Event
MSE Seminar: Dr. Olivier Delaire, Duke University
Wednesday, October 2, 2024
3:30 p.m.
Room 2108 Chemical and Nuclear Engineering Building
Sherri Tatum
301-405-5240
statum12@umd.edu
The dynamics of atoms in solids – from early breakthroughs to current challenges
Abstract: From Einstein’s and Debye’s models for the heat capacity [1,2], through Peierls’ early theory of thermal conductivity [3], and the Bardeen-Cooper-Schrieffer theory of superconductivity [4], the importance of atomic motions in solids has been established early on as a central aspect of materials science. Solids are not static and the motions of ions within them (vibrational or diffusive) underlie many thermodynamic and transport properties. Probing and rationalizing the atomic dynamics is important from both a fundamental standpoint and to enable the design and engineering of desired material properties. Yet, the complex dynamics and couplings between degrees-of-freedom underpinning numerous material properties remain insufficiently understood. This talk will illustrate how experiments with neutrons and x-rays, coupled with large-scale atomistic modeling and machine learning, can provide key insights toward designing materials with improved performance. Examples will include studies of :
- correlated disorder in metal halide perovskites whose soft lattice leads to strongly damped phonon modes and structural fluctuations [5,6]
- ionic diffusion process in `superionic’ conductors and solid-state electrolytes for batteries [7,8,9]
References:
[1] A. Einstein, Ann. Phys. 22, 800 (1907). [2] P. Debye, Ann. Phys. 39 (4): 789–839 (1912).
[3] R. Peierls, Ann. Phys. 395, 1055–1101 (1929).
[4] J. Bardeen, L. N. Cooper, and J. R. Schrieffer, Phys. Rev. 106, 162 (1957)
[5] T. Lanigan-Atkins*, X. He*, et al. “Two-dimensional overdamped fluctuations of soft perovskite lattice in CsPbBr3”, Nature Materials (2021)
[6] X. He, M. Krogstad, M K Gupta, et al. “Multiple lattice instabilities and complex ground state in Cs2AgBiBr6”, PRX Energy 3, 013014 (2024).
[7] J. L. Niedziela, et al.“Selective Breakdown of Phonon Quasiparticles across Superionic Transition in CuCrSe2”, Nature Physics (2019)
[8] M. K. Gupta, et al. “Fast Na diffusion and anharmonic phonon dynamics in superionic Na3PS4”, Energy and Environmental Science (2021)
[9] Q. Ren, M.K. Gupta et al. “Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag8SnSe6”, Nature Materials (2023).
Bio: 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 materials science, condensed matter physics and solid-state chemistry, with an emphasis on atomic dynamics. We perform neutron and x-ray experiments to probe the atomic structure and dynamics in solids, from fast ionic diffusion in solid-state electrolytes to phonon transport and thermal conductivity in thermoelectrics, or electron-phonon coupling and structural transitions in metal-halide perovskites for photovoltaics and optoelectronics. Our experiments map spatio-temporal correlations, revealing details of complex atomic dynamics, disorder and correlations. Further, our atomistic simulations help rationalize experimental results, for example with DFT, ab-initio molecular dynamics and machine-learning accelerated simulations. Website: delaire.pratt.duke.edu
