The Interplay and Contrasts Involved in the Chemistry, Physics, and Crystal Structures of

As has been emphasized frequently in this monograph, the electron concentration plays a crucial role in control of phase stability as well as numerous physical properties of alloys. In Chapter 1, we have introduced two different notions of electron concentration: one is the e/a, appearing in connection with the Hume-Rothery electron concentration rule, and the other is the VEC, i.e., the number of electrons per atom, including the d-electrons being involved in the valence band. ἀ e VEC is obviously a key parameter in determining the Fermi level when first-principles band calculations are carried out to study the band structure. One must cautiously select either the e/a or the VEC as an electron concentration parameter, depending on the situation involved.