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[<davidmlove86@hotmail.com>]

Hello,

I have done a convergence calculation of ecut using 4 kpt for a 10,0 nanotube
(see below: nt100.in). I then plotted the energy of the conduction band as a
function of different ecut values for each of the k points. I did this by
extracting the data from the produced eigenvalue files.

Once I converged my input values I determined the conduction band structure
using the density file from the previous converged calculation as an input 
(see
below: nt100bands.in).

However, I realized that the energy values of the conduction band structure
plot do not equal the values of the energies at the same k points and band in
the initial density calculation!

I suspect that when abinit is going through the k points in the density
calculation (nt100.in), that the first k point in the calculation is not
actually the 0 k-point, i.e. (0,0,0).

Could someone please tell me how I can determine the actual k points? Or even
better, any thoughts on why the energy values of the same k point and in the
same band do not equal each other in the density calculation (nt100.in) and in
the band structure calculation (nt100bands.in)? 

Thank you.

Regards,
David


############################## nt100.in #####################################
#ecut convergence for nt calc

ndtset 8

#Definition of the planewave basis set
ecut: 5.0    ecut+ 5

prteig 1
prtden 1
prtwf 1

kptopt 1         
ngkpt 8 1 1      
nshiftk 1        
shiftk 0.5 0.0 0.0
nkpt 4

nband 100

#Definition of the SCF procedure
nstep 20          # Maximal number of SCF cycles
toldfe 1.0d-6
diemac 10
diemix 0.33

#definition of unit cell
acell  0.80559E+01  0.80559E+01  0.80559E+01
rprim       # primitive cell definition
 0.00000E+00  0.00000E+00  0.10000E+01
 0.30000E+01  0.00000E+00  0.00000E+00
 0.00000E+00  0.30000E+01  0.00000E+00

#definition of atom types 
ntypat  1
znucl   6

#definition of basis
natom   40
typat   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1 
 
1   1   1   1   1   1   1
   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
xcart       # cartesian co-ords of atoms (bohr radii)
 0.74024E+01  0.00000E+00  0.00000E+00
 0.70401E+01  0.22875E+01  0.67133E+01
 0.70401E+01  0.22875E+01  0.40280E+01
 0.59887E+01  0.43510E+01  0.26853E+01
 0.59887E+01  0.43510E+01  0.00000E+00
 0.43510E+01  0.59887E+01  0.67133E+01
 0.43510E+01  0.59887E+01  0.40280E+01
 0.22875E+01  0.70401E+01  0.26853E+01
 0.22875E+01  0.70401E+01  0.00000E+00
 0.00000E+00  0.74024E+01  0.67133E+01
 0.00000E+00  0.74024E+01  0.40280E+01
-0.22875E+01  0.70401E+01  0.26853E+01
-0.22875E+01  0.70401E+01  0.00000E+00
-0.43510E+01  0.59887E+01  0.67133E+01
-0.43510E+01  0.59887E+01  0.40280E+01
-0.59887E+01  0.43510E+01  0.26853E+01
-0.59887E+01  0.43510E+01  0.00000E+00
-0.70401E+01  0.22875E+01  0.67133E+01
-0.70401E+01  0.22875E+01  0.40280E+01
-0.74024E+01  0.00000E+00  0.26853E+01
-0.74024E+01  0.00000E+00  0.00000E+00
-0.70401E+01 -0.22875E+01  0.67133E+01
-0.70401E+01 -0.22875E+01  0.40280E+01
-0.59887E+01 -0.43510E+01  0.26853E+01
-0.59887E+01 -0.43510E+01  0.00000E+00
-0.43510E+01 -0.59887E+01  0.67133E+01
-0.43510E+01 -0.59887E+01  0.40280E+01
-0.22875E+01 -0.70401E+01  0.26853E+01
-0.22875E+01 -0.70401E+01  0.00000E+00
 0.00000E+00 -0.74024E+01  0.67133E+01
 0.00000E+00 -0.74024E+01  0.40280E+01
 0.22875E+01 -0.70401E+01  0.26853E+01
 0.22875E+01 -0.70401E+01  0.00000E+00
 0.43510E+01 -0.59887E+01  0.67133E+01
 0.43510E+01 -0.59887E+01  0.40280E+01
 0.59887E+01 -0.43510E+01  0.26853E+01
 0.59887E+01 -0.43510E+01  0.00000E+00
 0.70401E+01 -0.22875E+01  0.67133E+01
 0.70401E+01 -0.22875E+01  0.40280E+01
 0.74024E+01  0.00000E+00  0.26853E+01



