Benchmark Many-Body <i>GW</i> and Bethe–Salpeter
Calculations for Small Transition Metal Molecules
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Abstract
We study the electronic and optical
properties of 39 small molecules
containing transition metal atoms and 7 others related to quantum-dots
for photovoltaics. We explore in particular the merits of the many-body <i>GW</i> formalism, as compared to the ΔSCF approach within
density functional theory, in the description of the ionization energy
and electronic affinity. Mean average errors of 0.2–0.3 eV
with respect to experiment are found when using the PBE0 functional
for ΔSCF and as a starting point for <i>GW</i>. The
effect of partial self-consistency at the <i>GW</i> level
is explored. Further, for optical excitations, the Bethe–Salpeter
formalism is found to offer similar accuracy as time-dependent DFT-based
methods with the hybrid PBE0 functional, with mean average discrepancies
of about 0.3 and 0.2 eV, respectively, as compared to available experimental
data. Our calculations validate the accuracy of the parameter-free <i>GW</i> and Bethe–Salpeter formalisms for this class of
systems, opening the way to the study of large clusters containing
transition metal atoms of interest for photovoltaic applications