D. Kussmann et al., SYNTHESES AND CRYSTAL-STRUCTURES OF CACUGE, CAAUIN, AND CAAUSN - 3 DIFFERENT SUPERSTRUCTURES OF THE KHG2 TYPE, Zeitschrift fur anorganische und allgemeine Chemie, 624(11), 1998, pp. 1727-1735
Citations number
25
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
Zeitschrift fur anorganische und allgemeine Chemie
The intermetallic compounds CaCuGe, CaAuIn, and CaAuSn can be prepared
from the elements in sealed tantalum tubes or in glassy carbon crucib
les in a high-frequency furnace. Their crystal structures were determi
ned from single crystal X-ray data. The three compounds crystallize wi
th the same subcell structure (KHg2), however, they form three clearly
perceptible superstructures with different unit. cells, but all in sp
ace groups Pnma: a = 2124.9(6) pm, b = 436.0(2) pm, c=749.4(5)pm, Z=12
, wR2=0.0789, 1303 F-2 values, 56 variables for CaCuGe town structure
type), a = 738.2(1) pm, b = 459.4(1) pm, c = 839.4(2) pm, Z = 4, wR2 =
0.0651, 656 F-2 values, 20 variables for CaAuIn (TiNiSi type), a=3690
.3(3)pm, b=470.5(1)pm, c=813.6(2)pm, Z=20, wR2=0.1294, 1730 F-2 values
, 92 variables for CaAuSn (new structure type). The three structures m
ay be considered as superstructures of the KHg2 type with an ordered a
rrangement of the transition metal and germanium (indium, tin) atoms o
n the mercury position. Each calcium atom in the structures of CaCuGe,
CaAuIn, and CaAuSn has an distinctly ordered near-neighbor environmen
t of six transition metal (T) and six p element (X) atoms in the form
of two counter-tilted T3X3 hexagons. All known superstructures of the
KHg2 type are described in terms of a group-sub-group scheme.