View source for POTCAR

The {{FILE|POTCAR}} file essentially contains the pseudopotential for each atomic species used in the calculation. If the number of species is larger than one, one simply concatenates the {{FILE|POTCAR}} files of the species. On a UNIX machine you might type the line

 cat ~/pot/Al/POTCAR ~/pot/C/POTCAR ~/pot/H/POTCAR > POTCAR

to concatenate three {{FILE|POTCAR}} files. The first file will correspond to the first species in the {{FILE|POSCAR}} and the {{FILE|INCAR}} file etc. 
{{NB|mind| It is a frequent error to give the wrong ordering in the {{FILE|POTCAR}} file!}}

For VASP version ≥ 3.2, the {{FILE|POTCAR}} file also contains information about the atoms, i.e., their mass [[POMASS]], their number of valence electrons [[ZVAL]], the energy of the reference configuration for which the pseudopotential was created, etc. If tags for the mass and valence exist in the {{FILE|INCAR}} file, they are checked against the parameters found in the {{FILE|POTCAR}} file, and error messages are printed. The  {{FILE|POTCAR}} files also contain a default energy cutoff ([[ENMAX]] and [[ENMIN]]); therefore, it is no longer necessary to specify {{TAG|ENCUT}} in the {{FILE|INCAR}} file. The value in the {{FILE|INCAR}} file overwrites the default in the {{FILE|POTCAR}} file. For {{FILE|POTCAR}} files with more than one species, the maximum cutoffs ([[ENMAX]] or [[ENMIN]]) are used for the calculation.
{{NB| important | The {{FILE|POTCAR}} file is meant to be used as read-only by the user. There is no standard usage of VASP that requires modifying the POTCAR file. Specifically do not modify the LEXCH tag in the POTCAR file: VASP recalculates the exchange-correlation energy inside the PAW sphere using the functional specified in the INCAR file and corrects the atomic energies. For this to work properly, the original LEXCH tag must not be modified in the POTCAR file.}}

To decide which potentials to use in your calculations visit our list of [[available PAW potentials]]

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[[The_VASP_Manual|Contents]]

[[Category:Files]][[Category:Input files]]