X-ray structure determination of pseudomerohedrally twinned CoGe1.5S1.5 and CoGe1.5Se1.5, absorption correction

The crystal structures of the mixed skutterudites CoGe1.5S1.5 and CoGe1.5Se1.5 were determined by X-ray diffraction of powder samples and pseudomerohedral multiple twins (space group R3, No. 146, Z = 24, CoGe1.5S1.5: a = 1133.63(10) pm, c = 1391.76(9) pm, R(F)= 2.2%, 4288 unique reflections; CoGe1.5Se1.5: a = 1173.00(8) pm, c = 1441.1(3) pm, R(F) = 2.8%, 828 unique reflections). The triple pseudomerohedral twins are connected by three twofold rotation axes, which are linked by a threefold rotation axis. An absorption correction was performed by an intensity and volume ratio weighted empirical method. The intensity data for CoGe1.5Se1.5 were collected in two different azimuth and theta positions in order to minimise the absorption effects. The structures obtained are compared with those of binary skutterudites with respect to symmetry relations of the space groups and bonding of the rhombic Ge(2)X(2) units (X = S, Se), which partly reveal antiaromatic 4 pi electron behavior.