The microscopic migration of group V adatoms on a Ga-terminated GaAs(0 0 1) surface is investigated by performing first-principle calculations using density functional theory and a slab model of the surface. It is found that the hopping barrier energies of the As and P adatoms on Ga-terminated GaAs(0 0 1) surface are anisotropic and that the hopping barrier energies of those are lower than that of the Ga adatom. Comparing the hopping barrier energies of the As and P adatoms, the migration of the As adatom is easier than that of the P adatom. (C) 2002 Elsevier Science B.V. All rights reserved.