Multiscale modeling of crowdion and vacancy defects in body-centered-cubic transition metals
- Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)
- EURATOM/UKAEA Fusion Association, Culham Science Centre, Oxfordshire OX14 3DB (United Kingdom)
We investigate the structure and mobility of single self-interstitial atom and vacancy defects in body-centered-cubic transition metals forming groups 5B (vanadium, niobium, and tantalum) and 6B (chromium, molybdenum, and tungsten) of the Periodic Table. Density-functional calculations show that in all these metals the axially symmetric <111> self-interstitial atom configuration has the lowest formation energy. In chromium, the difference between the energies of the <111> and the <110> self-interstitial configurations is very small, making the two structures almost degenerate. Local densities of states for the atoms forming the core of crowdion configurations exhibit systematic widening of the ''local'' d band and an upward shift of the antibonding peak. Using the information provided by electronic structure calculations, we derive a family of Finnis-Sinclair-type interatomic potentials for vanadium, niobium, tantalum, molybdenum, and tungsten. Using these potentials, we investigate the thermally activated migration of self-interstitial atom defects in tungsten. We rationalize the results of simulations using analytical solutions of the multistring Frenkel-Kontorova model describing nonlinear elastic interactions between a defect and phonon excitations. We find that the discreteness of the crystal lattice plays a dominant part in the picture of mobility of defects. We are also able to explain the origin of the non-Arrhenius diffusion of crowdions and to show that at elevated temperatures the diffusion coefficient varies linearly as a function of absolute temperature.
- OSTI ID:
- 21055095
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 76, Issue 5; Other Information: DOI: 10.1103/PhysRevB.76.054107; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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