[Pw_forum] Help in using xcrysden for making structures

Neel Singh neelphysics at yahoo.in
Fri Sep 4 18:14:16 CEST 2009


hi,
 I need some help in drawing crystal using xcrysden. Sir/Madam, let us take the case of FCC for which ibrav=2, and celldm(1)=9.000. Now if i know that i have 18 atoms in my unit cell and i know the Cartesian co-ordinates{x,y,z} of each atom in angstrom/bhor. I want to know that how can i draw my unit cell with giving positions of all the atoms without using the symmetries by xcrysden??. Means like if i specifiy,
& system
ibrav=2, celldm(1)=9.00, nat=1,......
ATOMIC POSITIONS{angstrom} 
A  0  4.5 0

now if we visualise this type of structure with Xcrysden, we found a number of atoms genrated due to symmetry. If i make a file like 
 & system

ibrav=2, celldm(1)=9.00, nat=18,......

ATOMIC POSITIONS{angstrom} 

A  0  4.5 0
/
18 times we have specified the co-ordinates
/
/
A  4.5 0 0 
Xcrysden will give warning like atom 10 and 90 are very close like that.
Sir i want to know is there any way so that i can make my PWSCF input file with angstrom/bohr postions such that with one atomic postion Xcrysden will show only one atom??
Means i will give 18 atomic postions and xcrysden will produce 18 atom unit cell without using symmatries. 

Thanks for your help,
Neel Singh,
Univeristy of Delhi,
India



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