Hume-Rothery stabilisation mechanism and d-states-mediated Fermi surface–Brillouin zone interactions in structurally complex metallic alloys

Abstract

The stability of Co₂Zn₁₁ and Al₈V₅ gamma-brasses, both of which are composed of a transition metal element and polyvalent elements Zn or Al, can be discussed in terms of d-states-mediated Fermi surface–Brillouin zone (FsBz) interactions in the context of first-principles full-potential linearised augmented plane wave (FLAPW) band calculations. A FsBz-induced pseudogap is revealed in the FLAPW-Fourier spectrum, though it is hidden behind a much larger d-band in the total density of states. The stability range of three families of complex metallic alloys (CMAs) that include gamma-brasses, RT-, MI- and Tsai-type 1/1-1/1-1/1 approximants and 2/1-2/1-2/1 approximant, each of which is characterised by = 18, 50 and 125, respectively, can be well scaled in terms of the number of electrons per unit cell (e/uc) given by the product of the number of atoms per unit cell and the e/a value determined by the Hume-Rothery plot on the basis of the FLAPW-Fourier method. This is taken as the evidence for the justification of the Hume-Rothery stabilisation mechanism for all these CMAs having a pseudogap at the Fermi level.

Keywords:

• Hume-Rothery stabilisation mechanism
• Hume-Rothery plot
• d-states-mediated Fermi surface–Brillouin zone interaction
• approximant
• gamma-brass

Acknowledgements

One of the authors (UM) is grateful for the financial support of the Grant-in-Aid for Scientific Research (Contract No. 20560620) from the Japan Society for the Promotion of Science.