## 2 Materials and Methods
### Experimental Details
#### 2.2.2 Characterization  
The pristine fullerite C\({}_{60}\) and its samples after HIP treatment were characterized using a number of chemical and physical analysis methods. XRD were conducted using equipment from the Center of \"physics and technology of micro- and nanostructures\" at the Institute for Physics of Microstructures of RAS and Raman Spectroscopy--usingequipment from the Center of Collective Use at the Institute of Geology of Komi Science Center of the Ural Branch of RAS.  
XRD analysis of the pristine C\({}_{60}\) powder and HIP-treated materials was performed with CuK\({}_{\alpha}\)-radiation using a Bruker D8 Discover X-ray diffractometer (Bruker Corp., Billerica, MA, USA) in the 0-20 symmetrical geometry with a Gobel mirror, an equatorial Soller slit with the angular divergence of 2.5\({}^{\circ}\), and a slit of 1.5 mm on the primary beam. The obtained diffraction patterns were processed using DIFFRAC.EVA V.3.0 software (Bruker Corp., Billerica, MA, USA) with the PDF-2 (2012) powder diffraction database.  
Raman studies were conducted at room temperature using an Ar laser with the 1 mW power and 488 nm wavelength. Spectra were recorded using a monochromator with the 600 lines/mm diffraction grating in the 100-4000 cm\({}^{-1}\) range. The spatial and spectral resolution was 1 \(\upmu\)m and 1 cm\({}^{-1}\), respectively. Each spectrum was the result of three accumulations with a 10 s exposure. The spectra fitting was performed by LabSpec V.5.36 software (Horiba, Ltd., Kyoto, Japan).  
All NEXAFS spectroscopy data were obtained at the Berliner Elektronenspeicherring fur Synchrotronstrahlung (BESSY II), Helmholtz-Zentrum, Berlin, Germany, using synchrotron radiation (SR) of the Russian-German beamline (RGBL) [31; 32]. C 1s NEXAFS spectra were measured using total electron yield (TEY) mode with correct consideration of non-monochromatic background and instrumental distortions. For energy calibration of these spectra, the energy positions of the first- and second-order light-excited Au 4f\({}_{7/2}\) photoelectron (PE) lines were used. The spectral variation of the photon flux was measured by recording a TEY signal from a clean Au plate. The photon energy resolution in the vicinity of the C 1s (\(\sim\)280 eV) absorption edge was set to 50 meV.  
XPS studies were carried out using an ESCAlab 250 Xi X-ray photoelectron spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) with AlK\(\alpha\) radiation (1486.6 eV) of X-ray tube to excite PE spectra at room temperature equipped with the electron-ion sample charge compensation system (the resource center in the Science Park at St. Petersburg State University, \"physical methods for surface research\"). The C 1s and O 1s core level and survey PE spectra were obtained with a total energy resolution of about 0.3 eV at the pass energy of 50 eV and 100 eV, respectively. The experimental particularities and the used equipment characteristics are described in more detail elsewhere [29; 33]. Samples for XPS and NEXAFS spectroscopy were prepared by pressing fullerene powder into the copper plate surface.  
All Raman, NEXAFS, and XPS measurements were performed for a series of samples at different points for each one, and their results had good reproducibility.