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Binding energy calculation Date: 2006/10/12 03:08 Name: K. Bart   <kk.bart@gmail.com> Dear Professor Ozaki, I am not a specialist in this field, so excuse me if this is a trivial question. I calculated the binding energy of the W-O dimer (Tungsten Oxide) as a function of interatomic distance. I set the calculations and got results, but the resulting curve seems to be scattered. I also calculated the O-O dimer in the analogous way, to test my calculations, and got a minimum energy at a distance 1.4 angstrom instead of the literature value of 1.2. I would be very grateful if you could point me what am I doing wrong and suggest how to set these calculations in the appropriate way to get precise results. For tungsten, I used W11.0 and W_PBE VPS from your database (2006) and took s2p1d1f1. Below you can find my input file. Best Regards K. Bart ==================================================================== System.CurrrentDirectory ./ # default=./ System.Name WO level.of.stdout 1 # default=1 (1-3) level.of.fileout 1 # default=1 (1-3) # # Definition of Atomic Species # Species.Number 2 <Definition.of.Atomic.Species W W11.0-s2p1d1f1 W_PBE O O6.0--s1p1 O_GGA Definition.of.Atomic.Species> # # Atoms # Atoms.Number 2 Atoms.SpeciesAndCoordinates.Unit Ang # Ang|AU <Atoms.SpeciesAndCoordinates 1 W 0.000 0.000 0.000 12.0 16.0 2 O 0.000 0.000 1.900 4.0 2.0 Atoms.SpeciesAndCoordinates> Atoms.UnitVectors.Unit Ang # Ang|AU <Atoms.UnitVectors 12.0000 0.0000 0.0000 0.0000 12.0000 0.0000 0.0000 0.0000 12.0000 Atoms.UnitVectors> # # SCF or Electronic System # scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW scf.SpinPolarization on # On|Off scf.ElectronicTemperature 600.0 # default=300 (K) scf.energycutoff 160.0 # default=150 (Ry) scf.maxIter 70 # default=40 scf.EigenvalueSolver cluster # 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 0.010 # default=0.30 scf.Min.Mixing.Weight 0.001 # default=0.001 scf.Max.Mixing.Weight 0.050 # default=0.40 scf.Mixing.History 7 # default=5 scf.Mixing.StartPulay 20 # default=6 scf.criterion 1.0e-8 # default=1.0e-6 (Hartree) # # 1D FFT # 1DFFT.NumGridK 900 # default=900 1DFFT.NumGridR 900 # default=900 1DFFT.EnergyCutoff 3600.0 # default=3DFFT.EnergyCutoff*3.0 (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 6.3 # default=5.0 (Ang) orderN.NumHoppings 2 # default=2 orderN.KrylovH.order 500 # default=400 orderN.recalc.EM off # # restart using *.rst # scf.restart off # on|off, default=off # # MD or Geometry Optimization # MD.Type nomd # Nomd|Constant_Energy_MD|Opt MD.maxIter 1 # default=1 MD.TimeStep 1 # default=0.5 (fs) MD.Opt.criterion 1.0e-5 # default=1.0e-4 (Hartree/bohr) # # Band dispersion # Band.dispersion off # on|off, default=off # 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 on # on|off, default=off =====================================================================================

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Re: Binding energy calculation ( No.1 ) Date: 2006/10/12 23:05 Name: T.Ozaki Hi, Could you check the standard output ? If you see "The system is molecule." in the standard output, it is Okay. But I wonder that the part "molecule" can be "chain", "slab", or "bulk", since the cutoff radius of basis function for W is long. Then, the "molecular calculation" you intend becomes the band calculation. The cell size should be determined by the largest distance between atoms you try, and should be fixed during the calculation of energy curve. Otherwise, you will have some artifact effect arising from the unit cell size. Also, the pseudopotential of W is a deep one. Thus, the dependency on "scf.energycutoff" should be checked carefully. As for O2 case, with above things the basis set convergence should be checked. Elements in the sixth and seventh columns tend to requires a large number of basis function for the convergence. You can find the convergence properties of the O2 bond length with respect to basis functions in Phys. Rev. B 69, 195113 (2004). http://netserver.aip.org/cgi-bin/epaps?ID=E-JCPSA6-121-301439 Regards, TO

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