ABINIT Discussion Forums

Dear all;,
I tried to make the band structure of monolayer of Cobalt, but what I get is just flat band ,
I attached the input file and the band structure I got ,
I will be grateful for any feedback or remaks
Thank you very much for your comprehnsion
with nice regards

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# Crystalline Cobalt 13/06/2020
#
# Computation of the band structure.
# First, a SCF density computation, then a non-SCF band structure calculation.

ndtset 2

#Dataset 1 : usual self-consistent calculation
kptopt1 3 # Option for the automatic generation of k points,
# taking into account the full symmetry
#ngkpt1 4 4 1
prtden1 1 # Print the density, for use by dataset 2
toldfe1 1.0d-12 # This value is way too large for most realistic studies of materials
prtdos2 2
#prtdos1 2
ngkpt1 12 12 1
#Dataset 2 : the band structure
iscf2 -2
getden2 -1
kptopt2 -3 # nb of segments Only 2 segment: G->K and K->M to compare with VASP results
nband2 9
ndivk2 100 70 37 # 10, 12 and 17 divisions of the 2 segments, delimited
# by 3 points.
kptbounds 0 0 0 # Gamma
2/3 -1/3 0 # K
1/2 0 0 # M
0 0 0 # Gamma

tolwfr2 1.0d-12
enunit 1 # Will output the eigenenergies in eV



#Definition of the unit cell
#acell 4.737732368 4.737732368 7.690240466
#angdeg 90 90 120

acell 4.737732368 4.737732368 7.690240466
rprim 0.8660254038E+00 5.0000000000E-01 0.0000000000E+00
-0.8660254038E+00 5.0000000000E-01 0.0000000000E+00
0.0000000000E+00 0.0000000000E+00 1.0000000000E+00

pseudos "Co.GGA_PBE-JTH"

#Definition of the atom types
ntypat 1 # There is one types of atoms
znucl 27 # 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 Silicon.


#Definition of the atoms
natom 6 # There are three atoms
typat 1 1 1 1 1 1 # They are of type 1 Mo,type 2 sulphur .
#xred # This keyword indicate that the location of the atoms
# 1/3 2/3 1/4
# 2/3 1/3 3/4
#or
xcart
0. 0. 0. #Bohr
4.7377 0 0. #Bohr
0 0. 7.96024 #Bohr
4.7377 0 7.96024 #Bohr
2.36885 4.102968 0. #Bohr
2.36885 4.102968 7.96024 #Bohr




#Definition of the planewave basis set
ecut 20.0 # Maximal kinetic energy cut-off, in Hartree

#Definition of the SCF procedure
nstep 50 # Maximal number of SCF cycles
diemac 12.0 # Although this is not mandatory, it is worth to
# precondition the SCF cycle. The model dielectric
# function used as the standard preconditioner
# is described in the "dielng" input variable section.
# Here, we follow the prescription for bulk silicon.

# add to conserve old < 6.7.2 behavior for calculating forces at each SCF step
optforces 1
prtebands 2
prtgeo 2
pawovlp -1
pawecutdg 30

-------------

Dear Abdullah,

The structure that one gets from your input file is not a correct one.
The Co atoms that are in the (x,y, 0) plane are too close to the atoms that in your structure are in the (x,y, 7.96024) plane ( Please see the figure with the overlapping spheres when the latter atoms are folded back in the primary unit cell due to the periodic boundary conditions(PBC) ).

Moreover Co contains in bulk 2 atoms in the primitive cell, so you could start for the monolayer with one atom in the unit cell with the appropriate lattice vectors, for example:

acell 4.737732368 4.737732368 15.0000 # the z direction should be large enough to eliminate the interaction between the single-layer and the replicas due to PBC. You will need to perform a convergence study for the total energy with respect to the size of the cell in the z-direction.

xcart
0.00000 0.000000 0.00000 #Bohr - Only one atom in the unit cell like, for example, in the case of graphene

Please let me know if you have any further questions.
Good luck!
Bogdan