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Abstract:
A new ternary phase with a composition of Al3AuIr has been found in the
Al-rich area of the Al-Au-Jr system. Differential thermal analysis
indicates a melting point of 990 degrees C, and single-crystal X-ray
diffraction measurements reveal that this ternary phase adopts a Ni2Al3
structure type (space group P (3) over bar m1) with a = 4.2584(5) A and
c = 5.1991(7) A. This compound is isostructural to the Al(3)Cu(15)Coos
phase also found in the Al-rich part of the Al-Cu-Co ternary diagram.
Experimental evidence combined with ab initio calculations point toward
an Al3AuIr phase mechanism. Quantum chemical calculations indicate
two-center and multicenter interactions in the Al3AuIr phase. Layered
distribution of two-center interactions separated by regions with four-
and five-center bonds suggests a preferential cleavage of the material
at puckered planes perpendicular to the [001] direction.
