Ternary Arsenides Research Articles

Tuning interchain ferromagnetic instability in A2Cr3As3 ternary arsenides by chemical pressure and uniaxial strain

We analyze the effects of chemical pressure induced by alkali metal substitution and uniaxial strain on magnetism in the A2Cr3As3 (A = Na, K, Rb, Cs) family of ternary arsenides with quasi-one dimensional structure. Within the framework of the density functional theory, we predict that the non-magnetic phase is very close to a 3D collinear ferrimagnetic state, which realizes in the regime of moderate correlations, such tendency being common to all the members of the family with very small variations due to the different interchain ferromagnetic coupling. We uncover that the stability of such interchain ferromagnetic coupling has a non-monotonic behavior with increasing the cation size, being critically related to the degree of structural distortions which is parametrized by the Cr-As-Cr bonding angles along the chain direction. In particular, we demonstrate that it is boosted in the case of the Rb, in agreement with recent experiments. We also show that uniaxial strain is a viable tool to tune the non-magnetic phase towards an interchain ferromagnetic instability. The modifcation of the shape of the Cr triangles within the unit cell favors the formation of a net magnetization within the chain and of a ferromagnetic coupling among the chains. This study can provide relevant insights about the interplay between superconductivity and magnetism in this class of materials.

Observation of an Unexpected n-Type Semiconducting Behavior in the New Ternary Zintl Phase Eu3InAs3

The ternary arsenides Eu3InAs3 and Sr3InAs3 have been obtained by reactions of the elements in In flux at 1373 K. Structure elucidation by single-crystal X-ray diffraction reveals that Eu3InAs3 and...

Niobium-bearing arsenides and germanides from elemental mixtures not involving niobium: a new twist to an old problem in solid-state synthesis.

Three isostructural transition-metal arsenides and germanides, namely niobium nickel arsenide, Nb0.92(1)NiAs, niobium cobalt arsenide, NbCoAs, and niobium nickel germanide, NbNiGe, were obtained as inadvertent side products of high-temperature reactions in sealed niobium containers. In addition to reporting for the very first time the structures of the title compounds, refined from single-crystal X-ray diffraction data, this article also serves as a reminder that niobium containers may not be suitable for the synthesis of ternary arsenides and germanides by traditional high-temperature reactions. Synthetic work involving alkali or alkaline-earth metals, transition or early post-transition metals, and elements from groups 14 or 15 under such conditions may yield Nb-containing products, which at times could be the major products of such reactions.

Investigation of the substitution at the anionic positions BaT2As2 (T = Fe, Ni) superconductors

The possibilities of electron/hole doping of two ternary arsenides, BaFe2As2 and BaNi2As2, via partial substitution at the arsenic position by 16 and 14 group elements, have been studied. While no substitution has been observed for chalcogens, BaFe2As2 incorporates Sb, Si, and Ge at the As site; BaNi2As2 incorporates Sb, Ge, Sn, and Pb. The observed results can be tentatively explained suggesting that 14 group elements are incorporated into the BaT2As2 structures as X6− 2 dumbbells.

ChemInform Abstract: Ternary Arsenides ATt3As3 (A: K, Rb; Tt: Ge, Sn) with Layered Structures.

AbstractThe title compounds are prepared from the elements (alumina crucible, 600—650 °C, 10 d).

Ternary arsenides RECo5As3 (RE = Y, Gd, Tb, Dy, Ho, Er)

A series of new ternary arsenides RECo5As3 (RE = Y, Gd, Tb, Dy, Ho, Er) was synthesized from pure constituents. The crystal structure of TbCo5As3 and ErCo5As3 was determined by X-ray single-crystal diffraction, the structure of the other arsenides was refined from X-ray powder diffraction data. These compounds are isotypic with the YCo5P3 structure (space group Pnma, Pearson code oP36): a = 12.249(8), b = 3.803(5), c = 10.749(5) Å for GdCo5As3; a = 12.2350(10), b = 3.7896(2), c = 10.7290(7) Å, (R1 = 0.030 (wR2 = 0.038) for 828 reflections with Io > 2σ(Io)) for TbCo5As3; a = 12.225(2), b = 3.781(7), c = 10.715(5) Å for DyCo5As3; a = 12.214(4), b = 3.775(4), c = 10.709(1) Å for HoCo5As3; a = 12.2033(7), b = 3.7685(2), c = 10.7009(4) Å, (R1 = 0.039 (wR2 = 0.062) for 921 reflections with Io > 2σ(Io)) for ErCo5As3. The structure contains distorted trigonal prisms [AsRE2Co4] condensed together by edges from RE atoms to infinite zig-zag chains. TbCo5As3 was identified as having an antiferromagnetic ground state with the Néel temperature TN = 55–60 K, which is obscured by spurious metallic Co.

