Structure of a polytype of the inorganic misfit-layer compound (PbS)1.18TiS2

A second modification is reported of the inorganic misfit-layer compound (PbS${)}_{1.18}$ ${\mathrm{TiS}}_2$. It is found to be a true polytype of the previously analyzed monoclinic form. The AB stacking of layers in the latter is replaced by a stacking ABA’B’ in this orthorhombic modification. Single-crystal x-ray diffraction measurements (Mo Kα radiation, λ=0.710 73 Å) were performed on a crystal of (PbS${)}_{1.18}$ ${\mathrm{TiS}}_2$. The structure is described by two modulated subsystems (ν=1,2), which have the (${\mathbf{a}}_{\nu 2}^{\mathrm{*}}$,${\mathbf{a}}_{\nu 3}^{\mathrm{*}}$) reciprocal-lattice plane in common. A superspace embedding follows from four reciprocal-lattice vectors, given by ${\mathbf{a}}_1^{\mathrm{*}}$=${\mathbf{a}}_{11}^{\mathrm{*}}$, ${\mathbf{a}}_2^{\mathrm{*}}$=${\mathbf{a}}_{12}^{\mathrm{*}}$, ${\mathbf{a}}_3^{\mathrm{*}}$=${\mathbf{a}}_{13}^{\mathrm{*}}$, and ${\mathbf{a}}_4^{\mathrm{*}}$=${\mathbf{a}}_{21}^{\mathrm{*}}$.