FERWE: Difference between revisions
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To set the occupancies, specify | To set the occupancies, specify | ||
{{TAG|FERWE}} = f(1) f(2) f(3) ... f({{TAG|NBANDS}}×N<sub>'''k'''</sub>) | {{TAG|FERWE}} = f(1) f(2) f(3) ... f({{TAG|NBANDS}}×N<sub>'''k'''</sub>) | ||
The occupancies must be specified for all bands and k points. The band index runs fastest. The occupancies must be between 0 and 1. | The occupancies must be specified for all bands and k points. | ||
The band index runs fastest. | |||
The occupancies must be between 0 and 1. | |||
In the case of spin-polarized calculations ({{TAG|ISPIN}}=2), {{TAG|FERWE}} sets the occupancies of the states in the up-spin channel. | |||
Specify the occupancies of the states in the down-spin channel by means of the {{TAG|FERDO}} tag. | |||
{{NB|mind|VASP changes the number of bands {{TAG|NBANDS}} to accommodate your parallel setup. If {{TAG|NBANDS}} is inconsistent with the number of elements you provide with {{TAG|FERWE}} VASP will exit with an error message. The used {{TAG|NBANDS}} is indicated in the error message. Adjust the occupancies provided to {{TAG|FERWE}} to this new value. Alternatively, you can choose an {{TAG|NBANDS}} as the common factor of all your parallel setups to avoid changes in the number of bands (see [[NBANDS#Parallelization|here]]).}} | |||
The occupancies are even kept fixed during ionic relaxations or molecular dynamics simulations. However, keeping the orbital occupancies fixed, requires that the orbital order does not change during the self-consistency cycle or during the optimization of the orbitals. Imagine, for instance, that the eigenenergy of the 65th orbital moves below the orbital energy of the 64th orbital. Then the subspace diagonalization step will swap both orbitals, but the occupancies will remain as read from the INCAR file (this means that the originally unoccupied 65th orbital will move to the 64th place and it will hence become occupied). This problem can be often circumvented by specifying {{TAG|LDIAG}}=.FALSE. in the INCAR file. | The occupancies are even kept fixed during ionic relaxations or molecular dynamics simulations. However, keeping the orbital occupancies fixed, requires that the orbital order does not change during the self-consistency cycle or during the optimization of the orbitals. Imagine, for instance, that the eigenenergy of the 65th orbital moves below the orbital energy of the 64th orbital. Then the subspace diagonalization step will swap both orbitals, but the occupancies will remain as read from the INCAR file (this means that the originally unoccupied 65th orbital will move to the 64th place and it will hence become occupied). This problem can be often circumvented by specifying {{TAG|LDIAG}}=.FALSE. in the INCAR file. | ||
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Note that the partial occupancies are also written to the {{FILE|OUTCAR}} file, but in this case they are multiplied by 2, i.e. they are between 0 and 2. | Note that the partial occupancies are also written to the {{FILE|OUTCAR}} file, but in this case they are multiplied by 2, i.e. they are between 0 and 2. | ||
== Related tags and articles == | == Related tags and articles == | ||
Revision as of 10:13, 24 February 2025
FERWE = [real array]
Description: FERWE sets the occupancies of the states for ISMEAR=-2.
To set the occupancies, specify
FERWE = f(1) f(2) f(3) ... f(NBANDS×Nk)
The occupancies must be specified for all bands and k points. The band index runs fastest. The occupancies must be between 0 and 1.
In the case of spin-polarized calculations (ISPIN=2), FERWE sets the occupancies of the states in the up-spin channel. Specify the occupancies of the states in the down-spin channel by means of the FERDO tag.
| Mind: VASP changes the number of bands NBANDS to accommodate your parallel setup. If NBANDS is inconsistent with the number of elements you provide with FERWE VASP will exit with an error message. The used NBANDS is indicated in the error message. Adjust the occupancies provided to FERWE to this new value. Alternatively, you can choose an NBANDS as the common factor of all your parallel setups to avoid changes in the number of bands (see here). |
The occupancies are even kept fixed during ionic relaxations or molecular dynamics simulations. However, keeping the orbital occupancies fixed, requires that the orbital order does not change during the self-consistency cycle or during the optimization of the orbitals. Imagine, for instance, that the eigenenergy of the 65th orbital moves below the orbital energy of the 64th orbital. Then the subspace diagonalization step will swap both orbitals, but the occupancies will remain as read from the INCAR file (this means that the originally unoccupied 65th orbital will move to the 64th place and it will hence become occupied). This problem can be often circumvented by specifying LDIAG=.FALSE. in the INCAR file.
Note that the partial occupancies are also written to the OUTCAR file, but in this case they are multiplied by 2, i.e. they are between 0 and 2.