High-pressure structural properties of anthracene up to 10 GPa

This study concentrates on the crystal structure of anthracene (C14H10) under high pressure as a representative of the polyacene family. Angle-dispersive x-ray diffraction experiments from crystalline powder were performed using synchrotron radiation and a diamond anvil cell with a pressure-transmitting medium to keep hydrostatic condition. The structural data were analyzed by Rietveld refinements to obtain molecular arrangements and lattice parameters as a function of pressure up to 10.2 GPa. The lattice parameters a, b, and c decrease by 1.19 A (-13.9%), 0.53 A (-8.8%), and 0.68 A (-6.1%), respectively, while the monoclinic angle β increases by 2.5 deg. in this pressure region. The layer distance is also significantly decreased by 0.83 A (-9.0%). The detailed analysis of the arrangement of the molecules within the crystal structure reveals that the molecular planes become more and more parallel relative to each other. The closest intermolecular distance decreases from 3.6 A at ambient pressure to 2.8 A (-22.0%) at 10.2 GPa