The long-period superlattice in CuAu II

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Abstract
We report the results of a series of calculations of the electronic structure of ordered, equi-atomic CuAu. We have investigated the effects of the creation of superzone boundaries on the Fermi surface of CuAu I when the long-period superlattice, the CuAu II phase, is formed. The new boundaries destroy appreciable regions of Fermi surface, thus favouring the formation of the latter phase. The positions of the boundaries are related directly to the period of the long-period superlattice and we have investigated their dependence on the electron/atom ratio and pressure. We find that the results are in very good agreement with previous experimental measurements of the average domain size in CuAu II. Thus, we provide strong evidence that Fermi surface topology plays an important role in determining the period of the long-period superlattice in CuAu II.