No GGA exchange functional can simultaneously produce the correct contribution
to the exchange energy density and exchange potential in the asymptotic region
of molecular systems,
Phys. Rev. A
(1994), 49, pp. 2421. and existing GGA exchange-correlation (XC) potentials decay much faster than the correct XC potential in the asymptotic region. 170 J. Chem. Phys.
(2000), 113, pp. 8918. High-lying occupied orbitals and low-lying virtual orbitals are therefore too loosely bound, and becomes far smaller than the ionization energy, despite the exact condition that these should be the same for the exact functional. 1112 J. Chem. Phys.
(1996), 105, pp. 3142. , 1204 J. Chem. Phys.
(2003), 119, pp. 2978. Moreover, response properties may be poorly predicted from TDDFT calculations with GGA functionals. 1112 J. Chem. Phys.
(1996), 105, pp. 3142. Long-range corrected hybrid DFT (LRC-DFT), described in Section 5.6, has greatly remedied this situation, but is more expensive that KS-DFT with GGA functionals due to the use of Hatree-Fock exchange. The asymptotic corrections described in this section are designed to remedy the same problems but within the GGA framework.