When: Friday July 22, 2011 from 11:30 AM to 12:30 PM
Where: Cabot Division Room at Mallinckrodt
What: John is up for group meeting:
"Title:
Is quantum chemistry ready for coherent transport, and vice-versa?
Abstract:
The question of incoherent or coherent energy transport boils down to
roughly whether the reorganization energy or the site coupling are the
larger quantity. On the molecular scale, both are < 300 cm^{-1}=1kcal/mol,
whereas TDDFT is routinely in error by 1600 cm^{-1}. Can quantum chemistry
predict coherent transport? Likewise should we even consider running a TDC
coupling if the fate of transport rests on so little energy?
I report on my efforts to reproduce a dimer coherent transport experiment
without assuming system information or a bath spectral density. A few slides
will survey the differences between the Hamiltonians one usually assumes for
a transport model, and those which one might calculate via quantum
chemistry. Three related molecules whose transport has been
well-characterized are then simulated in detail. It's found that the usual
assumptions about negligibly short range of non-classical coulomb couplings
is thoroughly violated when chromophores are less than 5 Angstroms apart.
Likewise that Quantum Chemistry's excited state methods are barely up-to the
task of predicting these phenomena. "
--
Joel Yuen-Zhou
PhD candidate in Chemical Physics
Harvard University CCB,
12 Oxford St. Mailbox 107,
Cambridge, MA, USA.
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