[Wien] difference of min- energy point and zero -force point

[naser zare]

Dear Stefaan,
  Thank you very much for your reply.
  I should mention that:
  1)the discrepancy in position is 0.122A(1.544A for  min-energy and 1.666 A for zero-point)
  2)convergence criteria for energy is  0.0001ry and for charge is 0.002 and when I use from
  mini for force is 4 mry/au
  3)I use RK=7  and mesh 18X18X18  for bulk and 10X10X1 for asupercell  with 38 atoms and a surface cell(2X2) .I study about work function and I use from this parameters because :a)give me good value  for  workfunction  and   b)for  avoid of  computational cost of large parameters.
  4)when I used mini , I  move only one atom (  like when I obtain min of energy ) and all atoms of slab are fixed.
   
  I have a question,can I  fell sure that point obtained from plot of total energy  versus distance  of atom from surafce  is true point and my problem is calculation of force?with attention to this point  that min-energy is obtained  in smaller time by plot total energy  versus  distance of atom from surafce    with respect to use of mini.. 
   
    thank you  very much for your attention.
 Best Regards.
 Nasser Zare Dehnavi


Stefaan Cottenier <Stefaan.Cottenier at fys.kuleuven.be> wrote:
  
You need to provide more information, for instance:

* How big is the discrepancy in position?
* How well are your calculations converged and what are your 
convergence criteria?
* Did you verify your basis set and k-mesh are well enough to provide 
good forces?
* When you used mini, did you move only one atom, or all of them?
*...

Stefaan



Quoting naser zare :

> Hello
> Dear all:
> I use from Wien2k 6.4. I want to obtain position of adsorption of 
> atom on a surface.I do it in two way :1)I move atom towards 
> surface step by step and I plot total energy
> versus distance from surface and I obtain point of min energy and 
> 2)I relax position of atom by MINI, but these two point are not 
> the same.on the other hand ,point that obtained by Mini has not 
> lowest energy. I want to know reason of this problem .thank you 
> very much for your attention.
> Best Regards.
> Nasser Zare Dehnavi
>
>
>
>
> ---------------------------------
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-- 
Stefaan Cottenier
Instituut voor Kern- en Stralingsfysica
K.U.Leuven
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