[Pw_forum] Doubt in spin-orbit coupling results

[Padmaja Patnaik]

Thanks a lot GS. 

I was waiting for some suggestions. As u have advised I need to study more about collinear and non-collinear formalism. About the system I am working on --  SiC doped with Cr. I am taking various supercells and Cr as a dilute impurity, doing relaxed and unrelaxed calcualtions for magnetic properties. Hope this is enough and would expect some suggestions for the magnetic moment problem.

Thanks and regards,
Padmaja Patnaik
Research Scholar
Dept of Physics
IIT Bombay
Mumbai, India


________________________________
Message: 2
Date: Tue, 20 Sep 2011 12:28:58 +0200
From: Gabriele Sclauzero <gabriele.sclauzero at epfl.ch>
Subject: Re: [Pw_forum] Doubt in spin-orbit coupling results
To: Padmaja Patnaik <padmaja_patnaik at yahoo.co.uk>,    PWSCF Forum
    <pw_forum at pwscf.org>
Message-ID: <BE7B21AF-2135-4CB9-9A66-6128CBB6A4FE at epfl.ch>
Content-Type: text/plain; charset="iso-8859-1"

Dear  Padmaja Patnaik,

    in order to include spin-orbit interaction in the KS equations (lspinorb=.true.) one needs to use a formalism for noncollinear magnetization (noncolin=.true.). This means that there is no preferential axis for the magnetization, which is a vector field, (m_x(r),m_y(r),m_z(r)) in this case.
Therefore, in general one cannot define "spin up" and "spin down" (unless the ground state of the system is collinear, e.g. m_x=m_y=0 for each r). That's why the code does not give two distinct components of the DOS in the noncollinear formalism.

What you should do depends on what you are looking for... first I would suggest that you try to understand the difference between the collinear and noncollinear formalisms, in order to be able to interpret the results.

About the total magnetic moment, I can't say anything because you didn't say a word about your system.


GS

Il giorno 12/set/2011, alle ore 07.06, Padmaja Patnaik ha scritto:

> Hi All
> 
> I am doing spin-orbit coupling calculations. To get spin-polarized calculations with spin-orbit coupling I mentioned in the input for scf,
>  lspinorb=.true.,
>  noncolin=.true.,
>  starting_magnetization(1)=0.5,
>  starting_magnetization(2)=0.5,
> After this scf calculations I am doing the nscf calculation and finally the density of states and partial density of states. What I expect is it should give me both up and down spin DOS separately but I didnt get that. The input,  nspin=2 in the input and get spin polarized results with both up and down spin density of states given separately which can be plotted. Can anybody please suggest what to do? Another doubt is the total magnetic moment is found to be zero (with spin-orbit interaction) which was earlier (without spin-orbit interaction) found to be 2 BohrMagneton./cell. 
> 
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