Extrapolation of polymer gap by combining cluster and periodic boundary condition calculations with Hückel theory

This study has proposed a Huckel theory-based extrapolation scheme for estimating the highest occupied molecular orbital (HOMO)-the lowest unoccupied molecular orbital (LUMO) gap of polymers without resorting to periodic boundary condition calculations using plane wave functions with hybrid functionals. The extrapolation scheme similar to ONIOM combines pure density functional theory (DFT) using plane wave functions for polymers and hybrid DFT using Gaussian functions for oligomers. We numerically assessed the scheme for polythiophene and 380 polymers and confirmed its accuracy and efficiency for polymer screening. Therefore, this scheme can be a screening methodology to estimate HOMO-LUMO energy gaps.