When using the DIM tag we give a size for the supercell. Why do we do that? Isn't the VASP (DFT) relaxed cell itself a supercell.
Let's say I generate a large randomized special quasi-random structure of 48 atoms. Why can't I then directly use this cell to find displacements instead of making a 2x2x2 or other kind of bigger cell?
Also, please help me understand how should I choose the size? Should it be 2x2x2 or 3x3x3 or bigger, also should I make it cubic if my DFT relaxed supercell isn't cubic? Eg. (for the later): If my DFT relaxed supercell is a 3x2x1 sqs, then should I use 2x3x6 in the DIM tag in PHONOPY?
The supercell in phonopy is chosen to ensure that there is no self-interaction of the displaced atom with itself (possible due to periodic boundary conditions). Therefore if your original cell is large enough (~10 Angstrom is usually enough) there is no need to use a bigger supercell.
Hello everyone,
Phonon calculations (Phonon Band Structures, Phonon DOS, and thermal properties) in materials science using VASP and phonopy are explained on the Youtube Channel. Please find the link below:
https://bit.ly/2UtvbHE
https://www.youtube.com/watch?v=FX7WjL074g4
Best regards,
Rasoul Khaledialidusti
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