Studies of atomic diffusion in Ni-Pt solid solution by x-ray photon correlation spectroscopy.

Atomic scale x-ray photon correlation spectroscopy (aXPCS) was used to study atomic diffusion in the Ni(97)Pt(3) solid solution with both a single crystal and a polycrystalline sample. Different jump diffusion models are discussed using experimental results and Monte Carlo simulations. The sensitivity of aXPCS experiments to short-range order (in this case governed by a strong Pt-Pt repulsive force) is demonstrated. The activation energy of 2.93(10) eV as well as diffusivities in the range of 10(-23) m(2) s(-1) at 830 K agree very well with the results of tracer diffusion studies at much higher temperatures.