[Wien] optimization

[Santhy Jaiker]

Dear Blaha,
  Thank you.  Then i can find the minimum energy structure with low RKMAX.  After that using minimum energy structure lattice parameter with actual RKMAX, i have to run SCF and mini.  am i correct? 

Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:
  Yes, but you would NEVER do the whole optimization with this large parameter,
only at the very end you switch to it.

Santhy Jaiker schrieb:
> 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 
/* 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
> --------------------------------------------------------------------------
> 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:
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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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P.Blaha
--------------------------------------------------------------------------
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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