Fig. 1: Structural evolutions of Rb6Re6S8I8 upon compression.
a Pressure-dependent in situ synchrotron-based XRD pattern, showing structural amorphization starting at ~12 GPa. The XRD pattern collected at ambient pressure is highlighted in gray, and indicates that no crystalline phase transition occurred prior to amorphization. b and c Evolution of the interatomic distance and bond angles under pressure, suggesting differential rigidity. We identify two distinct compression behaviors dominated by the significantly soft Rb-I(2) framework and the cage-structured Re-S-I(1) sublattice that is extremely insensitive to pressure. d Pressure dependence of the Raman spectra upon compression. e Pressure dependence of the full width at half maximum (FWHM) of the representative Raman modes, which are nearly unchanged upon compression. f First and second derivatives of the Re L3 edge \(\mu (E)\) plotted versus the photon energy of Re6Rb6S8I8 at different pressures upon compression. g Constant edge energy (E0) and white line energy (Ew) during the investigated compression process. h Pressure dependence of the XAS Fourier transform magnitude as a function of interatomic distance and fittings based on nearest neighbor (Re-S) at selected pressures. i Fitted interatomic Re-S distance. The low R-factors, which are on the order of 10-4 show the high goodness of fit. During the whole compression process up to 25.4 GPa, no obvious change occurs in the interatomic distance within the [Re6S8I6]4- cluster. The error bars in (g and i) denote the fitting errors.
