Speaker
Description
Neutron scattering is an ideal probe of the atomic structure and dynamics in solids, from fast ionic diffusion in solid electrolytes to lattice dynamics in thermoelectrics or ferroelectrics. These dynamics bridge the time-scales probed by quasielastic and inelastic neutron scattering (QENS/INS). This presentation will illustrate the complementarity of QENS -both coherent and incoherent- and INS, as well as opportunities to leverage machine learning and large-scale atomistic simulations. Examples will focus on fast ion diffusion in superionic conductors [1-5].
The design of new solid-state electrolytes (SSEs) for future solid-state batteries hinges on identifying key diffusion mechanisms that can improve material performance. While static structural descriptors have been correlated with fast diffusion, the host framework flexibility and vibrations and their complex dynamic coupling with mobile ions remain insufficiently understood. Phonons describe the atomic dynamics in crystalline materials, a convenient basis to encode possible minimum energy pathways for ion migration, and provide insights into correlated ion jumps. We investigated a series of halide and sulfide fast Na+/Li+ ion conductors, using a combination of coherent/incoherent QENS, INS, ab-initio molecular dynamics (AIMD), and machine-learning molecular dynamics (MLMD). In several instances, we find that soft anharmonic phonon modes play an important role in facilitating ionic hops, reflecting the softness in the potential energy surface. Further, the different coherent/incoherent components of QENS, supplemented with large-scale MLMD simulations, provide intricate details of the diffusion process. These results offer detailed microscopic insights into the dynamic mechanisms of fast ion diffusion in solid-state electrolytes.
[1] J. L. Niedziela, et al., Nature Physics 15, 73–78 (2019)
[2] M. K. Gupta, et al., Energy and Environmental Science 14, 6554-6563 (2021)
[3] M.K. Gupta et al., Advanced Energy Materials 12, 2200596 (2022)
[4] Q. Ren et al., Nature Materials 22, 999–1006 (2023)
[5] J. Ding et al., Nature Physics 21, 118–125 (2025).
