  The challenge of finding an absolute reference energy from first-principles
simulations to realigning semiconductor's valence band-top and conduction
band-bottom, a theoretical methodology is proposed based on plane-wave
calculations as implemented within state-of-art density functional theory. We
have studied some of inorganic binary semiconductors, including both oxides and
non-oxides, as for example rutile- and anatase TiO2, wurtzite ZnO, rutile SnO2,
blende phase of GaP, GaAs, InP, ZnTe, CdS, CdSe, and SiC, those are well known
and qualitatively important for photoelectrochemical, optoelectronic device
applications in their standalone and/or heterostructure morphologies. The
calculated band-edges of these well known semiconductors are realigned with
respect to our proposed absolute vacuum reference energy, which is defined with
our proposed corrections and compared to their available experimental values
from flat-band measurement. The prediction is reasonably well agreed with known
experimental flat-band measured data. Our estimated mean absolute error bar for
these set of eleven compounds is ~ 0.17 eV, closer to the known experimental
limit 0.10-0.20 eV.
