[en] The research concerns the theory of chemisorption of molecules on solid surfaces: the development of a general formalism, and specific applications to the hydrogen-titanium system. The objective is to develop a suitable formalism for treating electronic interactions at an ab initio level when both localized and delocalized interactions occur, as in the case of molecular adsorption on a metallic surface. For H₂ and CO adsorption on titanium, the goal is a determination of the energetics of adsorption and molecular dissociation as a function of surface site. The first phase of the research concerned primarily the formalism and the second the modeling of the titanium surface, preparatory to the chemisorption studies. The final phase of the research has dealt with applications of the chemisorption theory to several systems: H₂ on Ti(0001), CO on Ti(0001), interstitial H in titanium, H on Cu(100) and H₂ dissociation on Cu(100). Work on stepped copper surfaces and CO interactions with Ni(100) was also begun. With the exception of the latter two projects now underway, the results of all studies have been published. Brief summaries of the individual projects are included in this report