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The quaternary rare-earth phosphides REMnCu(4)P(3) (RE = Gd-Ho) were obtained from direct reactions of the elements at 800 °C. They are the first examples in which ordering of two different transition-metal atoms takes place within the orthorhombic YCo(5)P(3)-type structure [Pearson symbol oP36, space group Pnma, Z = 4; a = 12.667(2)-12.6489(4) Å, b = 3.8119(7)-3.7755(1) Å, and c = 10.895(2)-10.8632(4) Å for RE = Gd-Ho]. Columns of trigonal prisms centered by P atoms are connected in propellor-shaped units in zigzag arrangements to generate square-pyramidal (CN5) sites that are occupied by Mn atoms and tetrahedral sites (CN4) that are occupied by Cu atoms. Spin-polarized band-structure calculations predict that the hypothetical compound YMnCu(4)P(3) will exhibit magnetic ordering. Electrical resistivity measurements on TbMnCu(4)P(3) indicate a poor metal.

KCdGeAs2 (I) and RbCdGeAs2 (II) are prepared by solid state reactions of stoichiometric mixtures of the elements (alumina crucible in evacuated silica tube, 650 °C (I) and 600 °C (II), 10 d).

The title compounds are prepared by arc melting of stoichiometric amounts of the elements followed by annealing (evacuated quartz tubes, 770 K, 720 h).

Three series of quaternary pnictides, LnCuZnAs2 (Ln: Y, La—Nd, Sm, Gd—Lu), LnAgZnP2 (Ln: La—Nd, Sm, Gd—Dy), and LnAgZnAs2 (Ln: La—Nd, Sm, Gd—Dy) are prepared by solid reaction of the elements (evacuated silica tubes, 1.

The new title compounds (RE: Y, La—Er) are prepared from stoichiometric mixtures of the elements at 1050 °C (14 d) for the sulfides and at 900 °C (5 d) for the selenides, respectively.

The title compounds are prepared from stoichiometric mixtures of the elements (silica tubes, 1050 °C, 96 h) and characterized by powder and single crystal XRD, XPS, magnetic susceptibility measurements, and TB-LMTO-ASA band structure calculations.

The title compounds are synthesized from stoichiometric mixtures of the elements (alumina crucibles, 600 °C, 10 d) and characterized by single crystal XRD and TB-LMTO-ASA band structure calculations.

which has a superconducting transition temperature of 2.3 K, provides an excellent opportunity tostudytheinterplayofsuperconductivityandmagnetismnearanantiferromagneticquantumcriticalpoint.Previousstudies have explored the effects of electron doping, magnetic field, and positive pressure on this system. Todetermine the effect of hole doping, we have grown single crystals of Ce(Co

The ternary pnictides Rb4Zn7As7 and Rb7Mn12Sb12 and their quaternary derivatives Rb4Mn3.5Zn3.5Sb7 and Rb7Mn4Cd8Sb12 have been prepared by reactions of the elements at 600 °C. They crystallize in two new structure types: orthorhombic Rb4Zn7As7-type (space group Cmcm, Z = 4; a = 4.1883(4) Å, b = 24.844(2) Å, c = 17.6056(17) Å for Rb4Zn7As7; a = 4.3911(8) Å, b = 26.546(5) Å, c = 18.743(4) Å for Rb4Mn3.5Zn3.5Sb7) and monoclinic Rb7Mn12Sb12-type (space group C2/m, Z = 2; a = 26.544(12) Å, b = 4.448(2) Å, c = 16.676(8) Å, β = 103.183(8)° for Rb7Mn12Sb12; a = 27.009(4) Å, b = 4.5752(7) Å, c = 16.727(3) Å, β = 103.221(2)° for Rb7Mn4Cd8Sb12). These related structures contain corrugated anionic layers built up by connecting ribbons of edge-sharing tetrahedra in a zigzag-like manner with chains of Mn-centered square pyramids located at the hinges. Homoatomic pnicogen-pnicogen bonding occurs in the form of Pn2 pairs. The compounds are formally deficient by one electron per formula unit, as confirmed by band structure calculations which reveal the location of the Fermi level just below a small gap in Rb4Zn7As7 or a pseudogap in Rb7Mn12Sb12.

Ln4Mn2InGe4 (Ln: La Nd, Sm, Gd—Tm, Lu) are prepared by arc melting of stoichiometric mixtures the elements and annealing at 800 °C (evacuated silica tubes, 12 d).

Rb2Cd5As4 (I), Rb2Zn5Sb4 (II) and the solid solution Rb2Cd5(As,Sb)4 (III) are prepared by melting of the elements (Nb tubes in evacuated silica ampule; (I): 923 K, 7 d, ice quenching, (II): 823 K, 10 d, cooling rate 3 K/h).

