n- to p‑Type Conductivity Transition of Lu<sub>3</sub>N@C<sub>80</sub> Due to Anisotropic Deformation of Fullerene\nand Pyramidalization of Endohedral Clusters

The endohedral fullerene\nLu<sub>3</sub>N@C<sub>80</sub> was examined\nusing in situ high-pressure measurements, which included electrical\ntransport, Fourier-transform infrared spectroscopy, and Raman spectroscopy,\nin combination with theoretical calculations. Lu<sub>3</sub>N@C<sub>80</sub> was found to undergo a reversible n- to p-type conversion\nat ∼8.9 GPa. This p-type semiconductor remains stable up to\n25 GPa. The fullerene cage collapses at ∼29 GPa, resulting\nin an irreversible p- to n-type conversion. Raman, infrared, and X-ray\nabsorption spectroscopy reveal that an anisotropic distortion of the\ncarbon cage and a pyramidalization of the planar Lu<sub>3</sub>N clusters\noccur during compression. Density functional theory simulations indicate\nthat the p orbitals of C atoms in the fullerene cage primarily contribute\nto the density of states (DOS). Pressure-induced deformation of the\nfullerene cage dominates the DOS changes in the conduction and valence\nbands close to the Fermi level. The findings elucidate the relationship\nbetween the conductivity and structural changes in the endohedral\nclusters.