  We report an experimental and theoretical analysis of the sqrt(3)x
sqrt(3)-R30 and 2x2 reconstructions on the NiO (111) surface combining
transmission electron microscopy, x-ray photoelectron spectroscopy, and
reasonably accurate density functional calculations using the meta-GGA hybrid
functional TPSSh. While the main focus here is on the surface structure, we
also observe an unusual step morphology with terraces containing only even
numbers of unit cells during annealing of the surfaces. The experimental data
clearly shows that the surfaces contain significant coverage of hydroxyl
terminations, and the surface structures are essentially the same as those
reported on the MgO (111) surface implying an identical kinetically-limited
water-driven structural transition pathway. The octapole structure can
therefore be all but ruled out for single crystals of NiO annealed in or
transported through humid air. . The theoretical analysis indicates, as
expected, that simple density functional theory methods for such
strongly-correlated oxide surfaces are marginal, while better consideration of
the metal d-electrons has a large effect although, it is still not perfect.
