Pressure effects on the electrical transport properties of benzene

The electrical transport properties of C6H6 under a high pressure of up to 50.0 GPa were systematically studied using alternate-current impedance spectra measurements and first-principles calculations. The bulk resistances of C6H6 decreased with increasing pressure due to the coupling of & pi; and & pi;* bands under compression. The two discontinuous changes of the bulk resistances can be found at 4.3 and 9.0 GPa, attributed to the pressure-induced structural phase transitions of C6H6. The decrease in & epsilon;(r) under compression indicated that the degree of dipole polarization and bound electrons was weakened. Furthermore, the orientation polarization cannot keep pace with the change in the AC electric field, giving rise to relaxation polarization and energy loss. By first-principles calculations, it can be found that the increased overlap of & pi; and & pi;* at the interstitial site between two adjacent molecules leads to a narrower band gap in benzene and an increase in polarization.