WIEN2k-FAQ: Construction of supercells

©1997-1999 by P. Blaha, K. Schwarz and J. Luitz

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For most (simple) supercells you can start with the regular case.struct file and use the "supercell" program (x supercell) to generate the supercell-struct file.

For more complicated cases we also provide an octave-based program "structeditor", which is a very powerful and flexible tool to manipulate strcutures (for more info read the UG).

However, when you construct supercells, it is usually NOT possible just to double the cells and leave all atoms at their ideal and equivalent positions. This would lead to large multiplicities (e.g. in big supercells even more than 48 atoms could be "equivalent" and of course there is NO SPACEGROUP corresponding to this type of cell, since they all can be reduced by translation symmetry.

So during setup, you have at least to:

Then run init_lapw Note, that WIEN always preserves symmetry. So when you want to allow certain relaxations around an impurity, it might be necessary to displace some atoms by hand to break the high symmetry and allow such relaxations.

Peter Blaha,