The curious case of the structural phase transition in SnSe insights from neutron total scattering.

At elevated temperatures SnSe is reported to undergo a structural transition from the low symmetry orthorhombic GeS-type to a higher symmetry orthorhombic TlI-type. Although increasing symmetry should likewise increase lattice thermal conductivity, many experiments on single crystals and polycrystalline materials indicate that this is not the case. Here we present temperature dependent analysis of time-of-flight (TOF) neutron total scattering data in combination with theoretical modeling to probe the local to long-range evolution of the structure.

Investigation of the monopole magneto-chemical potential in spin ices using capacitive torque magnetometry.

The single-ion anisotropy and magnetic interactions in spin-ice systems give rise to unusual non-collinear spin textures, such as Pauling states and magnetic monopoles. The effective spin correlation strength (J) determines the relative energies of the different spin-ice states. With this work, we display the capability of capacitive torque magnetometry in characterizing the magneto-chemical potential associated with monopole formation.

Metal Halide Scaffolded Assemblies of Organic Molecules with Enhanced Emission and Room Temperature Phosphorescence.

Ionically bonded organic metal halide hybrids have emerged as versatile multicomponent material systems exhibiting unique and useful properties. The unlimited combinations of organic cations and metal halides lead to the tremendous structural diversity of this class of materials, which could unlock many undiscovered properties of both organic cations and metal halides. Here we report the synthesis and characterization of a series benzoquinolinium (BZQ) metal halides with a general formula (BZQ)PbX (X = Cl, Br), in which metal halides form a unique two-dimensional (2D) structure.

Enhanced thermoelectric performance of heavy-fermion compounds Yb Zn ( = Co, Rh, Ir) at low temperatures.

Thermoelectricity allows direct conversion between heat and electricity, providing alternatives for green energy technologies. Despite these advantages, for most materials the energy conversion efficiency is limited by the tendency for the electrical and thermal conductivity to be proportional to each other and the Seebeck coefficient to be small. Here we report counter examples, where the heavy fermion compounds Yb Zn ( = Co, Rh, Ir) exhibit enhanced thermoelectric performance including a large power factor ( = 74 μW/cm-K; = Ir) and a high figure of merit ( = 0.

BaCrNH: A New Nitride-Hydride with Trigonal Planar Cr.

The nitride-hydride BaCrNH was obtained in single crystalline form using flux growth techniques based on alkaline earth metals. BaCrNH crystallizes in the hexagonal space group P6/ m (Nr 176), with the lattice parameters a = 8.0270(2) Å, c = 5.

Modification of spin-ice physics in thin films.

We present an extensive study on the effect of substrate orientation, strain, stoichiometry, and defects on spin-ice physics in thin films grown onto yttria-stabilized-zirconia substrates. We find that growth in different orientations produces different strain states in the films. All films exhibit similar -axis lattice parameters for their relaxed portions, which are consistently larger than the bulk value of 10.

Blue Emitting Single Crystalline Assembly of Metal Halide Clusters.

The rich chemistry of organic-inorganic metal halide hybrids has enabled the development of a variety of crystalline structures with controlled morphological and molecular dimensionalities. Here we report for the first time a single crystalline assembly of metal halide clusters, (CNH)(PbCl)PbCl, in which lead chloride tetrahedrons (PbCl) and face-sharing lead chloride trimer clusters (PbCl) cocrystallize with organic cations (CNH) to form a periodical zero-dimensional (0D) structure at the molecular level. Blue light emission peaked at 470 nm with a photoluminescence quantum efficiency (PLQE) of around 83% was realized for this single crystalline hybrid material, which is attributed to the individual lead chloride clusters.

Luminescent zero-dimensional organic metal halide hybrids with near-unity quantum efficiency.

Single crystalline zero-dimensional (0D) organic-inorganic hybrid materials with perfect host-guest structures have been developed as a new generation of highly efficient light emitters. Here we report a series of lead-free organic metal halide hybrids with a 0D structure, (CNHX)SnX (X = Br, I) and (CNH)SbX (X = Cl), in which the individual metal halide octahedra (SnX) and quadrangular pyramids (SbX) are completely isolated from each other and surrounded by the organic ligands CNHX and CNH, respectively. The isolation of the photoactive metal halide species by the wide band gap organic ligands leads to no interaction or electronic band formation between the metal halide species, allowing the bulk materials to exhibit the intrinsic properties of the individual metal halide species.

Bulk assembly of organic metal halide nanotubes.

The organic metal halide hybrids welcome a new member with a one-dimensional (1D) tubular structure. Herein we report the synthesis and characterization of a single crystalline bulk assembly of organic metal halide nanotubes, (CHN)PbBr. In a metal halide nanotube, six face-sharing metal halide dimers (PbBr) connect at the corners to form rings that extend in one dimension, of which the inside and outside surfaces are coated with protonated hexamethylenetetramine (HMTA) cations (CHN).

Synthesis and Crystal Structure of the Layered Lanthanide Oxychlorides BaLnOCl.

Single crystals of a new family of layered lanthanide oxychlorides, BaLnOCl (Ln = Gd-Lu), have been synthesized from a molten barium flux. This family crystallizes in the space group I4/mmm (No. 139; Z = 2) with lattice parameters a = 4.

Uncovering the Origin of Divergence in the CsM(CrO) (M = La, Pr, Nd, Sm, Eu; Am) Family through Examination of the Chemical Bonding in a Molecular Cluster and by Band Structure Analysis.

A series of f-block chromates, CsM(CrO) (M = La, Pr, Nd, Sm, Eu; Am), were prepared revealing notable differences between the Am derivatives and their lanthanide analogs. While all compounds form similar layered structures, the americium compound exhibits polymorphism and adopts both a structure isomorphous with the early lanthanides as well as one that possesses lower symmetry. Both polymorphs are dark red and possess band gaps that are smaller than the Ln compounds.

Highly Efficient Broadband Yellow Phosphor Based on Zero-Dimensional Tin Mixed-Halide Perovskite.

Organic-inorganic hybrid metal halide perovskites have emerged as a highly promising class of light emitters, which can be used as phosphors for optically pumped white light-emitting diodes (WLEDs). By controlling the structural dimensionality, metal halide perovskites can exhibit tunable narrow and broadband emissions from the free-exciton and self-trapped excited states, respectively. Here, we report a highly efficient broadband yellow light emitter based on zero-dimensional tin mixed-halide perovskite (CNHBr)SnBrI (x = 3).

Three-dimensional shoulder kinematics during a pressure relief technique and wheelchair transfer.

Objective: To assess 3-dimensional scapulothoracic and glenohumeral kinematics in able-bodied subjects during a weight-relief raise and while transferring to and from a wheelchair.

Design: Repeated-measures analysis of variance.

Setting: Research laboratory.