Furthermore, a very similar trend is seen with DFT-calculated band gaps. Work previously published by Wolverton et. al. shows a slope of about 0.9 on a plot of DFT-calculated band gap energies versus experimental band gap energies. Not only is the slope non-1, but also it is very similar to the slope observed in the formation energy case in figure . Furthermore, this is a raw DFT output, not a difference of DFT outputs, where error cancellation could cause additive errors to appear as proportional errors.