A HIGH-RESOLUTION ELECTRON-MICROSCOPY STUDY OF THE STRUCTURE OF THE (1 0,2/1)-DECAGONAL AND (1/1,1/1)-DECAGONAL APPROXIMANTS IN GA6MN5/

Structural models of the two closely related orthorhombic approximants in the Ga6Mn5 alloy, the (1/0, 2/1) approximant with a = 0.77 nm, b = 1.25 nm and c = 2.36nm and the (1/1,1/1) approximant with a = 1.26 (a pproximate to 0.77 tau where tau = (1 + 5(1/2))/2) nm, b = 1.25 nm and c = 1.48 (2.36/tau) nm, have been deduced from their high-resolution electron microscopy (HREM) images and from the known structures of the orthorhombic Al60Mn11Ni4 (1/0,2/1) and Al3Mn (1/1,1/1) approximants. Experimental and simulated electron diffraction patterns and (010) HRE M images are compared. Some typical domain and fault structures in the se two approximants in the (010) HREM images are discussed.