How to correctly set magnetization in CP2K

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Diego López

no leída,
29 may 2023, 11:25:0929/5/23
a cp2k
Dear CP2k users, I am interested on the study of Y3Fe5O12 and now I am trying to set the adequate magnetization for Fe atoms. The unit cell has 40 Fe atoms and the magnetic ground state experimentally observed is ferrimagnetic (24 Fe atoms spin up and 16 Fe atoms spin down).

Which is the proper way to specify the magnetization of the system? &MAGNETIZATION or &BS? Are they compatible? How would be the &BS specification for this case?

Thanks in advanced. 

Regards,
Diego

Krack Matthias

no leída,
30 may 2023, 7:31:1130/5/23
a cp...@googlegroups.com

Dear Diego

 

Both keywords can be used to define the initial atomic states and the total magnetization of the system in conjunction with the MULTIPLICITY keyword. The &BS section provides a more detailed (orbital resolved) control.

 

HTH

 

Matthias

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Diego López

no leída,
30 may 2023, 8:22:0330/5/23
a cp2k
Dear Krack,

thank you a lot for your comments. The &BS section seems to be really usefull but I am struggling to obtain the actual electronic configuration of my system (Y3Fe5O12). I am trying to model theese Fe3+ (d5) ions, where Fe1 will be spin up and Fe2 will be spin down using the attatched &BS section on the input. 

&KIND Fe1
      ELEMENT Fe
      BASIS_SET SZV-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q16
      &BS
       &ALPHA
       NEL -2 -1
       L    0  2
       N    4  3
      &END
      &BETA
       NEL -2 -4
       L    0  2
       N    4  3
      &END
      &END
    &END KIND
    &KIND Fe2
      ELEMENT Fe
      BASIS_SET SZV-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q16
      &BS
       &ALPHA
       NEL -2 -4
       L    0  2
       N    4  3
      &END
      &BETA
       NEL -2 -1
       L    0  2
       N    4  3
      &END
      &END
    &END KIND

The electronic configuration of Fe is [Ar] 4s2 3d6 and  the one of Fe3+ ions is [Ar] 3d5, so I tried to extract both 4s electrons and 1 of 3d in each spin orientation, but in the output I see that there is something wrong:

Guess for atomic kind: Fe1

 Electronic structure
    Total number of core electrons                                         10.00
    Total number of valence electrons                                      11.50
    Total number of electrons                                              21.50
    Multiplicity                                                         triplet
    Alpha Electrons
    S   [  1.00  1.00] 1.00
    P   [  3.00] 3.00
    D      2.50
    Beta Electrons
    S   [  1.00  1.00] 1.00
    P   [  3.00] 3.00
    D      1.00

Guess for atomic kind: Fe2

 Electronic structure
    Total number of core electrons                                         10.00
    Total number of valence electrons                                      11.50
    Total number of electrons                                              21.50
    Multiplicity                                                         triplet
    Alpha Electrons
    S   [  1.00  1.00] 1.00
    P   [  3.00] 3.00
    D      1.00
    Beta Electrons
    S   [  1.00  1.00] 1.00
    P   [  3.00] 3.00
    D      2.50

How could I configure the &BS section to obtain an accurate description of my system?

Thanks in advanced.

Best,
Diego

Marcella Iannuzzi

no leída,
30 may 2023, 9:02:4730/5/23
a cp2k
Dear Diego

The initialisation of the atomic orbitals' occupation is done as for a restricted case. 
Then for the unrestricted case, it is simply divided by 2.
Hence for Fe one considers 6 electrons in 3d. To get the high spin state, one should add 4 electron in Alpha and remove 4 in Beta, or viceversa.
The resulting electronic structure should then show 5 electrons in Alpha and 1 in Beta.

Best
Marcella 

Krack Matthias

no leída,
30 may 2023, 9:13:4830/5/23
a cp...@googlegroups.com

Hi Diego

 

For Fe(+3) d^5 spin-up try

 

&ALPHA

N    4  3

L    0  2

NEL -2 +4

&END ALPHA

&BETA

N    4  3

L    0  2

NEL -2 -6

&END BETA

 

Switch ALPHA and BETA for spin down.

Diego López

no leída,
30 may 2023, 9:47:5630/5/23
a cp2k
Dear Krack

Thank you so much for your comment. I performed a calculation with this set up and the output now reads:

Electronic structure
    Total number of core electrons                                         10.00
    Total number of valence electrons                                      13.00
    Total number of electrons                                              23.00
    Multiplicity                                                          sextet

    Alpha Electrons
    S   [  1.00  1.00] 1.00
    P   [  3.00] 3.00
    D      5.00

    Beta Electrons
    S   [  1.00  1.00] 1.00
    P   [  3.00] 3.00
    D      0.00

The occupations of the p and d orbitals now look perfect, but if I am not wrong the occupation of the s orbitals should be 0. Is this ok for you or there is some problems here?

Best,
Diego

Krack Matthias

no leída,
30 may 2023, 9:58:1830/5/23
a cp...@googlegroups.com

Dear Diego

 

That’s fine. Fe-q16 is a semi-core pseudopotentials with 3s^2 3p^6 4s^2 3d^6 as valence electrons and thus you have to consider the two 3s electrons from the 3s^2 3p^6 semi-core states.

Diego López

no leída,
30 may 2023, 10:04:4130/5/23
a cp2k
Dear Krack

Ok, understood. Thank you a lot for your time, your comments are really useful for me.

Best,
Diego

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