Available PAW potentials - VASP Wiki (2024)

Projector augmented wave (PAW) potentials are available for all elements in the periodic table from the VASP Portal. These are pseudopotentials for the PAW method and are stored in POTCAR files. The distributed PAW potentials have been generated by G. Kresse following the recipes discussed in ^[1], whereas the PAW method has been first suggested and used by Peter Blöchl ^[2]. Therefore, if you use any of the supplied PAW potentials, you should include these two references.

Except for the 1st-row elements, all PAW potentials are designed to work reliably and accurately at an energy cutoff of roughly 250 eV. This is a key aspect of making the calculation computationally cheap. The default energy cutoff is set by the ENMAX tag in the POTCAR file. Generally, the PAW potentials are more accurate than ultra-soft pseudopotentials (US-PP). There are two reasons for this: First, the radial cutoffs (core radii) are smaller than the radii used for US-PP. Second, the PAW potentials reconstruct the exact valence wavefunction with all nodes in the core region. Since the core radii of the PAW potentials are smaller, the required energy cutoffs and basis sets are also larger. If such high precision is not required, the older US-PP can be used in principle, but it is discouraged. This is because the energy cutoffs have not changed appreciably for C, N, and O. Thus, the increase in the basis-set size will usually be small so that calculations for compounds that include any of these elements are not more expensive with PAW than with US-PP.

For some elements several PAW versions exist. The standard version has no extension. The extension _h implies that the potential is harder than the standard potential and hence requires a greater energy cutoff. The extension _s means that the potential is softer than the standard version. The extensions _pv and _sv imply that the and semi-core states are treated as valence states (i.e. for V_pv the states are treated as valence states, and for V_sv the and states are treated as valence states). PAW files with an extension _d, treat the semi core states as valence states (for Ga_d the states are treated as valence states).

The valence configuration underlying each PAW potential can be inferred from the ZVAL tag and the table written below Atomic configuration in the POTCAR file. The table lists first the core states and then the valence states. Hence, the final rows those occupancies add up to ZVAL comprise the valence configuration. Note that this can differ from the ground-state configuration in vacuum and that the rows are not ordered by energy. For instance, for Gd_3 strongly localized, semi-core electrons are treated as core states despite being higher in energy than other valence states.

In the following, we will present the available PAW potentials. All distributed potentials have been tested using standard DFT-"benchmark" runs; see the data_base file in the released tar files. We strongly recommend using the POTCAR-files version 5.4 that is available as a download on the VASP Portal. The currently distributed POTCAR files of version 5.4 possess a unique SHA hash. The POTCAR-files version 5.2 is also quite popular and has been used in the Materials Project. Differences between version 5.4 and 5.2 are usually small and limited to few elements/POTCAR files. Each POTCAR file of version 5.2 that is presently available on the VASP Portal also possesses a unique SHA hash, and they have been slightly edited in the text part of the headers, which is irrelevant to VASP calculations. If strict compatibility is required to the versions previously available at the univie server, one can also download the versions "VASP release PAW POTCAR files: LDA & PBE, 5.2 & 5.4 (original univie release version)".

Below, recommended potentials are reported in boldface.

All reported potentials are for PBE calculations. Therefore, the reported energy cutoffs might differ slightly for LDA potentials and different releases.

Recommended potentials for DFT calculations

The following table lists the PAW potentials for VASP.

Important Note: If dimers with short bonds are present in the compound (H₂O, O₂, CO, N₂, F₂, P₂, S₂, Cl₂), we recommend to use the _h potentials. Specifically, C_h, O_h, N_h, F_h, P_h, S_h, Cl_h. Note that the listed default energy cutoffs might slightly change between different releases as noted above.

In version 5.4, W_sv has replaced the potential W_pv, and the At_d POTCAR file is no longer available because the potential leads to fairly large errors in the lattice constants.

