Density-functional errors in ionization potential with increasing system size

作者：Whittleton Sarah R^*; Vazquez Xochitl A Sosa; I**orn Christine M; Johnson Erin R

来源：Journal of Chemical Physics, 2015, 142(18): 184106.

DOI：10.1063/1.4920947

This work investigates the effects of molecular size on the accuracy of density-functional ionization potentials for a set of 28 hydrocarbons, including series of alkanes, alkenes, and oligoacenes. As the system size increases, delocalization error introduces a systematic underestimation of the ionization potential, which is rationalized by considering the fractional-charge behavior of the electronic energies. The computation of the ionization potential with many density-functional approximations is not size-extensive due to excessive delocalization of the incipient positive charge. While inclusion of exact exchange reduces the observed errors, system-specific tuning of long-range corrected functionals does not generally improve accuracy. These results emphasize that good performance of a functional for small molecules is not necessarily transferable to larger systems.

• 出版日期2015-5-14