ELPH NBANDS SUM: Difference between revisions
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This tag is useful for studying the convergence of the self-energy with respect to the number of intermediate states. | This tag is useful for studying the convergence of the self-energy with respect to the number of intermediate states. | ||
At a certain point, including more bands in the summation over states should no longer change the result. | At a certain point, including more bands in the summation over states should no longer change the result. | ||
{{NB|mind|When computing the renormalization of the electronic bandstructure, a large number of intermediate states may be necessary to reach convergence. If the self-energy still changes noticeably around {{ | {{NB|mind|When computing the renormalization of the electronic bandstructure, a large number of intermediate states may be necessary to reach convergence. If the self-energy still changes noticeably around {{TAG|ELPH_NBANDS_SUM|{{TAG|ELPH_NBANDS}}}}, then you may have to increase {{TAG|ELPH_NBANDS}}.}} | ||
==Related tags and articles== | ==Related tags and articles== | ||
Latest revision as of 08:06, 24 October 2025
ELPH_NBANDS_SUM = [integer array]
Default: ELPH_NBANDS_SUM = ELPH_NBANDS
Description: Number of intermediate states to include in the computation of the phonon-induced electron self-energy.
| Mind: Available as of VASP 6.5.0 |
The computation of the self-energy is achieved via a sum over intermediate states [math]\displaystyle{ |\Psi_{m \mathbf{k} + \mathbf{q}}\rangle }[/math]. ELPH_NBANDS_SUM specifies the maximum number of bands, [math]\displaystyle{ N_{\text{b}} }[/math], such that [math]\displaystyle{ m }[/math] runs from [math]\displaystyle{ 1 \ldots N_{\text{b}} }[/math].
Multiple values can be specified for ELPH_NBANDS_SUM, in which case the self-energy is computed once for each value. The results are reported in separate groups inside the vaspout.h5 file:
/results/electron_phonon/electrons/self_energy_1 /results/electron_phonon/electrons/self_energy_2 /results/electron_phonon/electrons/self_energy_3 ...
This tag is useful for studying the convergence of the self-energy with respect to the number of intermediate states. At a certain point, including more bands in the summation over states should no longer change the result.
Mind: When computing the renormalization of the electronic bandstructure, a large number of intermediate states may be necessary to reach convergence. If the self-energy still changes noticeably around ELPH_NBANDS_SUM = ELPH_NBANDS, then you may have to increase ELPH_NBANDS.
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