Hanyu (Alice) Zhang with  Jennifer Carter

Analyzing the Internal Structure of Bulk Metallic Glasses through X-ray Absorption Fine Structure (XAFS) Spectroscopy

This project is aimed at using computational tools to see if current theory predicts the changes in XAFS spectra seen in experimental data. The objective of this project is to analyze the accuracy of current molecular dynamics (MD) simulations to predict the amorphous structure of metallic glasses as characterized by x-ray absorption fine-edge structure (XAFS) experiments. If successful, this project will expand our underlying understanding of the formation of these amorphous substances.

Bulk metallic glasses are solid metallic structures with their atoms arranged in a non-crystalline random fashion. Due to their glassy structures with no defects, these materials have superior strength when compared to their crystalline counterparts, and are as shapeable and moldable as plastics (Demetriou et al. 2011). The objective of this project is to test our current understanding of these materials by comparing computer simulated structures and their real-life counterparts. This will be achieved by analyzing the accuracy of current molecular dynamics (MD) simulations to predict the amorphous structure of metallic glasses as measured by x-ray absorption fine-edge structure (XAFS) experiments. The influence of composition and processing techniques on the final structure is being explored on bulk metallic glasses made from Ni, Co, Ta, and Nb. This project utilizes Large-scale Atomic/Molecular Massively Parallel Simulator (http://lammps.sandia.gov/), a MD software, to build the structures and a combination of the Demeter-XAFS analysis package and Python for data analysis. We are analyzing how closely the computer-generated, simulated, structure matches with experimentally measured and simulated x-ray spectroscopy spectra. The experimental data for the project has already been successfully collected.