Short-range order in Ni-rich Ni-W alloys investigated by synchrotron measurements and first-principles calculations

Ni-rich Ni-W alloys show a whole zoo of short-range order phenomena as observed by diffuse X-ray scattering. It will be shown that the quantitative analysis of these patterns can be successfully performed by the combination of X-ray scattering and ab-initio based calculations. For the latter, the combination of density functional theory with the cluster expansion method as realized in the computer code UNCLE and Monte-Carlo simulations is applied. This allows us to predict the short-range order in real and k-space as a function of concentration and temperature. The predicted patters are compared with experimental data. It turns out that the short-range order in Ni-W can only be explained by the simultaneous existence of different structure types, where the D16 compound plays one important role.