  Reporting extensions of a recently developed approach to density functional
theory with correct long-range be-havior (Phys. Rev. Lett. 94, 043002 (2005)).
The central quantities are a splitting functional gamma[n] and a complementary
exchange-correlation functional. We give a practical method for determining the
value of \gamma in molecules, assuming an approximation for XC energy is given.
The resulting theory shows good ability to reproduce the ionization potentials
for various molecules. However it is not of sufficient accuracy for forming a
satisfactory framework for studying molecular properties. A somewhat different
approach is then adopted, which depends on a density-independent \gamma and an
additional parameter w eliminating part of the local exchange functional. The
values of these two parameters are obtained by best-fitting to experimental
atomization energies and bond-lengths of the molecules in the G2(1) database.
The optimized values are gamma=0.5 a_0^{-1} and w=0.1 . We then examine the
performance of this slightly semi-empirical functional for a variety of
molecular properties, comparing to related works and to experiment. We show
that this approach can be used for describing in a satisfactory manner a broad
range of molecular properties, be they static or dynamic. Most satisfactory is
the ability to describe valence, Rydberg and inter-molecular charge-transfer
excitations.
