The Structure And Iuminescence Property Of Hydrogenated Fullerene C₇₀H₈₀ Under High Pressure

It's a new intersection to investigate the structure and character of hydrogen fullerenes under high pressure. Hydrogen fullerene is a new generation of hydrogen storage material. It is significant for the future of science to provide the necessary theoretical background application support.So far, there are little related reports about the structure and properties of hydrogen fullerenes under high pressure. It is a virginal research field, and there are many interesting and meaningful phenomena worth exploring. Compare the differences between fullerene and hydrogen fullerenes such as the crystal structure, molecular vibration and so on. In order to resolve these problems, we invest the sample under high pressure. And in this way we can develop the potential applications of this new energy storage material.In this paper, we study the molecular structure and vibration of C₇₀H₃₈. Furthermore, we focus on the changes that induced in pressure and the H atoms addition. And we invest whether hydrogen fullerenes are more stable than fullerenes under high pressure.The sample C₇₀H₃₈ is provided by Thomas from Sweden, which is reduced C70 under high hydrogen pressure. We measure C₇₀H₃₈ IR spectrum, and simulate its IR spectra by the Dmol3 module of Material Studio. Comparing the experimental and theoretical results, we give the correspondence between IR peaks and molecular vibration modes. This provides basic information for further invest C₇₀H₃₈ structure under high pressure.Furthermore, we get the XDR (powder diffraction pattern) information of C₇₀H₃₈. We find that the sample contain two mixed phases with hcp (a=11.08,c=18.32) and fcc (a=15.8). Comparing with C70, C₇₀H₃₈ crystal lattice expends about 17% which is due to the addition of hydrogen atoms. According to the peaks intensity ratio, we find that most sample belong to fcc phase.In situ high-pressure X-ray diffraction spectroscopy have been performed on C₇₀H₃₈ and the pressure reached 40GPa. As mentioned before sample is mixed structure contained fcc phase and hcp phase. With increasing pressure hcp structure transmit to fcc structure, so fcc structure is more stable than hcp under high pressure. Spacing distance is reducing with the pressure increasing,and there is a inflexion at 3GPa which is caused by the orientation of molecule from disorder to order. In the high-pressure XRD experiments, hcp phase almost transmit to fcc phase up to 40 GPa, and C₇₀H₃₈ retained the initial fcc structure when the pressure was released.At the same time we study IR spectra of C₇₀H₃₈ under high pressure. The vibrations linked to only carbon atoms in the cage exhibit a blue shift, while the C-H stretching vibrations show red shift with increasing pressure. These results indicate a change in the interaction between hydrogen and neighboring cages. The presence of hydrogen in the structure could also explain why molecular still keep integrated after quenching. Meanwhile it is the reason for the molecular structure of C₇₀H₃₈ is more stable than C70.