[Wien] Ghost band come from large charge fluctuation

Thu Mar 10 07:24:08 CET 2005

You would reduce your RMT radii, and/or switch off the
in1new x temporarily (or at lease increase x to 6 or
more) -- if you use it, and let us know if reducing
the RMT could disapear the ghostband.

Your,
Saeid.

--- liyh <lyhua at fudan.edu.cn> wrote:

> Thanks very much to Marks!
> There are still some problem not resolved.
> As to avoid the large charge fluctuation we set the
> mixing parameter to 0.000001 and using PRATT 
> method, but this can not resolve the problem and we
> still meet a ghost band in the second iteration.
> these are the charge values from  *.scf file.
> 
>        CHARGES OF NEW CHARGE DENSITY
> :NTO  : TOTAL   INTERSTITIAL CHARGE= 94.6816509
> :NTO001: TOTAL   CHARGE IN SPHERE  1 = 29.4424658
> :NTO002: TOTAL   CHARGE IN SPHERE  2 = 29.4509322
> :NTO003: TOTAL   CHARGE IN SPHERE  3 = 29.4516257
> :NTO058: TOTAL   CHARGE IN SPHERE 58 = 31.3918238
> :NTO059: TOTAL   CHARGE IN SPHERE 59 = 31.3923983
> :NTO060: TOTAL   CHARGE IN SPHERE 60 = 31.3947743
> 
> :NEC01: NUCLEAR AND ELECTRONIC CHARGE
> 1920.000001919.94705   1.00003
> 
> 
>        CHARGES OF OLD CHARGE DENSITY
> :OTO  : TOTAL   INTERSTITIAL CHARGE= 93.6597633
> :OTO001: TOTAL   CHARGE IN SPHERE  1 = 29.5825628
> :OTO002: TOTAL   CHARGE IN SPHERE  2 = 29.5924149
> :OTO003: TOTAL   CHARGE IN SPHERE  3 = 29.5924481
> :OTO058: TOTAL   CHARGE IN SPHERE 58 = 31.1741086
> :OTO059: TOTAL   CHARGE IN SPHERE 59 = 31.1741104
> :OTO060: TOTAL   CHARGE IN SPHERE 60 = 31.1743886
> 
> :NEC02: NUCLEAR AND ELECTRONIC CHARGE
> 1920.000001916.59208   1.00178    <---------- total
> charge created from dstart
> 
> 
> :DIS  :  CHARGE DISTANCE       0.2025040
>        PRATT MIXING SCHEME WITH 0.000
> 
>        CHARGES OF MIXED CHARGE DENSITY
> :CTO  : TOTAL   INTERSTITIAL CHARGE= 97.0676867
> :CTO001: TOTAL   CHARGE IN SPHERE  1 = 29.5825627
> :CTO002: TOTAL   CHARGE IN SPHERE  2 = 29.5924149
> :CTO003: TOTAL   CHARGE IN SPHERE  3 = 29.5924481
> :CTO058: TOTAL   CHARGE IN SPHERE 58 = 31.1741086
> :CTO059: TOTAL   CHARGE IN SPHERE 59 = 31.1741104
> :CTO060: TOTAL   CHARGE IN SPHERE 60 = 31.1743886
> 
> :NEC03: NUCLEAR AND ELECTRONIC CHARGE
> 1920.000001920.00000   1.00000
> 
> Because the mixing value are very small so CTO001
> and OTO001 are nearly equal, this is correct.
> But if we look at the value of ": TOTAL  
> INTERSTITIAL CHARGE" it still fluctuated so much, 
> from 93.6597633 to 97.0676867, this maybe the reason
> of ghost bands. I am so surprise to it.
> Does the mixing parameter have no influnce to this
> value?
> And I find the total charge value not correct which
> created from dstart.
> 
> 
> >In addition to the points Peter made about using
> the original case.in1 and
> >not using -in1new until you are close to the
> solution (and not being too
> >concerned about ghostbands until you are close),
> let me add something
> >about mixing.
> >
> >Please, DO NOT SIMPLY REDUCE THE MIXING FACTOR. A
> rather major change in
> >the mixing was made a couple of releases ago:
> >	1) Introduction of a plane wave scaling term (PW)
> >	2) Addition of an output of the plane wave
> convergence :PLANE
> >	3) Addition of a diagnostic parameter :DIRB
> >	4) Addition of an auto-restart of the Broyden
> cycle
> >
> >In iterative numerical methods scaling is VERY
> important, and has a
> >huge effect. The UG is not very detailed about
> these (Peter: perhaps
> >should add something, perhaps even a FAQ). I've
> attached a file "Check"
> >which I suggest you put in your $HOME/bin and run
> every now and then to
> >monitor the progress.
> >
> >Key points:
> >	a) :DIRB gives the modulus of the Broyden step the
> algorithm is
> >using, the modulus of the Pratt step (it does not
> use it) and the angle
> >between the two. If this angle is more than about
> 45 degrees in 99% of the
> >cases this means that your plane scaling term is
> too large. Reduce it,
> >remove *bro* files and continue. (I prefer a value
> of 0.25 for my initial
> >estimate of this, smaller than Peter's default of
> 0.5, not sure which is
> >"best".) If the angle gets really large, > 138 at
> present, the algorithm
> >abandons the previous Broyden history and restarts
> with a small Pratt
> >step.
> >	b) In most cases "sloshing" is due to poor
> convergence of the
> >plane waves (:PLANE). If the atomic-sphere charge
> convergence (:DIS) is
> >oscillating but the plane wave convergence is
> improving DO NOT WORRY, this
> >is OK. In my experience, it is only when :PLANE is
> less than about 0.01
> >that the iterations start to converge. I never use
> -in1new before
> >obtaining reasonable convergence of both :DIS and
> :PLANE.
> >
> >Caveat: There is a pathalogical case which Peter
> found once, and I have
> >also found in a seperate system. At least in my
> case it appears to be
> >oscillations which can go unstable between some
> spin-up and spin-dn states
> >very close to the Fermi energy. These presumable
> contain both
> >atomic-sphere and plane wave components so a
> relative scaling is not
> >helping enough. If anyone has any ideas about how
> to handle such a problem
> >in terms of scaling let me know off-line.
> >
> >N.B., testconv -p :PLA works to test the plane wave
> convergence, but at
> >present is not built into the runXYZ scripts but
> can easily be added.
> >
> >-----------------------------------------------
> >Laurence Marks
> >Department of Materials Science and Engineering
> >MSE Rm 2036 Cook Hall
> >2220 N Campus Drive
> >Northwestern University
> >Evanston, IL 60201, USA
> >Tel: (847) 491-3996 Fax: (847) 491-7820
> >email: L - marks @ northwestern . edu
> >http://www.numis.northwestern.edu
> >-----------------------------------------------
> >
> 
> = = = = = = = = = = = = = = = = = = = =
> 			
> 
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡ÖÂ
> Àñ£¡
>  
> 				 
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡liyh
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡lyhua at fudan.edu.cn
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡2005-03-10
> 
> 
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