[DFTB-Plus-User] Bulk/slab Fe optimization problems using pbc-0-3 or trans3d-0-1 parameters

[Branislav Milovanović]

Dear Bálint,
I recompiled program and now I get reasonable structures.
I tried two different setups for unit cell and got relatively good values:
ShellResolvedSCC = YesShellResolvedSpin = No
Lattice parameter = 2.9338 A and nearest neighbor distance = 2.54078 A
ShellResolvedSCC = NoShellResolvedSpin = Yes
Lattice parameter = 2.9393 A and nearest neighbor distance = 2.54553 A
which is quite close to the experimental values: 2.910 A and 2.52013 A
However, when I try to simulate 7x7x4 Fe(110) slab using LatticeOpt = Yes and hexagonal symmetry I get quite distorted geometry.Do you think this is just a parameter set inherited problem or maybe DFTB+ is only good when using cubic symmetry? 
Kind regards,Branislav
On Mon, 30-01-2023 08:53, Bálint Aradi <aradi at uni-bremen.de> wrote:
> Dear Branislav,
> 
> could you try to set ShellResolvedScc = Yes for the iron calculation? 
> Does this improve reuslts?
> 
> Best regards,
> 
> Bálint
> 
> 
> On 28.01.23 14:18, Branislav Milovanović wrote:
> > Dear DFTB+ users,
> > 
> > I am experiencing problems with bulk Fe (iron) optimization using 
> > pbc-0-3 or trans3d-0-1 parameters.
> > Namely, I wanted to optimize Fe unit cell first, then supercell, then to 
> > construct slab Fe(100) surface and later
> > to try and investigate adsorption of different organic molecules on 
> > Fe(110) surface (using mio-1-1 + trans3d-0-1 parameters set).
> > 
> > I've tried all kind of different setup in the DFTB+ input but somehow my 
> > system always fell apart during the optimization runs.
> > Fe-Fe distances become too large, >3.5 A and experimental values are 
> > ~2.86 A. Here is my current input file:
> > 
> > Geometry = GenFormat {
> >    <<< geo.gen
> > }
> > 
> > Driver = GeometryOptimisation {
> >    Optimiser = Rational {
> >      DiagLimit = 1.00E-002
> >    }
> >    LatticeOpt = Yes
> >    FixAngles = Yes
> >    FixLengths = {No No No}
> >    Isotropic = Yes
> >    MovedAtoms = "1:-1"
> >    Convergence = {
> >      GradElem = 0.00001
> >      DispElem = 0.0001
> >    }
> >    MaxSteps = 1000
> >    OutputPrefix = "geo_end"
> >    AppendGeometries = Yes
> > }
> > 
> > Hamiltonian = DFTB {
> >    SCC = Yes
> >    SCCTolerance = 1.0E-9
> >    MaxSCCIterations = 500
> >    Charge = 0
> >    Solver = RelativelyRobust {}
> >    ThirdOrder = No
> >    ThirdOrderFull = No
> >    Mixer = Broyden {
> >      MixingParameter = 0.20000000000000001
> >      InverseJacobiWeight = 1.0000000000000000E-002
> >      MinimalWeight = 1.0000000000000000
> >      MaximalWeight = 100000.00000000000
> >      WeightFactor = 1.0000000000000000E-002
> >    }
> >    Filling = Fermi {
> >      Temperature = 1500.000
> >    }
> >    KPointsAndWeights = SuperCellFolding {
> >      8 0 0
> >      0 8 0
> >      0 0 8
> >      0.5 0.5 0.5
> >    }
> >    ShellResolvedSCC = Yes
> > #  ShellResolvedSpin = Yes
> >    SpinPolarisation = Colinear {
> >      UnpairedElectrons = 4
> >      RelaxTotalSpin = Yes
> >    }
> >    SpinConstants = {
> >      Fe = {
> >     -0.0160    -0.0124    -0.0035     # pbc
> >     -0.0124    -0.0280    -0.0010
> >     -0.0035    -0.0010    -0.0155
> > #-0.016 -0.012 -0.003             # trans3d
> > #-0.012 -0.029 -0.001
> > #-0.003 -0.001 -0.018
> > }
> >    }
> >    SlaterKosterFiles = Type2FileNames {
> >      Prefix = 
> > "/home/branislavm/branislavm/Programs/Potentials/slako/pbc/pbc-0-3/"    
> >    # 
> > "/home/branislavm/branislavm/Programs/Potentials/slako/mio-1-1+trans3d-0-1/"
> >      Separator = "-"
> >      Suffix = ".skf"
> >      LowerCaseTypeName = No
> >    }
> >    MaxAngularMomentum = {
> >      Fe = "d"
> > #    C = "p"
> > #    O = "p"
> > #    H = "s"
> >    }
> > #  Dispersion = DftD4 {
> > #    s6 = 1.0000000
> > #    s8 = 1.1948145
> > #    s9 = 0.0000000
> > #    a1 = 0.6074567
> > #    a2 = 4.9336133
> > #    s10 = 0.000000
> > #    alpha = 16.000
> > #  }
> >    PolynomialRepulsive = {}
> >    OldSKInterpolation = No
> >    RangeSeparated = None {}
> >    ReadInitialCharges = No
> >    InitialCharges = {}
> >    ConvergentSCCOnly = Yes
> >    HCorrection = None {}
> >    ElectricField = {}
> >    OnSiteCorrection = {}
> >    Solvation = {}
> >    Electrostatics = GammaFunctional {}
> >    ForceEvaluation = "Traditional"
> > }
> > 
> > ParserOptions = {
> >    ParserVersion = 12
> >    WriteHSDInput = Yes
> >    StopAfterParsing = No
> >    IgnoreUnprocessedNodes = No
> > }
> > 
> > Reks = None {}
> > 
> > Analysis = {
> >    ProjectStates = {}
> >    WriteEigenvectors = No
> >    WriteBandOut = No
> >    MullikenAnalysis = No
> >    AtomResolvedEnergies = No
> >    CalculateForces = No
> > }
> > 
> > ExcitedState = {}
> > 
> > Options = {
> >    WriteDetailedOut = Yes
> >    WriteAutotestTag = No
> >    WriteDetailedXML = No
> >    WriteResultsTag = No
> >    RandomSeed = 0
> >    WriteHS = No
> >    WriteRealHS = No
> >    MinimiseMemoryUsage = No
> >    ShowFoldedCoords = No
> >    TimingVerbosity = 1
> >    WriteChargesAsText = Yes
> > }
> > 
> > 
> > I would appreciate if someone could point me out where I'm making mistakes.
> > Thanks in advance!
> > 
> > Kind regards,
> > Branislav
> > 
> > 
> > _______________________________________________
> > DFTB-Plus-User mailing list
> > DFTB-Plus-User at mailman.zfn.uni-bremen.de
> > https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
> 
> --
> Dr. Bálint Aradi
> Bremen Center for Computational Materials Science, University of Bremen
> http://www.bccms.uni-bremen.de/cms/people/b-aradi/
> 
> 
> 
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