MedeA Application Notes for Automotive
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Interfaces are present in most materials and have a large impact on mechanical properties such as stiffness and yield strength. Given that the properties of an interface can radically change by the presence of even minute amounts of impurities, it is of great interest to predict the effect of segregated atoms at interfaces. As systematic experimental information on the impact of specific defect types on the grain boundary strength is hard to obtain, computational modelling is of great help. 
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Accurate measurements of diffusion coefficients of atoms in solids are difficult and deviations between different experiments can be several orders of magnitude. For the benchmark case of hydrogen diffusion in nickel first-principles calculations give a remarkable agreement with available experimental data especially near room temperature. Thus, computations of diffusion coefficients can be comparable in reliability with measured data. Simulations are possible for situations such as high strain, or slow processes where measurements are difficult or impractical. 
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The temperature-induced phase transition from monoclinic to tetragonal ZrO₂ is predicted from first principles calculations using a quasi-harmonic approach for the vibrational enthalpy and entropy. The computed transition temperature is within 15% of the experimental value. Relative trends due to vacancies, alloying elements, and mechanical stress can be expected to have a higher accuracy. The present results show the importance of thermal expansion, which is here also obtained from first principles. 
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First-principles calculations reveal a three-fold increase in the Young’s modulus of graphite as it is lithiated (C→LiC₆). A linear expression is determined that describes the approximate stiffness of Li intercalated graphite as a function of loading which may lead to greatly improved continuum models of electrode deformation and failure. 
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Hydrides containing alkaline-earth metals are prototypes for hydrogen storage materials. For this purpose the heat of formation and the mechanical properties are of fundamental interest. First- principles electronic structure methods provide systematic values for these materials properties. The agreement with experimental data for the heat of formation is good. Presently, no experimental data for the elastic coefficients of these metal hydrides are available thus leaving the computed data as the sole source. 
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