Choosing pseudopotentials

From VASP Wiki

Several pseudopotential variants labeled by suffixes exist for many elements. When making a choice, it is necessary to balance computational cost, accuracy, and transferability.

  • To set up a minimal working example of your calculation, follow prepare a POTCAR.
  • Try to create a smaller test calculation and perform your own tests to confirm if the quantity of interest is sensitive to the choice of the pseudopotential. It might be possible to opt for a computationally cheaper POTCAR and gain performance. On the other hand, it could be necessary to opt for a computationally demanding setup to obtain correct results.
  • With the aspects described in the next section in mind, carefully look over the recommendations for each group in the periodic table.

Aspects to refine the choice of pseudopotentials

Aspect 1: Analyze the geometry of your structure for short bonds and the valency of the ions.

Short bonds will require harder potentials, and semicore states might have to be treated as valence for certain chemical bonding. For some elements, variants for specific valency exist; for example, the suffix _2 or _3 can be used to describe fixed divalent or trivalent Lanthanides.

Aspect 2: Consider the physical or chemical property that is the objective of your calculation.

If you are only interested in a rough structure optimization, soft potentials (_s) with minimal valency may suffice. This approach might also work for phonon calculations that rely on large supercells.
On the other hand, when optimizing a magnetic structure, it may be necessary to include semicore states in the valence (_pv and _sv).
For the computation of optical properties, it is crucial to use GW potentials.

Aspect 3: Scrutinize the requirements of the method or algorithm used in your calculation.

For any calculation involving unoccupied states significantly above the Fermi energy, the _GW variants of potentials are superior and should be used. Particularly, all kinds of calculations within many-body perturbation theory need a high number of empty bands. Therefore, when GW, BSE, etc. is performed, the GW potentials should be used throughout the workflow.
For Hartree-Fock and hybrid caluclations should not be performed with soft potentials (_s). Moreover, any calculations where you switch the exchange-correlation functional should not be performed with soft potentials (_s).
For standard DFT-ground-state calculations, using _GW or _h potentials is usually unnecessary unless, e.g., the property of interest or geometry of the structure, demands it.

