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convergent problem during optimization with applying electric field
Date: 2023/11/20 16:58
Name: Tao

Hello everyone, Does anyone has the experience of optimizing a defected structure under z-axis electric field?
Recently, because I need to incvestigate the effect of electric field on structure and the system (slab model) is slightly large, So, I tried to optimize it using openmx. But I can't get enough convergent accuracy (force convergence criterion), which is set to 5x10^-4 Hatree/Bohr. After about 200 optmization iterations, the ouput shows that maximum force exhibit no decrease tendency in the following iterations, at least in the next 100 iterations it looks like this. The max force fluctuated around 0.01 Hatree/Bohr. I have tried to change different optimizer or increase the value of scf.cutoffenergy. those attempts still fail to decrease the Maximum force of the system. I hope I can get some suggestion on it? many thanks for your help. following information are the input parameter setting:

###################0 relax and 1 fixed#########################
<MD.Fixed.Cell.Vectors
    1 1 1
    1 1 1
    1 1 1
MD.Fixed.Cell.Vectors>

scf.XcType                    GGA-PBE
scf.SpinPolarization          off
scf.ElectronicTemperature    300.0
scf.energycutoff              300.0
scf.maxIter                  100
scf.EigenvalueSolver          band


scf.Kgrid                    1  1  1
scf.Mixing.Type              rmm-diisk
scf.Init.Mixing.Weight        0.05
scf.Min.Mixing.Weight        0.01
scf.Max.Mixing.Weight        0.30
scf.Mixing.History            25
scf.Mixing.StartPulay        15
scf.criterion                1.0e-7

######cell and geometry optimization############

MD.Type                    Opt      # Nomd|Opt|DIIS|OptC|RFC5|BFGS|RF|EF
MD.Opt.DIIS.History          5        # default=3  the behavior of quasi Newton methods is controlled by MD.Opt.DIIS.History and MD.Opt.StartDIIS
MD.Opt.StartDIIS            15        # default=5  The geometry optimization steps before starting the DIIS-type method is performed by the steepest decent method.
MD.Opt.EveryDIIS          10000      # default=10 
MD.maxIter                  200        # default=1
MD.Opt.criterion          5.0e-4      # default=1.0e-4 (Hartree/bohr)
#MD.Type                      nomd
#MD.maxIter                    1
#MD.TimeStep                  1.0
#MD.Opt.criterion              0.0003

#electric field
scf.Electric.Field  0.0 0.0 3.0  # default=0.0 0.0 0.0 (GV/m)

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