Structures of the quaternary iron germanium antimonides R1-x(R,Fe)6Ge4(Ge,Sb)2 (R=Ti, Cr, Mn), filled derivatives of FeGe1-xSbx

Three members of a new family of quaternary iron germanium antimonides, R1-x(R,Fe)(6)Ge-4(Ge,Sb)(2) (R=Ti, Cr, Mn) have been synthesized through reaction of the elements. The structures of Ti0.5Fe6Ge5Sb (a=8.8452(11) Angstrom, c=7.9785(9) Angstrom), Cr0.8Fe5.3Ge5.2Sb0.8 (a=8.8504(12) Angstrom, c=8.0246(10) Angstrom), and Mn1.8Fe4.6Ge4.9Sb1.1 (a=8.9099(13) Angstrom, c=7.9665(9) Angstrom) have been determined by single-crystal X-ray diffraction. They crystallize in the hexagonal space group D-6h(1)-P6/mmm with Z=3. The structures consist of 3636 nets of metal atoms and 6(3) nets of Ge atoms that are stacked alternately along the c direction leaving open hexagonal channels. These channels are filled by R atoms, metalloid dumbbells (Ge-2, GeSb, or Sb-2), and, in the case of Cr0.8Fe5.3Ge5.2Sb0.8, isolated Ge atoms. The new compounds may be considered as filled variants of FeGe1-xSbx, or, alternatively, as substitutional derivatives of R(R,Fe)(6)Ge-6. (C) 2001 Elsevier Science B.V. All rights reserved.