Cluster of framework considerations for the structures of Tl7Sb2, α-Mn, Cu5Zn8and their variants Li22Si51, Cu41Sn11, Sm11Cd45, Mg6Pd and Na6Tl with octuple unit cells

Hellner, E.; Koch, Elke

doi:10.1107/s0567739481000016

Cited by 19 publications

(3 citation statements)

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“…According to the group–subgroup relations, Mg 29– x Pt 4+ y is a face-centered 2 × 2 × 2 superstructure of primitive Pd 8 Cd 43 (space group P 4̅3 m , a = 9.9415 Å, Figure S4), whichin turncan be derived from the γ-brass arrangement. Usually the γ-brass derivatives are described by means of the nested polyhedral approach, − analyzing the nearest environment of the high-symmetry points. In the case of Mg 29– x Pt 4+ y , these are the point symmetry complexes 4̅3 m at (000), ( 1 / 4 1 / 4 1 / 4 ), ( 1 / 2 1 / 2 1 / 2 ), and ( 3 / 4 3 / 4 3 / 4 ), as well as at translationally equivalent points (Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…A common strategy to describe a CMA from a geometric point of view is the grouping of atoms into local atomic arrangements (crystallographic clusters), which makes the crystal structure easier to visualize, perceive, and understand the geometric organization; it reduces the degree of complexity and allows one to relate the CMA to simpler crystal structures. − , This is the nested polyhedral unit approach, , which was introduced first for the description of the γ-brass structure . The choice of a crystallographic cluster is considered as reasonable, if its shells are as spherical as possible and are quite separate with respect to the distances between the shells and with respect to the center of the nested polyhedrons.…”

Section: Introductionmentioning

confidence: 99%

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Mg_29–xPt_4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Agnarelli¹,

Prots²,

Ramlau³

et al. 2022

Inorg. Chem.

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Mg 29−x Pt 4+y represents the family of complex intermetallic compounds (complex metallic alloys, CMAs). It crystallizes in the cubic non-centrosymmetric space group F4̅ 3m with a = 20.1068(2) Å and around 400 atoms in a predominantly ordered arrangement. The local disorder around the unit cell origin is experimentally resolved by single-crystal X-ray diffraction in combination with atomic-resolution transmission electron microscopy (TEM, high-angle darkfield scanning TEM) studies. The quantum theory of atoms in molecules-based analysis of atomic charges shows that the unusual mixed Mg/Pt site occupation around the origin results from local charge equilibration in this region of the crystal structure. Chemical bonding analysis reveals for Mg 29−x Pt 4+y �rather unexpected for a crystal structure of this size�space-separated regions of hetero-and homoatomic bonds involving three to six partners (bonding inhomogeneity). Pt-containing 11-and 13-atomic units formed by heteroatomic 3a-, 4a-, and 5a-bonds are condensed via edges and faces to large super-tetrahedrons, which are interlinked by Mg-only 6a-bonds. Spatial separation of the regions with different bonding features is the key difference between the title compound and other CMAs, which are characterized by a predominantly homogeneous distribution of heteroatomic bonds.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mg_29–xPt_4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Agnarelli¹,

Prots²,

Ramlau³

et al. 2022

Inorg. Chem.

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“…[18][19][20] The γ-brass type structures crystallize in the space group I � 43m with a lattice parameter, a � 9 Å and contain ~52 atoms in one unit cell. γ-brass type structures can be described by a 26-atom cluster, [7,23,24] which is built up by four atomic shells.…”

Section: Introductionmentioning

confidence: 99%

Structural and Theoretical Investigations on the Unique Coloring Scheme of the γ‐Brass Type Phase: Cu_5+δCd_8‐δ(−1.0≤δ≤0.1)

Roy

Harshit

Mondal

et al. 2022

Zeitschrift anorg allge chemie

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Dedicated to Professor Mercouri Kanatzidis on the occasion of his 65th birthdayThe crystal structure of the γ-brass type Cu 5 + δ Cd 8-δ (-1.0 � δ � 0.1) in the CuÀ Cd binary system has been analyzed by powder and single crystal X-ray diffraction. All the compounds crystallize in the cubic space group I � 43m (217). Mixing of Cu with Cd leads to a significant phase width. At the limiting composition, a previously unreported ordered compound Cu 4 Cd 9 is formed. The structure of all compounds is described by a 26-atom γcluster. Electronic structure calculations on the model structure built according to the ordered "Cu 4 Cd 9 " , show the presence of a pseudo-gap at the Fermi level in the electronic density of states, which is consistent with other γ-brass type phases. However, the site preference of Cu and Cd atoms is different from the other reported γ-brass type structures in the Zn-and Cd-rich phases. To address the "coloring problem", a series of model structures were constructed with the composition Cu 4 Cd 9 and their total energies were compared with first-principle calculations using ABINIT code. LOBSTER package was implemented to extract the bonding information by crystal orbital Hamilton population calculations.

