## 3 Results and Discussion
### HIP-Treated Fullerite C\({}_{60}\) Study  
At the first stage, the study of the structural transformation of fullerite C\({}_{60}\) during the HIP treatment was carried out by such traditional methods as XRD and Raman spectroscopy. The first method allows one to obtain the bulk structural characteristic of the condensed phase and its distortions in the transformation process as a whole, and the second characterizes the changes in the system states at the level of an individual molecular cluster of C\({}_{60}\). However, these methods turn out to be of little information when it is necessary to analyze the C\({}_{60}\) molecule transformations and the formation of new stable carbon clusters. Therefore, the photoelectron and absorption X-ray spectroscopy was also used to characterize the structural changes in fullerite. The XPS and NEXAFS techniques make it possible to obtain the data on the nanoscale atomic structure of the sample and analyze the nearest surroundings and the charge state of an atom that absorbed an X-ray quantum. In other words, these methods also provide quantitative information on the local atomic and electronic structure of the sample. Figure 2 shows the diffraction patterns of the pristine fullerite C\({}_{60}\) and four samples of fullerite C\({}_{60}\) HIP-treated at a pressure of 0.1 GPa and temperatures of 920, 1120, 1170 and 1270 K for 3 h in an Ar atmosphere. The stable phase of pure fullerite C\({}_{60}\) at atmospheric pressure and room temperature is the fcc one with the Fm3m spatial symmetry group. In the pristine C\({}_{60}\) XRD pattern, the characteristic features of the fullerite C\({}_{60}\) fcc phase the (200) and (400) diffraction peaks are missing due to C\({}_{60}\) molecule rapid rotation at atmospheric pressure and room temperature. The characteristic features of the X-ray diffraction pattern of the fullerite C\({}_{60}\) fcc phase are the (200) and (400) diffraction peaks missing at atmospheric pressure and room temperature due to C\({}_{60}\) molecule rapid rotation. With increasing temperature, strong structural changes in diffractograms due to the transition from the fcc molecular crystal to an amorphous solid-state phase are observed. A series of clear narrow peaks in the region 20 = 10-24\({}^{\circ}\) in the fcc diffraction pattern of the fullerite C\({}_{60}\) phase shows that the starting material is a molecular crystal with a high degree of perfection. On the diffractograms at a 920 K temperature there is no shift, broadening and splitting of these diffraction peaks. This suggests that the C\({}_{60}\) cluster remains the main structural unit of the system and, at the same time, there is no change in the distances between fullerene molecules. However, a noticeable change in the relative intensities of the diffraction lines and the appearance of weak additional reflexes in the region of large diffraction angles of 40-50\({}^{\circ}\) are observed, which indicates a distortion of the structure of the initial crystalline phase structure and the beginning of the process of forming a chemical bond between C\({}_{60}\) molecules. With a further increase in temperature to 1120 K, a slight broadening of the main diffraction peaks is observed, indicating the formation of covalent C\(-\)C bonds and a change in the distances between the molecules. The appearance of two wide-diffuse lines located in the 15-30\({}^{\circ}\) and 40-50\({}^{\circ}\) regions on diffractograms is the beginning of the C\({}_{60}\) cluster destruction. When the temperature rises to 1170 K, the destruction increases, and at 1270 K the diffraction lines in the angle range of 10-24\({}^{\circ}\), characteristic of the molecular cluster, disappear and two wide lines at angles of -22\({}^{\circ}\) and -44\({}^{\circ}\) are observed. The obtained data demonstrate that the limit of the cluster C\({}_{60}\) thermal stability at a pressure of 0.1 GPa is ~1000 K and corresponds to the thermal stability limit of the C\({}_{60}\) fullerene molecule at atmospheric pressure [68].