[Wien] Problems of the query and convergence test about MAE calculation

[Peter Blaha]

Please follow closely the instructions given in the link you found in 
the mailing list.

| Firstly, I have lowered the symmetry of case.struct by comparing the 
different magnetization directions.


Good. This should mean that when you run init_so with different 
directions of magnetization, you should NOT get any symmetry lowering 
anymore. This is a VERY important step !

Then I executed the following commands for the convergence tests of 
RKMAX and k-mesh (-numk) :

> init_lapw –b –vxc 13 –ecut -7.0 –rkmax XX –numk XXXXX –sp (changing 
> the –rkmax and -numk)
>
> init_so_lapw
>
> init_orb_lapw -orb
>
These initialization steps needs to be done ONLY ONCE with the lowest 
symmetry struct file. Generating different RKMAX, k-mesh or E-max you do 
by directly editing   case.in1,  or running      x kgen -so

For the force theorem, you would first run without SO, but with a very 
good E-convergence criterium:

runsp -orb -ec 0.000001

save_lapw no-so

Now you run the lapw1/so/2 steps  as given in the link (don't forget to 
add   -orb in the   x lapwso -up -orb  step (not in the lapw1 steps). 
The number you are interested is the "sum of eigenvalues" in case.scf2up/dn.

Repeat it for the other magnetization direction. and compare the 
difference in the "sum of eigenvalues". This is the MAE.

Now do the convergence tests:     x kgen -so   (10x as many k-points as 
before) and run the steps above. If the energy difference is stable, 
your k-mesh is fine.

Edit case.in1 and change Emax (in steps of 5 Ry) (RKmax; in steps of 1). 
run the steps above and compare the E difference ...

------------------------------

Once you are done, you can also do it fully self-consistently:

runsp -so -orb -ec 0.000001

save so-001

change magnetization direction in   case.inso

runsp ...

save so-110            (and maybe 111)

Compare :ENE of the saved scf files. The E-difference should be similar 
to the force-theorem results.


> runsp_lapw –so –orb
>
> In addition, I studied the following links for MAE calculation for the force theorem, but I have some questions about it.
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14849.html
> In the above links, there are some description of convergence tests of 
> EMAX and k-mesh, “Important: Increase Emax in case.in1 to a VERY large 
> number (10 Ry), and test your results with respect to this EMAX. 
> Increase the k-mesh (for the final low-symmetry struct file) to a very 
> good one AND TEST the convergence. of your results.”
> I am not sure how EMAX and k-mesh convergence tests should be carried 
> out. The Emax value is set in the init_so procedure, right? Then which 
> procedure should be executed the convergence test? In addition, which 
> data I should focus on and what are the convergence criteria.
> Thank you for your reply in advance.
> Best regards
> Yours Chen
>
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-- 
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Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
Email:peter.blaha at tuwien.ac.at           
WWW:http://www.imc.tuwien.ac.at       WIEN2k:http://www.wien2k.at
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