Computations of Ground State and Excitation Energies of Poly(3-methoxy-thiophene) and Poly(thienylene vinylene) from First Principles

摘要

Ground state and excitation energies of poly(3-methoxy-thio-phene) (PMT) and poly(thienylene vinylene) (PTV) conjugated polymers are studied by first principles density functional theory (DFT). Two basic approaches of computational chemistry and physics are compared: time dependent DFT (TDDFT) of clusters and ab initio pseudopotentials within a standard DFT (PP-DFT) of infinite polymer chains. We demonstrate that series of excitation energies of PMT calculated by TDDFT with increased unit numbers converge well to the real experimentally measured energy gaps. Combination of TDDFT cluster method with PP-DFT approach for infinite chain provides single-gap quasiparticle correction value needed for optical calculations. Infinite chain model is used to calculate optical absorption of PTV.