Axel Gudat

Li3FeN2, a ternary nitride with ∞1[FeN4/23-]-chains: Crystal structure and magnetic properties

Abstract Li3FeN2 was prepared from the melt under nitrogen and the crystal structure was determined by single-crystal diffraction (Ibam; a = 487.2(1) pm, b = 964.1(2) pm, c = 479.2(1) pm, Z = 4). The crystal structure can be described in terms of a fluorite superstructure which contains infinite chains 1 ∞ [FeN 4 2 3−] of edge-sharing FeN4 tetrahedra. Measurements of the magnetic susceptibilities vs. temperature reveal Curie-Weiss behaviour. Magnetic ordering occurs below 10 K. The calculated magnetic moment of 1.7(1) μB indicates a low spin state of the Fe3+ ion.

On the crystal structure of Ba8Ni6N7, a low valency nitridon1ccolate with infinite helical [Ni-N] zigzag chains

Abstract Ba8Ni6N7 was prepared from mixtures (pressed pellets) of BaNiN and Ba3N2 (molar ratio 1:1) at 800 °C under nitrogen. The crystal structure was determined by single-crystal X-ray diffraction ( C2 c ; a = 948.7(4) pm, b = 1657.8(6) pm, c = 1213.7(7) pm; β = 107.05(5)°; Z = 4). The rather complex new structure type is generated by distorted nitrogen coordination octahedra (NBa6, NBa4Ni2(cis) and NBa4Ni2(trans)) which share common edges as well as common corners. Barium is in a threefold (trig, planar) and a fourfold (distorted tetrahedral) nitrogen environment. Nickel (nearly linear coordination, N-Ni-N angle: 162.4(5)°–176.4(4)dg) and nitrogen (distance Ni[2]-N[6]: 175.6(10)–181.0(14) pm) are arranged to form infinite helical [Ni-N] zigzag chains which run parallel to the c ∗ direction.

Ternary and quaternary metal-nitrides in the Li-Sr-Ni-N-system

Abstract Single crystals of ternary and quaternary phases of the Li-Sr-Ni-N-system were grown from the melt under nitrogen and were investigated by X-ray diffraction methods. The crystal structures are classified into the following groups: i. solid solutions (substitutional type) of the Li 3 N-structure (Li 1−x Ni x [Li 2 N]), ii. structures containing fragments of the Li 3 N-structure (Li 4 SrN 2 , LiSrN and Li 4 Sr 2 (Li 0.8 .Ni 0.2 )N 3 and iii- structures which can be derived from interstitial binary metal nitrides of the first transition series (Li 3 Sr 3 Ni 4 N 4 ). The crystal structure of SrNiN is not quite clear at present, but shows close relations to the crystal structure of BaNiN (Sr(Ni 1−x Li x )N, resp.).

Ternäre Nitride des Lithiums mit den Elementen Cr, Mo und W / Ternary Lithium Nitrides with Elements Cr, Mo and W

The ternary compounds were prepared by reaction of the transition metals with Li3N melt under nitrogen. The crystal structures of Li6MeN4 (P42/nmc, Z = 2; Me = Mo: a = 667.3(1) pm, c = 492.5(3) pm; Me = W: a = 667.9(1) pm, c = 492.7(1) pm) and Li15Cr2N9 (P4/ncc, Z = 4; a = 1023.3(5) pm, c = 938.9(7) pm) can be described as fluorite-type superstructures with the lithium and transition metal atoms in tetrahedral holes of the nearly fcc nitrogen arrangement and with an ordered distribution of defects within the cation substructure. In addition, the ternary system Li–Cr–N contains the compound Li6CrN4 with a crystal structure which is not quite clear at present, but which shows close relations to the structures of Li6MeN4 (Me = Mo, W). The previously reported compounds Li9MeN5 (Me = Cr, Mo, W) have not been observed during this study. The respective Cr compound in fact is a nitride-oxide (nitride-imide) of composition Li14Cr2N8(O,NH) with a crystal structure (P3̄, Z = 1, a = 579.9(1) pm, c = 826.3(6) pm) also showing a fluorite-type superstructure.

Ca[(Ni1−xLix)N]: limited solid solutions (0 ⩽ x ⩽ 0.58) in the system Ca[NiN] (Y[CoC]-type structure)-Ca[LiN] (modified fluorite-type structure)

Abstract Solid solutions of composition Ca[(Ni 1− x Li x )N] (0 ⩽ x ⩽ 0.58) were prepared as polycrystalline materials by annealing mixtures of the ternary components Ca[NiN] and Ca[LiN]. Single crystals of the limiting composition Ca[(Ni 0.42 Li 0.58 )N]were grown from the melt (tetragonal, P 4 2 / mmc ; a = 372.3(1) pm, c = 665.6(1) pm; Z = 2; D x = 3.03 g cm −3 ). The crystal structure of the mixed crystal series (Y[CoC] type) contains linear ∞ 1 [(Ni 1− x Li x )N 2/2 ] chains with bond lengths ranging from 179.0 pm ( x = 0) to 186.1 pm ( x = 0.58).

(Li1-xNix)Li4Sr2N3: An “intergrowth-structure” of (Li1-xNix)SrN and Li4SrN2

Abstract (Li1-xNix)Li4Sr2N3 (x=0.22) was prepared by the reaction of lithium and strontium (molar ratio 2:1) in a nickel crucible with nitrogen at 900 °C, followed by cooling to room temperature (20 °C h−1). The crystal structure was determined by single-crystal X-ray diffraction (Cmmm; a=376.7(1) pm, b=2073.9(3) pm, c=391.6(1) pm; z=4). Infinite two-dimensional fragments of the Li4SrN2 structure and the LiSrN structure alternate along the [010] direction and are condensed via common strontium sites. Strontium is tetrahedrally coordinated by nitrogen. The Li-N frameworks show close structural relationships to sections of the Li3N-type structure.

Die Kristallstrukturen der isotypen Verbindungen Ba3[MoN4] und Ba3[WN4] / The Crystal Structures of the Isotypic Compounds Ba3[MoN4] and Ba3[WN4]

The isotypic ternary compounds Ba3[MoN4] and Ba3[WN4] were prepared by reaction of the transition metals with barium (Ba3N2, resp.) under nitrogen. The crystal structures were determined by single crystal X-ray diffraction: Ba3[MoN4] (Ba3[WN4]): Pbca; Z = 8; a = 1083.9(3) pm (1091.8(3) pm), b = 1030.3(3) pm (1037.5(3) pm), c = 1202.9(3) pm (1209.2(4) pm). The structures contain isolated tetrahedral anions [MN4]6- (M = Mo, W) which are arranged in form of slightly distorted hexagonal layers and which are stacked along [010] with the sequence (···AB···). Two of the three Ba atoms are situated between, the third one is placed within the layers of [MN4]-groups. In this way the structures can be derived from the Na3As structure type.