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the SCF steps is so much on each EF step....
Date: 2007/09/21 19:58
Name: Liger Chen   <>

Hi all :

I have used OPENMX for nanowire systerms. In bigger case( atom number 100-200), I find that the scf step is hard to converge.In each ionic step( structure optimizing step), the SCF must run about 100+ atep to reach the parameters be :

scf.Init.Mixing.Weight 0.130 # default=0.30
scf.Min.Mixing.Weight 0.001 # default=0.001
scf.Max.Mixing.Weight 0.20 # default=0.40

Kerker.factor 1.8
scf.Mixing.History 7 # default=5
scf.Mixing.StartPulay 11 # default=6

scf.criterion 1.0e-6 # default=1.0e-6 (Hartree)

MD.Opt.criterion 1.0e-4

And there is about 100 ionic steps for EF-structure optimizing converge. For the same case, instead of DC, but band method, the SCF steps is just about 40. So , may I ask, is DC method makes much SCF step to converge? That is normal behavior ?

thank you !!

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Re: the SCF steps is so much on each EF step.... ( No.1 )
Date: 2007/09/25 17:05
Name: T.Ozaki


It is noted that the DC method solves approximately the eigenvalue problem
in O(N) operation. And if the parameters for the DC method are too inaccurate,
such a behaviour can be expected. In this case, since the charge density is
inaccurately evaluated, the Hartree potential evaluated by Poisson's equation
becomes inconsistent with the charge density calculated by the DC method,
leading to many SCF iterations.

As the parameters are set severely, it is expected that the situation becomes better.

Best regards,

Unable to converge properly ( No.2 )
Date: 2007/10/22 21:14
Name: asaaravind  <>

I am a new user of openmx and I am doing a geometry optimization of GaN nano wire with 180 atoms...
These are my SCF parameters...

scf.SpinPolarization off # On|Off|NC
scf.ElectronicTemperature 300.0 # default=300 (K)
scf.energycutoff 500.0 # default=150 (Ry)
scf.maxIter 100 # default=40
scf.EigenvalueSolver cluster # DC|GDC|Cluster|Band
scf.Kgrid 1 1 1 # means n1 x n2 x n3
scf.Mixing.Type rmm-diis # Simple|Rmm-Diis|Gr-Pulay|Kerker|Rmm-Diisk
scf.Init.Mixing.Weight 0.30 # default=0.30
scf.Min.Mixing.Weight 0.001 # default=0.001
scf.Max.Mixing.Weight 0.400 # default=0.40
scf.Mixing.History 7 # default=5
scf.Mixing.StartPulay 15 # default=6
scf.criterion 1.0e-10 # default=1.0e-6 (Hartree)
scf.lapack.dste dstevx

I am not able to get forces and energies converged ...
Could you please tell me waht is wrong in my input settings,
Thanks in Advance,
Asa Aravindh.S

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