Extensive
benchmarks of exchange-correlation functionals on real X-ray resolved
nanoclusters have been carried out and reported here for the first time.
The systems investigated and used for the tests
are two undecagold and
one Au24+-based nanoclusters stabilized by thiol
and phosphine ligands.
Time-dependent density-functional theory has been
used to compare calculations with experimental data on optical gaps. It
has been observed that GGA functionals employing PBE-like correlation
(viz., PBE itself, B-PBE, B-P86, and B-PW91) coupled with an improved
version of the LANL2DZ pseudopotential and basis set provide accurate
results for both the structure and optical gap of gold nanoclusters, at a
reasonable computational cost. Good geometries have been also obtained
using some global hybrid (e.g., PBE0, B3-P86, mPW1-PW91) and
range-separated hybrid (e.g., HSE06) functionals making use of PBE-like
correlation, even though they yield optical gaps overestimating the
experimental findings up to 0.5 eV. Popular exchange-correlation
combinations such as B-LYP and B3-LYP deform cluster geometry during
structural optimization, probably due to the LYP correlation. Effects of
the stabilizing organic ligands on the properties of metal cores have
been probed simulating the nanoclusters at the density-functional level
of theory retaining the organic coating. This paper provides a useful
contribution to the simulations of structural and optoelectronic
properties of larger metal–organic particles suitable for a wide range
of nanotechnological applications.
source - pubs.acs.or
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