Regensburg 2019 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 23: Methods in Computational Materials Modelling (methodological aspects, numerics)

MM 23.4: Talk

Wednesday, April 3, 2019, 11:00–11:15, H44

The Anharmonicity of Al self-diffusion — Raynol Dsouza, •Liam Huber, Blazej Grabowski, and Joerg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

To study kinetic properties, e.g. diffusion, at the atomistic scale with molecular dynamics (MD) it is usually necessary to operate at very high temperatures where processes occur at high rates, or to use some approximation or acceleration scheme. At low temperatures it is common to use the quasi-harmonic approximation (QHA), where finite-T effects are represented using phonon calculations. However, even for the relatively simple thermodynamic property of vacancy formation in aluminum, anharmonic effects not captured by QHA appear well below room temperature [1].

In this work, we apply the finite temperature string method [2] to study the effect of these anharmonicities on Al self-diffusion. This technique allows us to probe the temperature range above the threshold at which QHA begins to lose validity, but still well below the temperature at which calculation by direct MD becomes feasible. Finally, we consider the combination of thermodynamic integration [3] with FTS in order to capture anharmonic behaviour with the full power and accuracy of quantum mechanics.

[1] Glensk et al. Phys Rev X 4 (2014)

[2] Vanden-Eijnden and Venturoli, J Chem Phys 130 (2009)

[3] Duff et al. Phys Rev B 91 (2015)