calculating the graphene DOS using tetrahedron method

[samabdel]

I have calculated the DOS of graphene using the following input:
-------------------------------------------------------------------------
acell 4.6411685 4.6411685 12
xred 0 0 0
1/3 1/3 0

rprim 1.0 0.0 0.0 # Hex. primitive vectors(to be scaled by acell)
0.5 0.8660254037844386 0.0
0.0 0.0 1.0

ntypat 1
znucl 6

#DA : Definition of the atoms

natom 2
typat 1 1

#DPWset : Definition of the plane wave basis set

ecut 35

#Dkptgrid : Definition of the k-points grid

#kptopt 1
kptopt 3
nshiftk 1
shiftk 0.0 0.0 0.0
ngkpt 10 10 1

nband 6
occopt 3
tsmear 0.006
#DSCFproc : Definition of the SCF procedure
prtdos 1
prtden 1
nstep 50
toldfe 1e-8
------------------------------------------
But when I try to use the tetrahedron method (prtdos=2) I get a dos with a gap at the Fermi level of around 1.36 eV (0.05 Htr).
Many thanks.

[MPis86]

Dear Samabel
probably the band gap come from the k point sampling that fails to get the K point. You can try to increase the number of k-points in your sampling. I'm not so experienced with the option you used in the definition of the primitive vectors. However you can try a sempling n n 1 with n a multiple of 3. This should include the K point. Finally, probably the distance between two slab (acell(3)) is too small.
hope it helps
Michele

[samabdel]

Dear Michele,
You're right. Apparently that was a problem of k-point sampling.
Thank you so much,
Yours,
Samir

[Seba Darshan]

hai

I am trying to plot the DOS of graphene using Xmgrace. I got the dos file after running the input file. But for plotting the dos file in xmgrace in Linux, I understood the command to be used is as follows (from ABINIT tutorials)

xmgrace -block filename_DOS -bxy 2:3

But the columns 2 and 3 corresponds to DOS and Integr. DOS repectively.

I would like to know whether this command is correct? Because we want Dos versus energies in electron-volts.
Also I would like to know how can I plot the energies in electron volts instead of Hartree that DOS file shows.

Regards
seba

[ilukacevic]

Hi!

For future reference you can use enunit variable set to 1 (http://www.abinit.org/documentation/helpfiles/for-v7.6/input_variables/vargs.html#enunit). This will give you energies in eV. Actually, I'm not sure whether this works for DOS files, too. Try it.

As you already have a DOS file, just convert Ha into eV, using whatever way you want (awk, for example). I think that you can even operate the wanted column inside Xmgrace to give you eV.

Best regards,

Igor

[Seba Darshan]

hai

I would like to know how can I convert hartree to electron volts using awk. I don't know how to do this. Can you shed some light on this.

As you have mentioned how can I operate the wanted column in Xmgrace corresponding to energy (in Hartrees) to give its values in electronvolts.

Hope for a positive reply,

Seba