When: Tomorrow Monday Apr 16 from 12 to 1 PM
Where: Cabot Division Room at Mallinckrodt
What: Roberto is defending his thesis:
"Quantum Chemistry in Nanoscale Environments: Insights on
Surface-Enhanced Raman Scattering and Organic Photovoltaics
Abstract
The understanding of molecular effects in nanoscale environments is
becoming increasingly
relevant for various emerging fields. These include spectroscopy for
molecular identification
as well as in finding molecules for energy harvesting. Theoretical quantum
chemistry has
been increasingly useful to address these phenomena to yield an
understanding of these
effects.
In the first part of this dissertation, we study the chemical effect of
surface-enhanced
Raman scattering (SERS). We use quantum chemistry simulations to study the
metalmolecule
interactions present in these systems. We find that the excitations that
provide
a chemical enhancement contain a mixed contribution from the metal and the
molecule.
Moreover, using atomistic studies we propose an additional source of
enhancement, where a
transition metal dopant surface could provide an additional enhancement. We
also develop
methods to study the electrostatic effects of molecules in metallic
environments. We study
the importance of image-charge effects, as well as field-bias to molecules
interacting with
perfect conductors. The atomistic modeling and the electrostatic
approximation enable us
to study the effects of the metal interacting with the molecule in a
complementary fashion,
which provides a better understanding of the complex effects present in
SERS.
In the second part of this dissertation, we present the Harvard Clean
Energy Project,
a high-throughput approach for a large-scale computational screening and
design of organic
photovoltaic materials. We create molecular libraries to search for
candidates structures and
use quantum chemistry, machine learning and cheminformatics methods to
characterize
these systems and find structure-property relations. The scale of this
study requires an
equally large computational resource. We rely on distributed volunteer
computing to obtain
these properties.
In the third part of this dissertation we present our work related to the
acceleration of
electronic structure methods using graphics processing units. This hardware
represents a
change of paradigm with respect to the typical CPU device architectures. We
accelerate the
resolution-of-the-identity Møller-Plesset second-order perturbation theory
algorithm using
graphics cards. We also provide detailed tools to address memory and
single-precision issues
that these cards often present."
--
Joel Yuen-Zhou
PhD candidate in Chemical Physics
Harvard University CCB,
12 Oxford St. Mailbox 107,
Cambridge, MA, USA.
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