Contribution à l'étude d'alliages de métaux simples à seuil de démixtion par la méthode des pseudopotentiels : cas du lithium-sodium et de l'aluminium-indium

Abstract : One studies the possibility of describing transitions from liquid phase - liquid in simple metal alloys presenting a threshold of decomposition starting from the theory from the pseudopotentials and the associated effective potentials. More precisely, one considers on the one hand, of the pseudopotentials to conservative standard without adjustable parameters and, on the other hand, various local models with one or two parameters, with for objective establishing the chain of relations: pseudopotentiel3potentiel effectif3structure+dCmixtion in alloy. From this point of view, the relevant sizes necessary to the study of decomposition are, in general, the factors of structure partial of alloys, and, in particular, the factor of structure of fluctuation concentration-concentration Scc(q) of Bhatia-Thornton. Indeed the divergence of this size, close to the origin of the module of the vector of diffusion (q = 0), signature of an instability spinodal, is more easily verifiable in experiments than on the other factors. Thus by this approach, the localization of the line spinodal according to the concentration of the species was made possible. Initially, the development in disturbance "RPA" of the model of the hard spheres to highlight a divergence of the factors of structure was employed, because of its simplicity and its speed of numerical execution. Systematic was applied to the cases of the alloys Li-Na, AI-In known for their broad zone of decomposition. The validity of the qualitative conclusions obtained starting from the "RPA" was then checked by a rigorous determination of the factors of structure per digital simulation of the molecular dynamic type. The aptitude of the various models of pseudopotentials to predict decomposition could be thus discussed
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Aziza Khayoussef. Contribution à l'étude d'alliages de métaux simples à seuil de démixtion par la méthode des pseudopotentiels : cas du lithium-sodium et de l'aluminium-indium. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 2007. Français. ⟨NNT : 2007METZ023S⟩. ⟨tel-01748996⟩

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