  The interface structure of Fe/MgO(100) magnetic tunnel junctions predicted by
density functional theory (DFT) depends significantly on the choice of exchange
and correlation functional. Bader analysis reveals that structures obtained by
relaxing the cell with the local spin-density approximation (LSDA) display a
different charge transfer than those relaxed with the generalized gradient
approximation (GGA). As a consequence, the electronic transport is found to be
extremely sensitive to the interface structure. In particular, the conductance
for the LSDA-relaxed geometry is about one order of magnitude smaller than that
of the GGA-relaxed one. The high sensitivity of the electronic current to the
details of the interface might explain the discrepancy between the experimental
and calculated values of magnetoresistance.