Hydrogen-like potentials are supplied for a valency between 0.25 and 1.75, as listed in the table below. Further potentials might become available, and the list is not always up to date. Mind that the POTCAR files restrict the number of digits for the valency (typically 2, at most 3 digits). That is, using three H.33 potentials does not yield 0.99 electrons and not 1.00 electron. This can cause hole- or electron-like states that are undesirable. The solution is to slightly adjust the NELECT tag in the INCAR file.

Recommended potentials for GW/RPA calculations

The available GW potentials are listed in the table below. For DFT calculations, the GW potentials yield virtually identical results as the PAW potentials recommended for DFT calculations above. That is, one can use the GW potentials instead of the potentials discussed above for DFT calculations without deteriorating the results. In fact, we have evidence from comparison with all-electron calculations that the GW potentials are slightly superior even for DFT calculations. They are certainly superior for excited-state properties, GW calculations, random phase approximation (RPA) calculations, and in general for any explicitly correlated wave function calculation (MP2, coupled-cluster).

In general, the GW potentials yield much better scattering properties at high energies well above the Fermi level, i.e., typically up to 10-20 Ry above the vacuum level.

Important Note: If dimers with short bonds are present in the compound (O₂, CO, N₂, F₂, P₂, S₂, Cl₂), we recommend to use the _h potentials. Specifically, C_GW_h, O_GW_h, N_GW_h, F_GW_h.

The C_GW_new, N_GW_new, O_GW_new, and F_GW_new POTCAR files, use the f-pseudopotential as local potential and possess d-projectors. In contrast, the C_GW, N_GW, O_GW, and F_GW POTCAR files use the d-pseudopotential as local potential and possess no d-projectors. Calculations usually converge faster with respect to the energy cutoff ENMAX using the C_GW, N_GW, O_GW, and G_GW potentials. Whether the new potentials possess a precision advantage over the old potentials is not entirely clear. In theory, they should be more precise for correlated wavefunction calculations. However, in practice, the improvements seem modest and often do not justify the greater computational load.

Further recommendations regarding PAW potentials

In the following, we further explain the potentials for element groups.

1st row elements

For the 1st row elements, three PAW versions exist. For most purposes, the standard version of PAW potentials is most appropriate. They yield reliable results for energy cutoffs between 325 and 400 eV, where 370-400 eV are required to predict vibrational properties accurately. Binding geometries and energy differences are already well reproduced at 325 eV. The typical bond-length errors for first row dimers (N₂, CO, O₂) are about 1% compared to more accurate DFT calculations. The hard pseudopotentials _h give results that are essentially identical to the best DFT calculations presently available (FLAPW, or Gaussian with very large basis sets). The soft potentials are optimized to work around 250-280 eV. They yield reliable description for most oxides, such as V_xO_y, TiO₂, CeO₂, but fail to describe some structural details in zeolites, i.e., cell parameters, and volume.

For Hartree-Fock (HF) and hybrid functional calculations, we strictly recommend using the standard, standard GW, or hard potentials. For instance, the O_s potential can cause unacceptably large errors even in transition metal oxides. Generally, the soft potentials are less transferable from one exchange-correlation functional to another and often fail when the exact exchange needs to be calculated.

Alkali and alkali-earth elements (simple metals)

For Li (and Be), a standard potential and a potential that treats the shell as valence states are available (Li_sv, Be_sv). One should use the _sv potentials for many applications since their transferability is much higher than the standard potentials.

For the other alkali and alkali-earth elements, the semi-core and states should be treated as valence states as well. For lighter elements (Na-Ca) it is usually sufficient to treat the and states as valence states (_pv), respectively. For Rb-Sr the , , and , states, respectively, must be treated as valence states (_sv). The standard potentials are listed below. The default energy cutoffs are specified as well but might vary from one release to the other.

