[QE-users] Naive question of choosing the number of unit cell to calculate vibrational frequencies

[ludwigboltzmann.sc10 at nycu.edu.tw]

Dear QE users:I have a naive question of how to determine the number of unit cell to I need to calculate vibrational frequencies.(at Gamma point)
In the below 2 paper, I saw authors choosing 4 unit cells of perovskite (MAPbI3) for phonon calculation.
However, I do not know what number of unit cell should I use? Is their any way to determine it ?
Sincerely,
National Yang Ming Chiao Tung University
HY Lu



Ref:1. https://pubs.acs.org/doi/epdf/10.1021/acs.jpcc.5b074322.https://scholar.google.com/citations?view_op=view_citation&hl=en&user=4Ncn-GUAAAAJ&sortby=pubdate&citation_for_view=4Ncn-GUAAAAJ:9yKSN-GCB0IC
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