An attempt has been made to simulate LiH crystal surface and to examine the binding energies and configurations of He and Ne on regular (flat), irregular (kinks and steps) and defected (cation vacancies, F1, F and F2) surfaces using the Hartree–Fock SCF and second order Møller–Plesset perturbation methods of ab initio theory. The adatom–surface interactions were modified dramatically in the presence of irregular and defected surfaces and the most stable adsorption was associated with the cation vacancies, anion vacancies as well as the cation three-coordinated kinks above which the adatoms were tilted 458 away from the surface normal. Repulsive interactions and steric constraints are shown to play the dominant role. q1999 Elsevier Science Ltd. All rights reserved.