A new rhombohedral modification of EuNi₅In

Abstract

A rhombohedral modification of europium pentanickel indide, r-EuNi(5)In, crystallizes in the R ̅3m space group and adopts the UCu(5)In structure type. The structure is closely related to the hexagonal, h-EuNi(5)In, form (CeNi(5)Sn type). Both EuNi(5)In modifications are composed of CaCu(5) (EuNi(5))-, MgCu(2) (InNi(2))- and NiAs (EuNi)-type slabs in a 1:2:1 ratio. The atoms in the structure have high coordination numbers, viz. 20 and 18 for europium, 14 for indium, and 12 and 10 for nickel. The structure features a two-dimensional network of (2)(∞)[Ni(8)] tetrahedral clusters arranged in the ab plane.

Magnetocaloric Behavior in Ternary Europium Indides EuT5In: Probing the Design Capability of First-Principles-Based Methods on the Multifaceted Magnetic Materials

“…The applications of DFT-based methods to forecast the properties of hypothetical compounds have found their way into synthesis planning as they allows predicting compound formations, accelerating the discoveries of new materials. , Because recent explorations of the Eu–Ni–In , and the Eu–Au–In systems revealed two different structure types, while maintaining the same overall EuT 5 In compositions, the total energies have been evaluated for two possible EuCu 5 In models with both the EuNi 5 In and the EuAu 5 In structures (Figure ). This approach will reveal if the adoption of a structure type for the unknown EuCu 5 In is preferred due to steric (Ni (1.24 Å) and Cu (1.32 Å) have similar atomic covalent radii) or electronic (Cu and Au have the same valence electron counts) reasons.…”

“…In addition to the models of “EuAu 5 In”- I to “EuAu 5 In”- VI , the total energy was also evaluated for a hypothetical rhombohedral EuNi 5 In-type “EuAu 5 In” representative (“EuAu 5 In”- rh ) to identify the structural preferences between the rhombohedral and the tetragonal structure types for EuAu 5 In. A comparison of the total energies for “EuAu 5 In”- rh and “EuAu 5 In”- I indicates that the tetragonal one is preferred over the EuNi 5 In-type species.…”

“…Geometrical and (chemical) bonding analyses were accomplished for "EuT 5 In" models (T = Cu, Au) that adopt the EuNi 5 In-type 26 as well as the YbMo 2 Al 4 -type 29 to reveal the causes for the preferences to crystallize with a particular type of structure. From these analyses it is clear that the tetragonal structure is preferred for EuAu 5 In due to geometrical reasons ("optimal packing of atoms"), while the rhombohedral structure is favored for EuCu 5 In because of the driving force to maximize overall bonding.…”

“…One structurally diverse − class of intermetallic compounds that also reveals a range of interesting properties, e.g., hydrogen storage capabilities, heavy Fermion anomalies, and Kondo effects, ,, is a family with the general formula RT 5 M (R = rare-earth element, T = transition metal, M = post-­transition metal, for some cases, mixed with T). Our impetus to isolate a representative of the rhombohedral EuNi 5 In-type for the unknown EuCu 5 In was motivated by a recent examination of the Eu–Ni–In system indicating that the intercalation of hydrogen has a substantial impact on the structure as well as the physical properties of EuNi 5 In . On the other hand, investigation of the Eu–Au–In system points to the presence of a tetragonal, YbMo 2 Al 4 -type derived disordered crystal structure for EuAu 5 In, which has the same valence electron count as tentative EuCu 5 In, yet one has to keep in mind that the influence of relativistic effects increases considerably from copper to its heavier homologue gold .…”

“…Unit Cell Volume, Space Filling, and Total Energies per f.u. of Diverse "EuCu 5 In" and "EuAu 5 In" Models a The structures of EuCu 5 In and "EuAu 5 In"-rh are based on the EuNi 5 In26 -type (R3̅ m; No. 166), while the model of "EuCu 5 In"-I is derived from the structure of "EuAu 5 In"-I (P4mm; No.…”