Recommendations and advice

Recommended PAW potentials

The table directly below highlights recommended PAW potentials in bold.
These potentials are not ideal for calculations involving a large number of excited states as needed, e.g., for optical properties or many-body perturbation theory.
Standard PBE potentials (potpaw.64)
Potential name Number of valence electrons Valence electron configuration ENAMX [eV]
H 1 1s1 250.0
H.25 0.25 1s0.25 250.0
H.33 0.33 1s0.33 250.0
H.42 0.42 1s0.42 250.0
H.5 0.5 1s0.5 250.0
H.58 0.58 1s0.58 250.0
H.66 0.66 1s0.66 250.0
H.75 0.75 1s0.75 250.0
H1.25 1.25 1s1.25 250.0
H1.33 1.33 1s1.33 250.0
H1.5 1.5 1s1.5 250.0
H1.66 1.66 1s1.66 250.0
H1.75 1.75 1s1.75 250.0
H_AE 1 1s1 1000.0
H_h 1 1s1 700.0
H_s 1 1s1 200.0
He 2 1s2 478.896
He_AE 2 1s2 2135.871
Li 1 2s1 140.0
Li_sv 3 1s2 2s1 499.034
Be 2 2s1.99 2p0.01 247.543
Be_sv 4 1s2 2s1.99 2p0.01 308.768
B 3 2s2 2p1 318.614
B_h 3 2s2 2p1 700.0
B_s 3 2s2 2p1 269.245
C 4 2s2 2p2 400.0
C_h 4 2s2 2p2 741.689
C_s 4 2s2 2p2 273.911
N 5 2s2 2p3 400.0
N_h 5 2s2 2p3 755.582
N_s 5 2s2 2p3 279.692
O 6 2s2 2p4 400.0
O_h 6 2s2 2p4 765.519
O_s 6 2s2 2p4 282.853
F 7 2s2 2p5 400.0
F_h 7 2s2 2p5 772.626
F_s 7 2s2 2p5 289.837
Ne 8 2s2 2p6 343.606
Na 1 3s1 101.968
Na_pv 7 2p6 3s1 259.561
Na_sv 9 2s2 2p6 3s1 645.64
Mg 2 3s2 200.0
Mg_pv 8 2p6 3s2 403.929
Mg_sv 10 2s2 2p6 3s2 495.223
Al 3 3s2 3p1 240.3
Si 4 3s2 3p2 245.345
P 5 3s2 3p3 255.04
P_h 5 3s2 3p3 390.202
S 6 3s2 3p4 258.689
S_h 6 3s2 3p4 402.436
Cl 7 3s2 3p5 262.472
Cl_h 7 3s2 3p5 409.136
Ar 8 3s2 3p6 266.408
K_pv 7 3p6 4s1 116.731
K_sv 9 3s2 3p6 4s1 259.264
Ca_pv 8 3p6 4s2 119.559
Ca_sv 10 3s2 3p6 4s2 266.622
Sc 3 3d2 4s1 154.763
Sc_sv 11 3s2 3p6 3d2 4s1 222.66
Ti 4 3d3 4s1 178.33
Ti_pv 10 3p6 3d3 4s1 222.335
Ti_sv 12 3s2 3p6 3d3 4s1 274.61
V 5 3d4 4s1 192.543
V_pv 11 3p6 3d4 4s1 263.673
V_sv 13 3s2 3p6 3d4 4s1 263.673
Cr 6 3d5 4s1 227.08
Cr_pv 12 3p6 3d5 4s1 265.681
Cr_sv 14 3s2 3p6 3d5 4s1 395.471
Mn 7 3d6 4s1 269.864
Mn_pv 13 3p6 3d6 4s1 269.864
Mn_sv 15 3s2 3p6 3d6 4s1 387.187
Fe 8 3d7 4s1 267.882
Fe_pv 14 3p6 3d7 4s1 293.238
Fe_sv 16 3s2 3p6 3d7 4s1 390.558
Co 9 3d8 4s1 267.968
