[QE-users] value of S^2 in LSDA

[Christoph Wolf]

Dear Professor Giannozzi,

Thank you very much for your help, indeed the spinsq routine does what I
need (and testing it within CP gives me good values for <S^2>). If it is
not too much to ask, what would be your best quick guess as to where the
routine could be interfaced with PWSCF without too much tinkering? I am
unfortunately not very familiar with the code structure of QE.

I see from spinsq that it requires the psi, <psi|beta> and rhor. I can't
quite figure out the second variable; in cpr.f90 spinsq is called as

IF ( tstdout) CALL spinsq ( c0_bgrp, bec_bgrp, rhor )

I believe the first variable is usually called evc in pwscf but I am not
sure if bec_bgrp here is the one from becmod in /Modules?

Any help is much appreciated!

With best wishes,
Chris

On Tue, 4 Aug 2020 at 21:02, Paolo Giannozzi <p.giannozzi at gmail.com> wrote:

> There is a simple routine in CP that estimates the amount of "spin
> contamination": CPV/src/spinsq.f90. Hope this helps (but I am not sure it
> will!)
>
> Paolo
>
> On Sun, Jul 26, 2020 at 8:36 AM Christoph Wolf <wolf.christoph at qns.science>
> wrote:
>
>> Dear all,
>>
>> I am navigating in circles here, I hope someone can "kick" me in the
>> right direction ;)
>>
>> When estimating the "spin-contamination" literature (e.g. JP Malrieu,
>> Chem Rev 2014, 114, 429 ff) mentions that the degree of contamination is
>> estimated by the deviation of <BS|S^2|BS> and <HS|S^2|HS> from their ideal
>> (Ising wave-function type) values. I have a system in which the two
>> spin-centers seem spatially well-separated and indeed I find that the LDOS
>> indicates negligible overlap of the magnetic orbitals on the two centers.
>> However I also wanted to check if the Noodleman condition is satisfied,
>> e.g. if <S^2>_{HS}-<S^2>_{BS}~(S_max)^2.
>>
>> However, I can't figure out if this is calculated in PWSCF at some point?
>> Or does literature suggest to calculate this "by hand" possibly from the
>> output of the Hubbard U routine where I have account of the individual
>> electrons?
>>
>> Any help is appreciated, have a great weekend!
>>
>> Best,
>> Chris
>>
>> --
>> Postdoctoral Researcher
>> Center for Quantum Nanoscience, Institute for Basic Science
>> Ewha Womans University, Seoul, South Korea
>>
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>
>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>

-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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