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Segregated light elements at grain boundaries in niobium and molybdenum

: Janisch, R.; Elsässer, C.


Physical Review. B 67 (2003), No.22, Art. 224101, 11 pp.
ISSN: 0163-1829
ISSN: 1098-0121
ISSN: 0556-2805
Journal Article
Fraunhofer IWM ()
Korngrenze; interstitielle Fremdatome; kubisch-raumzentrierte Metalle; ab-initio-Dichtefunktionaltheorie; Mixed-Basis-Pseudopotential-Theorie

The influence of the interstitial impurities B, C, N, O and H on the cohesion an d structure of Sigma 5 (310) [001] grain boundaries (GB) in body-centered cubic (bcc) Nb and Mo is investigated by the local density functional theory (LDFT), using the mixed-basis pseudopotential approach. The analysis of interface energies and geometric translation states, site-projected densities of states and bondi ng electron densities yields systematic trends: B and C from covalent bonds with the nearest host-metal neighbors, strengthen the interfacial cohesion by inducing covalent metal-metal bonds across the interface, and favour a mirror-symmetri c GB, while N, O and H form polar bonds, cause interfacial embrittlement and bre ak the mirror symmetry of the GB. The LDFT restults support the qualitative validity of empirical models of Cottrell and of Rice and Wang for bcc transition metals.