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Structural and Superconducting Transitions in Mg_{1-x}Al_{x}B_2

Sergey V. Barabash·David Stroud
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Abstract

From systematic ab initio calculations of the alloy system Mg_{1-x}Al_{x}B_2, we find a strong tendency for the formation of a superstructure characterized by Al-rich layers. We also present a simple model, based on calculated energies and an estimate of the configurational entropy, which suggests that the alloy has two separate concentration regimes of phase separation, with critical points near x = 0.25 and x = 0.75. These results, together with calculations of electronic densities of states in several ionic arrangements, give a qualitative explanation for the observed structural instabilities, as well as the x-dependence of the superconducting T_c for x<0.6.

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Sergey V. Barabash, David Stroud. 2002-02-26. Structural and Superconducting Transitions in Mg_{1-x}Al_{x}B_2. https://doi.org/10.1103/physrevb.66.012509

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