Evaluating Fast Methods for Static Polarizabilities on Extended Conjugated Oligomers

Given the importance of accurate polarizability calculations to many chemical applications, coupled with the need for efficiency when calculating the properties of sets of molecules or large oligomers, we present a benchmark study examining possible calculation methods for polarizable materials. We first investigate the accuracy of highly-efficient semi-empirical tight-binding method GFN2-xTB, and the popular D4 dispersion model, comparing its predicted additive polarizabilities to ωB97X-D results for a subset of PubChemQC and a compiled benchmark set of molecules spanning polarizabilities from approximately 3-600 Å^3, with a few compounds in the range of approximately 1200-1400 Å^3. Although we find GFN2 to have large errors with polarizability calculations, on large oligomers it would appear a quadratic correction factor can remedy this. We also compare the accuracy of DFT polarizability calculations run using basis sets of varying size and level of augmentation, determining that a non-augmented basis set may be used for highly polarizable species in conjunction with a linear correction factor to achieve accuracy extremely close to that of aug-cc-pVTZ.