FIRST PRINCIPLES CALCULATIONS OF AG2AL STABILITY AND ELECTRONIC-PROPERTIES

The first principles layer Korringa-Kohn-Rostoker computational method is used to distinguish between two proposed atomic configurations for the binary Al-Ag h.c.p. intermediate phase, gamma, of composition Ag2 Al. A comparison between the calculated total energies of the two conf igurations is supported by a comparison of the resulting electron dens ity of states to existing electron spectroscopy data. The present calc ulations indicate that the lowest internal energy is obtained for the atomic configuration reported by Howe et al. from atomic resolution TE M studies of partially coherent plates of the gamma' transition phase. The gamma' phase is identical to the equilibrium gamma phase except f or the absence of misfit dislocations at the broad faces of the plates . The h.c.p, gamma' structure possesses basal planes alternating in co mposition from pure Ag to AgAl2 and exhibits both short range order wi thin the basal planes as well as long range order over alternate basal planes.