Electron Diffraction Tomography on Two-Phase Nanolamellae of Topochemically Synthesized Cu(Sb2S3)Cl

The dark red semiconductor Cu(Sb2S3)Cl was obtained by leaching the layered precursor Cu(Sb2S3)[AlCl4] in a 0.1 M aqueous HCl solution. The selective extraction of AlCl3 yielded a mica-like lamellar product of poor crystallinity. Misalignment of lamellae down to the nanoscale prevented structure determination by conventional single-crystal X-ray diffraction, but a combination of transmission electron microscopy, selected area electron diffraction, and selected area electron precession diffraction tomography on a nanoscale spot with largely ordered crystalline lamellae revealed the crystal structures of two intergrown modifications. Orthorhombic o-Cu(Sb2S3)Cl and monoclinic m-Cu(Sb2S3)Cl have similar layers to the precursor and differ only in the stacking of the layers. These consist of uncharged Sb2S3 strands, whose sulfide ions, together with chloride ions, coordinate the copper(I) cations. Only one chloride ion remained from the [AlCl4]− group. DFT calculations confirm the structure solution for the orthorhombic form and suggest that the monoclinic structure is metastable against transformation to o-Cu(Sb2S3)Cl.


Crystal
).The acquisition tilt axis coincides with the TEM goniometer axis ( angle tilting axis).The 3D-PED volume reconstruction was made using PETS 2.0 and the images using VESTA 3 software.Reflections in the upper Laue zones (e.g.h1l, h3l, or 2kl) appear somewhat elongated or diffuse, which is an effect of the superposition with the twinned monoclinic form and small domain sizes.).The acquisition tilt axis coincides with the TEM goniometer axis ( angle tilting axis).The 3D-PED volume reconstruction was made using PETS 2.0 and the images using VESTA 3 software.The sequence of projections from top to bottom is correlated to that in Figure S4.Reflections in the upper Laue zones (e.g.hk1, hk3, or h2l) appear somewhat elongated or diffuse, which is an effect of the superposition of twin domains, the intergrowth with the orthorhombic form, and small domain sizes.

Crystal Structure Details and Crystallographic Data
for 1o and 2o Table S3.Atomic coordinates and isotropic displacements parameters for m-Cu(Sb2S3)Cl obtained from crystal 3m.
UV-Vis Spectroscopy Figure S1.Unit cell of the crystal structure of Cu(Sb2S3)[AlCl4] (left) and top view on a single layer (right).

Figure S4 .
Figure S4.Projections of the 3D-PED diffraction volume of Crystal 2o.The majority phase (84%) is orthorhombic o-Cu(Sb2S3)Cl.The projections are (a) along a* axis, (b) along b* axis and (c) along c* axis.The 3D-PED diffraction volume (reciprocal-space volume) was reconstructed from 89 2D-SA-PED images (selectedarea electron diffraction mode) obtained by stepwise tilt in the range 41° to 47° (tilt step 1°).The acquisition tilt axis coincides with the TEM goniometer axis ( angle tilting axis).The 3D-PED volume reconstruction was made using PETS 2.0 and the images using VESTA 3 software.Reflections in the upper Laue zones (e.g.h1l, h3l, or 2kl) appear somewhat elongated or diffuse, which is an effect of the superposition with the twinned monoclinic form and small domain sizes.

Figure S5 .
Figure S5.|E 2 -1| statistics for Crystal 2o.The value of |E 2 -1| = 0.722 suggests a non-centrosymmetric structure for o-CuSb2S3Cl.The expected value is 0.736 for an acentric structure and 0.968 for a centrosymmetric one.

Figure S6 .
Figure S6.(a) Crystal 3m of Cu(Sb2S3)Cl chosen for diffraction tomography (SA-PEDT).The selected area is marked with a red circle.(b) Hole (ca.300 nm) of the selected area (SA) aperture (ca.300 nm) enclosing the area marked in (a) with a red circle.The top of the beam stop is also visible.After crystallographic analysis, the selected area of crystal 3m was found to consist of 63% m-Cu(Sb2S3)Cl and 37% o-Cu(Sb2S3)Cl.

Figure S7 .
Figure S7.Projections of the 3D-PED diffraction volume of crystal 3m.The majority phase (63%) is monoclinic m-Cu(Sb2S3)Cl.The projections are (a) along b*m axis, (b) along c*m axis and (c) along a*m axis.The 3D-PED diffraction volume (reciprocal-space volume) was reconstructed from 90 2D-SA-PED images (selectedarea electron diffraction mode) obtained by stepwise tilt in the range 43° to 46° (tilt step 1°).The acquisition tilt axis coincides with the TEM goniometer axis ( angle tilting axis).The 3D-PED volume reconstruction was made using PETS 2.0 and the images using VESTA 3 software.The sequence of projections from top to bottom is correlated to that in FigureS4.Reflections in the upper Laue zones (e.g.hk1, hk3, or h2l) appear somewhat elongated or diffuse, which is an effect of the superposition of twin domains, the intergrowth with the orthorhombic form, and small domain sizes.

Figure S9 .
Figure S9.Powder X-ray diffraction pattern for a Cu(Sb2S3)Cl sample (CuKα1 radiation, λ = 1.54059Å).The Le Bail method was used to obtain lattice parameters for the orthorhombic (Pmc21) and the monoclinic (P21/m) modifications.Measured intensities are displayed as red points, the calculated pattern is displayed as a blue curve.At the bottom, reflection positions are marked by vertical black lines.The difference curve between the observed and calculated intensities is shown in black.Several reflections are indexed (red indices for o-Cu(Sb2S3)Cl and black indices for m-Cu(Sb2S3)Cl).The powder is textured (preferred orientation of platelets), and the h00o/0k0m reflections are significantly sharper than the other reflections.

Figure S10 .
Figure S10.The stacking of the layers in Cu(Sb2S3][AlCl4] and the two polymorphs of Cu(Sb2S3)Cl can be represented in a highly reduced way, focusing on the Cu-Cl dumbbells of the [CuS3Cl] tetrahedra in the corresponding projections along the long (about 10.6 Å) axis of the layers.From left to right: Cu-Cl dumbbells of the [CuS3Cl] tetrahedra in Cu(Sb2S3][AlCl4] o-Cu(Sb2S3)Cl, and m-Cu(Sb2S3)Cl.The light blue arrows indicate the layer shift in the two polymorphs of Cu(Sb2S3)Cl relative to the precursor compound.

Figure S11 .
Figure S11.UV-Vis absorption spectrum of Cu(Sb2S3)Cl.The inlet shows a TAUC plot, estimating a direct band gap of 1.54 eV.

Figure S13 .
Figure S13.Total density of states (DOS) and local density of states (LDOS) for the atoms in o-Cu(Sb2S3)Cl (calculated with PBE functional).Note that the scale for the LDOS of Cu is different from other elements.

Table S2 .
Atomic coordinates and isotropic displacements parameters for o-Cu(Sb2S3)Cl obtained from crystals 1o and 2o as well as from DFT-based structure optimization (from the space group P1 adapted to Pmc21).