WIEN2k-FAQ: Charged cells

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

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"Charged" cells will most likely require the construction of supercells, (see the faq on creating supercells) and this hole discussion targets charged impurities, vacancies,....

• Setup your supercell, put impurities, vacancies,.. (all with neutral atoms!)
• Run a standard initialization (init_lapw) with NEUTRAL atoms. Don't fiddle around with case.inst (positively charged atoms may work (and one can neglect the warnings "NUMBER OF ELECTRONS NE IZ "), but most negative ions are unstable in DFT and will not work.
• run_lapw (again for neutral atoms !) . Save the results using "save_lapw case_neutral"
• Edit case.in2: In the second line you see the number of electrons NE. Add or remove an electron to get the desired charged state.
• Edit case.inm: The first line must read:
  

   BROYD  1.0   YES        (when you added an electron at step 4     or
   BROYD -1.0   YES        (when you removed an electron at step 4
  

  The position of "YES" is important!!! When reading characters in Fortran one must use a fixed format (or put characters into quotes).
• run_lapw
• I NEVER run init_lapw again!!! Usually init_lapw should be run only ONCE in a directory, because any changes which would require rerunning init_lapw (symmetry changes,....) should be done in a fresh "case"