[Wien] DOS plots for fixed spin moment LDA+U calculations

[Laurence Marks]

I believe the problem here is that you have misunderstood the role of fixed
spin moment calculations.

In some cases there may be more than one fixed-point for a spin polarized
calculator, i.e. two or more local minima with different spins. It can be
useful to try and force a particular spin state, for instance to see if it
is stable. The FSM code does this by controlling the relative number of
up/dn electrons. For instance, with -m 8 there are always 8 more electrons
in the up levels than the down, the Fermi level is not the same for the
up/dn states.

The FSM code only gets you close to a possible spin state, it does not
yield a true fixed point. After doing the FSM calculation in all cases I
can think of you need to remove the case.broyd* files and use runsp again.
It may stabilize to a moment of 8, or it may not. You can't tell the
electrons what to do!

If you want to look at what the FSM calculation did, ignoring that it is
not representative of anything, you have to do some tricks. Depending upon
the current state of your directory you may have files case.in2up,
case.in2dn and case.in2_fsm. The last one has the right number of valence
electrons, similar to when you had when you did a straight runsp (and saved
the results I hope). The in2up file will have 8 more, and in2dn 8 less. You
will need to look at the csh script runfsm and see what it actually does
for a normal lapw2, and then adapt this by hand adding -qtl. (I don't have
the script handy.) I do not think there is a simple script in Wien2k to do
this.

---
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
http://www.numis.northwestern.edu
Corrosion in 4D http://MURI4D.numis.northwestern.edu
Partner of the CFW 100% gender equity project, www.cfw.org/100-percent
Co-Editor, Acta Cryst A

On May 20, 2016 22:46, "saurabh singh" <saurabhiitmandi at gmail.com> wrote:

> Dear All users,
>
> Hope many people have faced similar problem in fixed spin moment DOS
> calculations
> I found problem in calculating DOS in fixed spin moment calculation. The
> similar question asked long before
> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg00449.html
>  but there is no answer given for that.
> In our case I do the LDA+U calculation I do follow the following step
> before calculating DOS
> 1. init_lapw
> 2.runsp_lapw  -cc 0.0001
> 3. runsp_lapw -orb -cc 0.0001
> 4. runfsm_lapw -orb -m 8 -cc 0.0001
>
> I get total spin magnetic moment in unit cell 8.0001 μB.  I do follow the
> instruction of user manual where it is recommended that one should run x
> lapw1 -orb -up before calculating the DOS. So i did it then i executed
> following command
> x lapw2 -qtl -up
> configure_init_lapw
> x tetra -up
>
> the above three command with dn. I calculated total DOS in present case.
> The problem I faced that
>
> 1. As per the manual "only case.vectordn is ok, but case.vectorup is NOT
> the proper up-spin vector and MUST NOT be used for the calculations of QTLs
> (and DOS). It must be regenerated by x lapw1 -up ". Its ok then why if I
> calculate first the dos for dn spin and then follow the required correction
> of case.vectorup by running the x lapw1 -up command it gives two different
> fermi level in qtlup and qtldn file. This is done by the following steps :
> After SCF convergence
> x lapw2 -qtl -dn
> configure_init_lapw
> x tetra -dn
> x lapw1 -orb -up
> x lapw2 -qtl -up
> x tetra -up
>
> I also integrated DOS (case.dosevup/dn) for up and dn spin and found the
> difference in the integrated value at Fermi level (0 eV) is  nearly 3.07.
> If the above steps is right it should be nearly 8
> 2. If I follow the following steps
> x lapw1 -orb -up
> x lapw2 -qtl -up
> configure_init_lapw
> x tetra -up
> x lapw2 -qtl -dn
> x tetra -dn
>
> Then I got same Fermi level in both the qtlup and qtldn file. But again
> the difference at  Fermi level (i.e. 0 eV) in integrated value of up and
> down spin DOS is nearly 6.13, where as it should be nearly 8.
>
> I do not understand why this is happening. Can any one give the proper
> steps of finding the DOS for the fixed spin moment calculation. Where I am
> doing the mistakes or which procedure followed by me is wrong. I will be
> very grateful to you.
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20160520/849892f2/attachment.html>
-------------- next part --------------
_______________________________________________
Wien mailing list
Wien at zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html