Das Verhalten der Alkalimetalle zu Halbmetallen. XI. Die Kristallstruktur von NaSi und NaGe

Abstract

Die Kristallstrukturen von NaSi und NaGe wurden mit Hilfe moderner Methoden bestimmt. Beide Verbindungen sind zwar analog aufgebaut, aber nicht streng isotyp (Raumgruppe C 2h6C 2/c bzw. C 2h5P 21/c). Wie in den Verbindungen der höheren Alkalimetalle1) werden auch hier Si4‐ bzw. Ge4‐Tetreader gebildet. Die Umgebung der Si‐ bzw. Ge‐Teilchen mit Alkalimetallatomen ist unregelmäßig. Die Übereinstimmung zwischen berechneten und beobachteten Strukturfaktoren ist gut: NaSi: R0,07; R′0,10 für insgesamt 125 Reflexe (h 0 l) und (h k 0); NaGe: R0,08; R′0,13 für insgesamt 1300 Reflexe (h k l).

Synthesis of the intermetallic clathrate Na2Ba6Si46 by oxidation of Na2BaSi4 with HCl

“…The precursor for the oxidation reaction was obtained by annealing a compact pill of a 2:1 mixture of NaSi [10] [11] powders at 873 K for 5 d in a closed Ta ampoule [1]. A single phase of Na 2 BaSi 4 was only formed after a second heat treatment at 1073 K in a closed ampoule.…”

Structure and bonding model for Na2Tl

“…However, a number of crystal structures were found in which the electronegative species form welldefined isoelectronic tetrahedra. These structures include NaPb (Marsh & Shoemaker, 1953), KSn, KPb, RbSn, RbPb, CsSn, and CsPb (Hewaidy, Busmann & Klemm, 1964), KGe, KSi, RbGe, RbSi, CsGe, and CsSi (Busmann, 1961), NaSi and NaGe (Witte, Schnering & Klemm, 1964), BaSi2 (Sch~ifer, Janzon & Weiss, 1963, and probably white (yellow) phosphorus (Hultgren, Gingrich & Warren, 1935) and, also likely, the metastable allotropes of arsenic and antimony (Wells, 1950). It may be noted from the stoichiometries of these phases that in every instance the number of the p electrons of the more electronegative species plus the number of valence electrons of the electropositive species, if any, averages to the same three electrons per atom of the species forming the tetrahedra.…”

Mixed Tetrahedral Zintl Clusters: Single Crystal Structure Determination of [Si4‐xGex]4−, [(MesCu)2(Si4‐xGex)]4−, and the 29Si MAS NMR Spectra of A4Si2Ge2 (A=K, Rb)

“…Data for binary phases and for Na 4 Si 2 Ge 2 are taken from literature. [10,11,14,15,18] Cell volumes of K 2 Rb 2 Si 4 , K 4 Si 2 Ge 2 and Rb 4 Si 2 Ge 2 are calculated from powder X-ray diffraction data (see Figure S1, S2, and S3 in the Supporting Information). The parameter x displays the amount of Ge in the tetrahedral subunit.…”