Scaling down the Perdew-Zunger self-interaction correction in many-electron regions

摘要

Semilocal density functional approximations(DFAs)for the exchange-correlation energy suffer from self-interaction error,which is believed to be the cause of many of the failures of common DFAs,such as poor description of charge transfer and transition states of chemical reactions.The standard self-interaction correction(SIC)of Perdew and Zunger mends some of these failures but spoils such essential properties as thermochemistry and equilibrium bond lengths.The Perdew-Zunger SIC seems to overcorrect many-electron systems.In this paper,we propose a modified SIC,which is scaled down in many-electron regions.The new SIC has an improved performance for many molecular properties,including total energies,atomization energies,barrier heights of chemical reactions,ionization potentials,electron affinities,and bond lengths.The local spin-density approximation(LSDA)benefits from SIC more than higher-level functionals do.The scaled-down SIC has only one adjustable parameter.Rationalization of the optimal value of this parameter enables us to construct an almost-nonempirical version of the scaled-down SIC-LSDA,which is significantly better than uncorrected LSDA and even better than the uncorrected generalized gradient approximation.We present an analysis of the formal properties of the scaled-down SIC and define possible directions for further improvements.In particular,we find that exactness for all one-electron densities does not guarantee correct asymptotics for the exchange-correlation potential of a many-electron system.