Crystal structure and terahertz spectroscopy of α,α,α', α'-tetrabromo-p-xylene modeled using solid-state density functional theory

The previously unknown crystal structure of α,α, α',α'-tetrabromo-p-xylene has been determined using single-crystal X-ray diffraction, and it was discovered that the molecular packing primarily involves electrostatic interactions between neighboring molecules. Due to the unusual nature of the packing in this system, the vibrational motions were investigated. The low energy lattice and molecular vibrations unique to molecular crystals were measured in the terahertz (THz) region (10-100 cm ^-1). These vibrational motions were then reproduced using solid-state density functional theory (DFT) as implemented in CRYSTAL09, and it was found that the majority of the motions in this region involve either whole molecular translation or molecular scissoring.