Co_pv 15 3p6 3d8 4s1 271.042
Co_sv 17 3s2 3p6 3d8 4s1 390.362
Ni 10 3d9 4s1 269.532
Ni_pv 16 3p6 3d9 4s1 367.986
Cu 11 3d10 4s1 295.446
Cu_pv 17 3p6 3d10 4s1 368.648
Zn 12 3d10 4s2 276.723
Ga 3 4s2 4p1 134.678
Ga_d 13 3d10 4s2 4p1 282.691
Ga_h 13 3d10 4s2 4p1 404.601
Ge 4 4s2 4p2 173.807
Ge_d 14 3d10 4s2 4p2 310.294
Ge_h 14 3d10 4s2 4p2 410.425
As 5 4s2 4p3 208.702
As_d 15 3d10 4s2 4p3 288.651
Se 6 4s2 4p4 211.555
Br 7 4s2 4p5 216.285
Kr 8 4s2 4p6 185.331
Rb_pv 7 4p6 4d0.001 5s0.999 121.882
Rb_sv 9 4s2 4p6 4d0.001 5s0.999 220.112
Sr_sv 10 4s2 4p6 4d0.001 5s1.999 229.353
Y_sv 11 4s2 4p6 4d2 5s1 202.626
Zr_sv 12 4s2 4p6 4d3 5s1 229.898
Nb_pv 11 4p6 4d4 5s1 208.608
Nb_sv 13 4s2 4p6 4d4 5s1 293.235
Mo 6 4d5 5s1 224.584
Mo_pv 12 4p6 4d5 5s1 224.584
Mo_sv 14 4s2 4p6 4d5 5s1 242.676
Tc 7 4d6 5s1 228.694
Tc_pv 13 4p6 4d6 5s1 263.523
Tc_sv 15 4s2 4p6 4d6 5s1 318.703
Ru 8 4d7 5s1 213.271
Ru_pv 14 4p6 4d7 5s1 240.049
Ru_sv 16 4s2 4p6 4d7 5s1 318.855
Rh 9 4d8 5s1 228.996
Rh_pv 15 4p6 4d8 5s1 247.408
Pd 10 4d9 5s1 250.925
Pd_pv 16 4p6 4d9 5s1 250.925
Ag 11 4d10 5s1 249.844
Ag_pv 17 4p6 4d10 5s1 297.865
Cd 12 4d10 5s2 274.336
In 3 5s2 5p1 95.934
In_d 13 4d10 5s2 5p1 239.211
Sn 4 5s2 5p2 103.236
Sn_d 14 4d10 5s2 5p2 241.083
Sb 5 5s2 5p3 172.069
Te 6 5s2 5p4 174.982
I 7 5s2 5p5 175.647
Xe 8 5s2 5p6 153.118
Cs_sv 9 5s2 5p6 6s1 220.318
Ba_sv 10 5s2 5p6 5d0.01 6s1.99 187.181
La 11 4f0.0001 5s2 5p6 5d0.9999 6s2 219.292
La_s 9 5p6 5d1 6s2 136.53
Ce 12 4f1 5s2 5p6 5d1 6s2 273.042
Ce_3 11 5s2 5p6 5d1 6s2 176.506
Ce_h 12 4f1 5s2 5p6 5d1 6s2 299.9
Pr 13 4f2.5 5s2 5p6 5d0.5 6s2 337.25
Pr_3 11 5s2 5p6 5d1 6s2 181.719
Pr_h 13 4f2.5 5s2 5p6 5d0.5 6s2 400.742
Nd 14 4f3.5 5s2 5p6 5d0.5 6s2 338.34
Nd_3 11 5s2 5p6 5d1 6s2 182.619
Nd_h 14 4f3.5 5s2 5p6 5d0.5 6s2 402.016
Pm 15 4f4.5 5s2 5p6 5d0.5 6s2 340.358
Pm_3 11 5s2 5p6 5d1 6s2 176.959
Pm_h 15 4f4.5 5s2 5p6 5d0.5 6s2 404.406
Sm 16 4f5.5 5s2 5p6 5d0.5 6s2 341.177
Sm_3 11 5s2 5p6 5d1 6s2 177.087
Sm_h 16 4f5.5 5s2 5p6 5d0.5 6s2 405.382
Eu 17 4f6.5 5s2 5p6 5d0.5 6s2 344.705
Eu_2 8 5p6 6s2 99.328
Eu_3 9 5p6 5d1 6s2 129.057
Eu_h 17 4f6.5 5s2 5p6 5d0.5 6s2 403.212
Gd 18 4f7.5 5s2 5p6 5d0.5 6s2 342.859
Gd_3 9 5p6 5d1 6s2 154.332
Gd_h 18 4f7.5 5s2 5p6 5d0.5 6s2 407.403
Tb 19 4f8.5 5s2 5p6 5d0.5 6s2 340.855
Tb_3 9 5p6 5d1 6s2 155.613
Tb_h 19 4f8.5 5s2 5p6 5d0.5 6s2 405.043
Dy 20 4f9.5 5s2 5p6 5d0.5 6s2 341.547
Dy_3 9 5p6 5d1 6s2 155.713
Dy_h 20 4f9.5 5s2 5p6 5d0.5 6s2 405.886
Ho 21 4f10.5 5s2 5p6 5d0.5 6s2 343.845
Ho_3 9 5p6 5d1 6s2 154.137
Ho_h 21 4f10.5 5s2 5p6 5d0.5 6s2 415.91
Er 22 4f11.5 5s2 5p6 5d0.5 6s2 346.295
Er_2 8 5p6 6s2 119.75
Er_3 9 5p6 5d1 6s2 155.037
Er_h 22 4f11.5 5s2 5p6 5d0.5 6s2 429.583
Tm 23 4f12.5 5s2 5p6 5d0.5 6s2 344.206
Tm_3 9 5p6 5d1 6s2 149.221
Tm_h 23 4f12.5 5s2 5p6 5d0.5 6s2 419.812
Yb 24 4f13.5 5s2 5p6 5d0.5 6s2 344.312
Yb_2 8 5p6 6s2 112.578
Yb_3 9 5p6 5d1 6s2 188.359
Yb_h 24 4f13.5 5s2 5p6 5d0.5 6s2 409.285
Lu 25 4f14 5s2 5p6 5d1 6s2 255.695
Lu_3 9 5p6 5d1 6s2 154.992
Hf 4 5d3 6s1 220.334
Hf_pv 10 5p6 5d3 6s1 220.334
Hf_sv 12 5s2 5p6 5d4 237.444
Ta 5 5d4 6s1 223.667
Ta_pv 11 5p6 5d4 6s1 223.667
W 6 5d5 6s1 223.057
W_sv 14 5s2 5p6 5d5 6s1 223.057
Re 7 5d6 6s1 226.216
Re_pv 13 5p6 5d6 6s1 226.216
Os 8 5d7 6s1 228.022
Os_pv 14 5p6 5d7 6s1 228.022
Ir 9 5d8 6s1 210.864
Pt 10 5d9 6s1 230.283
Pt_pv 16 5p6 5d9 6s1 294.607
Au 11 5d10 6s1 229.943
Hg 12 5d10 6s2 233.204
Tl 3 6s2 6p1 90.14
Tl_d 13 5d10 6s2 6p1 237.053
Pb 4 6s2 6p2 97.973
Pb_d 14 5d10 6s2 6p2 237.835
Bi 5 6s2 6p3 105.037
Bi_d 15 5d10 6s2 6p3 242.839
Po 6 6s2 6p4 159.707
Po_d 16 5d10 6s2 6p4 264.565
At 7 6s2 6p5 161.43
Rn 8 6s2 6p6 151.497
Fr_sv 9 6s2 6p6 7s1 214.54
Ra_sv 10 6s2 6p6 7s2 237.367
Ac 11 6s2 6p6 6d1 7s2 172.351
Th 12 5f1 6s2 6p6 6d1 7s2 247.306
Th_s 10 5f1 6p6 6d1 7s2 169.363
Pa 13 5f1 6s2 6p6 6d2 7s2 252.193
Pa_s 11 5f1 6p6 6d2 7s2 193.466
U 14 5f2 6s2 6p6 6d2 7s2 252.502
U_s 14 5f2 6s2 6p6 6d2 7s2 209.23
Np 15 5f3 6s2 6p6 6d2 7s2 254.26
Np_s 15 5f3 6s2 6p6 6d2 7s2 207.713
Pu 16 5f4 6s2 6p6 6d2 7s2 254.353
Pu_s 16 5f4 6s2 6p6 6d2 7s2 207.83
Am 17 5f5 6s2 6p6 6d2 7s2 255.875
Cm 18 5f6 6s2 6p6 6d2 7s2 257.953
Cf 20 5f8 6s2 6p6 6d2 7s2 414.614
The following table highlights recommended PAW potentials for calculations involving many states above the Fermi energy in bold.
