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geometry optimization problem Date: 2008/11/04 00:02 Name: Yuzheng Guo Steepest decent optimization is used to find the minimum energy in a large super cell. However sometimes the energy and force will have a sudden large increase: --------------------------------------------------------- MD_iter SD_scaling |Maximum force| Maximum step Utot 73 2.51554024 0.00948052 0.01262015 -11142.90310599 74 2.51554024 0.00927013 0.01234009 -11142.90553023 75 2.51554024 0.00944966 0.01257907 -11142.90802843 76 2.51554024 0.00967166 0.01287459 -11142.91169641 77 3.01864829 0.01021463 0.01631685 -11142.91426104 78 3.01864829 0.01220600 0.01949787 -11142.92500751 79 3.01864829 0.96178986 1.53636312 -11107.12602026 80 3.01864829 2.67706198 4.27633880 -11107.16899469 81 0.75466207 66.38256664 26.50987793 -11057.45364218 82 0.75466207 46.77610004 18.68003551 -11100.66550706 83 0.75466207 55.37926956 22.11571125 -11111.64298766 84 0.75466207 3.91499889 1.56345481 -11127.04855713 85 0.90559449 1.75866415 0.84278703 -11130.64075227 86 0.90559449 0.50638261 0.24266867 -11134.48035956 ------------------------------------------------------- My super cell is 128 Fe atoms with random position distribution: Fe Fe4.5opt-s1p2d1 Fe_GGA7 The input file is attached below. The only possible reason is that perhaps the MDstep(1fs) is too large. But I suppose that steepest decent method will not use MD step. According to my knowledge there should be some parameter to control the trial step in this method but I did not found it in the manual. Could anyone shed some lights on this problem? Thanks. Yuzheng Guo ------------------------------------------------------- scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW scf.SpinPolarization on # On|Off scf.partialCoreCorrection On # On|Off scf.ElectronicTemperature 300.0 # default=300 (K) scf.energycutoff 100.0 # default=150 (Ry) #scf.Ngrid 32 32 32 scf.maxIter 100 # default=40 scf.EigenvalueSolver band # Recursion|Cluster|Band scf.Kgrid 1 1 1 # means n1 x n2 x n3 scf.Mixing.Type rmm-diisk # Simple|Rmm-Diis|Gr-Pulay 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 13 # default=6 scf.criterion 1.0e-9 # default=1.0e-6 (Hartree) # # 1D FFT # 1DFFT.NumGridK 900 # default=900 1DFFT.NumGridR 900 # default=900 1DFFT.EnergyCutoff 3600.0 # default=3600(Ry) # # Orbital Optimization # orbitalOpt.Method off # Off|Unrestricted|Restricted orbitalOpt.InitCoes Symmetrical # Symmetrical|Free orbitalOpt.initPrefactor 0.1 # default=0.1 orbitalOpt.scf.maxIter 30 # default=12 orbitalOpt.MD.maxIter 20 # default=5 orbitalOpt.per.MDIter 2 # default=1000000 orbitalOpt.criterion 1.0e-4 # default=1.0e-4 (Hartree/borh)^2 # # output of contracted orbitals # CntOrb.fileout off # on|off, default=off Num.CntOrb.Atoms 1 # default=1 <Atoms.Cont.Orbitals 1 Atoms.Cont.Orbitals> # # SCF Order-N # orderN.HoppingRanges 9.2 # default=5.0 (Ang) orderN.NumHoppings 3 # default=2 orderN.KrylovH.order 600 # default=400 orderN.recalc.EM off # # restart using *.rst # scf.restart on # # MD or Geometry Optimization # MD.Type Opt # Nomd|Opt|DIIS|NVE|NVT_VS|NVT_NH MD.maxIter 100 # default=1 MD.TimeStep 1 # default=0.5 (fs) MD.Opt.criterion 1.0e-4 # default=1.0e-4 (Hartree/bohr) # # Band dispersion # Band.dispersion off # on|off, default=off <Band.KPath.UnitCell 3.56 0.00 0.00 0.00 3.56 0.00 0.00 0.00 3.56 Band.KPath.UnitCell> # if <Band.KPath.UnitCell does not exist, # the reciprical lattice vector is employed. Band.Nkpath 5 <Band.kpath 15 0.0 0.0 0.0 1.0 0.0 0.0 g X 15 1.0 0.0 0.0 1.0 0.5 0.0 X W 15 1.0 0.5 0.0 0.5 0.5 0.5 W L 15 0.5 0.5 0.5 0.0 0.0 0.0 L g 15 0.0 0.0 0.0 1.0 1.0 0.0 g X Band.kpath> # # MO output # MO.fileout off # on|off num.HOMOs 1 # default=2 num.LUMOs 1 # default=2 MO.Nkpoint 1 # default=1 <MO.kpoint 0.0 0.0 0.0 MO.kpoint> # # DOS and PDOS # Dos.fileout off # on|off, default=off Dos.Erange -20.0 20.0 # default = -20 20 Dos.Kgrid 12 12 12 # default = Kgrid1 Kgrid2 Kgrid3 HS.fileout off # on|off, default=off

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