These structures, available in CIF format, also contain the full stiffness tensor of second-order elastic constants, which were calculated with the GULP software 46 using the BKS interatomic potential. However, we find that the results obtained by this method have low reliability, with values of K varying between -27 000 and 20 500, and a significant fraction (≃ 8%) of structures being not mechanically stable (i.e. having at least one negative eigenvalue to the elastic tensor ). We thus used only the structural information in the database and relied on our machine learning approach to provide estimates for K and G with greater accuracy.