[Wien] core hole

[Jorissen Kevin]

Thanks for previous comments - a few more thoughts :
 
Just to be really clear : no, you don't normally add a core hole after scf  ; you do it before scf, like your colleague said.  Let us check the users guide on this point : if it is unclear (or wrong), then we need to change it.
 
 
Two more remarks I want to make :
1/ Usually you will do this core hole calculation in a supercell (eg., 2*2*2 times the primitive unit cell) to keep core hole atoms of neighbouring cells far enough apart.
 
So, the standard way of doing a core hole is :
In a new directory, create a supercell, initialize, edit case.inc (remove electron) and case.inm (or case.in2(c) ) (add electron) to implement the core hole, run scf-calculation, run telnes2.
 
2/ It is actually possible to introduce the core hole in steps - that is, set up the supercell, not add the core hole, converge the ground state (scf), then add the core hole, then converge again (scf).  In some cases, this may help the final scf convergence.  Hopefully, with the improved mixer schemes we have these days, such strategies are not necessary anymore.
 
 
There is an unfortunate typo in Florent's e-mail : he refers to either adding a -1 * e "background charge" in case.inm ("background charge" doesn't really mean anything except that it keeps WIEN2k from renormalizing the electron density - it's like telling WIEN2k "it's okay you're missing one electron, don't try to compensate for it") ; or to adding the core electron you've removed from the core in case.inc into the valence band by increasing the number of valence electrons in case.in2(c) (not case.inm) by +1.  Both options gave quite similar results in the cases where I've compared them.  Just like Florent, I usually go with the background charge in case.inm.  However, I don't think one approach is more evil than the other.
 
 
Let us know if you have more questions.
 
best regards,
 
 
 
 
Kevin Jorissen
University of Washington
Dept. of Physics
Box 351560
Seattle, WA-98195-1560
U.S.A.
 
phone +1 206 543 3904 
fax +1 206 685 0635 
e-mail kevin.jorissen at ua.ac.be 
web page http://fraangelico.phys.washington.edu/~jorissen

________________________________

From: wien-bounces at zeus.theochem.tuwien.ac.at on behalf of Florent Boucher
Sent: Wed 7/11/2007 6:11
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] core hole


Dear BoKang,
if you expect an effect from the core hole, you have to allow it.
For this, you should reoptimize the density (and effective potential) by doing SCF calculations including this core hole.
You should then keep in mind that your system will miss an electron into the core. So, if you change nothing, WIEN will renormalazied the density in order to find a number of electron equal to the sum of the Z numbers (this is in mixer).
To overcome this trouble, you have the choice either to add an extra charge -1 into the inm file  (that just tell to WIEN that you are working with a missing electron) (this is the best I think) or to add an extra electron into the inm file (I don't like this option).
Regards
Florent

? ? a écrit : 

	Dear wien users,
	 
	       Recently, when I calculated the EELS , I wanted to add a core hole in my calculation. Accounting to the Manual, I added the core hole after scf and before calculation of the spectra. But someone tell me , I should add the core hole after initialization and before scf. I don't know which method of adding an core hole is right?
	 
	     Any reply will be appreciated!
	 
	   Best wishes!
	   
	                                                                          BoKang  

	

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