123 research outputs found
Effects of aluminum on hydrogen solubility and diffusion in deformed Fe-Mn alloys
We discuss hydrogen diffusion and solubility in aluminum alloyed Fe-Mn
alloys. The systems of interest are subjected to tetragonal and isotropic
deformations. Based on ab initio modelling, we calculate solution energies,
then employ Oriani's theory which reflects the influence of Al alloying via
trap site diffusion. This local equilibrium model is complemented by
qualitative considerations of Einstein diffusion. Therefore, we apply the
climbing image nudged elastic band method to compute the minimum energy paths
and energy barriers for hydrogen diffusion. Both for diffusivity and solubility
of hydrogen, we find that the influence of the substitutional Al atom has both
local chemical and nonlocal volumetric contributions.Comment: 9 page
Understanding anharmonicity in fcc Materials: From its origin to ab initio strategies beyond the quasiharmonic approximation
We derive the Gibbs energy including the anharmonic contribution due to phonon-phonon interactions for an extensive set of unary fcc metals (Al, Ag, Au, Cu, Ir, Ni, Pb, Pd, Pt, Rh) by combining density-functional-theory (DFT) calculations with efficient statistical sampling approaches. We show that the anharmonicity of the macroscopic system can be traced back to the anharmonicity in local pairwise interactions. Using this insight, we derive and benchmark a highly efficient approach which allows the computation of anharmonic contributions using a few T=0K DFT calculations only. © Published by the American Physical Society 2015
Random phase approximation up to the melting point: Impact of anharmonicity and nonlocal many-body effects on the thermodynamics of Au
Application of the generalized gradient corrected functional within standard density-functional theory results in a dramatic failure for Au, leading to divergent thermodynamic properties well below the melting point. By combining the upsampled thermodynamic integration using Langevin dynamics technique with the random phase approximation, we show that inclusion of nonlocal many-body effects leads to a stabilization and to an excellent agreement with experiment. © Published by the American Physical Society
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