[CP2K-user] [CP2K:20887] Enforcing an specific occupation of d orbitals

Krack Matthias matthias.krack at psi.ch
Fri Nov 8 16:17:55 UTC 2024


Dear Andres

Such an explicit 0 or 1 occupation pattern cannot be enforced after the first SCF iteration step. Only the distribution of the available density in the selected orbital shell can be influenced with the keywords ORBITALS (which orbitals are occupied) and NELEC (distribution between the spin channels). You can use this print key<https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/PLUS_U.html> for tracing the orbital occupations of the selected shell.

Best

Matthias

From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of oandr... at gmail.com <oandresg15 at gmail.com>
Date: Friday, 8 November 2024 at 16:34
To: cp2k <cp2k at googlegroups.com>
Subject: Re: [CP2K:20888] Enforcing an specific occupation of d orbitals
Dear Matthias ,

Thank you ,
Here I have defined two types of Fe , where in Fe1
I would like that Fe1 spin occupation is
   spin up      dz2=  1 dxz=  1, dyz=  1, dx2-y2=  1 dxy=  0,

  spin down  dz2= 0 dxz=  0, dyz=  1, dx2-y2=  1 dxy=  0,



And for Fe2
   spin up      dz2=  0 dxz=  0, dyz=  1, dx2-y2=  1 dxy=  0,

  spin down  dz2= 1 dxz=  1, dyz=  1, dx2-y2=  1 dxy=  0,



I dont understand how can i distinguish in ORBITALS between spin up and down.



Here is the input

&KIND "Fe1"
       BASIS_SET "TZV2P-MOLOPT-PBE-GTH-q16"
       POTENTIAL "GTH-PBE-q16"
      &DFT_PLUS_U
        L 2
        U [eV] 6.0
        &ENFORCE_OCCUPATION on
                MAX_SCF 5
        #For spin Up dz2=  1 dxz=  1, dyz=  1, dx2-y2=  1 dxy=  0,
        NELEC 4 2
        ORBITALS -1 0 +1 +2
        SMEAR
        &END
        &END DFT_PLUS_U
       &BS T
         &ALPHA
           NEL -2 2
           L 0 2
           N 4 3
         &END ALPHA
         &BETA
           NEL -2 -2
           L 0 2
           N 4 3
         &END BETA
       &END BS
   &END KIND

   &KIND "Fe2"
       BASIS_SET "TZV2P-MOLOPT-PBE-GTH-q16"
       POTENTIAL "GTH-PBE-q16"
      &DFT_PLUS_U
        L 2
        U [eV] 6.0
        &ENFORCE_OCCUPATION on
        NELEC 2 4
        MAX_SCF 5
        # d(xy), d(yz), d(xz)
        ORBITALS -1 0 +1 +2
        SMEAR
        &END
        &END DFT_PLUS_U
       &BS T
         &ALPHA
           NEL -2 -2
           L 0 2
           N 4 3
         &END ALPHA
         &BETA
           NEL -2 2
           L 0 2
           N 4 3
         &END BETA
       &END BS
     &END KIND

best

Andres Ortega-Guerrero
El viernes, 8 de noviembre de 2024 a la(s) 3:11:01 p.m. UTC+1, Krack Matthias escribió:
You have to specify different atomic kinds for spin up and spin down, e.g. Fe_a and Fe_b, with different (complementary) &ALPHA ad &BETA sections in the &BS section for the initial guess.

From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of oandr... at gmail.com <oandr... at gmail.com>
Date: Friday, 8 November 2024 at 15:06
To: cp2k <cp... at googlegroups.com>
Subject: Re: [CP2K:20883] Enforcing an specific occupation of d orbitals
Dear Matthias ,
Many thanks!

If i may , I will ask a follow up , How do you distinguish between spin and spin down?

best

Andres
El viernes, 8 de noviembre de 2024 a la(s) 2:55:59 p.m. UTC+1, Krack Matthias escribió:
You can enforce an equal occupation of e.g. d(-2) d(-1) d(+1) in the first 5 SCF iterations with
L 2
&ENFORCE_OCCUPATION on
  MAX_SCF 5
  # d(xy), d(yz), d(xz)
 ORBITALS -2 -1 +1
  SMEAR
&END

Note, that some DFT+U input parameters are only available with CP2K/SIRIUS (pwdft) and vice versa.

From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of oandr... at gmail.com <oandr... at gmail.com>
Date: Friday, 8 November 2024 at 14:25
To: cp2k <cp... at googlegroups.com>
Subject: Re: [CP2K:20880] Enforcing an specific occupation of d orbitals
Dear Mathias ,

Thank for your response ,

I was wondering if you could maybe give an example ? I am still a lil lost on how is the format to represent what I got and/or the order

best

Andres Ortega-Guerrero
nanotech at surface
EMPA
El viernes, 8 de noviembre de 2024 a la(s) 11:23:17 a.m. UTC+1, Krack Matthias escribió:
Hi Andres

Yes, you can specify a list of orbitals by their M values for the chosen L value. By default, the orbitals are filled one by one with the available electrons. With SMEAR the electronic density is smeared in the selected orbitals for a given number of SCF steps (MAX_SCF) or until a certain SCF convergence threshold (EPS_SCF) is reached. Different orbitals, M values, can be selected for spin up and spin down.

HTH

Matthias

From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of oandr... at gmail.com <oandr... at gmail.com>
Date: Friday, 8 November 2024 at 10:32
To: cp2k <cp... at googlegroups.com>
Subject: [CP2K:20877] Enforcing an specific occupation of d orbitals
Dear Forum,

I am currently , trying to provide an starting electronic configuration to enforce the initial occupation of electrons in Fe.

I came accross with the option
ENFORCE_OCCUPATION for DFT+U

I was wondering if is possible to provide an initial occupation for the d orbitals in Fe
using the option


ORBITALS: integer= 0•<https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/SUBSYS/KIND/DFT_PLUS_U/ENFORCE_OCCUPATION.html#CP2K_INPUT.FORCE_EVAL.SUBSYS.KIND.DFT_PLUS_U.ENFORCE_OCCUPATION.ORBITALS>

Aliases: M

Usage: ORBITALS 0 +1 -1





For example if i would like a particular occupation like:

spin up      dz2=  1 dxz=  1, dyz=  1, dx2-y2=  1 dxy=  0,

spin down  dz2= 0 dxz=  0, dyz=  1, dx2-y2=  1 dxy=  0,



Like the control there is quantum espresso, starting_ns_eigenvalue



Is there any way to impose such starting occupation?



Best



Andres Ortega-Guerrero

nanotech at surfaces

EMPA




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