The GFN1-xTB model contains 15 global parameters, 2 element-pair-specific parameters, and 32 element-specific parameters of relevance to the species present in the optimization sets (H, C, N, O and S atoms). Initially, the Hessian was generated to probe the sensitivity of the parameters, however, we found it computationally feasible to employ a similar optimization strategy to the original GFN1-xTB paper, where we optimize all relevant parameters simultaneously. We utilize a modified version of an in-house pseudo-Newton-Raphson op-timizer by Jensen et al. for the optimization of a target function (T ) containing a linear combination of the difference in electronic binding energies (∆E b in kcal/mol and gradient norms (g norm ) in Hartree/Bohr radius at the current GFN1-xTB parameterization and the target ωB97X-D/6-31++G(d,p) level of theory: