how to read valence and valency in POTCAR files?

[alpinnovianus]

Dear admins,

I want to ask how to properly understand the POTCAR files.
Here I pasted the information from the Nd and Nd_3 PAW_PBE POTCAR.
I'm concerned on which electrons are the valence electrons in VASP.

From wikipedia, Nd has configuration [Xe] 4f4 6s2 (6 valence electrons).
However, in vasp potcars, it seems that more electrons are used as valence.

From the info below, am I right in my understanding below?

Nd POTCAR has 14 valence electrons, Nd_3 POTCAR has 11 valence electrons.
The valence electrons are found from counting backwards ZVAL from the atomic configuration part.
So 14 valence electrons for Nd POTCAR are three 4f electrons, one 5d electron, six 5p electrons, two 6s electrons, and two 5s electrons.
The rest are placed in the core.

and the 11 valence electrons for Nd_3 POTCAR are one 5d electron, six 5p electrons, two 6s electrons, and two 5s electrons.
The rest are placed in the core. [thus, no valence electrons are from f-orbitals]

Where do I find the information in the POTCAR regarding the valency?
From https://www.vasp.at/wiki/index.php/Avai ... f_elements, it seems that the Nd_3 POTCAR is for trivalent (+3) Nd, but I can't find this info in the POTCAR file headings. How do I read the formal valency in POTCAR?


PAW_PBE Nd 23Dec2003
14.0000000000000
parameters from PSCTR are:
VRHFIN =Nd : [core=Xe4]
LEXCH = PE
EATOM = 1563.0090 eV, 114.8779 Ry

TITEL = PAW_PBE Nd 23Dec2003
LULTRA = F use ultrasoft PP ?
IUNSCR = 1 unscreen: 0-lin 1-nonlin 2-no
RPACOR = 2.300 partial core radius
POMASS = 144.240; ZVAL = 14.000 mass and valenz
RCORE = 2.800 outmost cutoff radius
RWIGS = 2.800; RWIGS = 1.482 wigner-seitz radius (au A)
ENMAX = 253.189; ENMIN = 189.892 eV
RCLOC = 2.111 cutoff for local pot
LCOR = T correct aug charges
LPAW = T paw PP
EAUG = 569.081
DEXC = 0.000
RMAX = 2.866 core radius for proj-oper
RAUG = 1.300 factor for augmentation sphere
RDEP = 2.838 radius for radial grids
RDEPT = 2.183 core radius for aug-charge

Atomic configuration
14 entries
n l j E occ.
1 0 0.50 -43395.8284 2.0000
2 0 0.50 -7023.8779 2.0000
2 1 1.50 -6278.5293 6.0000
3 0 0.50 -1529.8923 2.0000
3 1 1.50 -1294.9659 6.0000
3 2 2.50 -969.3625 10.0000
4 0 0.50 -309.7144 2.0000
4 1 1.50 -232.6371 6.0000
4 2 2.50 -123.0911 10.0000
5 0 0.50 -43.6910 2.0000
6 0 0.50 -3.8688 2.0000
5 1 1.50 -24.6660 6.0000
5 2 2.50 -2.9249 1.0000
4 3 2.50 -6.9199 3.0000
Description
l E TYP RCUT TYP RCUT
0 -43.6909871 23 1.550
0 -3.8687511 23 2.350
1 -24.6660275 23 2.400
1 27.2116520 23 2.400
2 -2.9248929 23 2.500
2 13.6058260 23 2.500
3 -6.9198819 23 2.800
3 -8.1634956 23 2.800
Error from kinetic energy argument (eV)


--------------------------------------------------------



PAW_PBE Nd_3 06Sep2000
11.0000000000000
parameters from PSCTR are:
SHA256 = 90782177844a5d17e05a83442c3981b109958f4399d5595472847236a982ac31 Nd_3/POTCAR
COPYR = (c) Copyright 06Sep2000 Georg Kresse
COPYR = This file is part of the software VASP. Any use, copying, and all other rights are regulated by the VASP license agreement.
COPYR = If you do not have a valid VASP license, you may not use, copy or distribute this file.
VRHFIN =Nd : [core=Xe4]
LEXCH = PE
EATOM = 934.1494 eV, 68.6580 Ry

TITEL = PAW_PBE Nd_3 06Sep2000
LULTRA = F use ultrasoft PP ?
IUNSCR = 1 unscreen: 0-lin 1-nonlin 2-no
RPACOR = 2.400 partial core radius
POMASS = 144.240; ZVAL = 11.000 mass and valenz
RCORE = 2.800 outmost cutoff radius
RWIGS = 3.000; RWIGS = 1.588 wigner-seitz radius (au A)
ENMAX = 182.619; ENMIN = 136.964 eV
RCLOC = 2.418 cutoff for local pot
LCOR = T correct aug charges
LPAW = T paw PP
EAUG = 299.021
DEXC = 0.000
RMAX = 2.866 core radius for proj-oper
RAUG = 1.300 factor for augmentation sphere
RDEP = 2.838 radius for radial grids
RDEPT = 2.433 core radius for aug-charge

Atomic configuration
14 entries
n l j E occ.
1 0 0.50 -43395.8286 2.0000
2 0 0.50 -7023.8781 2.0000
2 1 1.50 -6278.5294 6.0000
3 0 0.50 -1529.8925 2.0000
3 1 1.50 -1294.9660 6.0000
3 2 2.50 -969.3626 10.0000
4 0 0.50 -309.7145 2.0000
4 1 1.50 -232.6371 6.0000
4 2 2.50 -123.0912 10.0000
4 3 2.50 -6.9199 3.0000
5 0 0.50 -43.6910 2.0000
6 0 0.50 -3.8688 2.0000
5 1 1.50 -24.6661 6.0000
5 2 2.50 -2.9249 1.0000
Description
l E TYP RCUT TYP RCUT
0 -43.6910211 23 2.800
0 -3.8687565 23 2.800
1 -24.6660554 23 2.800
1 13.6058260 23 2.800
2 -2.9249058 23 2.800
2 0.2001824 23 2.800
Error from kinetic energy argument (eV)

[alexey.tal]

Dear alpinnovianus,

From wikipedia, Nd has configuration [Xe] 4f4 6s2 (6 valence electrons).
However, in vasp potcars, it seems that more electrons are used as valence.

The valence electrons in the PAW are the ones treated explicitly, i.e. not frozen. Usually to achieve better accuracy more electrons are included in the valence then actually participating in the bonds formation.

Nd POTCAR has 14 valence electrons, Nd_3 POTCAR has 11 valence electrons.
The valence electrons are found from counting backwards ZVAL from the atomic configuration part.
So 14 valence electrons for Nd POTCAR are three 4f electrons, one 5d electron, six 5p electrons, two 6s electrons, and two 5s electrons.
The rest are placed in the core.

That is correct.

and the 11 valence electrons for Nd_3 POTCAR are one 5d electron, six 5p electrons, two 6s electrons, and two 5s electrons.
The rest are placed in the core. [thus, no valence electrons are from f-orbitals]

In Nd_3 POTCAR, one of the 4f electrons is placed in the 5d shell. The other three 4f electrons are moved to the core.

Where do I find the information in the POTCAR regarding the valency?
From https://www.vasp.at/wiki/index.php/Avai ... f_elements, it seems that the Nd_3 POTCAR is for trivalent (+3) Nd, but I can't find this info in the POTCAR file headings. How do I read the formal valency in POTCAR?

In the POTCAR file, the first line should tell you the type of the potential and the formal valence, for example "_3".