Ternary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) with layered structures

The four ternary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) were obtained by reaction of the elements at 600–650°C. They adopt an orthorhombic structure (space group Pnma, Z=4, with cell parameters ranging from a=9.9931(11)Å, b=3.7664(4)Å, c=18.607(2)Å for KGe3As3 to a=10.3211(11)Å, b=4.0917(4)Å, c=19.570(2)Å for RbSn3As3) containing corrugated [Tt3As3] layers built from Tt-centred trigonal pyramids and tetrahedra forming five-membered rings decorated with As handles. They can be considered to be Zintl phases with Tt atoms in +4, +3, and +1 oxidation states. Band structure calculations predict that these compounds are semiconductors with narrow band gaps (0.71eV in KGe3As3, 0.50eV in KSn3As3).

NaGe6As6: Insertion of sodium into the layered semiconductor germanium arsenide GeAs

Abstract NaGe6As6 is a ternary arsenide prepared by reaction of the elements at 650 °C. It crystallizes in a new monoclinic structure type [space group C2/m, Z = 2, a = 22.063(2), b = 3.8032(4), c = 7.2020(8) Å, β = 92.7437(15)°] that can be considered to be derived by inserting guest Na atoms between [Ge6As6] layers identical to those found in the layered binary arsenide GeAs. An unusual feature in both structures is the presence of ethane-like Ge2As6 units in staggered conformation, with Ge–Ge dumbbells oriented either parallel or perpendicular to the layers. Electronic band structure calculations have shown that the electron excess in NaGe6As6 is accommodated by raising the Fermi level across a 0.6 eV band gap in semiconducting GeAs so that it cuts the bottom of the conduction band, resulting in an n-doped semiconductor.

Synthesis, Crystal and Electronic Structures of the Pnictides AE3TrPn3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

The new ternary arsenides AE3TrAs3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3GaP3 and Ba3AlP3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3AlAs3 and Ba3AlAs3 adopt the Ba3AlSb3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3GaP3 and Ba3AlP3. The compounds Sr3GaAs3 and Ba3GaAs3 crystallize with the Ba3GaSb3-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3[Tr3+][Pn3−]3, or rather [AE2+]6[Tr2Pn6]12−, i.e., as Zintl phases.

Magnetic ordering and electronic structure of the ternary iron arsenide BaFe2As2

In this paper, we report structural parameters, magnetic ordering and the electronic structure of the tetragonal and orthorhombic ternary iron arsenide compound [Formula: see text]. Ab initio calculations are performed by the means of full-potential linearized augmented plane waves plus local orbitals method for both spin states. The local spin density plus Hubbard potential ([Formula: see text]) and generalized gradient plus Hubbard potential ([Formula: see text]) approximations are used to treat the exchange and correlation potentials. The results mainly show that orthorhombic [Formula: see text] compound has an antiferromagnetic spin ordering. Both spin-up and spin-down polarizations are considered to investigate the band structure, density of states and electron charge density. High density of states population at the Fermi level reveals metallic character of this material. The magnetism property arises essentially from the [Formula: see text] orbital of iron atom.

Narrowing the gap: from semiconductor to semimetal in the homologous series of rare-earth zinc arsenides RE(2-y)Zn4As4·n(REAs) and Mn-substituted derivatives RE(2-y)Mn(x)Zn(4-x)As4·n(REAs) (RE = La-Nd, Sm, Gd).

