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SUMMARY:Car and Parrinello meet Green and Kubo: simulating atomic heat tra
 nsport from equilibrium ab initio molecular dynamics - Prof. Stefano Baron
 i (Scuola Internazionale Superiore di Studi Avanzati)
DTSTART:20170223T113000Z
DTEND:20170223T123000Z
UID:TALK71278@talks.cam.ac.uk
CONTACT:Joseph Nelson
DESCRIPTION:Modern simulation methods based on electronic-structure theory
  have long been deemed unfit to compute heat transport coefficients within
  the Green-Kubo formalism. This is so because the quantum-mechanical energ
 y density from which the heat flux is derived is inherently ill defined\, 
 thus allegedly hampering the use of the\nGreen-Kubo formula. While this ob
 jection would actually apply to classical systems as well\, I will demonst
 rate that the thermal conductivity is indeed independent of the specific m
 icroscopic expression for the energy density and current from which it is 
 derived. This independence results from a kind of _gauge invariance_ stemm
 ing from energy conservation and extensivity\, which I will\nillustrate nu
 merically for a classical Lennard-Jones fluid. I will then introduce an ex
 pression for the adiabatic energy flux\, derived from density-functional t
 heory\, that permits the ab initio simulation of atomic thermal transport 
 using equilibrium molecular dynamics. The resulting methodology is demonst
 rated by comparing results from ab-initio and classical molecular-dynamics
  simulations of a model liquid-Argon system\, for which accurate inter-ato
 mic potentials are derived by the force-matching method\, and applied to c
 ompute the\nthermal conductivity of heavy water at ambient conditions. The
  problem of evaluating transport coefficients along with their accuracy fr
 om relatively short trajectories is finally addressed and discussed with a
  few representative examples.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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