These potentials are not necessarily superior (and even might be inferior) for calculations involving mostly occupied states, e.g., for structural relaxations or phonons. They are optimized for scattering properties high above the Fermi level and thus have advantages if many unoccupied states are involved, as for optical properties or many-body perturbation theory.
GW potentials
Potential name Number of valence electrons Valence electron configuration ENAMX [eV]
H_GW 1 1s1 300.0
H_GW_new 1 1s1 536.615
H_h_GW 1 1s1 700.0
He_GW 2 1s2 405.78
Li_AE_GW 3 1s2 2p1 433.699
Li_GW 1 2s1 112.104
Li_sv_GW 3 1s2 2p1 433.699
Be_GW 2 2s1.9999 2p0.001 247.543
Be_sv_GW 4 1s2 2p2 537.454
B_GW 3 2s2 2p1 318.614
B_GW_new 3 2s2 2p1 318.614
B_h_GW 3 2s2 2p1 731.373
C_GW 4 2s2 2p2 413.992
C_GW_new 4 2s2 2p2 433.983
C_h_GW 4 2s2 2p2 741.689
C_s_GW 4 2s2 2p2 304.843
N_GW 5 2s2 2p3 420.902
N_GW_new 5 2s2 2p3 452.633
N_h_GW 5 2s2 2p3 755.582
N_s_GW 5 2s2 2p3 312.986
O_GW 6 2s2 2p4 414.635
O_GW_new 6 2s2 2p4 466.797
O_h_GW 6 2s2 2p4 765.519
O_s_GW 6 2s2 2p4 334.664
F_GW 7 2s2 2p5 487.698
F_GW_new 7 2s2 2p5 480.281
F_h_GW 7 2s2 2p5 848.626
Ne_GW 8 2s2 2p6 432.275
Ne_s_GW 8 2s2 2p6 318.26
Na_sv_GW 9 2s2 2p6 3p1 372.853
Mg_GW 2 3s2 126.143
Mg_pv_GW 8 2p6 3s2 403.929
Mg_sv_GW 10 2s2 2p6 3d2 429.893
Al_GW 3 3s2 3p1 240.3
Al_sv_GW 11 2s2 2p6 3s2 3p1 411.109
Si_GW 4 3s2 3p2 245.345
Si_sv_GW 12 2s2 2p6 3s2 3p2 547.578
P_GW 5 3s2 3p3 255.04
S_GW 6 3s2 3p4 258.689
Cl_GW 7 3s2 3p5 262.472
Ar_GW 8 3s2 3p6 290.599
K_sv_GW 9 3s2 3p6 3d1 248.998
Ca_sv_GW 10 3s2 3p6 3d2 281.43
Sc_sv_GW 11 3s2 3p6 3d3 378.961
Ti_sv_GW 12 3s2 3p6 3d4 383.774
V_sv_GW 13 3s2 3p6 3d5 382.321
Cr_sv_GW 14 3s2 3p6 3d6 384.932
Mn_GW 7 3d6 4s1 278.466
Mn_sv_GW 15 3s2 3p6 3d7 384.627
Fe_GW 8 3d7 4s1 321.007
Fe_sv_GW 16 3s2 3p6 3d8 387.837
Co_GW 9 3d8 4s1 323.4
Co_sv_GW 17 3s2 3p6 3d9 387.491
Ni_GW 10 3d9 4s1 357.323
Ni_sv_GW 18 3s2 3p6 3d10 389.645
Cu_GW 11 3d10 4s1 417.039
Cu_sv_GW 19 3s2 3p6 3d10 4s1 467.331
Zn_GW 12 3d10 4s2 328.191
Zn_sv_GW 20 3s2 3p6 3d10 4s2 401.665
Ga_GW 3 4s2 4p1 134.678
Ga_d_GW 13 3d10 4s2 4p1 404.602
Ga_sv_GW 21 3s2 3p6 3d10 4s2 4p1 404.602
Ge_GW 4 4s2 4p2 173.807
Ge_d_GW 14 3d10 4s2 4p2 375.434
