making poscar file for a specified space group

[shyam]

Dear sir,
I have to make a poscar file for a orthorhombic crystal having space group P212121 and four molecules per unit cell.
Please help.
I have made a poscar file like this which i feel wrong somewhere.
orthorhombic:
1.0
6.046 0.0 0.0
0.0 12.271 0.0
0.0 0.0 5.804
2 1 3 7
direct
0.7283 0.0845 0.6281
0.4500 0.1850 0.7609
0.6557 0.1380 0.1857
0.5604 0.1414 0.6015
0.4767 0.1614 0.6015
0.2746 0.0916 0.3024
0.4357 0.2472 0.3376
0.7107 0.0593 0.2003
0.5947 0.1489 0.0177
0.7842 0.1917 0.2110
0.3188 0.0067 0.3057
0.1458 0.1050 0.1329
0.2100 0.1105 0.1329
Please correct this poscar file.
Thank u

[admin]

A specific space group corresponds to some regular distribution of atoms in space (crystal structure). What you have are molecules in the rectangular cell.

[shyam]

Dear sir,
My question was that if the molecule has 13 atoms and there are 4 molecules per unit cell and space group p212121 of that crystal then what will be my poscar file so that it shows 4 molecule per unit cell.

[admin]

You have coordinates of irreducible atoms in the orthorombic cell and you need to apply symmetry operations of the space group P212121 to get the complete crystal structure. This can be done using some crystallographic software (e.g. DIAMOND). Force field code GULP can do it as well.

[shyam]

Dear sir,
What i want to ask is my poscar file correct or not.
How can anybody guess that this is the job for a crystal for 4 molecules per unit cell and not 1 by seeing the poscar file

[admin]

Use some graphical software to have a direct look at your structure. Atomic arrangement is strange and one interatomic distance is as short as 0.4A. This is certainly not OK.

[shyam]

Dear sir,
Thank u very much for your guidance. Now i have used vesta software to make the poscar file for orthorhombic p212121 cell for my crystal.