Aliovalent anion substitution in materials allows for a different tuning of properties than either isovalent anion or cation substitution, as materials with different anion groups (e.g. halides vs. chalcogenides) tend to have very different band gaps and applications due to the large differences in orbital energies in the groups. Full aliovalent substitution, in which an anion is continuously replaced by another is somewhat rare, but has been demonstrated in some zincblende type photovoltaic materials , with the extreme case of InP-CdS solid solution allowing for band gap tuning from 1.3 eV to 2.6 eV, which occurs in a nonlinear fashion . Tuning the band gap from a narrow band gap (solar absorber) to wide gap (photocatalyst) is of interest, as materials that have intermediate or overlapping properties have unique applications e.g. for two photon absorption in photocatalysis and photovoltaics. Aliovalent substitution is a good candidate for this type of materials tuning.