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|  a bad relaxed structure from the RFC5 geometry optimizaiton |  | 
 Date: 2018/06/04 17:24
 Name: Jack
 
Dear all, 
 I am trying to use OpenMX to relax a simple system, TiO2 (the input file see below). The optimization algorithm is the OpenMX suggested RFC5. But after few relaxation steps, OpenMX generates a weird structure (-nan) and the electronic calculations cannot be converged.
 
 ******************************************************
 MD or geometry opt. at MD = 9
 *******************************************************
 
 WWW1 tmp1=-0.114862131431 tmp2=-917592780013761956375895808328198843994265663672291382938734586330842634652457763864576.000000000000
 <RF> |Maximum force| (Hartree/Bohr) =18.242384331415
 <RF> Criterion (Hartree/Bohr) = 0.000100000000
 
 Cell vectors and derivatives of total energy with respect to them
 a1(Ang.) = -nan -nan -nan dE/da1(a.u.) = -2.56150 0.51899 -0.72357
 a2(Ang.) = -nan -nan -nan dE/da2(a.u.) = 0.51899 -2.56150 -0.72357
 a3(Ang.) = -nan -nan -nan dE/da3(a.u.) = -1.14096 -1.14096 -5.13335
 
 
 
 TiO2 input OpenMX file is:
 
 DATA.PATH /data/jack/soft/openmx3.8/DFT_DATA13
 System.CurrrentDirectory ./ # default=./
 System.Name om
 level.of.stdout 1 # default=1 (1-3)
 level.of.fileout 1 # default=1 (1-3)
 
 #
 # restart using a restart file, *.rst
 #
 
 scf.restart off # on|off,default=off
 
 #
 # Definition of Atomic Species
 #
 
 Species.Number 2
 <Definition.of.Atomic.Species
 Ti Ti7.0-s2p2d1 Ti_PBE13
 O O6.0-s2p2d1 O_PBE13
 Definition.of.Atomic.Species>
 
 #
 # MD or Geometry Optimization
 #
 
 MD.Type RFC5 # Nomd|Opt|DIIS|NVE|NVT_VS|NVT_NH
 MD.Opt.DIIS.History 3 # default=7
 MD.Opt.StartDIIS 5 # default=5
 MD.Opt.EveryDIIS 100000 # default=10
 MD.maxIter 100 # default=1
 MD.TimeStep 0.5 # default=0.5 (fs)
 MD.Opt.criterion 1.0e-4 # default=1.0e-4 (Hartree/bohr)
 
 #
 # SCF or Electronic System
 #
 
 scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW
 scf.SpinPolarization off # On|Off
 scf.ElectronicTemperature 300.0 # default=300 (K)
 scf.energycutoff 150.0 # default=150 (Ry)
 scf.maxIter 170 # default=40
 scf.EigenvalueSolver band # Recursion|Cluster|Band
 scf.Mixing.Type rmm-diisk # Simple|Rmm-Diis|Gr-Pulay
 scf.Init.Mixing.Weight 0.010 # default=0.30
 scf.Min.Mixing.Weight 0.001 # default=0.001
 scf.Max.Mixing.Weight 0.200 # default=0.40
 scf.Mixing.History 6 # default=5
 scf.Mixing.StartPulay 12 # default=6
 scf.criterion 1.0e-9 # default=1.0e-6 (Hartree)
 scf.system.charge 0.0 # default=0.0
 scf.Kgrid 6 6 10
 
 #
 #Atoms
 #
 
 Atoms.Number 6
 <Atoms.SpeciesAndCoordinates
 1 Ti 0.0000000000000000 0.0000000000000000 0.0000000000000000 6.0 6.0
 2 Ti 0.5000000000000000 0.5000000000000000 0.5000000000000000 6.0 6.0
 3 O 0.3045041660932300 0.3045041660932300 -0.0000000000000000 3.0 3.0
 4 O 0.6954958339067701 0.6954958339067701 0.0000000000000000 3.0 3.0
 5 O 0.1954958339067700 0.8045041660932299 0.5000000000000000 3.0 3.0
 6 O 0.8045041660932299 0.1954958339067700 0.5000000000000000 3.0 3.0
 Atoms.SpeciesAndCoordinates>
 Atoms.UnitVectors.Unit Ang
 <Atoms.UnitVectors
 4.6296885670066326 0.0000000000000000 0.0000000000000000
 0.0000000000000000 4.6296885670066326 0.0000000000000000
 0.0000000000000000 0.0000000000000000 2.9427426777121406
 Atoms.UnitVectors>
 
 Any suggestion is welcomed.
 Thanks
 Jack
 
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