Ideal and single determinant S**2

[Elham M.Goliaei]

Dear all,

    I have done geometry optimization using cp2k, I started by low spin configuration for Co(2+). According to below, my DFT section includes:

 

    &DFT

    LSD

    MULTIPLICITY 2

    RELAX_MULTIPLICITY 0.01

    ....

and I have just defined BS section for Co atom as below:

     &BS

        &ALPHA

          NEL +4 -2

          L 2 0

          N 3 4

        &END ALPHA

        &BETA 

          NEL +1 -2

          L 2 0

          N 3 4

        &END BETA 

      &END BS

 I noticed these values in the output:

Integrated absolute spin density  :                               2.7865063578

Ideal and single determinant S**2 :                    0.750000       1.647620

Can I have some explanation regarding "Ideal and single determinant S**2" values?

Best regards,

Elham

[hut...@chem.uzh.ch]

Hi

Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory
Attila Bangha Szabo, Neil S. Ostlund

See equations (2.271) and (2.272)

estimated S^2 expectation values for single determinant wavefunctions.

regards

Juerg Hutter
--------------------------------------------------------------
Juerg Hutter Phone : ++41 44 635 4491
Institut für Chemie C FAX : ++41 44 635 6838
Universität Zürich E-mail: hut...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
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-----cp...@googlegroups.com wrote: -----
To: "cp2k" <cp...@googlegroups.com>
From: "Elham M.Goliaei"
Sent by: cp...@googlegroups.com
Date: 12/06/2019 02:35PM
Subject: [CP2K:12608] Ideal and single determinant S**2

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[jiapeng Liu]

May I ask what is the meaning to have half electrons with alpha spin? According to my understanding, in the BS section, the real electrons with alpha spin is calculated as (7+4)/2=5.5 where 7 is the outer electron numbers of Co? And the electron with beta spin is (7+1)/2=4? Am I correct? I do not understand how the 5.5 electrons go? Thank you very much.

[Marcella Iannuzzi]

Dear Elham

for a configuration Co(2+) low spin, it is enough to remove the 4s, Why are you adding the 3d?

Anyway, these settings are just to guide the initial distribution of the orbitals' occupation. 

The density matrix is always rescaled in order to ensure the correct (integer) number of electrons per each spin channel, before the actual electronic structure calculation is started. 

Best regards

Marcella

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