ABINIT Discussion Forums

Dear All,
I have performed Band Structure Calculations on Sb2Te3 but although the main features compare well with published data and a castep calculation, the energy of all bands appears to be shifted up by 0.8 eV and I do not understand the reason. I have attached the bandstructure graphs from Castep and from Abinit to this post.

My procedure is as follows:

-Fully relax the atomic positions and cell geometry.
-Enter the relaxed cell structure into a new file for the band structure calculation.
-Do a single point energy calculation to generate the wavefunctions.
-Get the electron density from the previous calculation and do a non self consistent calculation

During the Band Structure calculation I do receive a few warnings regarding the hdr check. Specifcally:

-P-0000 hdr_check: WARNING -
-P-0000 input nkpt= 190 not equal disk file nkpt= 5
-P-0000 symafm:

and

-P-0000 hdr_check: WARNING -
-P-0000 Restart of self-consistent calculation need translated wavefunctions.
-P-0000 Indeed, critical differences between current calculation and
-P-0000 restart file have been detected in:
-P-0000 * the number, position, or weight of k-points
-P-0000 * the format of wavefunctions (istwfk)


I would be grateful if somebody could explain where I am making a mistake and how I can resolve the hdr_check warnings. I guess that my problem is related to these warnings.

Thanks,
Rob


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I am running:

.Version 6.8.1 of ABINIT
.(MPI version, prepared for a x86_64_linux_gnu4.4 computer)

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My i/p file for relaxing the structure is:

ndtset 2 # atom position and geom
ionmov 2 # move atoms
optcell1 0
optcell2 2

getxred -1
getwfk -1

ntime 500 # Maximum number of optimization steps
nstep 200

dilatmx 1.05 # Maximum scaling allowed for lattice parameters
ecutsm 0.5 # Energy CUToff SMearing

# Structure
spgroup 166 #Space Group (1=p1)
spgaxor 2
natom 5
natrd 3
ntypat 2 #number of types of Atoms
znucl 51 52 #Z-number of atom types Sb51, Te52

typat 1 2 2
acell 10.60650792 10.60650792 10.60650792 angstroms
angdeg 23.48953218 23.48953218 23.48953218
xred
0.602824 0.602824 0.602824
0.785568 0.785568 0.785568
0 0 0

kptrlen 200
brvltt -1
diemac 12.0
ecut 36 #from the convergence study
ixc 11 #GGA

nband 20
nbdbuf 2
tolmxf 5.0d-9
toldff 5.0d-10

occopt 3 # Smearing of Bands
tsmear 0.001 Ha # Temperature of Smearing, 0.001 Ha = 27.2113845 meV = 315.773 Kelvin
prtcif 1
prtvol 2

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My Input file for calculating the band structure is:

ndtset 2
ionmov 0 #Single point energy calc
optcell 0

getxred2 -1
getwfk2 -1

ecutsm 0.5
iscf 7
npulayit 10

nstep1 100
nstep2 500

prtden 1 getden1 0 getwfk1 0 ! Usual file handling data
prtcif 1
prtdos 1
prtvol 2

#Data common to all datasets

###### STRUCTURE #########
spgroup 166 #Space Group (1=p1)
spgaxor 2 #Rhombohedral Lattice 2
natom 5
natrd 3
ntypat 2 #number of types of Atoms
znucl 51 52 #Z-number of atom types Sb51, Te52

typat 1 2 2

acell 10.60766 10.60766 10.60766 angstroms
angdeg 23.486 23.486 23.486

xred
0.602828 0.602828 0.602828
0.785558 0.785558 0.785558
0 0 0

###### K points #########
kptopt1 1
kptopt2 -4
ngkpt 10 10 10
nshiftk 1

iscf2 -2
ndivk2 10 27 27 27
kptbounds2
0.0 0.0 0.0 # G point
0.5 0.5 0.5 # Z point
0.5 0.5 0.0 # F point
0.0 0.0 0.0 # G point
0.0 0.5 0.0 # L point

brvltt -1

diemac 12.0
ecut 36
ixc 11
#tnons 72*0.0

#### Tolerances #####
tolwfr2 1.e-24
tolmxf 5.0d-9
toldff 5.0d-10

##### BANDS ######
nband 20
nbdbuf 2
occopt 3 # Smearing of Bands
tsmear 0.001 Ha # Temperature of Smearing, 0.001 Ha = 27.2113845 meV = 315.773 Kelvin
getden2 -1
enunit2 1

Hello,

I think that you did'nt align your Fermi level to 0 in the bandstructure from abinit, that's all
I guess Castep does align the Fermi level to 0 automatically. Check the Fermi level in the output file or in the eigenvalue file of abinit it should be around 0.8 eV.

David

Dear David,
It seems you are correct. I checked my output file more carefully and I found the following line.

Fermi (or HOMO) energy (hartree) = 0.03156 Average Vxc (hartree)= -0.30991

This equates to 0.86 eV. Do you know if there is an Abinit input parameter that will plot the band's energies relative to the Fermi level? I could bot find such a parameter.

Thanks,
Rob

Dear robsimps,

I do know about any variable which would do smth like that, but you can do it by hand using awk from command line. You just take away the Fermi energy value from each band energy and k-point:

awk '{print $1,$2-0.03156,$3-0.03156,$4-0.03156,....,$20-0.03156}' name_of_your_band_file > name_of_your_shifted_band_file

And then you plot the band structure from the shifted band file.

Hope this helps.

Igor L.

Dear Igor.
Thank you, I will edit my Awk script to take care of the offset.

Rob

Dear robsimps,
i have calculated band structure of Bi2Te3.it is different from other papers,one of my problems is i don't have numbers on the axis of energy(eV) as i see this segments in your band plot.would you please tell me why i don't have this segments in energy axis in my plot?
Best regards.
Mina.