First-principles localized cluster expansion study of the kinetics of hydrogen diffusion in homogeneous and heterogeneous Fe-Cr alloys

Abstract

Metal alloys have a wide range of technological applications, from structural materials to catalysts. In many situations the transport of hydrogen, whether intentionally for hydrogen storage and fuel cell applications or unintentionally in the case of tritium uptake in nuclear materials, is an important concern. Fe-Cr binary alloys, in particular, may be viewed as a simple model system to represent ferritic steels used in nuclear energy systems and, more generally, as a model binary alloy for examining the role of alloying elements on transport. In this work, we used density functional theory, cluster expansion, and kinetic Monte Carlo to study hydrogen kinetics in Fe-Cr alloys. In random homogenenous alloys, we observed that hydrogen diffusivity first decreased with increasing Cr content and then increased to its levels in pure Cr. Furthermore, the effects of heterogeneity, as might be induced by irradiation, were explored and it was concluded that local structural heterogeneities for the same overall Cr concentration may significantly affect the hydrogen diffusivity. The effect was attributed to the relative binding energy of hydrogen in different metals and this understanding was then utilized to predict hydrogen transport behavior in different element-segregated grain/grain boundary combinations and thus identify solute/solvent alloys where hydrogen transport might be either hindered or

Defect modeling and control in structurally and compositionally complex materials

“…For the second part, owing to the large number of configurations originating from the multi-components and/or low symmetry in complex materials, it becomes impractical to compute all possible defect configurations directly from first principles. In this case, constructing a structure-based model Hamiltonian using, for example, cluster expansion [50][51][52] or machine learning techniques [53][54][55][56][57][58][59] with firstprinciples inputs, is helpful. As an example, DeePMD 54 employs the advanced deep learning scheme implemented in TensorFlow 60 to fit a deep neural network potential for a given set of structure, energy and force data of a material obtained from first-principles calculations.…”

THEORETICAL AND NUMERICAL STUDY OF HYDROGEN DIFFUSION IN Zr-Nb ALLOYS

“…12 mostramos nuestros resultados para D H vs. % de Nb para diversas temperaturas. Este gráfico resulta similar a otro calculado por Samin et al [26] en el sistema Fe-Cr, BCC desordenado, utilizando otras metodologías (mucho más costosas). En literatura se ha notado [1] que a medida que la fase β se enriquece en Nb, disminuye el volumen de la misma y eventualmente pierde continuidad, lo cual produce un descenso de D H .…”

Tuning the Catalytic Activity of PdxNiy (x + y = 6) Bimetallic Clusters for Hydrogen Dissociative Chemisorption and Desorption

“…Furthermore, some studies have noted that the alloying design can be an effective method to improve the catalytic process. 40,57,58 Hence, the introduction of Ni into a pure Pd cluster may improve the catalytic performance and reduce the cost simultaneously.…”

“…Although noble metal catalysts like Pt or Pd are highly active in the dissociative chemisorption and desorption processes, they are not substantial when compared to Ni and may not justify the higher cost associated with the limited availability of the precious metals. Furthermore, some studies have noted that the alloying design can be an effective method to improve the catalytic process. ,, Hence, the introduction of Ni into a pure Pd cluster may improve the catalytic performance and reduce the cost simultaneously.…”

“…Furthermore, some studies have noted that the alloying design can be an effective method to improve the catalytic process. 40,57,58 Hence, the introduction of Ni into a pure Pd cluster may improve the catalytic performance and reduce the cost simultaneously. In addition to the theoretical studies on monometallic clusters like Pt, Pd, and Ni mentioned above, there have been studies of some noble bimetallic clusters like Au/Pd 43 and some bimetallic clusters of transition metals like Fe/Cr clusters and Al/Rh clusters.…”