POSCAR file

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yilmaz · #1 Post by **yilmaz** » Fri Aug 12, 2005 6:02 pm

hi
i need to consider atleast 150 atoms in the "supercell" i use and i have no idea what are the lattice vectors for that "supercell", which can fill up the space.
how can a ugly shape without any symmetry can be defined with three vector anyway?
if the "supercell" is made of fcc "unit cells" can i use that unit cell vectors for "supercell".?
may be i am thinking in a wrong way. please some help.

i have already looked at the examples in the workshops but no clue.
thank you.

#2 Post by **admin** » Wed Aug 17, 2005 1:12 pm

I suggest to construct the supercell by repeating one primitive cell
LxMxN times in 3D, by giving multiples of the lattice vetors which define the Bravais matrix accordingly.
e.g. for a simple cubic cell, extended to a LxMxN box, this would read
...
a_0 (lattice parameter of the primitive cell)
L 0.0 0.0
0.0 M 0.0
0.0 0.0 N
....
The specification of the positions of the atoms then depends on
whether you choose 'Direct' (re-scale with L,M and N) or 'Carthesian' please have a look at the online manual
http://cms.mpi.univie.ac.at/vasp/vasp/node63.html
concerning the specification of the atoms' positions.