############################ nt100bands.in #################################
#Definition of the planewave basis set
ecut 25.0

prteig 1
prtden 1
prtwf 1

iscf -2
getden -1
kptopt -1

# kgrid
ndivk 20
kptbounds 0.0 0.0 0.0
          1.0 0.0 0.0
tolwfr 1.0e-12
enunit 1

nband 100

#Definition of the SCF procedure
nstep 20          # Maximal number of SCF cycles
toldfe 1.0d-6
diemac 10
diemix 0.33

#definition of unit cell
acell  0.80559E+01  0.80559E+01  0.80559E+01
rprim       # primitive cell definition
 0.00000E+00  0.00000E+00  0.10000E+01
 0.30000E+01  0.00000E+00  0.00000E+00
 0.00000E+00  0.30000E+01  0.00000E+00

#definition of atom types 
ntypat  1
znucl   6

#definition of basis
natom   40
typat   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1 
 
1   1   1   1   1   1   1
   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
xcart       # cartesian co-ords of atoms (bohr radii)
 0.74024E+01  0.00000E+00  0.00000E+00
 0.70401E+01  0.22875E+01  0.67133E+01
 0.70401E+01  0.22875E+01  0.40280E+01
 0.59887E+01  0.43510E+01  0.26853E+01
 0.59887E+01  0.43510E+01  0.00000E+00
 0.43510E+01  0.59887E+01  0.67133E+01
 0.43510E+01  0.59887E+01  0.40280E+01
 0.22875E+01  0.70401E+01  0.26853E+01
 0.22875E+01  0.70401E+01  0.00000E+00
 0.00000E+00  0.74024E+01  0.67133E+01
 0.00000E+00  0.74024E+01  0.40280E+01
-0.22875E+01  0.70401E+01  0.26853E+01
-0.22875E+01  0.70401E+01  0.00000E+00
-0.43510E+01  0.59887E+01  0.67133E+01
-0.43510E+01  0.59887E+01  0.40280E+01
-0.59887E+01  0.43510E+01  0.26853E+01
-0.59887E+01  0.43510E+01  0.00000E+00
-0.70401E+01  0.22875E+01  0.67133E+01
-0.70401E+01  0.22875E+01  0.40280E+01
-0.74024E+01  0.00000E+00  0.26853E+01
-0.74024E+01  0.00000E+00  0.00000E+00
-0.70401E+01 -0.22875E+01  0.67133E+01
-0.70401E+01 -0.22875E+01  0.40280E+01
-0.59887E+01 -0.43510E+01  0.26853E+01
-0.59887E+01 -0.43510E+01  0.00000E+00
-0.43510E+01 -0.59887E+01  0.67133E+01
-0.43510E+01 -0.59887E+01  0.40280E+01
-0.22875E+01 -0.70401E+01  0.26853E+01
-0.22875E+01 -0.70401E+01  0.00000E+00
 0.00000E+00 -0.74024E+01  0.67133E+01
 0.00000E+00 -0.74024E+01  0.40280E+01
 0.22875E+01 -0.70401E+01  0.26853E+01
 0.22875E+01 -0.70401E+01  0.00000E+00
 0.43510E+01 -0.59887E+01  0.67133E+01
 0.43510E+01 -0.59887E+01  0.40280E+01
 0.59887E+01 -0.43510E+01  0.26853E+01
 0.59887E+01 -0.43510E+01  0.00000E+00
 0.70401E+01 -0.22875E+01  0.67133E+01
 0.70401E+01 -0.22875E+01  0.40280E+01
 0.74024E+01  0.00000E+00  0.26853E+01