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Convasp

Using PLATON

If you want to check the space group of your CONTCAR/POSCAR
 convasp -platon < POSCAR | platonSG 

If you want to check conventional unit cell lattice parameters, 'grep TITEL POTCAR' first, and then use:
$ convasp -names Na N H < CONTCAR | convasp -platon > cont.spf 
$ platon -c -o cont.spf

If you wish to find the atomic coordinates with high symmetry, use the following iterative process:
EDIT the .spf file to ensure the atoms are correct.
$ vi cont.eld 

Remove all the information after the line "HKLF blah blah"
$ cp cont.eld cont2.spf
$ platon -c -o cont2.spf

The crystal structure information will be at the top of cont2.eld file. Repeat if necessary until you find the crystal angles and the number of atoms at the top of the .eld file that you expect. Done!

To calculate Wyckoff positions, you can use the following tool:
http://stokes.byu.edu/findsym.html

Generating a supercell

Convasp can generate a supercell from a file which contains 9 numbers, giving elements a11,a12,a13,a21,a22,a23,a31,a32,a33 of the 3x3 supercell matrix

$ convasp -supercell file < POSCAR > POSCAR.new
$ cat POSCAR 
fccAl
4.000
1 0 0
0 1 0
0 0 1
4
Direct
0   0   0   Al
0.5 0.5 0   Al
0.5 0   0.5 Al
0   0.5 0.5 Al
$ cat sc.txt 
2 0 0
0 2 0
0 0 2
$ convasp -supercell sc.txt < POSCAR                                  
fccAl
1.0000000000
8.0000000000 0.0000000000 0.0000000000
0.0000000000 8.0000000000 0.0000000000
0.0000000000 0.0000000000 8.0000000000
32 
D
0.0000000000 0.0000000000 0.0000000000 Al
0.0000000000 0.0000000000 0.5000000000 Al
0.0000000000 0.5000000000 0.0000000000 Al
0.0000000000 0.5000000000 0.5000000000 Al
0.5000000000 0.0000000000 0.0000000000 Al
0.5000000000 0.0000000000 0.5000000000 Al
0.5000000000 0.5000000000 0.0000000000 Al
0.5000000000 0.5000000000 0.5000000000 Al
0.2500000000 0.2500000000 0.0000000000 Al
0.2500000000 0.2500000000 0.5000000000 Al
0.2500000000 0.7500000000 0.0000000000 Al
0.2500000000 0.7500000000 0.5000000000 Al
0.7500000000 0.2500000000 0.0000000000 Al
0.7500000000 0.2500000000 0.5000000000 Al
0.7500000000 0.7500000000 0.0000000000 Al
0.7500000000 0.7500000000 0.5000000000 Al
0.2500000000 0.0000000000 0.2500000000 Al
0.2500000000 0.0000000000 0.7500000000 Al
0.2500000000 0.5000000000 0.2500000000 Al
0.2500000000 0.5000000000 0.7500000000 Al
0.7500000000 0.0000000000 0.2500000000 Al
0.7500000000 0.0000000000 0.7500000000 Al
0.7500000000 0.5000000000 0.2500000000 Al
0.7500000000 0.5000000000 0.7500000000 Al
0.0000000000 0.2500000000 0.2500000000 Al
0.0000000000 0.2500000000 0.7500000000 Al
0.0000000000 0.7500000000 0.2500000000 Al
0.0000000000 0.7500000000 0.7500000000 Al
0.5000000000 0.2500000000 0.2500000000 Al
0.5000000000 0.2500000000 0.7500000000 Al
0.5000000000 0.7500000000 0.2500000000 Al
0.5000000000 0.7500000000 0.7500000000 Al

External links 

You will need convasp, a software written by Dane Morgan and Stefano Curtarolo. The newest version named aconvasp can be downloaded from Curtarolo Group's website.
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