If 1. you know there are 18 atoms in a unit cell 2. AND if you know their Cartesian coordinates 3. AND if you don't want to use the Bravais-lattice index,
you could use 1. ibrav=0 2. AND define your unit cell (using CELL_PARAMETERS): nothing more than the 3 "primitive" lattice vectors 3. AND ATOMIC_POSITIONS: I suggest that you should use crystal coordinates instead of using Cartesian coordinates. You can find description in http://www.quantum-espresso.org/input-syntax/INPUT_PW.html :) On Fri, Sep 4, 2009 at 12:14 PM, Neel Singh <neelphysics at yahoo.in> wrote: > 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 > > ------------------------------ > See the Web's breaking stories, chosen by people like you. Check out Yahoo! > Buzz <http://in.rd.yahoo.com/tagline_buzz_1/*http://in.buzz.yahoo.com/>. > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- -------------------------------------------------- Duy Le PhD Student Department of Physics University of Central Florida. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20090904/79ef42d9/attachment-0001.htm
