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Ab initio charge transport of ionic fluids invariance principles and topological invariants
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=xHFzYxiwqIo
Lennard-Jones Centre discussion group seminar by Dr Federico Grasselli from EPFL. • The Green-Kubo theory of linear response [1] allows one to extract the static electrical conductivity from the time-correlation function of the charge flux in equilibrium molecular dynamics simulations. While in a classical-ions picture the definition of a charge flux is immediate, things are in principle different from an ab initio perspective due to the continuous charge distribution of the electrons, and one must rely on the modern theory of polarization (MTP). This talk describes the combination of recently formulated invariance principles of transport coefficients [2] with arguments from charge-transport topological quantization [3] to prove that the same ab initio electrical conductivity of ionic fluids is exactly obtained if the time-dependent Born charge tensors, entering the MTP definition, are replaced by the time-independent integer oxidation numbers of the atoms [4]. Besides providing an alternative method to compute the ab initio electrical conductivity with no need for MTP calculations, this result offers a topology-based definition of oxidation numbers in disordered materials, demonstrated through numerical experiments on molten potassium chloride. Finally, the talk discusses non-stoichiometric systems, where quantized charge transport may occur without a net ionic displacement [5]. • References: • [1] M. S. Green, J. Chem. Phys. 20(8), 1281 (1952) • [2] A. Marcolongo, P. Umari, and S. Baroni, Nature Physics 12, 80 (2016); review: F. Grasselli and S. Baroni, Eur. Phys. J. B 94 , 160 (2021) • [3] D. J. Thouless, Phys. Rev. B 27 , 6083 (1983) • [4] F. Grasselli and S. Baroni, Nature Physics 15, 967 (2019) • [5] P. Pegolo, F. Grasselli and S. Baroni, Phys. Rev. X 10 , 041031 (2020); review: P. Pegolo, S. Baroni, and F. Grasselli, Ann. Phys. (Berlin) 534, 2200123 (2022) • The seminar was held on 23rd January 2023. • 🖥️ Check out our websites: https://linktr.ee/cumaterials
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