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Sich durchdringende polare und unpolare Untergitter in intermetallischen Phasen: die Struktur von NaCd₂

2007

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In den 1960er Jahren bestimmte Samson die Strukturen einiger der komplexesten intermetallischen Phasen, darunter NaCd2, Mg2Al3 und Cu3Cd4, die jeweils über 1000 Atome pro Elementarzelle aufweisen. Basierend auf den bemerkenswerten Arbeiten von Samson und Andersson verwenden wir quantenmechanische Rechnungen zur Beschreibung dieser Strukturen. Der formale Aufbau der Struktur auf der Grundlage der elektronischen Verhältnisse beginnt mit der relativ einfachen Mg17Al12‐Struktur und setzt sich bis zu Samsons NaCd2‐Struktur fort, wobei die Aufteilung in elektronenreiche und elektronenarme Gitterplätze (bezüglich der durchschnittlichen Elektronenzahl) bei beiden Strukturen das Vorliegen von Fragmenten des MgCu2‐Typs aufdeckt. Die äußeren und inneren Bereiche eines solchen Fragments weisen unterschiedliche Bindungsverhältnisse auf: Der innere Bereich ist eher polar, während die Grenzflächen relativ unpolar sind. Dieser Sachverhalt kann mit der Geometrie der Grenzflächenplätze begründet werden, die zugleich an elektronenreichen wie auch elektronenarmen Gittern beteiligt sind. Die polaren und unpolaren Gitterplätze in NaCd2 sind durch eine Minimalfläche, die D‐Fläche, voneinander getrennt. Die Argumente, die für eine solche Struktur sprechen, beruhen auf elektronischen Überlegungen. Ein entscheidendes Merkmal besteht darin, dass sich polare und unpolare Bindungstypen gegenseitig durchdringen. Diese Methode lässt sich auch auf andere Strukturen anwenden.

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Cluster of framework considerations for the structures of Tl₇Sb₂, α-Mn, Cu₅Zn₈and their variants Li₂₂Si₅₁, Cu₄₁Sn₁₁, Sm₁₁Cd₄₅, Mg₆Pd and Na₆Tl with octuple unit cells

Cited by 19 publications

References 4 publications

Mg_29–xPt_4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Mg_29–xPt_4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Structural and Theoretical Investigations on the Unique Coloring Scheme of the γ‐Brass Type Phase: Cu_5+δCd_8‐δ(−1.0≤δ≤0.1)

Sich durchdringende polare und unpolare Untergitter in intermetallischen Phasen: die Struktur von NaCd₂

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Cluster of framework considerations for the structures of Tl7Sb2, α-Mn, Cu5Zn8and their variants Li22Si51, Cu41Sn11, Sm11Cd45, Mg6Pd and Na6Tl with octuple unit cells

Cited by 19 publications

References 4 publications

Mg29–xPt4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Mg29–xPt4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Structural and Theoretical Investigations on the Unique Coloring Scheme of the γ‐Brass Type Phase: Cu5+δCd8‐δ(−1.0≤δ≤0.1)

Sich durchdringende polare und unpolare Untergitter in intermetallischen Phasen: die Struktur von NaCd2

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Cluster of framework considerations for the structures of Tl₇Sb₂, α-Mn, Cu₅Zn₈and their variants Li₂₂Si₅₁, Cu₄₁Sn₁₁, Sm₁₁Cd₄₅, Mg₆Pd and Na₆Tl with octuple unit cells

Mg_29–xPt_4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Mg_29–xPt_4+y: Chemical Bonding Inhomogeneity and Structural Complexity

Structural and Theoretical Investigations on the Unique Coloring Scheme of the γ‐Brass Type Phase: Cu_5+δCd_8‐δ(−1.0≤δ≤0.1)

Sich durchdringende polare und unpolare Untergitter in intermetallischen Phasen: die Struktur von NaCd₂