Asymptotically adjusted self-consistent multiplicative parameter exchange-energy-functional method: Application to diatomic molecules

Abstract

An asymptotically adjusted self-consistent $\ensuremath{\alpha}$ $(\mathrm{AASC}\ensuremath{\alpha})$ method is advanced for the purpose of constructing an accurate orbital-dependent local exchange potential with correct asymptotic behavior. This local potential is made up of the Slater potential plus an additional term containing a multiplicative parameter ${\ensuremath{\alpha}}_{x}$ (a self-consistently determined orbital functional) times a local response potential that is approximated using standard exchange-energy functionals. Applications of the $\mathrm{AASC}\ensuremath{\alpha}$ functionals to diatomic molecules yield significantly improved total, exchange, and atomization energies that compare quite well, but at a much lower computational cost, with those obtained by the exact orbital-dependent exchange energy treatment [S. Ivanov, S. Hirata, and R. J. Bartlett, Phys. Rev. Lett. 83, 5455 (1999); A. G\orling, Phys. Rev. Lett. 83, 5459 (1999)] (in fact, the present results are very close to the Hartree-Fock ones). Moreover, because in the $\mathrm{AASC}\ensuremath{\alpha}$ method the exchange potential tends toward the correct $(\ensuremath{-}1/r)$ asymptotic behavior, the ionization potentials approximated by the negative of the highest-occupied-orbital energy have a closer agreement with experimental values than those resulting from current approximate density functionals. Finally, we show that in the context of the present method it is possible to introduce some generalizations to the Gritsenko-van Leeuwen-van Lenthe-Baerends model [O. Gritsenko, R. van Leeuwen, E. van Lenthe, and E. J. Baerends, Phys. Rev. A 51, 1944 (1995)].