For H three POTCAR files exist. The H/POTCAR and H_200eV/POTCAR files actually contain the same PP. The only difference is that H_200eV has a lower default energy cutoff of 200 eV (the default cutoff for H is 340 eV). Up to now we have not found any difference between calculations using 200 and 340 eV, we therefore recommend to use only H_200eV (differences for the dimer are for instance less than ). If H is used together with hard elements like carbon VASP will anyway adopt the higher default cutoff of C. The third potential H_soft (generated by J. Furthmueller) should be used in conjunction with soft elements like Si, Ge, Te etc. As one can see from the data_base file H dimer length and vibrational frequencies are still quite reasonable.
For the first row elements two PP exist, we recommend the standard version, which gives very high accuracy. The second set ( B_s,C_s,O_s,N_s,F_s) is significantly softer and should be used only after careful testing. We have found that the second set is save if a hard species is mixed with a softer one (that is for instance the case in Si-C, Si-O , or even Ti-O ).
For In, Sn and Ga one should describe the 3d or 4d states as valence, corresponding PP can be found on the server in the directories
Ga_d, In_d, Sn_d, Pb_dIf one puts the 3d or 4d states in the core the results depend strongly on the location of the position of the d-reference energy. The d-reference energy for the conventional Ga, In, Sn and Pb PP (with d in the core) has been adjusted so that the equilibrium volume is within 1 for the Ga_d, In_d and Sn_d PP. This is clearly a fix, but results in reasonable pseudopotentials Mind that PP including d are currently missing for Ge, and for very accurate calculations such a PP might be required.
The following PP are currently available with p semi-core states
K_pv Ca_pv Sc_pv Ti_pv V_pv Fe_pv Rb_pv Y_pv Zr_pv Nb_pv Mo_pv Cs_pvFurther PP with semi-core states are planed for transition metals (especially for the 3d-transition metals, like Sr, W etc.).
For a few elements harder NC-PP exist which should be used in calculations under pressure and for ionic systems (usually one does not need semi-core states for these elements and the harder NC-PPs are an cost efficient alternative):
Na_h Mg_h Al_h Si_h
Some PP are probably still not perfect: Notably one might need PP with p-semi core states for Li, Be, Na and Mg, and for none of the PPs the lower lying s states have been unfrozen (the reason for that is that the current version of the PP generation program does not handle such cases).