sidered through the analysis of the MAE statistical function. Parallelly, we also carried out the analysis of the Pearson coefficient. It indicates the goodness of the linear correlation between experimental and theoretical data, see [Table [2](#tbl2){ref-type="other"}](#tbl2){ref-type="other"}. In most of the cases, the theoretical methods employed have a good correlation with the experimental data. This suggests the capability of the selected method of predicting, with fair accuracy, the right stability ranking of an all-silica zeolite set.

Mechanical Stability {#sec2.3}
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To tighten the comparison between different methods, we have predicted the second-order elastic properties of 9 out of 14 frameworks of the zeolite set at the HF-3c level of theory. The mechanical properties of the chosen zeolites have already been investigated in literature.^[@ref33]^ From the analysis of the elastic tensor, we have calculated and analyzed the Young's modulus (*E*) and shear modulus (*G*) values. These two quantities are useful for characterizing the stiffness of a material, and, therefore, they can be related to the mechanical stability of the zeolites. Due to the anisotropic nature of the crystals, *E* and *G* are directional properties, thus assuming different values depending on the direction within the crystal with respect to their evaluation. As we are only interested in checking the performance of HF-3c method with respect to the DFT reference values, we considered only the minimum and maximum values assumed by *E* and *G* for all zeolites. The reference values are computed by the B3LYP-D2/SVP method, which were taken from ref ([@ref33]). The comparison is reported in [Figure [5](#fig5){ref-type="fig"}](#fig5){ref-type="fig"}, the statistical analysis is reported in [Table S5](http://pubs.acs.org/doi/suppl/10.1021/acsomega.8b03135/suppl_file/ao8b03135_si_001.pdf), and all explicit values are reported in [Table S6](http://pubs.acs.org/doi/suppl/10.1021/acsomega.8b03135/suppl_file/ao8b03135_si_001.p