A SHIFT-LATTICE DESCRIPTION OF SOME FACE-CENTERED-CUBIC ALLOY SUPERSTRUCTURES - PART 2 - 2-DIMENSIONAL STRUCTURES

The structures of the experimentally prepared binary alloys Au31Mn9 (t wo forms), Au72Mn21, Au95Mn28, Au27Mn8, Au167Mn49 and Au3Mn tone form) , have been analysed and found to be two-dimensional shift-lattices. I t is shown that both the Au and Mn atom arrays lie upon separate but c omplementary shift-lattices. The known structures form only a small pa rt of an infinite family of commensurate and incommensurate structures which can be constructed by smoothly varying the shift-lattice parame ters applicable to the known phases. The two-dimensional shift-lattice structures described here are shown to be constructed from fragments of simpler one-dimensional shift-lattices analysed previously.