Difficulties of determining the binding energies and effective charges on the atoms are the main reason why no systematic explanation of the variation of the size of the energy gap among members of the simplest family of semiconductors—those with the zinc blende structure—has ever been given. It is shown that by the choice of suitable atomic parameters for discussing the activation energies of these compounds these difficulties may be avoided, and the variation of the size of the energy gap between one compound and another can be systematically accounted for. In the treatment which develops no particular distinction need be made between the III–V, II–VI, and I–VII compounds, and it is concluded that the anomalously high or low activation energies, which certain compounds appear to have, are just the result of the relative sizes of the cations and anions in influencing the polarization of the bonds.
Surface half-metallicity of CrAs in the zinc-blende structure