Materials Transactions Online

Transactions of the Japan Institute of Metals, Vol. 14 No. 4 (1973) pp.273-280
© 1973 The Japan Institute of Metals

Long Period Superstructures in Close Packed Phases and Their Interpretation*

Konrad Schubert**

A survey is given on long period superstructures of close packed metallic phases comprehending shift variants of the Cu3Au type, stacking variants of the Cu3Au type and structures which display both variations. Shift variants and stacking variants obey valence electron rules for the shift density and h-density respectively. For the shift density a cut off interval exists in the neighbourhood of the valence electron concentration 1. The atom positions in the neighbourhood of the shift plane are somewhat changed and a possible rule for these changes is given. The shift normal is a direction of minimum elastic modulus following the presently known structures. Whole number half periods are preferred and give therefore a plateau of the shift density in dependence of the valence electron concentration. Nonintegral half periods are firmly established. There is a connection between the change of the axial ratio of the substructure and the change of the valence electron concentration.This axial ratio change is reduced by a second shift system. Shift variants occur with approximate valence electron concentrations 1 and 3. The rule of minimum iteration is seldom violated in shift variants and in stacking variants. For all these facts interpretations considering the spatial correlation of the electrons are given. To confirm these interpretations several open problems which are enumerated must be solved.

(Received September 29, 1972)

* Paper given at the 9th International Congress of Crystal lography in Kyoto.

** Max Planck Institut für Metallforschung, Stuttgart, BRD.

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