Neue Arsenide mit ThCr₂Si₂- oder einer damit verwandten Struktur: Die Verbindungen ARh₂As₂ (A: Eu, Sr, Ba) und BaZn₂As₂ / New Arsenides with ThCr₂Si₂-type or Related Structures: The Compounds ARh₂As₂ (A: Eu, Sr, Ba) and BaZn₂As₂

Abstract

Four new arsenides of rhodium and zinc were prepared by heating mixtures of the elements at high temperatures (1000 -1200 • C) and investigated by single crystal X-ray methods. EuRh 2 As 2 (a = 4.067(1), c = 11.319(2)Å) and BaRh 2 As 2 (a = 4.053(1), c = 12.770(3)Å) crystallize with the well-known ThCr 2 Si 2 -type (I4/mmm; Z = 2). Due to the rigid layers of RhAs 4 tetrahedra, and to the atomic size of europium and barium, the As-As distances between the layers with values of 2.97 and 3.66Å, respectively, are very long. SrRh 2 As 2 is polymorphic and undergoes two phase transitions at about 190 and 282 • C. Main features of the three crystal structures are also layers of RhAs 4 tetrahedra. At room temperature α-SrRh 2 As 2 (a = 5.676(1), b = 6.178(2), c = 11.052(2)Å) probably crystallizes with the BaNi 2 Si 2 -type (Cmcm; Z = 4), whereas β -SrRh 2 As 2 (a = 5.760(3), b = 6.067(4), c = 11.264(5)Å, Fmmm, Z = 4) forms a new orthorhombically distorted variant of the ThCr 2 Si 2 -type. Single crystals grown in a flux of lead and quenched at high temperature show that the γ-phase (a = 4.112(1), c = 11.431(6)Å) crystallizes with the ThCr 2 Si 2 -type. The same is true for the high temperature modification of BaZn 2 As 2 (β -phase; a = 4.120(1), c = 13.578(1)Å), whereas the already known α-BaZn 2 As 2 forms the α-BaCu 2 S 2 -type (Pnma; Z = 4) consisting of a 3D-network of edge-and vertex-sharing ZnAs 4 tetrahedra with Ba atoms in the voids of this network.

Flux growth and structure of two compounds with the EuIn2P2structure type,AIn2P2(A= Ca and Sr), and a new structure type, BaIn2P2

“…Layered ternary compounds, AB 2 X 2 (A = rare earth or alkaline earth metal; B = main group, metalloid; X = main group 14-17 element) or 1-2-2 phases, favor the ThCr 2 Si 2 (I4/mmm) structure type, with the CaAl 2 Si 2 structure type (P3m1) as a distant second (Grytsiv et al, 2002;Hellmann et al, 2007). There are a few other less commonly observed structure types for layered main group metalloids, such as -BaCu 2 S 2 (Pnma; Leoni et al, 2003) observed for BaAl 2 Si 2 (Condron et al, 2007), and EuIn 2 P 2 (Jiang & Kauzlarich, 2006).…”

Electronic properties of novel 6 K superconductor LiFeP in comparison with LiFeAs from first principles calculations

“…Moreover, very recently a new "122" iron-free pnictides, namely, SrNi 2 As 2 , [22] were synthesized. These materials, where magnetic metal (Fe) is completely replaced by the other 3d magnetic metal (Ni) or non-magnetic metals (Ru, Rh) arsenic is completely replaced by other pnictogen -phosphorus, belong to the above mentioned "122" family and are low-temperature SC's (T C ~ 0.3-3.0K), see [21][22][23][24].…”

Superconductivity and Crystal Structures of (Ba1−xKx)Fe2As2 (x=0–1)

“…[19] A generally accepted key aspect for both LaFeAsO and BaFe 2 As 2 families is a magnetic and structural phase transition in the undoped phases, occurring at temperatures between 140-203 K. [10,[20][21][22] In the course of this transition, the tetragonal symmetry of the ThCr 2 Si 2 -type structure (space group I4/mmm) turns into the orthorhombic b-SrRh 2 As 2 -type [23] (space group Fmmm) before antiferromagnetic spin-ordering emerges. Recently, we have elucidated the spin structure of BaFe 2 As 2 by single-crystal neutron diffraction.…”