In order to support that the thermodynamic stability of r-BN, predicted in the presented work, does not arise from the use of particular van der Waals correction methods, we evaluate the relative stability between r-BN and h-BN at T = 0 K without the inclusion of the phonon zero-point motion by using different correction methods, i.e., DFT-D2 and DFT-TS methods. We find that in all cases r-BN is predicted to be thermodynamically favored over h-BN, indicating that our results are qualitatively robust regardless of which van der Waals correction method is used. Yu et al. The results in this study suggest r-BN to be the most favorable BN polytype at typical conditions for CVD of sp 2 -BN films, 1000 -10000 Pa and 1100-1500 °C (1400-1800 K). As thermally activated CVD is at thermal equilibrium, the results presented here yield questions for the conditions at which h-BN can be deposited. The authors have shown that phase determination of 0001 oriented sp 2 -BN films require advanced thin film X-ray diffraction techniques; glancing incidence diffraction of asymmetric peaks with 2θ angles unique for each structure and pole figure measurements. The authors have reported CVD of h-BN using α-Al2O3 (0001) with a strained AlN buffer layer as substrate at 1500 °C and 7000 Pa. These conditions yielded a polytype pure h-BN film of 4 nm before the h-BN stacking altered to that in r-BN and where r-BN grew to a total film thickness of 200 nm. The change in polytype was suggested to depend on latticemismatch-induced stress relaxation. As comparison, growth on 6H-SiC (0001) substrates resulted in a 200 nm as phase pure r-BN film, using the same CVD process conditions as on α-Al2O3 (0001).