Extrapolating unconverged GW energies to the complete basis set limit with linear regression
Résumé
The GW approximation to the electronic self-
energy is now a well-recognized approach to
obtain the electron quasiparticle energies of
molecules and in particular their ionization po-
tential and electron affinity. Though much
faster than the corresponding wavefunction
methods, the GW energies are still affected by
a slow convergence with respect to the basis
completeness. This limitation hinders a wider
application of the GW approach. Here we
show we can reach the complete basis set limit
for the cumbersome GW calculations solely
based on fast preliminary calculations with an
unconverged basis set. We introduce a lin-
ear model that correlates the molecular orbital
characteristics and the basis convergence er-
ror for a large database of about 600 states
in 104 organic molecules that contain H, C,
O, N, F, P, S, and Cl. The model employs
molecular-orbital-based non-linear descriptors
that encode efficiently the chemical space offer-
ing an outstanding transferability. Using a low
number of descriptors (17) the performance of
this extrapolation procedure is superior to the
earlier more physically-motivated approaches.
The predictive power of the method is finally
demonstrated for a selection of large acceptor
molecules.