 
Summary: Alternative separation of exchange and correlation in densityfunctional theory
R. Armiento*
Department of Physics, Royal Institute of Technology, AlbaNova University Center, SE106 91 Stockholm, Sweden
A. E. Mattsson
Computational Materials and Molecular Biology, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
Received 15 August 2003; published 30 December 2003
It has recently been shown that local values of the conventional exchange energy per particle cannot be
described by an analytic expansion in the density variation. Yet, it is known that the total exchangecorrelation
XC energy per particle does not show any corresponding nonanalyticity. Indeed, the nonanalyticity is here
shown to be an effect of the separation into conventional exchange and correlation. We construct an alternative
separation in which the exchange part is made well behaved by screening its longranged contributions, and the
correlation part is adjusted accordingly. This alternative separation is as valid as the conventional one, and
introduces no new approximations to the total XC energy. We demonstrate functional development based on
this approach by creating and deploying a localdensityapproximationtype XC functional. Hence, this work
includes both the theory and the practical calculations needed to provide a starting point for an alternative
approach towards improved approximations of the total XC energy.
DOI: 10.1103/PhysRevB.68.245120 PACS number s : 71.15.Mb, 31.15.Ew
KohnSham KS densityfunctional theory1
DFT is a
successful scheme for electron energy calculations. The long
