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MM: Fachverband Metall- und Materialphysik
MM 7: Transport - Atoms and Ions II
MM 7.3: Vortrag
Montag, 16. März 2020, 12:15–12:30, IFW A
Anharmonic self-diffusion coefficients using the finite temperature string method — •Raynol Dsouza1, Liam Huber1, Blazej Grabowski1, 2, and Jörg Neugebauer1 — 1Max Planck Institut für Eisenforschung, Düsseldorf — 2Department of Materials Design, Institute of Materials Science, University of Stuttgart
Simulating self-diffusion in solids using molecular dynamics (MD) usually requires high temperatures, where diffusion can occur at a high enough rate. Finite temperature effects can be well represented at low temperatures using phonon calculations in the well-known quasi-harmonic approximation (QHA). However, anharmonic effects that appear well below room temperature, even for a relatively simple thermodynamic property like vacancy formation, are not captured by QHA [1].
In this work, we apply the finite temperature string (FTS) method [2] in combination with thermodynamic integration [3] to obtain self-diffusion coefficients that capture anharmonic behavior. Using this technique, diffusion at temperatures above the threshold at which QHA begins to lose validity, as well as temperatures at which calculations by direct MD are feasible can be accessed. Performing a careful analysis, we obtain a good agreement between our results and those simulated by MD at high temperatures, which further extend down to low temperatures for FCC and BCC crystal systems.
[1] Glensk et al. Phys Rev X 4 (2014)
[2] Vanden-Eijnden and Venturoli, J Chem Phys 130 (2009)
[3] de Koning et al. Phys Rev B 70 (2004)