Benchmarking DFT methods for calculating reorganization energies in charge transport properties of organic semiconductors: A case study of nitro-aniline molecules

Abstract

Due to its occurrence in the exponential term of the Marcus–Hush hopping rate equation, precise prediction of the internal reorganization energy (${\lambda }_{\text{int}}$) is essential for reliable modeling of charge carrier mobility ($\mu$) in organic semiconductors. In this work, we calculated both hole (${\lambda }_{\text{h}}$) and electron (${\lambda }_{\text{e}}$) reorganization energies across three nitro-aniline push–pull isomers (ONA, MNA, PNA) by methodically benchmarking eighteen Density Functional Theory (DFT) functionals against the gold standard CCSD(T)/6-311++G(d,p) reference data. To demonstrate quantitative agreement, performance was evaluated using standard metrics (MAD, RMSD) supplemented by correlation coefficients ($R^2$). According to the analysis, double hybrid functionals: rev-DSD-PBEP86-D3 and rev-DSD-PBEP86-D3BJ functionals perform better with a Mean Absolute Deviation (MADs) of roughly 0.23 meV and a nearly perfect correlation with the CCSD(T) trend ($R^2>0.95$). On the other hand, hybrid functionals like M06 and CAM-B3LYP demonstrated notable discrepancies for specific isomers, underscoring their restricted suitability for precise $\lambda$ prediction. We recommend the rev-DSD-PBEP86-D3BJ methods as robust, less computationally demanding alternatives to CCSD(T) for these systems. This foundational work provides reliable DFT methods essential for subsequent accurate calculations of electronic coupling and charge transport mobilities, enabling future quantitative comparison with experimental data for nitro-aniline-like materials.