The quaternary germanides RE4Mn2InGe4 (RE = La-Nd, Sm, Gd-Tm, Lu) have been prepared by arc-melting reactions of the elements and annealing at 800 °C and represent the second example of the RE4M2InGe4 series previously known only for M = Ni. Single-crystal X-ray diffraction studies conducted on the earlier RE members of RE4Mn2InGe4 confirmed that they adopt the monoclinic Ho4Ni2InGe4-type structure [space group C2/m, a = 16.646(2)-15.9808(9) Å, b = 4.4190(6)-4.2363(2) Å, c = 7.4834(10)-7.1590(4) Å, β = 106.893(2)-106.304(1)° in the progression of RE from La to Gd]. The covalent framework contains Mn-centered tetrahedra and Ge2 dimers that build up [Mn2Ge4] layers, which are held weakly together by four-coordinate In atoms and outline tunnels filled by the RE atoms. This bonding picture is supported by band-structure calculations. An alternative description based on Ge-centered trigonal prisms reveals that RE4Mn2InGe4 is closely related to RE2InGe2. The electrical resistivity behavior of Pr4Mn2InGe4 is similar to that of Pr2InGe2.

Ten quaternary arsenides of title are prepared by reaction of stoichiometric mixtures of the elements (alumina crucible, 600—650 °C, 10 d).

The ternary rare-earth zinc arsenides RE Zn 2 As 3 ( RE =La–Pr) have been prepared by reactions of the elements at 800 °C. They adopt new tetragonal structure types, with the La member (space group I 4/ mmm , Z =4, a =4.1133(2) A, c =32.1246(14) A) differing from the Ce and Pr members (space group P 4/ nmm , Z =2, a =4.0804(6)–4.0534(12) A, c =16.089(5)–16.059(10) A, respectively) in the disposition of RE -centred square antiprisms on opposite sides of square As nets. The structures contain thick anionic slabs, built from edge-sharing ZnAs 4 tetrahedra, that can be considered either as stackings of three PbO-type layers or as fragments of the fluorite-type structure. These slabs are deficient in Zn and are reminiscent of the same features in binary arsenide Zn 3 As 2 . LaZn 2 As 3 exhibits temperature-independent paramagnetism whereas CeZn 2 As 3 follows modified Curie–Weiss behavior consistent with Ce 3+ species but with no occurrence of long-range ordering.

Two new ternary phases, (Mo1-xFex)2P (x = 0.30—0.82) and (Mo1-xFex)3P (x = 0.10—0.15) exist in the isothermal section of the title system at 800 °C.

The pnictides Ln2Mn3Cu9P7 (Ln: La—Nd, Sm, Gd—Dy) and Ln2Mn3Cu9As7 (Ln: La—Nd) are prepared from stoichiometric mixtures of the elements (800 °C, 14 d).

Experimental results of X-ray diffraction and X-ray photoelectron spectroscopy of fossil cutin from the compressed foliage of the Carboniferous tree fern Alethopteris pseudograndinioides, Cantabrian age, Sydney Coalfield, Canada, are presented in this paper. The light-colored cutin was obtained by oxidizing the compression in Schulze's solution in two stages for a total of 19 days. The broad peak in the powder diffractogram at 20° is characteristic of an average separation of ~4.4 Å between the methylenic hydrocarbon chains (CH2)n, whereas the sharper peaks at 26°–28° suggest that within a small fraction of the sample, the chains are more regularly separated. Most of the chains are likely randomly aligned to form a nematic structure. Elemental composition by mass amounts to 58.3% C, 1.1% N, 19.4% O, 19.7% Cl, and 1.5% Si, and the local chemical environment of C 1s, O 1s, and Cl 2p is probed. Cl content is a surprising result, and further research is needed for identifying chlorine-containing species. Fil: Stoyko, Stanislav S.. University of Alberta. Department of Chemistry; Canadá Fil: Rudyk, Brent W.. University of Alberta. Department of Chemistry; Canadá Fil: Mar, Arthur. University of Alberta. Department of Chemistry; Canadá Fil: Zodrow, Erwin L.. Cape Breton University. Palaeobiological Laboratory; Canadá Fil: D` Angelo, José Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina

The new title compounds are prepared from the elements with excess Ga acting as a self-flux (1000 °C, 7 h).

The title compound is synthesized by reaction of a stoichiometric mixture of the elements (alumina crucible, 850 °C for 2 d and 800 °C for 7 d).

The title compounds are prepared from stoichiometric mixtures of the elements (alumina crucible, 650 °C for K sample, 600 °C for Rb sample, 10 d) and characterized by single crystal XRD and TB-LMTO-ASA band structure calculations.

The new title compounds are prepared by reactions of stoichiometric mixtures of the elements (alumina crucible, 850 °C, 1—4 d) and characterized by single crystal XRD.

Stoichiometric reaction of the elements at high temperature yields the ternary arsenides K(2)Zn(5)As(4) (650 °C) and Rb(2)Zn(5)As(4) (600 °C). They adopt a new structure type (Pearson symbol oC44, space group Cmcm, Z = 4; a = 11.5758(5) Å, b = 7.0476(3) Å, c = 11.6352(5) Å for K(2)Zn(5)As(4); a = 11.6649(5) Å, b = 7.0953(3) Å, c = 11.7585(5) Å for Rb(2)Zn(5)As(4)) with a complex three-dimensional framework of linked ZnAs(4) tetrahedra generating large channels that are occupied by the alkali-metal cations. An alternative and useful way of describing the structure is through the use of stellae quadrangulae each consisting of four ZnAs(4) tetrahedra capping an empty central tetrahedron. These compounds are Zintl phases; band structure calculations on K(2)Zn(5)As(4) and Rb(2)Zn(5)As(4) indicate semiconducting behavior with a direct band gap of 0.4 eV.

