-100 -75 -50 -25 0 25 50 Fig. ). Comparison of the difference between the enthalpies of formation from the BEEF-vdW and RPBE functional using different sets of references to determine the elemental chemical potentials: least-squares regression, CH 4 /H 2 /H 2 O, and C 2 H 6 /H 2 /CO. The mean absolute deviation (MAD) is reported in the legend. b) Aligning the two DFT datasets for the test case with different xc-functionals using linear regression to determine the elemental chemical potentials.