[Solved] Convert FCC to SC

Total energy, geometry optimization, DFT+U, spin....

Moderator: bguster

Locked
Sunny
Posts: 10
Joined: Thu Jan 31, 2013 4:25 pm

[Solved] Convert FCC to SC

Post by Sunny » Thu Jan 31, 2013 4:56 pm

Hello!

At the moment I'm trying to convert tutorial #3 from the fcc coordinates to sc coordinates because I need the wavefunction in the whole cubic cell.

To do this, I started from the file tbase3_5.in by substituting the basis vectors with the simple cubic ones and replacing the k-vectors with their coordinates in cartesian space.

Code: Select all

rprim  1.0  0.0  0.0
       0.0  1.0  0.0
       0.0  0.0  1.0
kptbounds2  0.25  0.25  0.25 # L point
            0.0  0.0  0.0 # Gamma point
            0.0  0.0  0.5 # X point


The next step was the replacement of

Code: Select all

nshiftk1 1
shiftk 1  0.5 0.5 0.5


and finally the correction of the atom's positions.

Code: Select all

natom 8           # There are two atoms
typat 1 1 1 1 1 1 1 1        # They both are of type 1, that is, Silicon.
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
   0.0  0.0  0.0  # Triplet giving the REDUCED coordinate of atom 1.
   1/4  1/4  1/4  # Triplet giving the REDUCED coordinate of atom 2.
   2/4  2/4  0.0
   3/4  3/4  1/4
   2/4  0.0  2/4
   3/4  1/4  3/4
   0.0  2/4  2/4
   1/4  3/4  3/4


After adding the option

Code: Select all

chkprim 0
because the symmetry finder complained about not finding a primitive lattice, I got an unphysical bandstructure.

For example at Gamma, there is the lowest band, then a 6 times degenerate band followed by another 6 times degenerate band (when you also increase the number of bands).

Could anyone explain, what I am doing wrong? Any help is appreciated.

Thanks!

Sunny
Last edited by Sunny on Fri Feb 08, 2013 4:35 pm, edited 1 time in total.
Top
ljludwig
Posts: 77
Joined: Fri Jun 08, 2012 5:19 am

Re: Convert FCC to SC

Post by ljludwig » Tue Feb 05, 2013 7:25 pm

Can you upload the full input file?

In the meanwhile, did you redo the structural optimization?
Top
Sunny
Posts: 10
Joined: Thu Jan 31, 2013 4:25 pm

Re: Convert FCC to SC

Post by Sunny » Thu Feb 07, 2013 1:30 pm

The fault was on my end... I didn't think about folding of the bands in this cell which is kind of a supercell.


Thanks anyway!
Top
ljludwig
Posts: 77
Joined: Fri Jun 08, 2012 5:19 am

Re: Convert FCC to SC

Post by ljludwig » Thu Feb 07, 2013 8:12 pm

Sunny wrote:The fault was on my end... I didn't think about folding of the bands in this cell which is kind of a supercell.


Thanks anyway!


Ah, I see. If you think it is solved, could you please add "[Solved]" at the beginning of the title of your post?
It will be helpful for other people's future reference. Thanks.
Top
Locked

Return to “Ground state”