Optical properties of the 11-cis retinal molecule from time-dependent density functional theory
Date
2010-08-30
Authors
Nokwara, Nkululeko
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Abstract
Time Dependent Density Functional Theory (TDDFT) happens to be
at a momentous stage of its development, paralleled by the production of powerful
and very fast computers. Such a combination has made it possible to carry out abinitio
studies of the ground and excited states of such large molecules. Starting with
the ground state properties, TDDFT as implemented in the real space code, Octopus,
was used to calculate the optical properties of the molecule. In particular, the optical
absorption spectrum was computed in great agreement with experiment, but unexpected
extra properties are also predicted. Short and strong laser pulses (in one case I =
1013W=cm2 and in the other case I = 1016W=cm2) were shot through the molecule
theoretically and high harmonic generation (for I = 1013W=cm2) and coulomb explosion
(for I = 1016W=cm2) were observed. For each of the three scenarios studied here,
a QM/MM calculation was also carried out. Unfortunately, the overestimating (for
ionization) Local Density Approximation (LDA) for the exchange-correlation functional
was used throughout, since the more accurate exact exchange (EXX) over-burdened the
eight-core machine that was used in this work.