Structural study by X-ray diffraction and transmission electron microscopy of the misfit compound (SbS_1-xSe_x)_1.16(Nb _1.036S₂)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 (SbS_1-xSe _x) slabs stacking alternately with double NbS₂ layers and both can be treated as separate monoclinic subsystems. The (SbS _1-xSe_x) 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 {NbS ₆} 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) Å, c = 17.618(6) Å and β = 96.18(3)°, with incommensurability occurring along the b direction: b ₁ =3.3442(13)Å for the NbS₂ subsystem and b ₂ = 2.8755(13)Å for the (SbS_1-xSe_x) subsystem. The occurrence of diffuse scattering intensity streaked along c* indicates that the (SbS_1-xSe_x) subsystem is subjected to extended defects along the stacking direction.