Synchrotron x-ray diffraction and infrared spectroscopy studies of C$_{60}$H$_{18}$ under high pressure

\textit{In situ} high-pressure angle dispersive synchrotron X-ray diffraction and high-pressure mid-IR spectrum measurements of C$_{60}$H$_{18}$ were carried out up to 32 GPa and 10.2 GPa, respectively. Our diffraction data indicated the fcc structure of C$_{60}$H$_{18 }$was stable up to 32GPa. The bulk modulus B0 was determined to be 21$\pm$1.16 GPa, about 40{\%} higher than that of C$_{60}$. The C-H vibrations still existed up to 10.2 GPa and the vibration frequencies decreased with increasing pressure. IR active vibrational frequencies and their corresponding eigenvectors of C$_{60}$H$_{18}$ were simulated by DMOL$_{3}$. The effects of hydrogen in the fullerene molecular cage on the stability of structure under high pressure were discussed.