Formation enthalpies of vacancy-oxygen complexes and single vacancies in the core of grain boundaries in polycrystalline Cr, Ta, and W

Atomic probes (APs) 57Co(57Fe) are localized in the grain boundary (GB) core and adjacent regions of the lattice in polycrystalline metals by means of GB diffusion. Spectra of nuclear gamma resonance (NGR) of radiation of APs 57Co(57Fe) were used for analysis of the nearest neighborhood of APs. Vacancies, which are formed in the GB core of polycrystalline metals during annealing in a technical vacuum over the temperature range (0.2-0.4)Tmelt, are captured by traps (oxygen atoms) and form stable complexes with oxygen (complexes-VacO). For the first time, formation enthalpies Qcmpl,1 of complexes-VacO and formation enthalpies QVac,1 of single vacancies in the GB core in Cr, Ta, and W polycrystals have been determined from Arrhenius dependencies of the contribution δVac,1.