New layered compounds BaFMgPn (Pn= P, As, Sb and Bi), transition-metal-free representatives of the LaOAgS structure

Four new transition metal-free pnictide representatives of the LaOAgS structure type were predicted by DFT calculations and found in the BaFMgPn (Pn = P, As, Sb and Bi) family. The compounds adopt the tetragonal space group P4/nmm with the unit cell parameters a/c 4.3097(1) angstrom/9.5032(1) angstrom, 4.3855(1) angstrom/9.5918(1) angstrom, 4.5733(1) angstrom/9.8184(1) angstrom, and 4.6359(1) angstrom/9.8599(1) angstrom, respectively. According to the DFT calculations, these new compounds are semiconductors with band gaps steadily decreasing from Pn = P (ca. 2 eV) to Pn = Bi (ca. 1 eV). The corresponding strontium fluoride and rare-earth oxide analogs are unlikely to exist and have not been observed yet. The trends of the stability within 1111 and structurally and/or chemically related compounds based on a combined consideration of geometry and DFT calculations are discussed

Cs7Sm11[TeO3]12Cl16 and Rb7Nd11[TeO3]12Br16, the new tellurite halides of the tetragonal Rb6LiNd11[SeO3]12Cl16 structure type

The authors thank the Russian Foundation for Basic Researches for the support of this work under Grants No. 14-03-00604_a and 12-03-92604-KO_a. The X-ray study of compound II was made possible due to M.V. Lomonosov Moscow State University Programm of Development. PL thanks the University of St Andrews and EPSRC for DTA Studentships to CB and LJD.Two new rare-earth – alkali – tellurium oxide halides were synthesized by a salt flux technique and characterized by single-crystal X-ray diffraction. The structures of the new compounds Cs7Sm11[TeO3]12Cl16 (I) and Rb7Nd11[TeO3]12Br16 (II) (both tetragonal, space group I4/mcm) correspond to the sequence of [MLn11(TeO3)12] and [M6×16] layers and bear very strong similarities to those of known selenite analogs. We discuss the trends in similarities and differences in compositions and structural details between the Se and Te compounds; more members of the family are predicted.PostprintPeer reviewe

Synthesis of novel lead-molybdenum and lead-tungsten oxyhalides with the pinalite structure, Pb3MoO5Cl2 and Pb3WO5Br2

Two new quaternary lead oxyhalides, Pb3MoO5Cl2 and Pb3WO5Br2, have been prepared. They are isostructural with the mineral pinalite, Pb3WO5Cl2, and its barium analog. The crystal structure of Pb3MoO5Cl2 has been refined from powder neutron diffraction data to R-P = 0.0564 and R-wp = 0.0342. All these structures contain significantly stretched MO5 (M = Mo, W) square pyramids incorporated into the [Pb2O2] sheets. Bond valence sums indicate significant overbonding of one of the metal sites, which increases along with structural distortions when passing from Pb3MoO5Cl2 to Pb3WO5Cl2 and from Pb3WO5Cl2 to Ba3WO5Cl2. Possibilities of preparing isostructural and structurally related compounds are discussed.</p

A novel family of layered bismuth compounds II: the crystal structures of Pb_0.6Bi_1.4Rb_0.6O₂Z₂, Z=Cl, Br, and I

Using various synthetic approaches, we have prepared over 50 new multinary bismuth oxyhalides which crystallize in four layered structure types. Most of the compounds belong to the three previously reported structure types involving fluorite- and CsCl-like metal-oxygen vs. metal-halogen layers as well as single or double halide ion sheets. The majority of Bi(2-x)A(x)Q(0.6)O(2)Z(2) (A-Li, Na, K, Ca, Sr, Ba, Pb; Q=Rb Cs; Z=Cl, Br, I) compounds crystallize in the tetragonal structure of Pb0.6Bi1.4Cs0.60Cl2 (Y2) while both Bi(1.4)Ba(0.6)Q(0.6)O(2)I(2) (Q = Rb, Cs) oxyiodides adopt its orthorhombically distorted, partially ordered version. Due to the lower degree of substitution, the fluorite-like layers in the Y2 structure accommodate more A cations than previously known for related Bi compounds. However, very large Tl+ or Rb+ give compounds with another, as yet unknown, structure. We discuss the influence of size and charge of A cations and stoichiometry of [Bi(2-x)A(x)O(2)] fluorite layers on structure and stability of layered oxyhalides of bismuth. Also, we predict formation of isostructural compounds with smaller Q cations like Tl+ and K+. (C) 2003 Elsevier Science (USA). All rights reserved.</p

A novel family of layered bismuth compounds II: the crystal structures of Pb_0.6Bi_1.4Rb_0.6O₂Z₂, Z=Cl, Br, and I

Using various synthetic approaches, we have prepared over 50 new multinary bismuth oxyhalides which crystallize in four layered structure types. Most of the compounds belong to the three previously reported structure types involving fluorite- and CsCl-like metal-oxygen vs. metal-halogen layers as well as single or double halide ion sheets. The majority of Bi(2-x)A(x)Q(0.6)O(2)Z(2) (A-Li, Na, K, Ca, Sr, Ba, Pb; Q=Rb Cs; Z=Cl, Br, I) compounds crystallize in the tetragonal structure of Pb0.6Bi1.4Cs0.60Cl2 (Y2) while both Bi(1.4)Ba(0.6)Q(0.6)O(2)I(2) (Q = Rb, Cs) oxyiodides adopt its orthorhombically distorted, partially ordered version. Due to the lower degree of substitution, the fluorite-like layers in the Y2 structure accommodate more A cations than previously known for related Bi compounds. However, very large Tl+ or Rb+ give compounds with another, as yet unknown, structure. We discuss the influence of size and charge of A cations and stoichiometry of [Bi(2-x)A(x)O(2)] fluorite layers on structure and stability of layered oxyhalides of bismuth. Also, we predict formation of isostructural compounds with smaller Q cations like Tl+ and K+. (C) 2003 Elsevier Science (USA). All rights reserved.</p