General size-dependent switching of ADC(3) ionization-potential errors

Determine whether standard ADC(3) generally switches from overestimating to underestimating reference ionization potentials for increasingly large molecular systems.

Background

The conclusion revisits the results for acenes and oligothiophenes, where standard ADC(3) changes from positive to negative ionization-potential errors as system size increases. The EN correction acts in a fixed direction and therefore cannot uniformly improve results across both regimes.

The paper notes that a prior benchmark of medium-sized organic acceptors found slight ADC(3) overestimation, but this evidence does not establish whether a transition to underestimation is a general feature of larger systems. The author explicitly identifies this broader question as unresolved.