Identifying a Structural Preference in Reduced Rare-Earth Metal Halides by Combining Experimental and Computational Techniques

Abstract

The structures of two new cubic {TnLa 3 }Br 3 (Tn = Ru, Ir; I4 1 32, Z = 8; Tn = Ru: a = 12.1247(16) Å, V = 1782.4(4) Å 3 ; Tn = Ir: a = 12.1738(19) Å, V = 1804.2(5) Å 3 ) compounds belonging to a family of reduced rare-earth metal halides were determined by single-crystal X-ray diffraction. Interestingly, the isoelectronic compound {RuLa 3 }I 3 crystallizes in the monoclinic modification of the {TnR 3 }X 3 family, while {IrLa 3 }I 3 was found to be isomorphous with cubic {PtPr 3 }I 3 . Using electronic structure calculations, a pseudogap was identified at the Fermi level of {IrLa 3 }Br 3 in the new cubic structure. Additionally, the structure attempts to optimize (chemical) bonding as determined through the crystal orbital Hamilton populations (COHP) curves. The Fermi level of the isostructural {RuLa 3 }Br 3 falls below the pseudogap, yet the cubic structure is still formed. In this context, a close inspection of the distinct bond frequencies reveals the subtleness of the structure determining factors. ABSTRACT: The structures of two new cubic {TnLa 3 }Br 3 (Tn = Ru, Ir; I4 1 32, Z = 8; Tn = Ru: a = 12.1247(16) Å, V = 1782.4(4) Å 3 ; Tn = Ir: a = 12.1738(19) Å, V = 1804.2(5) Å 3 ) compounds belonging to a family of reduced rare-earth metal halides were determined by single-crystal X-ray diffraction. Interestingly, the isoelectronic compound {RuLa 3 }I 3 crystallizes in the monoclinic modification of the {TnR 3 }X 3 family, while {IrLa 3 }I 3 was found to be isomorphous with cubic {PtPr 3 }I 3 . Using electronic structure calculations, a pseudogap was identified at the Fermi level of {IrLa 3 }Br 3 in the new cubic structure. Additionally, the structure attempts to optimize (chemical) bonding as determined through the crystal orbital Hamilton populations (COHP) curves. The Fermi level of the isostructural {RuLa 3 }Br 3 falls below the pseudogap, yet the cubic structure is still formed. In this context, a close inspection of the distinct bond frequencies reveals the subtleness of the structure determining factors.

Electron Counting Rules and Electronic Structure in Tetrameric Transition-Metal (T)-Centered Rare-Earth (R) Cluster Complex Halides (X)

“…This structure is composed of {T 4 R c 10 R 6 e }type tetramers, which stem from the condensation of two dimers, {T 2 R 10 }, via three common edges ( Figure 3). Gd atoms that surround the Ru interstitials reside in 16 23 shows a distinctly different electronic structure relative to the tetragonal {Ru 4 Y 16 }I 20 -type structures. In particular, in the case of the monoclinic structure, significant Gd 5d and Ru 4d states lie in the same energy regions of the DOS curves as the Br 4p states.…”

“…22 Each {Ir 4 Y 16 } tetramer is encased by 24 inner bromido ligands capping 12 edges and 12 faces in a μ 2 -and μ 3 -like manner, respectively. The 12 outer Br a ligands reside in the inner coordination spheres of 10 nearest-neighboring tetramers and, in reply, 12 inner bromido ligands, Br i , connect each {Ir 4 Y 16 Figure 5(I)-a] unveils that the Ir 5d, Y 4d, and Br 4p states fall below a broad gap ranging from −1.93 to −0.79 eV. States near E F emanate from the Y 4d AOs with minor contributions from Ir 6p AOs.…”

“…22 The majority of these {T 4 R 16 }-type tetramers may be depicted as two perpendicularly arranged bioctahedra, {T 2 R 10 }, condensed via four common edges to form all vertices truncated T 3 supertetrahedra, {T 4 R 12 c R 4 e } (e = edge-sharing R atom; c = R atoms at the corners), 20−23 in which the T atoms form a tetrahedron. There is a second type of tetramer in which the {T 2 R 10 } bioctahedra share three common edges to aggregate to R 16 skeletons, {T 4 R c 10 R 6 e }, in which the four T atoms form a rhombus. This type has been observed solely for the compounds {B 4 Tb 16 }Br 23 and {Ru 4 Gd 16 }Br 23 .…”

High‐Pressure NiAs‐Type Modification of FeN

“…An insight into the electronic structure of NiAs-type Fe x N for x = 1was gained by examining band structure and density of states (DOS), while abonding analysis used the projected crystal orbital Hamilton populations (ÀpCOHP), avariant of the COHP technique [38] and their integrated values (ÀIpCOHP;C omputational Details are provided in the Supporting Information). Features at the Fermi level, E F ,i n the non-spin-polarized DOS and ÀpCOHP curves (Figure 5c,d) indicate an electronically unfavorable situation as E F falls into am aximum of the DOS curves [39] with strongly antibonding Fe-N interactions;s uch attributes at E F ,h owever,m ay also suggest that the material alleviates this unfavorable situation by approaching am agnetic state, [40] as indicated by Mçssbauer spectroscopy.…”

Revealing Tendencies in the Electronic Structures of Polar Intermetallic Compounds

“…Because the [TR 3 ]X 3 -type rare-earth transition-metal halides with group eight elements as endohedral atoms possess the same amounts of cluster-based electrons (CBEs), at this point, one may wonder which factors control the adaption of the respective type of structure. Examinations [64] of the electronic band structures and the nature of chemical bonding for isocompositional representatives of both [TR 3 ]X 3 -types with group eight interstitials indicate that the Fermi level in the cubic structure falls in a maximum of the DOS, while the Fermi level in the monoclinic [TR 3 ]X 3 -type representative is located in a narrow gap. The bonding in these rare-earth transition-metal halides is dominated by the heteroatomic R-T as well as R-X interactions beside minor, but evident R-R interactions ( Figure 1).…”