1108.3100 (M. Hellgren et al.)

Discontinuities of the exchange-correlation kernel and charge-transfer
excitations in time-dependent density functional theory    [PDF]

M. Hellgren, E. K. U. Gross

We identify the key property that the exchange-correlation (XC) kernel of
time-dependent density functional theory must have in order to describe
long-range charge-transfer excitations. We show that the discontinuity of the
XC potential as a function of particle number induces a space -and
frequency-dependent discontinuity of the XC kernel which diverges as
$r\to\infty$. In a combined donor-acceptor system, the same discontinuity
compensates for the vanishing overlap between the acceptor and donor orbitals,
thereby yielding a finite correction to the Kohn-Sham eigenvalue differences.
This mechanism is illustrated to first order in the Coulomb interaction.

View original: http://arxiv.org/abs/1108.3100