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Evaluating the GW Approximation with CCSD(T) for Charged Excitations Across the Oligoacenes
journal contribution
posted on 2016-04-28, 00:00 authored by Tonatiuh Rangel, Samia M. Hamed, Fabien Bruneval, Jeffrey B. NeatonCharged excitations
of the oligoacene family of molecules, relevant
for astrophysics and technological applications, are widely studied
and therefore provide an excellent system for benchmarking theoretical
methods. In this work, we evaluate the performance of many-body perturbation
theory within the GW approximation relative to new
high-quality CCSD(T) reference data for charged excitations of the
acenes. We compare GW calculations with a number
of hybrid density functional theory starting points and with eigenvalue
self-consistency. Special focus is given to elucidating the trend
of GW-predicted excitations with molecule length
increasing from benzene to hexacene. We find that GW calculations with starting points based on an optimally tuned range-separated
hybrid (OTRSH) density functional and eigenvalue self-consistency
can yield quantitative ionization potentials for the acenes. However,
for larger acenes, the predicted electron affinities can deviate considerably
from reference values. Our work paves the way for predictive and cost-effective GW calculations of charged excitations of molecules and
identifies certain limitations of current GW methods
used in practice for larger molecules.