On-line Colloquium: Atomic Dynamics in Energy and Functional Materials: Vibrations, Diffusion, and Phase Transitions

ABSTRACT

Investigating atomic motions in solids is critical to refine microscopic theories of transport and thermodynamics, in order to design improved materials. In particular, the behavior of atomic vibrations (phonons) is key to rationalize numerous functional properties, ranging from multiferroics for information processing and superionics for safer solid batteries, to thermoelectrics for cooling or waste-heat harvesting. Yet, textbook models of lattice dynamics often fall short in real materials. For instance, near phase transitions associated with lattice instabilities, strong anharmonic effects disrupt the conventional quasiharmonic phonon gas model. Large vibrational amplitudes also renormalize the electronic structure via the electron-phonon interaction. This presentation will highlight the importance of phonons in several classes of crystalline materials, including halide perovskite photovoltaics [1], thermoelectrics [2,3], and superionic conductors [4-6]. We use state-of-the-art neutron and x-ray scattering techniques to probe atomic structure and dynamics, from phonon propagation to understand thermal transport, to ionic hopping to understand solid-state diffusion. We perform complementary first-principles simulations augmented with machine-learning algorithms to rationalize scattering experiments, and identify underlying principles and descriptors enabling future materials design.

[1] T. Lanigan-Atkins, X. He, et al. Two-dimensional overdamped fluctuations of soft perovskite lattice in CsPbBr₃, Nat. Mater. 20, 977 (2021).   [2] J. Ding, et al. Anharmonic phonons and origin of ultralow thermal conductivity in Mg3Sb2 and Mg3Bi2, Sci. Adv. 7, eabg1449 (2021).   [3] T. Lanigan-Atkins, S. Yang, et al. Extended anharmonic collapse of phonon dispersions in SnS and SnSe, Nat. Commun. 11, 4430 (2020).   [4] J. L. Niedziela, et al. Selective Breakdown of Phonon Quasiparticles across Superionic Transition in CuCrSe₂, Nat. Phys. 15, 73 (2019).   [5] J. Ding, et al. Anharmonic lattice dynamics and superionic transition in AgCrSe₂, PNAS 117, 3930 (2020).   [6] M. Gupta, et al. Fast Na diffusion and anharmonic phonon dynamics in superionic Na₃PS₄, Energy Environ. Sci. 14, 6554 (2021).

BIOGRAPHY

Prof Olivier Delaire obtained his PhD in Materials Science from Caltech (2006). In 2008, he joined Oak Ridge National Laboratory as a Clifford Shull Fellow in the Neutron Sciences Directorate, later becoming Staff Researcher in the Materials Science and Technology Division (2012). In 2016, he took an Associate Professor position 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.

Register in advance for this meeting:
https://bit.ly/PHY20220414

After registering, you will receive a confirmation email containing information about joining the meeting.

*The information collected from you will be used solely for the purpose of processing your registration for the above online colloquium.