Finally, we repeated the calculations for amorphous structures with DFTB using the parameter sets A 0 and B 0 . A comparison between the resulting formation-energy residues with the corresponding quantities for A and B sets can be seen in Figure . From this data, we can conclude that the weight optimization procedure helps to increase the accuracy of the formation energy. This is especially true for set B, which gives lower residues than set B 0 for all concentrations. In the case of set A, the weight optimization procedure allows a better precision for 0.35 < Θ < 0.9 but not for the extreme Θ values. We remark that the optimized weights for this set focus the pair-repulsion parameterization in these intermediate alloys, while the weights for the pure elements are considerably smaller.