A homologous series of ternary rare-earth zinc arsenides, prepared by reactions of the elements at 750 °C, has been identified with the formula RE(2-y)Zn4As4·n(REAs) (n = 2, 3, 4) for various RE members. They adopt trigonal structures: RE(4-y)Zn4As6 (RE = La-Nd), space group R3̄m1, Z = 3; RE(5-y)Zn4As7 (RE = Pr, Nd, Sm, Gd), space group P3̄m1, Z = 1; RE(6-y)Zn4As8 (RE = La-Nd, Sm, Gd), space group R3̄m1, Z = 3. The Zn atoms can be partially substituted by Mn atoms, resulting in quaternary derivatives RE(2-y)Mn(x)Zn(4-x)As4·n(REAs). Single-crystal structures were determined for nine ternary and quaternary arsenides RE(2-y)M4As4·n(REAs) (M = Mn, Zn) as representative examples of these series. The structures are built by stacking close-packed nets of As atoms, sometimes in very long sequences, with RE atoms occupying octahedral sites and M atoms occupying tetrahedral sites, resulting in an intergrowth of [REAs] and [M2As2] slabs. The recurring feature of all members of the homologous series is a sandwich of [M2As2]-[REAs]-[M2As2] slabs, while rocksalt-type blocks of [REAs] increase in thickness between these sandwiches with higher n. Similar to the previously known related homologous series REM(2-x)As2·n(REAs) which is deficient in M, this new series RE(2-y)M4As4·n(REAs) exhibits deficiencies in RE to reduce the electron excess that would be present in the fully stoichiometric formulas. Enthalpic and entropic factors are considered to account for the differences in site deficiencies in these two homologous series. Band structure calculations indicate that the semiconducting behaviour of the parent n = 0 member (with CaAl2Si2-type structure) gradually evolves, through a narrowing of the gap between valence and conduction bands, to semimetallic behaviour as the number of [REAs] blocks increases, to the limit of n = ∞ for rocksalt-type REAs.

Ternary arsenides based on platinum–indium and palladium–indium fragments of the Cu3Au-type: Crystal structures and chemical bonding

Three metal-rich palladium–indium and platinum–indium arsenides, Pd5InAs, Pt5InAs, and Pt8In2As, were synthesized using a high-temperature ampoule technique. Their crystal structures were determined from Rietveld analysis of powder diffraction data. All the compounds crystallize in tetragonal system with P4/mmm space group (Pd5InAs: a=3.9874(1)Å, c=6.9848(2)Å, Z=1, Rp=0.053; Rb=0.013; Pt5InAs: a=3.9981(2)Å, c=7.0597(4)Å, Z=1, Rp=0.058, Rb=0.016; Pt8In2As: a=3.9872(3)Å, c=11.1129(7)Å, Z=1, Rp=0.047; Rb=0.014). The first two compounds belong to the Pd5TlAs structure type, while the third one is isotypic with the recently discovered Pd8In2Se. Main structural units in all arsenides are indium-centered [TM12In] cuboctahedra (TM=Pd,Pt) of the Cu3Au type, single- and double-stacked along the c axis in TM5InAs and Pt8In2As, respectively, alternating with [TM8As] rectangular prisms. DFT electronic structure calculations predict all three compounds to be 3D metallic conductors and Pauli-like paramagnets. According to the bonding analysis based on the electron localization function and electron localizability indicator topologies, all compounds feature multi-centered interactions between transition metal and indium in their heterometallic fragments. Additionally, pairwise interactions between platinum atoms are also observed, indicating a somewhat more localized bonding in the case of platinum-based compounds.

Two new arsenides, Eu7Cu44As23 and Sr7Cu44As23, with a new filled variety of the BaHg11 structure.

Two new ternary arsenides, namely, Eu7Cu44As23 and Sr7Cu44As23, were synthesized from elements at 800 °C. Their crystal structure represents a new filled version of the BaHg11 motif with cubic voids alternately occupied by Eu(Sr) and As atoms, resulting in a 2 × 2 × 2 superstructure of the aristotype: space group Fm3̅m, a = 16.6707(2) Å and 16.7467(2) Å, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity.

