In Situ Synchrotron X‑ray Diffraction and Raman Spectroscopy Studies of Gd@C<sub>82</sub>–S<sub>8</sub> under High Pressure

The structural transformation and mechanical properties of fullerenes under high pressure have attracted a significant interest. However, the research data on the large-cage endohedral metallofullerenes are still rare. Here, we first report high-pressure studies on a new cocrystal Gd@C<sub>82</sub>–S<sub>8</sub> by in situ X-ray diffraction (XRD) and Raman spectroscopy. The high-pressure XRD data and Raman findings provide consistent evidence of no structural phase transition in Gd@C<sub>82</sub>–S<sub>8</sub> before a pressure-induced irreversible amorphization at about 23 GPa and an anisotropic deformation of the C<sub>82</sub> cage upon compression. The bulk modules is as high as 44 GPa and the embedded Gd atom has a great effect on the pressure behavior of Gd@C<sub>82</sub>, especially on the restraint of the compression of the adjacent bonds. The assignment of Raman-active vibrational modes and their corresponding eigenvectors of Gd@C<sub>82</sub> are presented for the first time by the theoretical calculation. Our findings provide new insights into the structural transformation of metallofullerenes under pressure and even contribute to prepare desired carbon materials with new structures and properties.