Electronic Structure of Stacking Faults in Pd_1−x Cu _x , Pd_1−x Ag _x , and Ag_1−x Au _x Alloys

Abstract

A face-centered cubic (FCC) crystal can be viewed as the …ABCABCABC… stacking of (111) planes. Stacking faults are caused by the disruption of this perfect stacking sequence. The most common fault found in a face-centered cubic (FCC) crystal, the intrinsic stacking fault, results when one atomic plane (a C plane) is removed, i.e. …ABCABABC…. When a <110|-type dislocation separates into two partial dislocations, the crystal contains an intrinsic stacking fault bounded by the two partial dislocation cores. The energy of the stacking fault determines the degree of separation and mobility of these partial dislocations. Dislocation mobility and core structure are some of the factors that influence ductility. Intrinsic stacking faults in FCC noble metals have been extensively studied experimentally,^1,2and more recently theoretically.^3,4 Pd_1−x Ag _x and Ag_1−x Au _x alloys form a series of FCC solid solutions over the entire range of x, Pd_1−x Cu _x also form a series of FCC solid solutions, though there is long range ordering at certain compositions. Thus, these three systems provide an excellent test of theoretical predictions of stacking fault energies in FCC alloys.