While the trendline's slope was very close to one, the values calculated with GFN2/D4 were often substantially lower than those calculated with DFT, with di↵erences as great as over 100 Å3 between the two methods. This error appears to be somewhat systematic, as species with lower polarizabilities generally have smaller di↵erences in calculated values (Figure ) whereas those with high polarizabilities generally have larger di↵erences in calculated values (Figure ). A substantial number of species' values appear as outliers from the regression line, suggesting a level of random error in GFN2/D4 calculations. In order to further explore the performance of GFN2/D4 for large polarizability calculations, we pursued testing a smaller group of molecules with a wider range of polarizabilites.