Old friends in a new light: “SnSb” revisited

The binary pnictide ‘SnSb’ has been re-investigated using a combination of X-ray, synchrotron and electron diffraction as well as electron microprobe analysis. Its structure was found to be incommensurately modulated with an underlying rhombohedral parent structure of space group symmetry R3¯m (No. 166), unit cell parameters ah=bh=4.3251(4)Å, ch=5.3376(6)Å in the hexagonal setting. The incommensurate primary modulation wave vector qh=1.3109(9)ch* and the superspace group symmetry is R3¯m (0, 0, ∼1.311) (No. 166.1). The refinement of the incommensurate structure indicates that the satellite reflections arise from displacive shifts of presumably essentially pure Sn and Sb layers along the hexagonal c-axis, with increasing distance between the Sn-layers and decreasing distance between the Sb layers.

A [112¯]R≡[11¯0]h zone axis EDP typical of incommensurately modulated “SnSb”. Three integer indexation with the subscript “R” is with respect to the rhombohedral setting unit cell while the (3+1) integer (hklm) indexation with the subscript “h” is with respect to the hexagonal setting unit cell.Figure optionsDownload as PowerPoint slide