论文部分内容阅读
As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction pattes,the space group of fluorine at ambient pressure is in controversy.We successfully obtain its thermodynamically stable lowpressure phase,which shares the same structure as the earlier known C2/c.Further investigations on phonon spectra reveal the instability of the C2/m structure with imaginary frequency in the Brillouin zone and confirm the dynamically stable property of the C2/c structure at the same time.Compressing fluorine up to 8 GPa,the C2/c phase is found to undergo a phase transition to a new structure with a space group of Cmca.Electronic energy band structures indicate the insulating feature of C2/c and Cmca with no bands across the Fermi level.The infrared (1R) and Raman spectra of C2/c and Cmca at selected pressures are calculated to provide useful information to future experiments.