| Popis: |
The new inorganic misfit layer compound (LaSe)1.20(TiSe2)2 was prepared by high-temperature reaction of the elements. It can be regarded as an intercalate of TiSe2 with LaSe double layers inserted into every second van der Waals gap of the TiSe2 sandwiches (stage-2 intercalate). The structure, determined by single crystal X-ray diffraction on the basis of (3 + 1)-dimensional superspace, is described by two interpenetrating, incommensurately modulated subsystems. The first subsystem comprises of paired TiSe2 sandwiches. Its basic space group is C[unk](0.5957(4), −0.0004(10), −0.189(4)) and the lattice parameters are a 11 = 3.556(2) Å, a 12 = 6.120(2) Å, a 13 = 17.876(10) Å, α 1 = 86.71(3)°, β 1 = 92.93(3)°, and γ 1 = 90.03(3)°. The second subsystem comprises of LaSe double layers with basic space group C[unk](1.679(1), 0.001(2), 0.317(6)) and unit cell dimensions a 21 = 5.969(2) Å, a 22 = 6.118(2) Å, a 23 = 17.859(9) Å, α 2 = 86.69(3)°, β 2 = 89.33(4)°, and γ 2 = 90.01(3)°. The two subsystems have the common ([unk],[unk]) plane. Refinement on 1602 reflections with I > 2.5σ(I) converged to R = 0.126 (wR = 0.155) for the average structure. Stacking disorder of TiSe2 is found corresponding to displacements of the sandwiches along the [unk]21 axis; in the final structure model 9.9(4)% of TiSe2 is rigidly shifted by ½ [unk]11. |
