Low temperature phases in Ni-rich Ni-W and Ni-Re

It is known from experiment that the mechanical properties of Ni-based superalloys heavily depend on the individual amount of W and Re in the alloy. To understand this different behaviour a detailed knowledge of the zero Kelvin ground-state diagram would be of great importance. We find, by use of a density functional theory driven cluster expansion performed with the program package UNCLE, that the zero Kelvin ground-state diagrams for Ni-Re and Ni-W with all possible structures based on an fcc lattice up to 20 basis atoms differ significantly. While for Ni-Re we find only one ground-state i.e. the D1a structure at 20 at. % Re, for Ni-W there are six stable ground-states with concentrations less than 40 at. % W.