  The effect of the exchange-correlation potential in ab initio electron
transport calculations is investigated by constructing optimized effective
potentials (OEP) using different energy functionals or the electron density
from second-order perturbation theory. We calculate electron transmission
through two atomic chain systems, one with charge transfer and one without.
Dramatic effects are caused by two factors: changes in the energy gap and the
self-interaction error. The error in conductance caused by the former is about
one order of magnitude while that caused by the latter ranges from several
times to two orders of magnitude, depending on the coupling strength and charge
transfer. The implications for accurate quantum transport calculations are
discussed.
