View source for NBANDSEXACT

{{TAGDEF|NBANDSEXACT|[integer]}}
{{DEF|NBANDSEXACT|-1|for {{TAG|LALL_IN_ONE}}{{=}}.FALSE.|maximum number of plane waves|for {{TAG|LALL_IN_ONE}}{{=}}.TRUE.}}

Description: {{TAG|NBANDSEXACT}} specifies the number of bands used in the all-in-one mode of [[Many-body_perturbation_theory|many-body perturbation theory]] calculations.  
{{NB|mind|available as of VASP.6.4.0}}
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In the all-in-one mode, VASP automatically performs the necessary DFT steps prior to the many-body perturbation theory (MBPT) calculation, i.e. a DFT calculation with {{TAG|NBANDS}}, followed by an exact diagonalization of the Kohn-Sham Hamiltonian with {{TAG|NBANDSEXACT}} bands. 
Note, {{TAG|NBANDSEXACT}} is set by default to the maximum number of plane-waves given by the chosen energy cutoff for the orbitals {{TAG|ENCUT}}. 
In the all-in-one mode, the actual GW/RPA calculation is also performed with {{TAG|NBANDSEXACT}} bands. 
If {{TAG|NBANDS_WAVE}} is not set, all orbitals are written to {{FILE|WAVECAR}}, which potentially becomes huge in file size.
{{NB|tip|The {{TAG|NBANDS_WAVE}} tag can be used to limit the number of bands written to {{FILE|WAVECAR}} if {{TAG|LALL_IN_ONE}}{{=}}.TRUE.|:}}

The all-in-one mode is automatically enabled for {{TAG|ALGO}}=[EV]GW[0]R, RPA[R],ACFDT[R] if {{TAG|NBANDS}} is not set.
== Related tags and articles ==
{{TAG|ALGO}}, 
{{TAG|NBANDS}}
{{TAG|NBANDS_WAVE}}
{{TAG|LALL_IN_ONE}}
{{TAG|IALL_IN_ONE}}
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[[Category:INCAR tag]][[Category:Many-body perturbation theory]] [[Category:GW]][[Category:ACFDT]][[Category:Low-scaling GW and RPA]]