[Wien] convergence problem :: runsp_c_lapw

[Laurence Marks]

Why did you change case.inm away from the defaults?

a) Set the greed to 0.2 not 0.005. As I have said before, this does
not do what you think it does and concepts such as "reduce the mixing
factor if it does not converge" are wrong. Yes, wrong. Very wrong.
Completely wrong. Always wrong. To understand more please read Journal
of Chemical Theory and Computation 9 (2013) 2786.

b) Use MSR1, and in extreme cases perhaps MSEC3. Do not use BROYD.
Perhaps reduce the greed to 0.1, almost never less than this.

A little explanation. The factor of "0.005" is called the mixing
greed.in the spirit of algorithm greed (e.g.
http://en.wikipedia.org/wiki/Greedy_algorithm). If it is too large the
self-consistent iterations can become unstable. However, you rarely
need to deal with this and the mixer does. If you set it too a small
value (which you did) you are making the algorithm take such tiny
steps that it can starve to death. The code "honors" the user setting
of a very small value (at least in 12.1) under the assumption that the
user knows what he/she is doing.

On Thu, Apr 24, 2014 at 5:25 AM, Martin Gmitra <martin.gmitra at gmail.com> wrote:
> Dear Wien2k users,
>
> I am doing calculations of a hexaboride films invoking: runsp_c_lapw -so
> -eece
> My problem is two fold:
>
> (i) SCF calculations successfully converged for thin films (9 atomic units)
> and bulk systems. I do have a problem to converge a thicker film (11 atomic
> units) even TEMP broadening of 0.02 is used. The observations after 800
> iterations are following:
>
> (1) fermi energy is jumping (roughly) between two values
> :FER  : F E R M I - ENERGY(FERMI-SM.)=   0.3682855520
> :FER  : F E R M I - ENERGY(FERMI-SM.)=   0.3682855520
> :FER  : F E R M I - ENERGY(FERMI-SM.)=  -0.7779431003
> :FER  : F E R M I - ENERGY(FERMI-SM.)=  -0.7779431003
> :FER  : F E R M I - ENERGY(FERMI-SM.)=   0.3683943150
> :FER  : F E R M I - ENERGY(FERMI-SM.)=   0.3683943150
> :FER  : F E R M I - ENERGY(FERMI-SM.)=  -0.7767634505
> :FER  : F E R M I - ENERGY(FERMI-SM.)=  -0.7767634505
>
> (2) charge distance non uniformly oscillates between 0.1 and 0.001
> :DIS  :  CHARGE DISTANCE       ( 1.1067771 for atom    4 spin 1)
> 0.1064425
> :DIS  :  CHARGE DISTANCE       ( 0.0059078 for atom    6 spin 1)
> 0.0013328
> :DIS  :  CHARGE DISTANCE       ( 0.0092322 for atom    6 spin 1)
> 0.0015769
> :DIS  :  CHARGE DISTANCE       ( 0.0092664 for atom    6 spin 1)
> 0.0015106
> :DIS  :  CHARGE DISTANCE       ( 0.5478509 for atom    4 spin 1)
> 0.0466613
> :DIS  :  CHARGE DISTANCE       ( 0.0078766 for atom    6 spin 1)
> 0.0014700
> :DIS  :  CHARGE DISTANCE       ( 0.9814094 for atom    4 spin 1)
> 0.0939173
> :DIS  :  CHARGE DISTANCE       ( 0.0070829 for atom    6 spin 1)
> 0.0015672
> :DIS  :  CHARGE DISTANCE       ( 0.0411319 for atom    4 spin 2)
> 0.0053433
> :DIS  :  CHARGE DISTANCE       ( 0.0072009 for atom    6 spin 1)
> 0.0014308
> :DIS  :  CHARGE DISTANCE       ( 0.1357701 for atom    4 spin 2)
> 0.0150618
>
> (3) magnetic moments are zero within spheres whereas there is
> :MMTOT: SPIN MAGNETIC MOMENT IN CELL   =    -0.00010
> :MMINT: MAGNETIC MOMENT IN INTERSTITIAL =   -0.00003
>
> (4) my case.inm
> BROYD  0.0   YES  (BROYD/PRATT, extra charge (+1 for additional e), norm)
> 0.005           mixing FACTOR for BROYD/PRATT scheme
> 1.00  1.00      PW and CLM-scaling factors
> 9999  8         idum, HISTORY
>
> :MIX  :   MSEC3  REGULARIZATION: 2.50E-04  GREED: 0.005  Newton 1.000
> with PRATT after 100 iterations
> MIX  :   PRATT  REGULARIZATION: 2.50E-04  GREED: 0.005
>
> Do you have any hints how to converge the calculations?
>
> (ii) I am running the calculations with version 12.1. The runsp_c_lapw
> script has been updated (debugged) in version 13.1 but SCF diverges in my
> cases (thin and thicker films).
>
> Does anybody experience similar problem?
>
> Best regards,
> Martin Gmitra
> Uni Regensburg
>
>
>



-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi