The intermetallic compounds GdRe2Al10 and TbRe2Al10, crystallizing with a stacking variant of the YbFe2Al10 type structure

The new compounds GdRe2Al10 and TbRe2Al10 were obtained in well-crystallize d form by reaction of the elemental components with an excess of aluminum a fter dissolving the matrix in hydrochloric acid. They crystallize with a ne w structure type which has been determined for TbRe2Al10 from single-crysta l X-ray data: Cmcm, a = 932.2(1), b = 1030.4(1), c = 1803.2(3) pm, Z = 8, R = 0.031 for 1159 structure factors and 77 variable parameters. Of the two terbium sites, one does not have full occupancy with terbium, however, it m ay have mixed Tb/Al occupancy. The resulting compositions are Tb0.948(5)Re2 Al10 or Tb0.936(3)Re2Al10.064(3), respectively. The terbium atoms are coord inated by 4 Re and 16 Al atoms. The rhenium atoms are situated in distorted icosahedra formed by 2 Tb and 10 Al atoms. The nine different aluminum ato ms have between 12 and 14 neighbors (1 or 2 Tb, 2 Re, and between 8 and 11 Al atoms). The structure may be viewed as consisting of two kinds of altern ating layers. One of these is puckered, hexagonal close packed, with a mesh content of 4ReAl(3); the other is planar and less densely packed. It has t he mesh content 2TbAl(4). The same kinds of atomic layers have been found i n the structures of YbFe2Al10 and LuRe2Al10. Thus, the three structure type s may be considered as stacking variants of each other. The tetragonal CaCr 2Al10 (ordered ThMn12) type structure also belongs to this structural famil y, although the CaAl4 layers somewhat differ from the layers TbAl4, YbAl4, and LuAl4.