The title compounds are prepared from stoichiometric mixtures of the elements (800 °C, 7 d) and characterized by single crystal XRD, electrical resistivity measurements, and TB-LMTO-ASA band structure calculations.

The title compounds are prepared by reaction of “ZrCuGe” or “HfCuGe” precursors (obtained by arc melting of the elements) with As at 800 °C for two weeks.

The compounds LnZn3As3 (Ln: La—Nd, Sm) with polymorphic modifications different from the previously known forms and the corresponding compounds LnCd3As3 (Ln: La—Pr) are prepared from the elements (800 °C, 7 d) and characterized by powder and single crystal XRD, electrical resistivity and magnetic measurements, and TB-LMTO computations.

The title compounds are prepared from the elements (800 °C, 336 h) and characterized by powder and single crystal XRD, magnetic susceptibility and electrical resistivity measurements, and TB-LMTO band structure calculations.

The title compounds are prepared by arc-melting the elements followed by annealing at 800 °C for three weeks.

Ternary rare-earth zinc arsenides REZn(3)As(3) (RE = La-Nd, Sm) with polymorphic modifications different from the previously known defect CaAl(2)Si(2)-type forms, and the corresponding rare-earth cadmium arsenides RECd(3)As(3) (RE = La-Pr), have been prepared by reaction of the elements at 800 °C. LaZn(3)As(3) adopts a new orthorhombic structure type (Pearson symbol oP28, space group Pnma, Z = 4, a = 12.5935(8) Å, b = 4.1054(3) Å, c = 11.5968(7) Å) in which ZnAs(4) tetrahedra share edges to form ribbons that are fragments of other layered arsenide structures; these ribbons are then interconnected in a three-dimensional framework with large channels aligned parallel to the b direction that are occupied by La(3+) cations. All remaining compounds adopt the hexagonal ScAl(3)C(3)-type structure (Pearson symbol hP14, space group P6(3)/mmc, Z = 2; a = 4.1772(7)-4.1501(2) Å, c = 20.477(3)-20.357(1) Å for REZn(3)As(3) (RE = Ce, Pr, Nd, Sm); a = 4.4190(3)-4.3923(2) Å, c = 21.4407(13)-21.3004(8) Å for RECd(3)As(3) (RE = La-Pr)) in which [M(3)As(3)](3-) layers (M = Zn, Cd), formed by a triple stacking of nets of close-packed As atoms with M atoms occupying tetrahedral and trigonal planar sites, are separated by La(3+) cations. Electrical resistivity measurements and band structure calculations revealed that orthorhombic LaZn(3)As(3) is a narrow band gap semiconductor.

The title compounds are prepared from stoichiometric mixtures of the elements (900 °C, 7 d) and characterized by powder XRD, XPS, magnetic measurements, and TB-LMTO band structure calculations.

The rare-earth iron arsenides RE 12 Fe 57.5 As 41 (RE = La, Ce) have been prepared by direct reactions of the elements in the presence of a Sn flux. Analysis of single-crystal X-ray diffraction data reveals that they adopt a new orthorhombic structure type (Pearson symbol oP236, space group Pmmn, Z = 2; a = 10.8881(9) A, b = 25.753(2) A, c = 12.5436(10) A for RE = La; a = 10.8376(8) A, b = 25.639(2) A, c = 12.4701(9) A for RE = Ce). In this metal-rich arsenide, the complex three-dimensional network (derived from 4 RE, 24 Fe, and 17 As sites) can be described as being built from unusual wavelike layers of connected As-centered trigonal prisms. Five of the Fe sites are partially occupied. The electronic structure of these compounds was probed through core-line X-ray photoelectron spectra. Magnetic susceptibility measurements indicated ferromagnetic ordering at T c = 125 and 95 K for the La and Ce compounds, respectively. Electrical resistivity measurements on single crystals of Ce 12 Fe 57.5 As 41 showed metallic behavior with a prominent transition that coincides closely with the ferromagnetic ordering temperature.

A new ternary phosphide Y 6 Ni 15− x P 10+ y ( x =0.08, y =0.18) has been obtained in the Y–Ni–P system. Single crystals of this compound have been investigated on a Nonius KappaCCD X-ray diffractometer using Mo Kα radiation ( λ =0.071073 nm). The symmetry has been found to be hexagonal with space group P 6 3 / m and unit cell parameters a =1.6447(1) nm and c =0.37891(2) nm. Structure refinement including anisotropic displacement parameters led to the following results: R F =0.056 ( R w =0.047), GOF=1.060 for 558 reflections with F ( h k l ) > 4 σF ( h k l ). The ternary phosphide Y 6 Ni 15− x P 10+ y exhibits a new structure, which is derived from the Ce 6 Ni 15 P 10 and Nd 3 Ni 7 P 5 structure types.