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Resume: Nous etudions l'ingenierie geometrique des modeles de jauge supersymetriques de type GUT dans le cadre des supercordes type II. Ces constructions ont une interpretation naturelle en terme de la compactification de la theorie-F sur des varietes des Calabi-Yau a quatre dimensions complexes admettant des surfaces de del Pezzo d[P.sub.k] comme des quatrecycles. Nous presentons entre autres, des modeles locaux de la theorie-F, mettant en jeu des correspondances particulieres entre les algebres de Lie exceptionnelles, les sufaces d[P.sub.k] et les groupes de symetrie de jauge permettant ainsi de generer des modeles supersymetriques N = 1 a quatre dimensions presentant de grands interets phenomenologiques. Tout comme nous proposons certaines extensions de ces modeles, potentiellement prometteuses. PACS Nos : 11.25.-w, 12.10.-g, 11.25.Tq, 11.25.Mj We study the geometric structure of supersymmetric GUT gauge models in the type II superstring case. These are naturally interpreted in terms of the compactification of F-theory on four complex dimension Calabi-Yau varieties that admit d[P.sub.k] del Pezzo surfaces as four-cycles. Among others, we present local models of F-theory that involve special correspondences between the exceptional Lie algebras, the d[P.sub.k] surfaces, and the gauge symmetry groups, allowing us to generate four dimentional N = 1 supersymmetric models that have great phenomenological interest. We also offer some potentially interesting extensions of these models. [Journal translation], 1. Introduction Durant la derniere decennie, un interet croissant est porte aux liens existants entre la theorie des supercordes et la phenomenologie de la physique des particules elementaires autour du [...]

First-principles density functional calculations are used for studying the electronic structure and magnetic properties of Mn-doped ZnO, wurtzite crystal structure, with various defects. The studies that shown that higher values of Curie temperature are obtained for high concentration of vacancy defects sites in (Zn,Mn)O and for small concentration of vacancy defects sites in (Zn,Mn)(O,N).