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The crystal structure of a novel barium yttrium borate, Ba2Y5B5O17, was determined using a combination of ab initio global optimization algorithms and density functional theory calculations along with Rietveld refinement of high-resolution synchrotron X-ray powder diffraction data. Synthesized using a high-temperature solid-state route, the structure consists of edge- and corner-sharing Y- and Ba-centered polyhedra along with BO3 trigonal planes. Ba and Y occupy four crystallographically independent sites with two fully occupied by Y and two having a statistical mixture of Y and Ba. Substituting Ce3+ into the structure for Y3+ yields blue photoluminescence (λem = 443 nm) upon excitation with UV (λem = 365 nm) light. The emission of this new compound is efficient with an external quantum yield of 70% and is stable as a function of temperature with a quenching temperature of ≈400 K.

A new polymorph of MnP4 was prepared by reaction of the elements via chemical vapor transport with iodine as transporting agent. The crystal structure was refined using single-crystal diffraction data (space group Cc, no. 9, a = 5.1049(8) A, b = 10.540(2) A, c = 10.875(2) A, β = 93.80(2)°). The phase is called γ-MnP4 as it is isostructural with γ-FeP4. It is the fourth reported binary polymorph in the MnP4 system, all of which are stacking variants of nets built with manganese and phosphorus atoms. In γ-MnP4, there are two Mn-Mn distances (2.93 and 3.72 A) arising from a Peierls-like distortion effectively forming Mn2 dumbbells in the structure. Magnetic and electrical conductivity measurements show diamagnetism and a small anisotropic band gap (100-200 meV) with significantly enhanced conductivity along the crystallographic a axis. Calculations of the electronic and vibrational (phonon) structures show the P-P and Mn-P bonds within the nets are mainly responsible for the stability of the phase. The similar bonding motifs of the polymorphs give rise to the existence of numerous dynamically stable variants. The calculated Helmholtz energy shows the polymorph formation to be closely tied to temperature with the 6-MnP4 structure favorable at low temperatures, the 2-MnP4 favorable between approximately 800 and 2000 K, and 8-MnP4 preferred at high temperatures.

The title compound is characterized by powder XRD, conductivity and Seebeck coefficient measurements, solid state NMR spectroscopy, nanoindentation measurements, and DFT calculations.

The new title compound is synthesized by reaction of Nb, SnF2, and SnO in Sn flux (4:4:3:8 molar ratio; welded Nb containers, 600 °C, 7 d).

The title compounds are prepared by rapid microwave-assisted solid-state synthesis using stoichiometric amounts of La2O3, BaCO3, and Pd(acac)2 or Pt(acac)2 (alumina crucible, 1300 W, 15—20 min).

Polycrystalline samples of the boride series Ti9-xM2+xRu18B8 (M: Cr, Co, Mn, Ni) and single crystals of Ti8Co3Ru18B8 are prepared by arc melting of the elements.

Polycrystalline samples of Ba9 (Y1-xCex)2Si6O24 (x = 0—0.12 in steps of 0.02) and Ba9 (Y1-yScy) 1.94Ce0.06Si6O24 (y = 0.05—0.25 in steps of 0.05) are prepared by solid state reaction of stoichiometric mixtures of BaCO3, Y2O3, Sc2O3, SiO2, and CeO2 (5% H2/N2 atmosphere, 1350 °C, 4 h).

The electronic and magnetic structures of the tetragonal Cu2Sb-type 3d metal arsenides (M2As, M = Cr, Mn, Fe) were examined using density functional theory to identify chemical influences on their respective patterns of magnetic order. Each compound adopts a different antiferromagnetic (AFM) ordering of local moments associated with the 3d metal sites, but every one involves a doubled crystallographic c-axis. These AFM ordering patterns are rationalized by the results of VASP calculations on several magnetically ordered models using a × a × 2c supercell. Effective exchange parameters obtained from SPRKKR calculations indicate that both direct and indirect exchange couplings play essential roles in understanding the different magnetic orderings observed. The nature of nearest-neighbor direct exchange couplings, that is, either ferromagnetic (FM) or AFM, were predicted by analysis of the corresponding crystal orbital Hamilton population (COHP) curves obtained by TB-LMTO calculations. Interestingly, the magnetic structures of Fe2As and Mn2As show tetragonal symmetry, but a magnetostrictive tetragonal-to-orthorhombic distortion could occur in Cr2As through AFM Cr1-Cr2 coupling between symmetry inequivalent Cr atoms along the a-axis, but FM coupling along the b-axis. A LSDA+U approach is required to achieve magnetic moment values for Mn2As in better agreement with experimental values, although computations always predict the moment at the M1 site to be lower than that at the M2 site. Finally, a rigid-band model applied to the calculated DOS curve of Mn2As correctly assesses the magnetic ordering patterns in Cr2As and Fe2As.

Sc4Fe5Ge6.10Sn1.47 is identified as a product of the reaction of Sc, Fe, and Ge in a Sn flux.

The new compounds {MLa3}Br3 (M: Ru, Ir) are prepared from stoichiometric mixtures of LaBr3, La, and M (Ta containers, 1050 °C, 7 d).

The new complex boride phases Ti8Fe3Ru18B8 and Ti7Fe4Ru18B8 are synthesized by arc-melting of the elements.

The electronic structures of “Ti9-nFe2+nRu18B8” (n = 0, 0.5, 1, 2, 3), including the recently synthesized compounds Ti9-nFe2+nRu18B8 (n = 1, 2), are determined by TB-LMTO-ASA computations.

Zr2Fe0.87Ru5.13B2 and Zr2Fe0.82(Ru/Rh)5.18B2 are synthesized by arc melting of stoichiometric mixtures of the elements followed by annealing at 1000 °C (14 d).