Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 76: Methods in Computational Materials Modelling (methodological aspects, numerics)
MM 76.2: Vortrag
Freitag, 16. März 2018, 11:30–11:45, TC 006
Anharmonic Effects in Solids: Putting Third-Order Expansion to the Test — •Florian Knoop, Hagen-Henrik Kowalski, Matthias Scheffler, and Christian Carbogno — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
The standard ab initio formalism to compute thermal conductivities of solids relies on determining the second and third order force constants of the zero Kelvin potential-energy surface [1]. To understand the role of higher-order contributions not accounted for in such an approach, we investigate the thermal conductivities of a series of materials with increasing anharmonicity (e. g. Si, Ga2O3, CsCl, ZrO2) using two advanced methodologies: Temperature-dependent effective potentials, in which higher-order anharmonicity is incorporated by a renormalization of lower-order force constants via statistical finite-temperature sampling [2] and the ab initio Green-Kubo formalism, in which all anharmonic effects are assessed non-perturbatively through ab initio molecular dynamics simulations [3]. We describe the computational challenges, e. g., finite time and size effects and the choice of the exchange-correlation functional. Eventually, we discuss how the obtained quantitative thermal conductivities allow for a qualitative understanding of high-order anharmonic nuclear dynamics and the implications for other vibrational properties of real materials.
[1] D. A. Broido, et al., Appl. Phys. Lett. 91, 231922 (2007).
[2] O. Hellman and I. A. Abrikosov, Phys. Rev. B 88, 144301 (2013).
[3] C. Carbogno, R. Ramprasad, and M. Scheffler, Phys. Rev. Lett. 118, 175901 (2017).