We have used medium-energy ion-scattering with channeling and blocking
to study the surface structure of MgO(001). The ion scattering data s
how that UHV-cleaved crystals result in well ordered surfaces, while s
puttered/annealed samples show structural disorder. Surface blocking d
ips in both the 0 and Mg spectra are found to occur at angles very clo
se to the corresponding bulk blocking directions, indicating very smal
l surface relaxation and rumpling. A detailed R-factor analysis compar
ing the experimental spectra with results of Monte Carlo simulations f
or different structures gives a surface relaxation of - 1.0% +/-1.0% a
nd a rumpling of 0.5% +/- 1.0%. These results are in good agreement wi
th preliminary results from all-electron total-energy calculations and
imply that the surface O2- ions have small polarizations.