next up previous contents index
Next: TAGS for the rhfsps Up: The pseudopotential generation package Previous: PSCTR   Contents   Index


Default energy cutoff

The PSEUDO and POTCAR files generated by rhfsps and fourpot3 contain a default energy cutoff, which might be used for the calculations with VASP. The default cutoff guarantees reliable calculations, with errors in the eigenvalues smaller than $ 1 $ mRy (i.e. $ 13$ meV, for $ s$ elements the error is usually much smaller). This is sufficient as long as the stress tensor is not important, because Pulay contributions are usually not negligible for this cutoff. (increase the cutoff by a factor of 1.5 if Pulay contributions should be avoided).

The default energy cutoff works only for US-PP constructed with the RRKJ scheme. The default cutoff is proportional to the square of the highest expansion coefficient used in the RRKJ scheme[18,43].

$\displaystyle ENMAX=1.8 * q_{\rm high} * q_{\rm high} * 13.6058$ (11.2)

( $ q_{\rm high}$ is in a.u., whereas ENMAX is in eV, therefore the conversion factor 13.6058). There is also a line ENMIN in the POTCAR and PSEUDO file, ENMIN corresponds to the minimal energy required for a reasonable accurate calculation (for instance ENMIN is sufficient for molecular dynamics), ENMIN is calculated according to

$\displaystyle ENMIN=1.5 * q_{\rm high} * q_{\rm high} * 13.6058$ (11.3)

( $ q_{\rm high}$ is in a.u., whereas ENMIN is in eV, therefore the conversion factor 13.6058).


next up previous contents index
Next: TAGS for the rhfsps Up: The pseudopotential generation package Previous: PSCTR   Contents   Index
N.B. Requests for support are to be addressed to: vasp.materialphysik@univie.ac.at