The ABINIT Users Mailing List ( CLOSED )

[Masayoshi Mikami <mmikami@rc.m-kagaku.co.jp>]

Dear "ajlu@ustc.edu",

I have little time to go into detail, but I would like to suggest:

1) As noted in the Netiquette, please give information
 about pseudopotentials you adopted. From the WEB or your own ?
 Which type ? (TM, Teter, ... or else ?) It may be related to ecut etc.

2) Why don't we increase "nstep" ? "nstep 10" was sufficient ?
  You might have find some warnings about convergence about SCF cycle ?
  In any case, please check "Warnings" in your log file.
  In passing, how many k-points in this case ? (This may not be relevant
  for your present problem, but it would be a good custom to check...)

In passing, it appears confusion about the Brillouin zone
for the primitive and the conventional Si cell...
Your assignment (intention) about k-path seems for the primitive cell,
but you computed with the conventional cell... The special k points
have different names/positions for each Brillouin zone.

Namely, if you computed with the conventional cell (8 atoms),
the Brillouin zone seems like this:
http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-kv-list? 
gnum=221&fig=fm3qmp
FYI, the Brillouin zone for the primitive cell for Si seems like this:
http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-kv-list? 
gnum=227&fig=fm3qmf

Good continuation,
Masayoshi (would-be polyglot :-)

P.S. I would like to express "Muchas gracias" to the Bilbao  
Crystallographic site:
http://www.cryst.ehu.es/

On 2006/05/22, at 11:21, ajlu@ustc.edu wrote:

> When I used unit cell with 8 atoms to calculate the electronic band  
> structure of silicon, there are unexpected states within the band gap,  
> at Gamma point. How to deal with it?
>
> My input file is attached below.
>
>     ndtset   2
> #Dataset 1 : usual self-consistent calculation
>    kptopt1   1              # Kpoint option ( default 0.0 )
>   nshiftk1   1              # Number of shifts of k point grids
>    shiftk1   0.5  0.5  0.5  # These shifts will be the same for all  
> grids
>    prtden1   1              # Print the density, for use by dataset 2
>    toldfe1   1.0d-6         # Tolerance on the difference of total  
> energy
> #Dataset 2 : the band structure
>      iscf2  -2
>    getden2  -1
>    kptopt2  -3
>     nband2   32
>     ndivk2   10 12 17      # Number of divisions of k lines
> kptbounds2   0.5  0.5  0.5 # L point
>              0.0  0.0  0.0 # Gamma point
>              0.0  0.0  0.5 # X point
>              1.0  1.0  1.0 # Gamma point in another cell.
>    tolwfr2   1.0d-12
>    enunit2   1             # Will output the eigenenergies in eV
> #Definition of the unit cell
>     acell   3*10.217       # This is equivalent to   10.217 10.217  
> 10.217
>     rprim   1.0  0.0  0.0  # FCC primitive vectors (to be scaled by  
> acell)
>             0.0  1.0  0.0
>             0.0  0.0  1.0
>   chkprim   0
>    ntypat   1              # There is only one type of atom
>     znucl   14             # The atomic number of the type(s) of atom
>     natom   8              # There are two atoms
>     typat   8*1           # They both are of type 1, that is, Silicon.
>      xred                  # The location of the atoms
>             0.0  0.0  0.0  # Triplet giving the REDUCED coordinate of  
> atom 1.
>             0.5  0.5  0.0
>             0.0  0.5  0.5
>             0.5  0.0  0.5
>             1/4  1/4  1/4
>             3/4  3/4  1/4
>             1/4  3/4  3/4
>             3/4  1/4  3/4  # Triplet giving the REDUCED coordinate of  
> atom 2.
>      ecut   8.0            # Maximal kinetic energy cut-off, in Hartree
>     nstep   10             # Maximal number of SCF cycles
>    diemac   12.0           # Macroscopic dielectric constant diemac of  
> the system
>
>
> Thanks for your help.