzed by single-crystal X-ray diffraction. The compound η-AuCd(4) crystallizes in the hexagonal space group P6(3)/m (No. 176). The unit cell contains ∼273 atoms. The compound AuCd(4) represents a √3a × âˆš3a × c superstructure of the AgMg(4) type. The structure can be well described by icosahedral and trigonal-prismatic clusters. A phase transition to the high-temperature ε phase occurs exothermically at around 578 K. The compound is formed at a sharp valence electron concentration of 1.8 e/a. The compound can be understood within the framework of the Hume-Rothery stabilization mechanism.

Incommensurately modulated δ"-Au(1+x)Cd(2-x) formed by an unquenchable phase transformation from the γ-brass δ'-phase.

The synthesis and structural determination of the compound δ"-Au(1+x)Cd(2-x) (0.07 ≤ x ≤ 0.08) is reported. The structure may be formally derived from that of ξ-CoZn13, but elemental ordering causes an incommensurate modulation as determined by single-crystal X-ray diffraction at room temperature. The compound δ"-Au(3.23)Cd(5.76) crystallizes in the monoclinic super space group C2/m(0ß½)00 with lattice parameters a = 14.790(2) Å, b = 8.251(1) Å, c = 12.744(1) Å, ß = 115.182(9)° and a q-vector q = (0ß½), ß = 0.579b*. The δ"-phase is stable up to 652(1) K.

Au10Mo4Zn89: a fully ordered complex intermetallic compound analyzed by TOPOS.

The compound Au10Mo4Zn89 has been synthesized, and its structure has been analyzed by single-crystal X-ray diffraction. The compound crystallizes in cubic space group F43m (No. 216) with a unit cell that contains 412 atoms. The structure is largely tetrahedrally closely packed, but an octahedral arrangement of atoms is incompatible with tetrahedral close packing. The structure of the ordered Au10Mo4Zn89 compound has been described by using the algorithm of automatic geometric and topological analysis that is implemented in TOPOS as the "Nanoclustering" procedure.

Site preference and ordering induced by Au substitution in the γ-brass related complex Au-Cr-Zn phases.

The crystal chemistry of the ternary Au-Cr-Zn alloy was studied by means of synthesis, single crystal X-ray diffraction, and electron structure calculations. While the compound CrZn(∼17) represents the binary end-point of the homogeneity range, the inclusion of Au proves to be very site specific, and at the limiting composition Au10Cr4Zn89 the structure is completely ordered. The crystallographic site occupancy pattern calculated by the Local Density Approximation (LDA)-Density Functional Theory (DFT) parametrized extended Hückel (eH) Mulliken charge populations in Au10Cr4Zn89 agrees very well with the experimentally found site occupancy pattern.

Trinuclear nickel-lanthanide compounds.

The Schiff base compound 2,2'-{[(2-aminoethyl)imino]bis[2,1-ethanediyl-nitriloethylidyne]}bis-2-hydroxy-benzoic acid (H(4)L) as a proligand was prepared in situ from 3-formylsalicylic acid with tris(2-aminoethyl)amine (tren). The trinuclear 3d-4f metal complexes of this ligand {[Ln{Ni(H(2)L)(tren)}(2)](NO(3))(3)} (Ln = Gd, Dy, Er, Lu) could be obtained as single crystalline material by synthesizing the proligand in the presence of the metal salts [Ni(NO(3))(2)·(H(2)O)(6)] and [Ln(NO(3))(3)·(H(2)O)(m)] (Ln = Gd, Dy, Er, Lu). In the solid state, the complexes adapt a new V shaped structure. Mass spectrometric ion signals related to the trinuclear complexes were detected both in positive and negative ion mode via electrospray ionization mass spectrometry supporting the single crystal X-ray analysis. Hydrogen/deuterium exchange (HDX) experiments in solution support the fragmentation scheme. The magnetic studies on all these compounds suggest the presence of weak antiferromagnetic interactions between neighboring metal centers.

Structural impact of platinum on the incommensurably modulated γ-brass related composite structure Pd15Zn54.

The crystal structure of three incommensurately modulated γ-brass related composite structures in the Pd-Zn-Pt system has been solved from X-ray single crystal diffraction data using a 3 + 1-dimensional super space description. The compounds Pt(x)Pd(15-x)Zn(54) (x ≈ 6, 7, 10) crystallize in orthorhombic superspace group Fmmm(α00)0s0 (F = [(1/2, 1/2, 0, 0); (1/2, 0, 1/2, 0); (0, 1/2, 1/2, 0)] with the following fundamental cell dimensions: a = 4.265(1) Å, b = 9.132(1) Å, c = 12.928(2) Å, q ≈ 0.629a*; a = 4.284(1) Å, b = 9.151(2) Å, c = 12.948(4) Å, q ≈ 0.628a*; and a = 4.288(1) Å, b = 9.140(4) Å, c = 12.926(7) Å, q ≈ 0.627a*. Each structure is built by two sub-lattices-pentagonal antiprismatic columns parallel to [100] and a zigzag chain of Zn atoms running along the center of the column.