PNNL

Abstract

Previous computational modeling has shown that interstitial and substitutional He as well as He-divacancy clusters are strongly bound to extended defects in Fe such as dislocations, grain boundaries and particle-matrix interfaces. One aspect of the earlier work was the interaction of He with nanometer-scale, coherent particles embedded in an Fe matrix. Our earlier research also established that the core of an edge dislocation strongly traps He, thus we hypothesized that a semicoherent interface might be a stronger trap for He than a coherent interface due to the array of misfit dislocations needed to accommodate the lattice parameter mismatch between the particle and the matrix in the semicoherent case. In the present study we employ atomisitic simulations to compare the binding of HenVm complexes to coherent and semicoherent bcc Fe/ bcc Cu interfaces. The simulations show that the binding energy of HenVm complexes to a coherent Fe/Cu interface range from 0.35 eV for a single vacancy up to 0.70 eV for a He1V2 complex. A semicoherent interface was found to be a much stronger trap for He near the core of a misfit dislocation. Binding energies varied from 0.86 eV for a substitutional He atom up to 2.38 eV for a He1V2 complex. These binding energies were found to be significantly larger than the values obtained for simple edge dislocations in Fe. The trend in binding energies can be rationalized in terms of the spatial dependence of excess atomic volume for each interface.