(698b) Seeing Single Atoms in Materials Via Atomic Electron Tomography

The properties and performance of nanomaterials are directly tied to their three dimensional (3D) atomic arrangement and their local chemical environment. Knowledge of the 3D atomic arrangement can also offer insights for tuning the synthesis of nanomaterials with greater stability under relevant operating conditions. Acquiring 3D information from individual nanoparticles has been demonstrated with several (scanning) transmission electron microscopy (S/TEM)-based approaches. Among them, atomic electron tomography (AET) has emerged as a powerful, nondestructive tool capable of revealing the atomic structure of materials in three and, through time‑resolved measurements, four dimensions. By identifying the 3D atomic positions in materials with high precision and without assuming crystallinity, AET establishes a quantitative framework for nanomaterials characterization, linking chemical composition, structure, and functionality. Seminal examples wherein AET has unearthed the local structure of nanomaterials at the single‑atom level are (i) identifying the short‑ and medium‑range order in metallic glasses and other amorphous materials, (ii) correlating the atomic defects of doped 2D transition metal dichalcogenides (TMDs) to their electronic properties, (iii) capturing how atoms rearrange during early stages of crystal nucleation in four dimensions, and (iv) deciphering the chemical order/disorder in multicomponent nanoparticles, among others. The experimental atomic coordinates have also been used as direct input to density functional theory (DFT) calculations to correlate the measured (unrelaxed) 3D atomic structures with the physical, chemical, and electronic properties of materials, which have shown to provide more accurate predictions than using relaxed atomic coordinates. Here, we illustrate the unique capability of AET to obtain the 3D positions and chemical identity of individual atoms in both crystalline and disordered nanomaterials, and we highlight some potential future avenues through combination of AET with high-throughput, data-driven approaches for the discovery of novel materials for targeted applications.