Rossen, Yuval (2025) Atomic-Scale Magnetic and Structural Response to Vacancies in BCC Iron: A Density Functional Theory Study. Bachelor's Thesis, Applied Physics.
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Abstract
Understanding how vacancies reshape ferromagnetic iron is essential for modeling diffusion, creep, and irradiation damage in steels. Here we present a density-functional-theory investigation of a single vacancy in body-centered-cubic (bcc) iron, performed in a 54-atom supercell with a validated k-point mesh. Formation energies, magnetic moment maps, and displacement fields were obtained through simultaneous electronic and structural relaxation, using both PAW and ultrasoft pseudopotentials. We find a vacancy formation energy of 2.33 ± 0.05 eV; first-shell atoms relax inward by 3% and increase their magnetic moments by 10%, indicating strong short-range magneto-structural coupling. Magnetic and elastic perturbations decay with power-law behavior, confirming that finite-size effects dominate residual errors rather than numerical convergence. This benchmark supports the development of spin-lattice machine-learning potentials and aligns with the upper range of positron-annihilation measurements, demonstrating that accurate vacancy energetics require treating structural and magnetic degrees of freedom on equal footing.
| Item Type: | Thesis (Bachelor's Thesis) |
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| Supervisor name: | Giessen, E. van der and Maresca, F. |
| Degree programme: | Applied Physics |
| Thesis type: | Bachelor's Thesis |
| Language: | English |
| Date Deposited: | 14 Jul 2025 14:43 |
| Last Modified: | 14 Jul 2025 14:43 |
| URI: | https://fse.studenttheses.ub.rug.nl/id/eprint/36153 |
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