Eu₅Al₃Sb₆: Al₄ Tetrahedra Embedded in a Rock-Salt-Like Structure

Abstract

The new Eu 5 Al 3 Sb 6 phase has been successfully synthesized as a pure phase through Sn flux methods yielding large, high-quality crystals. This structure type features disordered Al clusters that appear in the form of dual tetrahedra. It crystallizes in the monoclinic C2/m space group exhibiting a rock-salt-like Eu−Sb framework with [Al 4 ] tetrahedra replacing some of the cationic Eu atoms (space group: C2/m, a = 8.151(1) Å, b = 14.181(2) Å, c = 8.145(1) Å, β = 109.577(2)°). The structure models the [Al 4 ] as dual tetrahedra with the Al atom sites 37.5% occupied along with Eu present on the central site at 8% occupancy and the remainder of the site being vacant. The presence of the [Al 4 ] cluster is further supported by HRTEM. Electronic structure calculations show that this material is a semimetal with observed band crossings close to the Fermi level. Strong Al−Sb antibonding interactions were found from COHP calculations close to the Fermi level and provide the rationale for the deficiency of the Al cluster. Mossbauer spectroscopy on Eu-151 and Sb-121 provides oxidation states of 2+ and 3− along with the local environment. Magnetic susceptibility measurements can be described well with a Curie−Weiss law where an effective moment of 7.80 μ B /mol Eu is obtained, consistent with Eu 2+ , and show canted antiferromagnetic behavior below 10 K. Temperature dependent resistivity shows a Kondo-like low-temperature upturn caused by enhanced scattering of the itinerant electrons with the 4f orbitals of Eu.

Advancing Heteroanionicity in Zintl Phases: Crystal Structures, Thermoelectric and Magnetic Properties of Two Quaternary Semiconducting Arsenide Oxides, Eu8Zn2As6O and Eu14Zn5As12O

“…To negate some of these effects, 4f orbitals were either excluded from the calculations or treated as core states in Eu 8 Zn 2 As 6 O and Eu 14 Zn 5 As 12 O, thus minimizing the influence of half-filled 4f orbitals, as expected for Eu 2+ species. This approach is widely used for Eu- and Yb-containing compounds, providing a reliable basis for preliminary analysis of the electronic structure. ,− …”

Effective optimization of atomic decoration in giant and superstructurally ordered crystals with machine learning

“…This is especially true when scattering cross-sections are similar among constituent species. For example, inorganic pseudobinary clathrates are most often reported with mixed occupancy among the framework sites 25,26,64 , and ambiguous chemical ordering is common among materials containing vacancies 23,24,28,29 . Recent studies have demonstrated substantial variation in SOF in pseudobinary inorganic clathrates, according to chemical composition, temperature, and synthesis method 25,26 .…”

Effective optimization of atomic decoration in giant and superstructurally ordered crystals with machine learning

“…For example, inorganic pseudobinary clathrates are most often reported with mixed occupancy among the framework sites, 25,26,64 and ambiguous chemical ordering is common among materials containing vacancies. 23,24,28,29 Recent studies have demonstrated substantial variation in SOF in pseudobinary inorganic clathrates, according to chemical composition, temperature, and synthesis method. 25,26 Additionally, site occupation factors can impact the mechanical, electronic, and thermal properties of a material.…”

“…The recent discovery of chemically driven superstructural ordering, [20][21][22] vacancy-ordering, 23,24 and order-disorder phase transitions 25,26 provides strong motivation for determining favorable decoration in large crystals. Nonetheless, characterizing the energetic influence of atomic interchange within a fixed geometry is useful for other endeavors, such as introducing dopants at various concentrations, selecting the optimal location of vacancies, resolving coordination in systems with mixed site occupancy, [27][28][29] or making atomic substitutions of any kind.…”