C. Druska et P. Bottcher, PREPARATION AND CRYSTAL-STRUCTURE OF CA5H G3 AND SR5CD3, Zeitschrift fur anorganische und allgemeine Chemie, 620(11), 1994, pp. 1845-1849
Citations number
28
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
Zeitschrift fur anorganische und allgemeine Chemie
Both the incongruently melting compounds, Ca5Hg3 and Sr5Cd3, have been
synthesized from stoichiometric amounts of the pure elements. They cr
ystallize with the Cr5B3 type of structure: space group I4/mcm, Z = 4;
Ca5Hg3 (Sr5Cd3): a = 818.9(1) (871.7(1)) pm, c = 1470.1(3) (1660.1(3)
)pm, c/a = 1.80 (1.90), R = 2.33% (2.97%). The most remarkable fragmen
ts are dumbbells X(2), which have interatomic distances only slightly
longer than the sum of Pauling's covalent radii: Hg-Hg (Cd-Cd) = 306 (
298) pm. The structure can be constructed by rhombic dodecahedra as th
e only constituent moieties. These rhombic dodecahedra are built up by
eight Ca (Sr) atoms and six Hg (Cd) atoms and are furthermore centere
d by an additional Ca (Sr) atom. Along [001] the rhombic dodecahedra s
hare common vertices, but along [110] they are interconnected via comm
on triangular faces. This kind of face sharing is responsible for the
short distances obtained between the polyhedra, which leads to the occ
urence of the dumbbells mentioned above.