a1 Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401
a2 Department of Physics, University of Vermont, Burlington, Vermont 05405–0125
a3 Department of Physics, Tulane University, New Orleans, Louisiana 70118
A definition for structure of atomic scale systems is introduced which extends the typical crystallographic description to include elements of the total charge density. We argue that the mechanical properties of intermetallic alloys are related to this extended structure. These relationships have their origin in the nature of the charge redistribution accompanying strain. The direction of this charge redistribution is determined solely by the extended structure, while its magnitude can be correlated with a quantification of this extended structure. We demonstrate these facts by determining the extended structure and nature of the charge redistribution resulting from uniaxial strain for two alloys with the L10 structure: CuAu and TiAl. While these alloys share the same crystallographic structure, their extended structures are different, with CuAu possessing the same extended structure as the allotropic fcc metals while TiAl does not. These different extended structures give rise to different charge redistributions, which are argued to be related to the intrinsically ductile behavior of CuAu and the tendency for TiAl to fail transgranularly.
(Received March 19 1992)
(Accepted October 29 1992)