Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 11: Electronic Structure Theory

O 11.3: Vortrag

Montag, 5. September 2022, 15:30–15:45, H6

Ab initio phonon self-energies: To screen, or not to screen — •Jan Berges¹, Nina Girotto², Tim Wehling³, Nicola Marzari^4,1, and Samuel Poncé⁵ — ¹University of Bremen, Germany — ²Institute of Physics, Zagreb, Croatia — ³University of Hamburg, Germany — ⁴EPFL, Switzerland — ⁵UCLouvain, Belgium

First-principles calculations of phonons are often based on the adiabatic approximation and a Brillouin-zone sampling that is not sufficient to capture Kohn anomalies. These shortcomings can be remedied through corrections to the phonon self-energy arising from the low-energy electrons. A well-founded correction method exists [Calandra, Profeta, and Mauri, Phys. Rev. B 82, 165111 (2010)], which only relies on readily available (adiabatically) screened quantities. However, many-body theory suggests to use one bare electron–phonon vertex in the phonon self-energy [Giustino, Rev. Mod. Phys. 89, 015003 (2017)] to avoid double counting. This can be seen as a limiting case of downfolding to partially screened phonons and interactions [Nomura and Arita, Phys. Rev. B 92, 245108 (2015)]. We compare these approaches using the examples of TaS2, MgB2, n-doped MoS2, and p-doped diamond. We confirm the robustness of the former method, while the latter allows for systematic improvements to describe correlations or metal–insulator transitions.