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SUMMARY:Ab initio charge transport of ionic fluids: invariance principles 
 and topological invariants - Federico Grasselli\, EPFL
DTSTART:20230123T140000Z
DTEND:20230123T143000Z
UID:TALK195970@talks.cam.ac.uk
CONTACT:Dr M. Simoncelli
DESCRIPTION:The Green-Kubo theory of linear response [1] allows one to ext
 ract the static electrical conductivity from the time-correlation function
  of the charge flux in equilibrium molecular dynamics simulations. \nWhile
 \, in a classical-ions picture\, the definition of a charge flux is immedi
 ate\, things are in principle different from an ab-initio perspective\, du
 e to the continuous charge distribution of the electrons\, and one must re
 ly on the modern theory of polarization (MTP).\nI combine recently formula
 ted invariance principles of transport coefficients [2] with arguments fro
 m 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 rep
 laced by the time-independent integer oxidation numbers of the atoms [4]. 
 \nBesides providing an alternative method to compute the ab initio electri
 cal conductivity with no need for MTP calculations\, this result offers a 
 topology-based definition of oxidation numbers in disordered materials\, a
 s I show through numerical experiments on molten potassium chloride. \nFin
 ally\, I discuss non-stoichiometric systems\, where quantized charge trans
 port may occur without a net ionic displacement [5].\n\nReferences:\n\n[1]
  M. S. Green\, J. Chem. Phys. 20(8)\, 1281 (1952)\n\n[2] A. Marcolongo\, P
 . Umari\, and S. Baroni\, Nature Physics 12\, 80 (2016)\; review: F. Grass
 elli and S. Baroni\, Eur. Phys. J. B 94\, 160 (2021)\n\n[3] D. J. Thouless
 \, Phys. Rev. B 27\, 6083 (1983)\n\n[4] F. Grasselli and S. Baroni\, Natur
 e Physics 15\, 967 (2019)\n\n[5] P. Pegolo\, F. Grasselli and S. Baroni\, 
 Phys. Rev. X 10\, 041031 (2020)\; review: P. Pegolo\, S. Baroni\, and F. G
 rasselli\, Ann. Phys. (Berlin) 534\, 2200123 (2022)
LOCATION:Zoom link: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHpt
 UXlRSkppQT09
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