The ABINIT Users Mailing List ( CLOSED )

["Corsin Battaglia" <corsin.battaglia@freesurf.ch>]

Dear abinit users

 

I am trying to calculate the bandstructure for the metallic compound NbS2.

In a first step, I computed the total energy. I used the Hartwigsen-Goedecker-Hutter pseudopotentials for Nb and S. For Nb, I used the one, which contains semicore states as well (I read somewhere that semicore states are necessary in an electronegative environment).

During the scf-cycle, there seem to be no convergence problems.

 

     iter   Etot(hartree)      deltaE(h)  residm     vres2    diffor    maxfor

 ETOT 14  -154.22694726148    -3.875E-11 1.106E-04 8.090E-09 1.155E-06 2.924E-02
 ETOT 15  -154.22694726148    -2.394E-12 1.110E-04 8.903E-10 2.442E-07 2.925E-02
 ETOT 16  -154.22694726148    -9.612E-13 4.247E-05 5.884E-10 3.020E-07 2.925E-02
 ETOT 17  -154.22694726148    -4.440E-13 3.888E-05 6.675E-12 1.490E-07 2.925E-02

The Fermi energy converges as well

11792: newocc : new Fermi energy is       0.247380 , with nelect=     50.000000
12728: newocc : new Fermi energy is       0.247382 , with nelect=     50.000000
13664: newocc : new Fermi energy is       0.247381 , with nelect=     50.000000
14600: newocc : new Fermi energy is       0.247381 , with nelect=     50.000000
15536: newocc : new Fermi energy is       0.247381 , with nelect=     50.000000
16472: newocc : new Fermi energy is       0.247381 , with nelect=     50.000000
17408: newocc : new Fermi energy is       0.247381 , with nelect=     50.000000

 

No warnings or errors up to this point.

In a second step, I calculated the bandstructure. When I plot the bandstructure, it looks very fuzzy, although the number of k-points was quite dense (50 k-points between Gamma and M).

 

For every k-point, abinit writes the following warning into the log file

 

17759: vtowfk: WARNING -
17760-  Wavefunctions not converged for nnsclo,ikpt=    1    1 max resid=  1.22992E+00

 

Another problem is that abinit stops after 50 k-points, although I intended to compute 125 k-points.

 

I have no clue, what I am doing wrong.

Thanks in advance for your help

 

Corsin

 

 

 

Here's are the files I used.

 

NbS2.files

 

NbS2.in
NbS2.out
NbS2i
NbS2o
NbS2
../../Pseudopotentials/41nb.13.hgh
../../Pseudopotentials/16s.6.hgh

 

NbS2.in

 

# 2H-NbS2 : computation of the total energy and bandstructure

#Definition of the unit cell
acell   3.31   3.31    11.89 angstrom
#rprim  0.866 -0.500   0.000     # It is better to define
#       0.000  1.000   0.000     # the primitive vectors
#       0.000  0.000   1.000     # using rprim
angdeg 90 90 120

 

#Definition of the atom types
ntypat 2          # There are two type of atoms
znucl 41 16       # 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.

 

#Definition of the atoms
natom 6           # There are six atoms
natrd 2           # Reads two atoms
typat 1 2         # type 1 is Nb, type 2 is S
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
   0.0  0.0  1/4  # Triplet giving the REDUCED coordinate of atom 1.
   1/3  2/3  1/8  # Triplet giving the REDUCED coordinate of atom 2.
                  # Note the use of fractions (remember the limited
                  # interpreter capabilities of ABINIT)
spgroup 194

 

#Definition of the occupation numbers
occopt 4
tsmear 0.01

 

#Read psp
npsp 2            # Read 2 psp files
ixc 1             # Nb is of type ixc 1. S is of type ixc 1.
                  # LDA. Nb contains semicores.

 

#Definition of the planewave basis set
ecut 10.0         # Maximal kinetic energy cut-off, in Hartree

 

ndtset 2

 

#Dataset 1: SCF GS calculation

 

#Definition of the k-point grid
kptopt1 1         # Option for the automatic generation of k points, taking
                  # into account the symmetry
ngkpt1 8 8 4      # This is the grid based on the primitive vectors
                  # of the reciprocal space

 

#Definition of the SCF procedure
iscf1 3           # SCF cycle, CG based on the minim of the energy
nstep1 250        # Maximal number of SCF cycles
toldfe1 1.0d-12    # Will stop when, twice in a row, the difference
                  # between two consecutive evaluations of total energy
                  # differ by less than toldfe (in Hartree)
#diemac 12.0      # For metals, we use the default 10^6.
nband1 35         # nband=nb of electrons in unit cell/2+(20% for metals)
                  # more bands are needed with semicore states
prtden1 1         # Print the density for use by dataset 2

 

#Dataset 2: band structure

 

iscf2 -2          # Non-SCF calculation
getden2 -1
kptopt2 -4        # Bandstructure with 4 lines
nband2 35         # 35 bands
ndivk2 50 25 50 10
kptbounds2      0.0  0.0  0.0 # Gamma point
                0.5  0.0  0.0 # M point
                2/3  2/3  0.0 # K point
                0.0  0.0  0.0 # Gamma point
                0.0  0.0  0.5 # A point
tolwfr2 1.0d-12   # Only admitted convergence criterion for non-SCF calculations
enunit2 1         # Output the eigenvalues in eV