First Principles Study of the Electronic Structure and Optical Properties of Pentacene under Pressure

Abstract

The geometrical, electronic and optical properties of crystalline pentacene have been investigated within the framework of density functional theory including van der Waals interactions. The computed lattice parameters and band gap have good agreement with experimental data. We study the geometrical, electronic and optical properties of the pentacene under the hydrostatic pressure of 0–20 GPa. A pressure induced decrease in the band gap is observed. Moreover, the evolution of absorption coefficient (α(ω)), reflectivity (R(ω)), and the real part of the refractive index (n(ω)) at high pressure are also presented. We can see that all the peaks of optical constants move towards a lower energies with increased pressure, meaning a red shift.