Negative and conventional magnetocaloric effects of a MnRhAs single crystal

We report on the magnetic and magnetocaloric properties of a MnRhAs single crystal. The ternary arsenide exhibits a rather complex magnetic behaviour. A first order metamagnetic type transition from antiferromagnetic (AFI) to ferromagnetic (“F”) states takes place at TT ∼ 158 K, and a second order transition from F to AFII states occurs at TC ∼ 196 K, the paramagnetic state occurring at T > TN = 238 K. Magnetic entropy changes were calculated using, Maxwell relation, and Clausius-Clapeyron equation. Both approaches are compared and discussed. The AFI-F transition in MnRhAs gives rise to an interestingly high level of negative magnetocaloric effect. Under a field change 0-1 T, the maximum magnetic entropy variation is about 3 J/kg K. For sufficiently high enough magnetic fields, the magnetocaloric working temperature range below 158 K can be covered. The F-AFII transition is accompanied by a relatively modest magnetocaloric effect (−2.3 J/kg K for 5 T at TC = 196 K), but it improves the working temperature span as well as the magnetocaloric properties. A minimum estimated refrigerant capacity of about 900 J/kg can be provided by a MnRhAs single crystal compound.

Homologous Series of Rare-Earth Zinc Arsenides REZn2–xAs2·n(REAs) (RE = La–Nd, Sm; n = 3, 4, 5, 6)

Four series of ternary rare-earth zinc arsenides have been prepared by reaction of the elements at 750 °C: RE4Zn(2-x)As5 forming for RE = La-Nd, Sm; and RE5Zn(2-x)As6, RE6Zn(2-x)As7, RE7Zn(2-x)As8 forming for RE = Ce, Pr, Nd, Sm. They crystallize in trigonal structure types in space group P3m1 with Z = 1 for RE4Zn(2-x)As5 and RE7Zn(2-x)As8, or space group R3m1 with Z = 3 for RE5Zn(2-x)As6 and RE6Zn(2-x)As7. Through the structural principle of intergrowing rocksalt-type [REAs] slabs of variable thickness within a parent CaAl2Si2-type structure containing Zn-deficient [Zn(2-x)As2] slabs built from edge-sharing Zn-centered tetrahedra, these ternary arsenides belong to a homologous series with the formulation REZn(2-x)As2·n(REAs) (n = 3, 4, 5, 6). Quaternary derivatives Ce4(Mn,Zn)(2-x)As5 and Ce6(Mn,Zn)(2-x)As7 were also obtained in which Mn partially substitutes for Zn. Band structure calculations predict that the electronic properties can be gradually modified from semiconducting to semimetallic behavior as more [REAs] slabs are introduced.

Ternary Arsenides A2Zn5As4 (A = K, Rb): Zintl Phases Built from Stellae Quadrangulae

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.

Crystal structure, electrical resistivity, and X-ray photoelectron spectroscopy of BaAg2As2

The ternary arsenide BaAg2As2 has been prepared by reaction of the elements at 850°C. Single-crystal and powder X-ray diffraction analysis revealed that it adopts the ThCr2Si2-type structure (Pearson symbol tI10, space group I4/mmm, Z=2, a=4.6025(3)Å, c=10.8672(6)Å at 295K) featuring [Ag2As2] layers interconnected by homoatomic As–As bonds along the c-direction. Band structure calculations indicate no gap at the Fermi level, and support the occurrence of strong As–As and weak Ag–Ag bonding. The asymmetric lineshape and the absence of a BE shift in the Ag 3d5/2 core-line peak relative to the element suggest delocalization of the Ag valence electrons. A significant negative BE shift (1.0eV) in the As 3d5/2 core-line peak relative to the element confirms the presence of anionic As atoms. A reversible transition is observed at 175K in the electrical resistivity, and is probably related to a structural phase transition.