Ge_sv_GW 22 3s2 3p6 3d10 4s2 4p2 410.425
As_GW 5 4s2 4p3 208.702
As_sv_GW 23 3s2 3p6 3d10 4s2 4p3 415.313
Se_GW 6 4s2 4p4 211.555
Se_sv_GW 24 3s2 3p6 3d10 4s2 4p4 469.344
Br_GW 7 4s2 4p5 216.285
Br_sv_GW 25 3s2 3p6 3d10 4s2 4p5 475.692
Kr_GW 8 4s2 4p6 252.232
Rb_sv_GW 9 4s2 4p6 4d1 221.197
Sr_sv_GW 10 4s2 4p6 4d2 224.817
Y_sv_GW 11 4s2 4p6 4d3 339.758
Zr_sv_GW 12 4s2 4p6 4d4 346.364
Nb_sv_GW 13 4s2 4p6 4d5 353.872
Mo_sv_GW 14 4s2 4p6 4d6 344.914
Tc_sv_GW 15 4s2 4p6 4d7 351.044
Ru_sv_GW 16 4s2 4p6 4d8 348.106
Rh_GW 9 4d8 5s1 247.408
Rh_sv_GW 17 4s2 4p6 4d9 351.206
Pd_GW 10 4d9 5s1 250.925
Pd_sv_GW 18 4s2 4p6 4d10 356.093
Ag_GW 11 4d10 5s1 249.844
Ag_sv_GW 19 4s2 4p6 4d11 354.43
Cd_GW 12 4d10 5s2 254.045
Cd_sv_GW 20 4s2 4p6 4d10 5s2 361.806
In_d_GW 13 4d10 5s2 5p1 278.624
In_sv_GW 21 4s2 4p6 4d10 5s2 5p1 366.771
Sn_d_GW 14 4d10 5s2 5p2 260.066
Sn_sv_GW 22 4s2 4p6 4d10 5s2 5p2 368.778
Sb_GW 5 5s2 5p3 172.069
Sb_d_GW 15 4d10 5s2 5p3 263.1
Sb_sv_GW 23 4s2 4p6 4d10 5s2 5p3 372.491
Te_GW 6 5s2 5p4 174.982
Te_sv_GW 24 4s2 4p6 4d10 5s2 5p4 376.618
I_GW 7 5s2 5p5 175.647
I_sv_GW 25 4s2 4p6 4d10 5s2 5p5 381.674
Xe_GW 8 5s2 5p6 179.547
Xe_sv_GW 26 4s2 4p6 4d10 5s2 5p6 400.476
Cs_sv_GW 9 5s2 5p6 5d1 198.101
Ba_sv_GW 10 5s2 5p6 5d1 6s1 267.02
La_GW 11 4f0.2 5s2 5p6 5d0.8 6s2 313.688
Ce_GW 12 4f1 5s2 5p6 5d1 6s2 304.625
Hf_sv_GW 12 5s2 5p6 5d4 309.037
Ta_sv_GW 13 5s2 5p6 5d5 286.008
W_sv_GW 14 5s2 5p6 5d6 317.132
Re_sv_GW 15 5s2 5p6 5d7 317.012
Os_sv_GW 16 5s2 5p6 5d8 319.773
Ir_sv_GW 17 5s2 5p6 5d9 319.843
Pt_GW 10 5d9 6s1 248.716
Pt_sv_GW 18 5s2 5p6 5d10 323.669
Au_GW 11 5d10 6s1 248.344
Au_sv_GW 19 5s2 5p6 5d11 306.658
Hg_sv_GW 20 5s2 5p6 5d10 6s2 312.028
Tl_d_GW 15 5s2 5d10 6s2 6p1 237.053
Tl_sv_GW 21 5s2 5p6 5d10 6s2 6p1 316.583
Pb_d_GW 16 5s2 5d10 6s2 6p2 237.809
Pb_sv_GW 22 5s2 5p6 5d10 6s2 6p2 317.193
Bi_GW 5 6s2 6p3 146.53
Bi_d_GW 17 5s2 5d10 6s2 6p3 261.876
Bi_sv_GW 23 5s2 5p6 5d10 6s2 6p3 323.513
Po_d_GW 18 5s2 5d10 6s2 6p4 267.847
Po_sv_GW 24 5s2 5p6 5d10 6s2 6p4 326.618
At_d_GW 17 5d10 6s2 6p5 266.251
At_sv_GW 25 5s2 5p6 5d10 6s2 6p5 328.529
Rn_d_GW 18 5d10 6s2 6p6 267.347
Rn_sv_GW 26 5s2 5p6 5d10 6s2 6p6 329.758

