ON QUADRUPLE-DEFECT FORMATION IN C15 LAVES PHASES

Arguments are given in favour of quadruple-defect formation in some La ves phases AB(2) with the C15 (MgCu2) structure. Such a defect consist s of three vacancies on the B sublattice combined with one anti-struct ure B atom. Using the Ising model and applying the Bra,ag-Williams app roximation, equations are derived for quadruple-defect content and vap our pressures as function of temperature. Possible experiments for mea suring these quantities are suggested. On the basis of simplified equa tions some consequences are elucidated.