Ab initio modeling of hydrogen pipe diffusion in palladium

Hydrogen;Diffusion;Simulation

Schiavone, Emily

关键词: Hydrogen;    Diffusion;    Simulation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/99456/SCHIAVONE-DISSERTATION-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

A hydrogen economy will require metals for separation, transport and/or storage. Therefore, we need to better understand the behavior of hydrogen in metals. Hydrogen in palladium is a model system, for which there exists an abundance of experimental data. Specifically, quasielastic neutron scattering (QENS) experiments, for the first time, directly measured hydrogen pipe diffusion. The diffusivities and energy barriers from ab initio simulations support these findings, but open questions remain, the most concerning of which pertains to the unusual jump distances reported from fitting the experimental data. Instead of comparing diffusivities and energy barriers from simulation with the parameters extracted from fits to the experimental data, we calculate the spherically-averaged incoherent scattering function to directly compare with experimental data. We find that the experimental fitting procedure introduces errors in the extracted diffusivities and jump distances. We also calculate the intermediate scattering function to compare our simulation results with a wider range of experimental data. From direct comparison of the intermediate scattering function, we find disagreement at small times, which is likely due to the contributions from the vibrational motion of the diffusing hydrogen atom, the host palladium atoms and resonate vibrations. This computational approach allows for validation against experiment, along with a more detailed understanding of the QENS results.