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[jiangx3@rpi.edu]

Dear all,

I want to optimize a structure with 26 carbons inside the supercell. But
I set nstep to 200 and it is still not converged. Also do you think
ecut=14 would be enough for this optimization? Thank you very much for
your suggestion!

Best regards,
Xueping Jiang




# Graphene-H2
# Structural optimization
# FHI-Pseudopotential, see http://www.abinit.org/downloads/psp-links
# First, a SCF optimization of the ionic positions only, then a full 
# optimization of cell geometry, taking into account the symmetry.

ndtset 2


#Definition of the planewave basis set
ecut 14.0         # Maximal kinetic energy cut-off, in Hartree


# Definition of the k-point grid
#kptopt  1          # Option for the automatic generation of k points,
                   # taking into account the symmetry
#nshiftk 1
#shiftk  0.0 0.0 0.0
#ngkpt   12 12 1 
nkpt 1

# Dataset1: usual self-consistent ground-state calculation with
# optimization of ionic positions

prtden1  1         # Print the density, for use by dataset 2
ionmov1  2         # Conduct structural optimization
optcell1 0         # Optimization of the ionic positions only
ecutsm1  0.5       # Energy cutoff smearing
ntime1   20        # number of structural optimization steps


# Dataset2: self-consistent GS calculation with full optimization of
# cell geometry
ionmov2   2          # Conduct structural optimization
optcell2  2          # Full optimization of cell geometry
ecutsm2   0.5        # Energy cutoff smearing; when optcell/=0, ABINI
                     # requires ecutsm to be larger than zero.
getxcart2 -1         # the result from the dataset1 will be used
dilatmx2  1.2      # maximum dilatation
ntime2    20         # number of structural optimization steps
prtgeo2   1          # Print the geometry analysis


#Definition of the unit cell
acell  7.31181 8.4432 20  Angstrom      
rprim  1.0     0.0   0.0   # primitive vectors (to be scaled by acell)
       0.0     1.0   0.0
       0.0     0.0   1.0

chkprim 0
#Definition of the atom types
ntypat 2          # There is only one type of atom
znucl 6 1           # The keyword "znucl" refers to the atomic number of the
                  # possible type(s) of atom. The pseudopotential(s)
                  # mentioned in the "files" file must correspond
                  # to the type(s) of atom. Here, the only type is Carbon.


#Definition of the atoms
natom 26           # There are two atoms
typat 24*1 2*2         # They both are of type 1, that is, Carbon.
xangst             0.52099583    1.79060496    4.17320659
                   0.52163927    4.57366256    4.17312571
                   2.77204261    5.85734112    4.17364757
                   2.77134325    0.50670674    4.17313330
                   5.14158642    1.87044135    4.17332852
                   9.67691265    1.84774428    4.17332245
                   5.14136955    4.49477997    4.17403707
                   9.67620053    4.51631041    4.17376356
                   7.42583956    5.80022882    4.17462335
                  12.04638093    5.87999603    4.17318818
                   7.42652015    0.56404204    4.17318660
                  12.04620138    0.48514240    4.17325848
                   0.52097344    9.80965859    4.17313482
                   0.52161123   12.59269352    4.17310276
                   2.77201790   13.87638193    4.17316194
                   2.77135044    8.52584783    4.17396389
                   5.14155236    9.88947635    4.17488102
                   9.67687984    9.86679235    4.17391970
                   5.14135414   12.51379698    4.17389878
                   9.67617405   12.53533253    4.17340487
                   7.42583098   13.81920054    4.17339900
                  12.04635042   13.89906742    4.17312371
                   7.42647671    8.58315792    4.17507757
                  12.04617038    8.50427534    4.17318599
                   5.48316350    7.19159450    7.07312400
                   4.71466350    7.19159450    7.07312400


  # position of the atoms in the unit cell
        


#Definition of the SCF procedure
nstep 200          # Maximal number of SCF cycles
diemac 4          # Although this is not mandatory, it is worth to
                  # precondition the SCF cycle.
                  # dielectric constant of graphene acc. to
                  # Phys. Rev. B 75, 205418 (2007)
toldff  1.0d-8    # tolerance for differences, stopping criterion