Selected members of the A2B3 (A = Sb, Bi; B = Se, Te) family are topological insulators. The Sb2Se3 compound does not exhibit any topological properties at ambient conditions; a recent high-pressure study, however, indicated that pressure transforms Sb2Se3 from a band insulator into a topological insulator above ~2 GPa; in addition, three structural transitions were proposed to occur up to 25 GPa. Partly motivated by these results, we have performed x-ray diffraction and Raman spectroscopy investigations on Sb2Se3 under pressure up to 65 GPa. We have identified only one reversible structural transition: the initial Pnma structure transforms into a disordered cubic bcc alloy above 51 GPa. On the other hand, our high-pressure Raman study did not reproduce the previous results; we attribute the discrepancies to the effects of the different pressure transmitting media used in the high-pressure experiments. We discuss the structural behavior of Sb2Se3 within the A2B3 (A = Sb, Bi; B = Se, Te) series.

High-pressure Raman spectroscopy and x-ray diffraction of Sb₂S₃ up to 53 GPa reveals two phase transitions at 5 GPa and 15 GPa. The first transition is evidenced by noticeable compressibility changes in distinct Raman-active modes, in the lattice parameter axial ratios, the unit cell volume, as well as in specific interatomic bond lengths and bond angles. By taking into account relevant results from the literature, we assign these effects to a second-order isostructural transition arising from an electronic topological transition in Sb₂S₃ near 5 GPa. Close comparison between Sb₂S₃ and Sb₂Se₃ up to 10 GPa reveals a slightly diverse structural behavior for these two compounds after the isostructural transition pressure. This structural diversity appears to account for the different pressure-induced electronic behavior of Sb₂S₃ and Sb₂Se₃ up to 10 GPa, i.e. the absence of an insulator-metal transition in Sb₂S₃ up to that pressure. Finally, the second high-pressure modification appearing above 15 GPa appears to trigger a structural disorder at ~20 GPa; full decompression from 53 GPa leads to the recovery of an amorphous state.

We have explored the high-pressure structural, vibrational, electronic, and magnetic behavior of the multiferroic $\mathrm{CoC}{\mathrm{r}}_2{\mathrm{O}}_4$ spinel up to 30 GPa by means of x-ray diffraction, Raman spectroscopy, and density functional theory calculations. Our investigations revealed a reversible tetragonal distortion of the starting cubic structure above 16 GPa. We suggest that the structural modification is mainly driven by magnetic effects induced under pressure. The results obtained are compared with the high-pressure behavior of related spinels.