[Wien] optimization

[Santhy Jaiker]

Dear Blaha, 
  Thanks for your reply.  
  I want to find the enthalpy of formation of Fe2Ti.  I know that RKMAX=10 is high for Fe2Ti.  I thought that higher RKMAX will increase the accuracy and computation time.   I have chosen convergence criteria for RKAMX is <5mev/atom (~0.0003Ry/atom).    For Fe in BCC and Ti in HCP, satisfies this condition when RKMAX is 10.  So highest RKMAX should be used to find out the energy of the elements and compound.   That’s why I used RKMAX=10.  
  Am I correct?


Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:  Certainly the message:
mini.error (stop in mini forces small)
is NOT an error, but leads to a stop because the optimization has finished properly.

The
lapw1.error (Cholesky INFO = 2198 'SECLR4' - POTRF (scalarpack/lapack) failed)
is a "real" error. Often it comes because your structure is wrong (sometimes the
optimization may break symmetry (move atoms in a symmetry breaking way!).

Otherwise, your RKMAX=10 may be too large.
Why would you do it that way ?

Start with the default (RKMAX=7). It is probably 100 times !!!! faster.
Anc once you have the minimum with RKMAX=7; you continue with RKMAX=8 and
check if the minimum has changed. If not, you are done.

Santhy Jaiker schrieb:
> I am trying to optimize Fe2Ti system for more than a month. Still i am 
> facing problem in it.
> 
> Structure Details: Positions of atoms Fe (0,0,0) and (0.1705,0.341,1/4)
> Ti (1/3,2/3,0.5647)
> a=b=4.794 A c=7.834 A 
> alpha=beta=90 degree gamma=120 degree
> Parameters: RMT (of Fe and Ti) =2 k point =76 IBZ Gmax=14
> mixer=0.20 RKmax=10
> 
> Force are there in atom 2 and atom 3
> 
> SCF and mini calculation runs nicely.
> During optimization with mini, varying volume from -5 to 0%, it 
> shows error in
> -3% volume reduction. It shows mini.error (stop in mini forces small)
> 
> Since i tried optimization without mini, it runs nicely from -5 to 0% 
> volume reduction. But it shows error in c/a ratio optimization. Both 
> mini.error (stop in mini forces small) and lapw1.error (Cholesky INFO = 
> 2198 'SECLR4' - POTRF (scalarpack/lapack) failed).
> 
> I know that i am doing mistake some where. Because of that i tried all 
> the possiblities. But i am not able to trace it out. Any suggestions 
> regarding this problem will be helpful. 
> 
> Thanks in advance
> 
> 
> Regards,
> Santhy Jaiker
> 
> Research Scholar,
> Materials Thermodynamics Lab,
> Department of Metallurgical and Materials Engineering,
> Indian Institute of Technology Madras,
> Chennai - 600 036, India
> Tel: 91-044-22575763
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-- 

P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671 FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/
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Regards,
  Santhy Jaiker
   
  Research Scholar,
  Materials Thermodynamics Lab,
  Department of Metallurgical and Materials Engineering,
  Indian Institute of Technology Madras,
  Chennai - 600 036,  India
  Tel: 91-044-22575763
**********************************************
A truly happy person is one
who can enjoy the scenery on a detour
**********************************************


       
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