Bridging neutron total scattering and atom-probe tomography for resolving amorphous and nanocrystalline structures

We propose a new approach to integrate neutron total scattering and atom-probe tomography (APT) through the Reverse Monte Carlo (RMC) method for resolving amorphous and nanocrystalline structures with a great degree of accuracy. Total scattering allows for the analysis of long-range average structure from Bragg scattering as well as local- and medium-range atomic structure from diffuse scattering, providing a powerful tool to characterize disordered, nanocrystalline and amorphous materials. The RMC analysis of total scattering data has long been employed to produce atomic configurations that match the experimental measurement [1]. While RMC is a stochastic approach for producing atomic models, it is often used as a refinement technique which in practice means the success often depends on finding a suitable starting configuration of atoms (∼20,000). Therefore, a starting configuration that is as close to the "true" one is desirable to aid the RMC modeling. In this regard, APT is a perfect fit in providing such a realistic starting configuration from a small portion of the reconstructed atomic map comprising hundreds of millions of atoms [2]. The proposed approach will be tested in two representative case studies: one for modeling the amorphous structure of Zr-Cu metallic glasses and the other for characterizing the sub-nano to nanoscale structure of γ′ nuclei precipitating from model Ni-based superalloys.