ELPH IGNORE IMAG PHONONS: Difference between revisions
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If imaginary phonon frequencies are encountered during an electron-phonon calculation, VASP simply stops. | If imaginary phonon frequencies are encountered during an electron-phonon calculation, VASP simply stops. | ||
If {{ | If {{TAG|ELPH_IGNORE_IMAG_PHONONS|True}}, VASP instead skips the q-points at which the phonon frequencies are imaginary. | ||
This can be useful since even a stable system can sometimes exhibit small imaginary phonon frequencies around the <math>\Gamma</math>-point due to numerical inaccuracies. | This can be useful since even a stable system can sometimes exhibit small imaginary phonon frequencies around the <math>\Gamma</math>-point due to numerical inaccuracies. | ||
Latest revision as of 08:07, 24 October 2025
ELPH_IGNORE_IMAG_PHONONS = [logical]
Default: ELPH_IGNORE_IMAG_PHONONS = .FALSE.
Description: If enabled, VASP ignores imaginary phonon frequencies during electron-phonon calculations.
| Mind: Available as of VASP 6.5.0 |
Imaginary phonon frequencies are often a sign that the system in question is not well-converged or not well-described by the simulation. In this case, the system should first be properly converged until stable (real) phonons are obtained.
| Mind: Imaginary phonon frequencies can also appear at phase transitions or other lattice instabilities. However, for perturbative electron-phonon calculations, you should always choose a stable equilibrium structure. |
If imaginary phonon frequencies are encountered during an electron-phonon calculation, VASP simply stops.
If ELPH_IGNORE_IMAG_PHONONS = True, VASP instead skips the q-points at which the phonon frequencies are imaginary.
This can be useful since even a stable system can sometimes exhibit small imaginary phonon frequencies around the -point due to numerical inaccuracies.