Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 56: New materials and concepts

HL 56.4: Vortrag

Freitag, 16. März 2018, 12:00–12:15, EW 202

Strong Anharmonic and Quantum-Nuclear Effects in the Low Temperature Dyamics of CsCl — •Hagen-Henrik Kowalski, Matthias Scheffler, and Christian Carbogno — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

In solid-state theory, the quasi-harmonic approximation is generally expected to hold for the description of the nuclear dynamics in crystals at temperatures ≪ 300 K. However, a recent experimental study [1] of single crystalline CsCl reveals that its thermal conductivity is comparable to those of amorphous materials (∼1 W/mK). Strong anharmonic effects hence appear to be active even at 50 K, a temperature at which the quantum-statistics for the nuclei is not negligible (CV < 65% of the Dulong-Petit value). Using first-principles calculations, we investigate the nature of these effects by performing fully anharmonic molecular dynamics with classical nuclei (MD) and path-integral MD simulations with quantum nuclei. The comparison with respective quasi-harmonic calculations confirms that pronounced quantum-nuclear and anharmonic effects are active in this material and reveals how the respective mechanisms couple. Eventually, we discuss how these effects can affect simulations of the thermal conductivity [2] and the resulting implications for simulations across material space.

[1] M. Sist, et al., Ang. Chemie 56, 3625 (2017).

[2] C. Carbogno, R. Ramprasad, and M. Scheffler, Phys. Rev. Lett. 118, 175901, (2017).

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