Ternary Arsenides A2Zn2As3 (A = Sr, Eu) and Their Stuffed Derivatives A2Ag2ZnAs3

The ternary arsenides A(2)Zn(2)As(3) and the quaternary derivatives A(2)Ag(2)ZnAs(3) (A = Sr, Eu) have been prepared by stoichiometric reaction of the elements at 800 °C. Compounds A(2)Zn(2)As(3) crystallize with the monoclinic Ba(2)Cd(2)Sb(3)-type structure (Pearson symbol mC28, space group C2/m, Z = 4; a = 16.212(5) Å, b = 4.275(1) Å, c = 11.955(3) Å, β = 126.271(3)° for Sr(2)Zn(2)As(3); a = 16.032(4) Å, b = 4.255(1) Å, c = 11.871(3) Å, β = 126.525(3)° for Eu(2)Zn(2)As(3)) in which CaAl(2)Si(2)-type fragments, built up of edge-sharing Zn-centered tetrahedra, are interconnected by homoatomic As-As bonds to form anionic slabs [Zn(2)As(3)](4-) separated by A(2+) cations. Compounds A(2)Ag(2)ZnAs(3) crystallize with the monoclinic Yb(2)Zn(3)Ge(3)-type structure (Pearson symbol mC32, space group C2/m; a = 16.759(2) Å, b = 4.4689(5) Å, c = 12.202(1) Å, β = 127.058(1)° for Sr(2)Ag(2)ZnAs(3); a = 16.427(1) Å, b = 4.4721(3) Å, c = 11.9613(7) Å, β = 126.205(1)° for Eu(2)Ag(2)ZnAs(3)), which can be regarded as a stuffed derivative of the Ba(2)Cd(2)Sb(3)-type structure with additional transition-metal atoms in tetrahedral coordination inserted to link the anionic slabs together. The Ag and Zn atoms undergo disorder but with preferential occupancy over four sites centered in either tetrahedral or trigonal planar geometry. The site distribution of these metal atoms depends on a complex interplay of size and electronic factors. All compounds are Zintl phases. Band structure calculations predict that Sr(2)Zn(2)As(3) is a narrow band gap semiconductor and Sr(2)Ag(2)ZnAs(3) is a semimetal. Electrical resistivity measurements revealed band gaps of 0.04 eV for Sr(2)Zn(2)As(3) and 0.02 eV for Eu(2)Zn(2)As(3), the latter undergoing an apparent metal-to-semiconductor transition at 25 K.

CaAl2Si2-type Arsenides RE2/3Zn2As2 (RE = La, Ce, Pr, Nd, Sm)

The ternary arsenides RE2/3Zn2As2 (RE = La, Ce, Pr, Nd, Sm) were synthesized from the elements in NaCl/KCl salt fluxes and were characterized by powder X-ray diffraction. The Ce2/3Zn2As2 structure was refined on the basis of single-crystal X-ray diffractometer data: CaAl2Si2 type, P¯3m1, Z = 1, a = 417.17(6), c = 703.7(1) pm, wR2 = 0.0353, 211 F2 values, 11 variables, SOF(Ce) = 62.9(5) %. The zinc and arsenic atoms form a two-dimensional network of edge-sharing ZnAs4/4 tetrahedra with Zn-As distances of 253 pm. These covalently bonded [Zn2As2]2− layers are separated and charge-balanced by the cerium atoms. Each cerium atom has a slightly distorted octahedral arsenic coordination (Ce-As 302 pm). The defect type of the RE2/3Zn2As2 arsenides is discussed with respect to isotypic sulfides RE2/3Cu2S2.

Ternary arsenides Zr(Si As1−)As with PbCl2-type (0 ≤x≤ 0.4) and PbFCl-type (x= 0.6) structures

The ternary zirconium silicon arsenides Zr(SixAs1−x)As have been prepared through reaction of the elements at 900 °C. Extensive solubility of Si in the parent binary arsenide ZrAs2 was established in the form of the solid solution Zr(SixAs1−x)As (0 ≤ x ≤ 0.4). Single-crystal X-ray structure determination of the end-member Zr(Si0.39(1)As0.61)As (orthorhombic PbCl2-type, space group Pnma, Z = 4, a = 6.6828(8) Å, b = 3.6377(4) Å, c = 9.1131(11) Å, V = 221.54(4) Å3) revealed that the Si atoms prefer to occupy the interior sites of a four-atom-wide polyanionic ribbon. When the Si composition is increased to x = 0.6, the new ternary arsenide Zr(Si0.57(1)As0.43)As was identified (tetragonal PbFCl-type, space group P4/nmm, Z = 2, a = 3.6539(7) Å, c = 8.2399(15) Å, V = 110.01(4) Å3), in which the Si atoms prefer to occupy the sites of a denser polyanionic square net. Core-line X-ray photoelectron spectra measured on metallic, plate-shaped crystals of Zr(Si0.6As0.4)As support the presence of anionic Si and As atoms. Band structure calculations on idealized ordered models of Zr(Si0.5As0.5)As suggest that a competition between Zr-anion and anion–anion bonding interactions takes place in both structures.