Structural study by X-ray diffraction and transmission electron microscopy of the misfit compound (SbS1-xSex)1.16(Nb1.036S2)2

In the Sb-Nb-S-Se system, a new misfit layer compound (MSL) has been synthesized and its structure was determined by combining single crystal X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It presents a composite crystal structure formed by (SbS1-xSex) slabs stacking alternately with double NbS2 layers and both can be treated as separate monoclinic subsystems. The (SbS1-xSex) slabs comprise a distorted, two-atom-thick layer with NaCl-type structure formed by an array of {SbX5} square pyramids joined by edges (X: S, Se); the NbS2 layers consist of {NbS6} trigonal prisms linked through edge-sharing to form sheets, just as in the 2H-NbS2 structure type. Both sublattices have the same lattice parameters a = 5.7672(19) A, c = 17.618(6) A and β = 96.18(3)o, with incommensurability occurring along the b direction: b1 = 3.3442(13) A for the NbS2 subsystem and b2 = 2.8755(13) A for the (SbS1-xSex) subsystem. The occurrence of diffuse scattering intensity streaked along c* indicates that the (SbS1-xSex) subsystem is subjected to extended defects along the stacking direction.