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Abstract

The embrittling effect of hydrogen atoms at grain boundaries is widely studied by means of density functional theory calculations. A first indicator on the effect of H on the interface cohesion is the change in the work of separation due to the impurity. The work of separation is simply the difference between the energy of the two free surfaces after a brittle cleavage of the interface, and the grain boundary energy. However, in the case of a grain boundary with segregated impurities and/or alloying atoms, several possibilities exist of how to distribute the segregants on the two surfaces. In this work we demonstrate the striking effect of different partition patterns and additional surface diffusion on the final effect of C and H atoms on the cohesive behavior of a bcc Fe Σ3(112)[110] symmetrical grain boundary. The change in the work of separation is further analyzed by decomposition into chemical and mechanical contribution according to the thermodynamic theory of Rice and Wang.