[Wien] Three questions

[Peter Blaha]

> 1. CHARGE CONVERGENCE: I know this has been discussed before, but it 
> seems it didn't change in Wien2k_18. Here is a typical example of the 
> charge convergence history of the last few iterations of FM+SOC 
> (ferromagnetic + spin orbit coupling) calculation:
> 
> :ENERGY convergence:  0 0.0001 .0001320450000000
> :CHARGE convergence:  0 0.001 .0027578
> :ENERGY convergence:  1 0.0001 .0000497650000000
> :CHARGE convergence:  0 0.001 .0050904
> :ENERGY convergence:  1 0.0001 .0000557650000000
> :CHARGE convergence:  0 0.001 .0004672
> :ENERGY convergence:  1 0.0001 .0000220050000000
> :CHARGE convergence:  1 0.001 -.0001786
> 
> Something strange happens with charge convergence, is this OK?

This is ok.


> 2. LIMITS in inso and in1c files: in order to avoid large vector files I 
> am changing the energy limits in inso and in1c files for band structure 
> calculations. SCF is done with default inso and in1c files, then I do 
> save_lapw, then I edit case.inso and case.in1c files, and then I do 
> FM+SOC band structure calculation:
> 
> #! /bin/bash
> x lapw1 -band -up -p
> x lapw1 -band -dn -p
> x lapwso -up -p
> 
> I am using emin/emax -0.5 0.5 in both files (inso and in1c) without 
> changing anything else, then I have bands from limited energy range. I 
> just want to make sure that this procedure is fine.

No, this is NOT ok. You must not change Emax in case.in1c !
If you do, your basis set for the spin-orbit step is limited and 
eigenvalues will change as compared to the scf calculation.
You can reduce emax in case.inso if you are not interested in the bands 
at higher energies.


> 3. FM+SOC convergence: I am doing FM+SOC calculations for different 
> in-plane magnetization M directions in a 2D Fe(001) ferromagnetic layer. 
> Actually an older Wien2k_14 version was not working well for this, 
> results for generic M directions were really strange. Wien2k_18 seems 
> much better, however, when starting things from the scratch (each M 
> angle completely separate calculation) it seems that for some M angles 
> the result is off, as if it didn't actually properly converge. I am 
> using a fairly dense mesh for SCF (2000k, 25 25 3), and -ec 0.0001 -cc 
> 0.001.  Should I maybe try -fermit setting in init_lapw, and what would 
> be a reasonable value? Do I always need to use instgen_lapw before 
> init_lapw when starting a new case? Should I perhaps do each next M 
> angle on top of a previously converged M angle (and save_lapw for each M 
> angle)?

Doing separate calculations for different directions may / may not yield 
correct results.
The proper (save) way is to use ONE case.struct file for all cases.
i) select all directions of magnetization first.
ii) Produce (using init_so) struct files, which are the same for all 
cases (do not change after init_so) and use this struct file for ALL 
(also non-so) calculations.
This works as:
a) generate normal struct file.
b) init -b -sp ....
c) init_so    with first direction, accept the generated structure
d) init_so    with second direction, accept ...
repeat this for all desired directions (or until you have a P1 structure 
(only identity).

e) with this setup (no new init_lapw !!!!) execute:
   runsp -ec ...      and save as   "non-so"
   runsp -so ...      and save as   "so-dir_2"
   restore non-so; edit case.inso and put the first direction in;
   runsp -so ...      and save as   "so-dir_1"

In this way, you can also compare the force-theorem  (:SUM of first 
iteration (2 numbers !) with the scf solution.



> 
> 
> Best,
> Lukasz
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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