Contrary to the common belief, these elements are exceedingly difficult to pseudize in particular in combination with strongly electronegative elements (F) errors can be larger than usual. The present potentials are very precise and should offer a very reliable description. For X_pv potentials the semi-core states are treated as valence, e.g., in Na and Mg, in K and Ca, etc. For X_sv potentials, the semi-core states are treated as valence, e.g., in Li and Be, in Na, etc.

d elements

The same applies to elements as for the alkali and earth-alkali metals: the semi-core states and possibly the semi-core states should be treated as valence states. In most cases, however, reliable results can be obtained even if the semi-core states are kept frozen. As a rule of thumb the states should be treated as valence states, if their eigenenergy lies above 3 Ry.

For X_pv potentials, the semi core states are treated as valence, whereas for X_sv pseudopotentials, the semi-core states are treated as valence. X_pv potentials are required for early transition metals, but one can freeze the semi-core states for late transition metals; particularly for noble metals.

When to switch from X_pv potentials to the X potentials depends on the required accuracy and the row for the elements, even the Ti, V, and Cr potentials give reasonable results but should be used with uttermost care. elements are most problematic, and I advice to use the X_pv potentials up to Tc_pv. For elements the states are rather strongly localized (below 3 Ry), since the shell becomes filled. One can use the standard potentials starting from Hf, but we recommend performing test calculations. For some elements, X_sv potential are available (e.g. Nb_sv, Mo_sv, Hf_sv). These potentials usually have very similar energy cutoffs as the _pv potentials and can also be used. For HF-type and hybrid functional calculations, we strongly recommend using the _sv and _pv potentials whenever possible.

p-elements including first row

For Ga, Ge, In, Sn, Tl-At, the lower-lying states should be treated as valence states (_d potential). For these elements, alternative potentials that treat the states as core states are also available but should be used with great care.

f elements

Due to self-interaction errors, electrons are not handled well by the presently available density functionals. In particular, partially filled states are often incorrectly described. For instance, all states are pinned at the Fermi-level, leading to large overbinding for Pr-Eu and Tb-Yb. The errors are largest at quarter, and three-quarter filling, e.g., Gd is handled reasonably well since 7 electrons occupy the majority shell. These errors are DFT and not VASP related. Particularly problematic is the description of the transition from an itinerant (band-like) behavior observed at the beginning of each period to localized states towards the end of the period. For the elements, this transition occurs already in La and Ce, whereas the transition sets in for Pu and Am for the elements. A routine way to cope with the inabilities of present DFT functionals to describe the localized electrons is to place the electrons in the core. Such potentials are available and described below; however, they are expected to fail to describe magnetic properties arising orbitals. Furthermore, PAW potentials in which the states are treated as valence states are available, but these potentials are expected to fail to describe electronic properties when electrons are localized. In this case, one might treat electronic correlation effects more carefully, e.g., by employing hybrid functionals or introduce on-site Coulomb interaction.

For some elements, soft versions (_s) are available as well. The semi-core states are always treated as valence states, whereas the semi-core states are treated as valence states only in the standard potentials. For most applications (oxides, sulfides), the standard version should be used since the soft versions might result in ghost-states close to the Fermi-level (e.g., Ce_s in ceria). For calculations on intermetallic compounds, the soft versions are, however, expected to be sufficiently accurate.

In addition, special GGA potentials are supplied for Ce-Lu, in which electrons are kept frozen in the core, which is an attempt to treat the localized nature of electrons. The number of f electrons in the core equals the total number of valence electrons minus the formal valency. For instance: According to the periodic table, Sm has a total of 8 valence electrons, i.e., 6 electrons and 2 electrons. In most compounds, Sm adopts a valency of 3; hence 5 electrons are placed in the core when the pseudopotential is generated. The corresponding potential can be found in the directory Sm_3. The formal valency n is indicted by _n, where n is either 3 or 2. Ce_3 is, for instance, a Ce potential for trivalent Ce (for tetravalent Ce, the standard potential should be used).

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