  First-principles calculations based on density functional theory and the
pseudo\-potential method have been used to investigate the influence of
gradient corrections to the standard LDA technique on the equilibrium structure
and energetics of rutile TiO$_2$ and SnO$_2$ perfect crystals and their (110)
surfaces. We find that gradient corrections increase the calculated lattice
parameters by roughly 3~\%, as has been found for other types of material.
Gradient corrections give only very minor changes to the equilibrium surface
structure, but reduce the surface energies by about 30~\%.
