For the initial proof of concept work, we used cheaper, non-corrected DFT for the prediction of the band gap, to see whether the ML models could predict the property. If so, it follows that ML methods would be capable of predicting band gaps calculated using more accurate but expensive DFT hybrid functionals, with similar accuracy. The DFT band gap value for the boron nitride bilayer is 3.94 eV for the AB' stacking configuration, which is close to the value of 4.01 eV obtained for same stacking (though using a different vdW method) reported in a recent work. These authors also reported the equilibrium stacking as AA', with a band gap of 4.34 eV. However, using the TS vdW method, the lowest energy stacking configuration is AB', and is only 3 meV lower in energy than AA'. To ensure consistency, we adopt the minimum energy stacking of the TS method. The band gap of each of the bilayers corresponds to a specific band gap alignment of the two constituting monolayers. While the alignments yield a band gap that is smaller than that of the monolayers, as is typically the case alignment, where two semiconducting interfaces form a metallic structure across the vdW vacuum. We will explore these structures in detail in a future contribution. We display the band alignment for two of them, namely HfS 2 |MoTe 2 and MoSe 2 |TiS 2 , in Figure The results of the ML predictions of the band gap are summarized in Table and Figure .