XPS

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General workflow

in preparation (currently just a sketch)

An XPS calculation is a single ionic step calculation, and involves the explicit computation of core levels for ONE selected atom in the POSCAR.

• For a converged structure select a single atom for which the core levels shifts will be calculated (link to gli script to be added)

• Create two separate subdirectries, (for example ./xpsini and ./xpsfin) and copy the the desired POSCAR to both

• copy the files corresponding to your typical setup to "xpsini"

• in ""xpsini"", insert tags for XPS calculation to INCAR:

   ICORELEVEL = 0     # State before excitation XPS
  #CLNT = 3           # atom type POSCAR; in this case third species in the POSCAR
  #CLN = 3            # main quantum number  
  #CLL = 2            # l quantum number; s=0, p=1, etc.; 
  #CLZ = 1            # number of electrons to be displaced. Do not use 0.5. 

• after the job is completed, grep ENTOT from the OUTCAR (let's call this value E1)

• copy the job files from ""xpsini"" to ""xpsfin""

• Replace tags for XPS calculation with:

   ICORELEVEL = 2     # XPS according to final state approximation; if ICORELEVEL=1 then the core level is computed without electron excitation
   CLNT = 3           # atom type POSCAR; in this case third species in the POSCAR
   CLN = 3            # main quantum number  
   CLL = 2            # l quantum number; s=0, p=1, etc.; 
   CLZ = 1            # number of electrons to be displaced. Do not use 0.5.    

• after the job is completed, grep ENTOT from the OUTCAR (let's call this value E2)

• The XPS shift (Exps) can be calculated as: Exps = E2 - E1

Alternatively:

compute just ICORELEVEL=2 with one positive charge in the system, then reference the core level energy (grep 3d OUTCAR #for the example above) to vacuum energy. (will elaborate in next edit)