Overall, the funneling approach is never more efficient than its weakest link given by the semiempirical step in 2, in which accuracy determines the number of structures that have to be optimized/have single points calculated at the DFT level. In this paper, we focus on reparameterizing the GFN1-xTB method based on DFT energies of atmospherically relevant molecular clusters yielding a GFN1-xTB model reparametrized based on ωB97X-D/6-31++G(d,p) for 'atmospheric molecular clusters' denoted AMC-xTB. This new parameterization is used to sample 288 large multi-acid-multi-base clusters containing AM equivalent to the clusters studied by Knattrup et al. 2 Methodology