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CATEGORIES:Electronic Structure Discussion Group
SUMMARY:Car and Parrinello meet Green and Kubo: simulating
atomic heat transport from equilibrium ab initio
molecular dynamics - Prof. Stefano Baroni (Scuola
Internazionale Superiore di Studi Avanzati)
DTSTART;TZID=Europe/London:20170223T113000
DTEND;TZID=Europe/London:20170223T123000
UID:TALK71278AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/71278
DESCRIPTION:Modern simulation methods based on electronic-stru
cture theory have long been deemed unfit to comput
e heat transport coefficients within the Green-Kub
o formalism. This is so because the quantum-mechan
ical energy density from which the heat flux is de
rived is inherently ill defined\, thus allegedly h
ampering the use of the\nGreen-Kubo formula. While
this objection would actually apply to classical
systems as well\, I will demonstrate that the ther
mal conductivity is indeed independent of the spec
ific microscopic expression for the energy density
and current from which it is derived. This indepe
ndence results from a kind of _gauge invariance_ s
temming from energy conservation and extensivity\,
which I will\nillustrate numerically for a classi
cal Lennard-Jones fluid. I will then introduce an
expression for the adiabatic energy flux\, derived
from density-functional theory\, that permits the
ab initio simulation of atomic thermal transport
using equilibrium molecular dynamics. The resultin
g methodology is demonstrated by comparing results
from ab-initio and classical molecular-dynamics s
imulations of a model liquid-Argon system\, for wh
ich accurate inter-atomic potentials are derived b
y the force-matching method\, and applied to compu
te the\nthermal conductivity of heavy water at amb
ient conditions. The problem of evaluating transpo
rt coefficients along with their accuracy from rel
atively short trajectories is finally addressed an
d discussed with a few representative examples.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
CONTACT:Joseph Nelson
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