Exploring The Structural Properties And Phase Transitions Of Aromatic Hydrocarbon Materials Under Extreme Conditions

Many scientists are making great effort to searching for the high temperaturesuperconductor. So far, there are several superconducting series discovered:1. Conventionalsuperconductor, which can be explained by BCS theory,2. Cuprate based superconductor,unconventional superconductor, cannot explained by BCS theory,3. Iron-basedsuperconductor,4. Organic superconductor, composed of the elements Carbon, Hydrogen,Boron. Organic materials are possibly a room temperature superconductor, which predicted bya scientists Little. Now People have discover about40K superconducting transition inFullerene and hydrocarbon material. And they found many unconventional superconductingfeatures in these kinds superconductor,1,strong electron-electron coupling,2, AFI transition,3Mott-metal transition, which imply these kind materials are not the simple superconductorexplained by BCS theory. Therefore, these superconducting series possibly have highsuperconducting transition temperature.The aromatic hydrocarbon superconductors are much simpler superconducting series,which have the highest superconducting transition temperature in organic superconductor.Some researches reveal that these materials have two-dimensional structure, strongelectron-phonon coupling and electron-electron coupling,5to33K superconductivity.Additionally, R. B. Aust group have investigated the physical properties of Pentacene(allotropy of Picene) under high pressure, which reveal the metallization at20GPa. Thesestudies show that pressure play an important role in these kinds of materials. Thus, it is verynecessary for us to investigate the physical properties of aromatic hydrocarbon under highpressure for deeper understanding of these kinds materials.In this paper, we present a high-pressure investigation of phenanthrene by combiningRaman scattering and synchrotron X-ray diffraction (XRD) up to30.8GPa. Our studiesprovide an investigation of the pressure-related changes in molecular vibrations and thecorresponding responses of the crystal structure in phenanthrene. From our studies threepossible phases are shown to exist in phenanthrene up to30.8GPa, where the correspondingunit cell of each phase is determined based on the XRD data obtained. Our results alsosuggest that under further compression to20GPa, phenanthrene transforms into amorphoushydrogenated carbon based on the Raman spectra; however, the XRD data suggest thatcrystalline regions exist up to30.8GPa leading to a local disordered state.Additionally, we present other study of aromatic hydrocarbon superconductor. We report a detailed Raman scattering study of Kxphenanthrene (0≤x≤6) at room temperature. Wedetermine the number of electrons transferred to the phenanthrene molecule. Our resultssuggest the phase separation and intermediate phase in the range x=0–6.0. Combined withdensity functional calculations, we obtain an experimental constraint on the superconductivityof potassium-intercalated phenanthrene.