Materials Science Research Lecture

NOTE! Every student or postdoc (any option!) will receive a $5 SmartCash "coffee credit" for each Materials Research lecture attended, in person or online. The credits will be tallied and issued after the last speaker of the term. *If you attend in person be sure to put your name on the sign-in sheet so you are counted.

Link to join Webinar: https://caltech.zoom.us/j/85010413991

Webinar ID 850 1041 3991

Abstract:

Investigating atomic motions in solids is critical to refine microscopic theories of transport and thermodynamics, in order to design improved materials. For instance, understanding the dynamics of ions is key to rationalize functional properties in numerous materials, ranging from superionic diffusion for solid-state batteries, to phase transitions and electron-phonon coupling in metal-halide perovskites, as well as nanoscale thermal transport in thermoelectrics for cooling or waste-heat harvesting. Yet, textbook models of atomic vibrations (phonons) often fall short in real materials, hindering material design. For instance, near phase transitions associated with lattice instabilities, strong anharmonic effects disrupt the conventional quasiharmonic phonon gas model. Large vibrational amplitudes, for example in crystals with soft bonds, also renormalize the electronic structure via the electron-phonon interaction. To reveal and clarify the ionic configurations and motions in real materials, our group uses state-of-the-art neutron and x-ray scattering techniques. Further, we perform first-principles simulations augmented with machine-learning algorithms to rationalize scattering experiments and identify underlying principles and descriptors enabling the design of future materials. This presentation will highlight the importance of investigating complex ion dynamics in several classes of materials, including halide perovskite photovoltaics [1], thermoelectrics [2,3], and superionic conductors [4,5,6].

[1] T. Lanigan-Atkins*, X. He* et al. "Two-dimensional overdamped fluctuations of soft perovskite lattice in CsPbBr3", Nature Materials 20, 977-983 (2021), https://doi.org/10.1038/s41563-021-00947-y

[2] J. Ding et al. "Anharmonic phonons and origin of ultralow thermal conductivity in Mg3Sb2 and Mg3Bi2", Science Advances 7:eabg1449 (2021). https://doi.org/10.1126/sciadv.abg1449

[3] T. Lanigan-Atkins*, S. Yang* et al. "Extended anharmonic collapse of phonon dispersions in SnS and SnSe", Nature Communications 11, 1-9 (2020). https://doi.org/10.1038/s41467-020-18121-4

[4] J. L. Niedziela et al. "Selective Breakdown of Phonon Quasiparticles across Superionic Transition in CuCrSe2", Nature Physics, 15, 73–78 (2019). https://doi.org/10.1038/s41567-018-0298-2

[5] J. Ding et al. "Anharmonic lattice dynamics and superionic transition in AgCrSe2", PNAS 117 (8) 3930-3937 (2020). https://doi.org/10.1073/pnas.1913916117

[6] M. Gupta et al. "Fast Na diffusion and anharmonic phonon dynamics in superionic Na3PS4", Energy and Environmental Science (2021), https://doi.org/10.1039/D1EE01509E

More about the Speaker:

Olivier Delaire obtained his PhD in Materials Science from Caltech (2006). He joined Oak Ridge National Laboratory as a Clifford Shull Fellow in the Neutron Sciences Directorate (2008), later becoming Staff Researcher in the Materials Science and Technology Division (2012). In 2016, he became Associate Professor in the Thomas Lord Department of Mechanical Engineering and Materials Science at Duke University, with secondary appointments in the Physics and Chemistry departments. The Delaire group at Duke carries research at the interface of energy research, condensed matter physics and solid-state chemistry, with an emphasis on atomic dynamics, for instance phonons in crystals and their interactions with electron or spin degrees-of-freedom, ionic diffusion, as well as phase transitions.