Selecting a pseudopotential set

Generally, we recommend using the latest release of pseudopotentials.
Tip: For compatibility reasons or to accurately reproduce another calculation, you might need to use another (older) pseudopotential release. Consult the list of available pseudopotentials.

Hydrogen-like atoms with fractional valence

Twelve hydrogen-like potentials are supplied for a valency between 0.25 and 1.75. Further potentials might become available, c.f. available pseudopotentials. These are useful, e.g., to passivate dangling surface bonds.
Mind: The POTCAR files restrict the number of digits for the valency (typically 2, at most 3 digits). Therefor, using three H.33 potentials does yield 0.99 electrons and not 1.00 electron. This can cause undesirable hole- or electron-like states. Set the NELECT tag in the INCAR file to correct the total number of electrons.

First-row elements

For the 1st row elements B, C, N, O, and F, three potential versions exist, the plain one, a hard version, and a soft version. 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 VxOy, 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.
Tip: If dimers with short bonds are present in the system (H2O, O2, CO, N2, F2, P2, S2, Cl2), we recommend using the _h potentials. Specifically, C_h, O_h, N_h, F_h, P_h, S_h, Cl_h, or their _GW counterparts. Otherwise, the standard version is often the best choice for first-row elements.

Alkali and alkali-earth elements (simple metals)

For Li (and Be), a standard potential and a potential that treats the 1s 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 s and p states should be treated as valence states as well. For lighter elements (Na-Ca), it is usually sufficient to treat the 2p and 3p states as valence states (_pv), respectively. For Rb-Sr, the 4s, 4p, and 5s, 5p states, must be treated as valence states (_sv).
Tip: For alkali and alkali-earth metals, the _sv variants should be chosen, other than for very light elements Na, Mg, K, and Ca, where _pv is usually sufficient.

p-elements

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

d-elements

For the d elements, applies the same as for the alkali and earth-alkali metals: the semi-core p states and possibly the semi-core s 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.
When to switch from X_pv potentials to the X potentials depends on the required accuracy and the row for the 3d elements, even the Ti, V, and Cr potentials give reasonable results but should be used with uttermost care. 4d elements are the most problematic, and we advise using the X_pv potentials up to Tc_pv. For 5d elements the 5p states are rather strongly localized (below 3 Ry), since the 4f shell becomes filled. One can use the standard potentials starting from Hf, but we recommend performing test calculations. For some elements, X_sv potentials 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.
Tip: As a rule of thumb the p states should be treated as valence states for d-elements, if their eigenenergy lies above 3 Ry.

f-elements

Due to self-interaction errors, f electrons are not handled well by the presently available density functionals. In particular, partially filled f states are often incorrectly described. For instance, all f 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 f 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 4f elements, this transition occurs already in La and Ce, whereas the transition sets in for Pu and Am for the 5f elements. A routine way to cope with the inabilities of present DFT functionals to describe the localized 4f electrons is to place the 4f electrons in the core. Such potentials are available and described below; however, they are expected to fail to describe magnetic properties arising f orbitals. Furthermore, PAW potentials in which the f states are treated as valence states are available, but these potentials are expected to fail to describe electronic properties when f electrons are localized. In this case, one might treat electronic correlation effects more carefully, e.g., by employing hybrid functionals or introducing on-site Coulomb interaction.
For some elements, soft versions (_s) are available as well. The semi-core p states are always treated as valence states, whereas the semi-core s 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 s ghost-states close to the Fermi-level (,e.g., Ce_s in ceria). The soft versions are, however, expected to be sufficiently accurate for calculations on intermetallic compounds.

Lanthanides with fixed valence

In addition, special GGA potentials are supplied for Ce-Lu, in which f electrons are kept frozen in the core, which is an attempt to treat the localized nature of f 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 f electrons and 2 s electrons. In most compounds, Sm adopts a valency of 3; hence 5 f 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).
Warning: f-elements are notoriously hard to describe with DFT due to self-interaction errors in the strongly localized orbitals. Placing some, or all, 4f electrons in the core can rectify this issue, but then the description of magnetism will fail and transferability will suffer.
Tip: If you are not interested in 4f-magnetism, and know the valency of your lanthanide, use the _2 or _3 potentials.

Test your setup

Even if you have taken a lot of care to optimize your pseudopotential choice, it is always good to perform some test calculations with other potentials, if necessary on a small prototype system. You might realize that you need extra accuracy, or that you are leaving performance on the table by using unnecessarily hard POTCARs for your problem.

Related tags and sections

POTCAR, Prepare a POTCAR, Available pseudopotentials

Theoretical background: Pseudopotentials, Theory: Pseudopotential basics, Projector-augmented-wave formalism