[CPMD-list] CHARGES for solids

[Axel Kohlmeyer]

On Tue, 29 May 2007, Jiri Houska wrote:

dear jiri,

JH> Dear all,
JH> when I tried to calculate atomic charges for TiN solid material I  
JH> received the error "ESP CHARGES| NUMBER OF FITTING POINTS 0". I found  
JH> that when this error was reported previously in 2004, prof. Hutter  
JH> replied "You have to use [for solids] one of the other possibilities  
JH> available in CPMD for this (Mulliken, Davidson, Hirshfeld)."

JH> Athough I do not fully understand that (I calculated ESP charges  
JH> succesfully for other solids on the same platform), the Hirshfeld  

whether the ESP fit works or not depends on the covalent radii
of the elements involved. please have a look at espchg.F.

JH> charges would be hopefully OK. However, is there any method to  
JH> calculate with cpmd ONLY the Hirsfeld ("INT")charges and not the ESP  
JH> charges? My understandng is that both is called by the same keyword  
JH> CHARGES ...

you'll have to modify the sourcecode in proppt.F to disable 
ESP charges. alternatively, you could implement a more generic
solution and add additional keywords to CHARGES to support all 
of the methods selectively (see e.g., egointer.F for how they 
are called) and send us a patch with the modifications for 
inclusion in the next version of CPMD. ;-)

cheers,
   axel.

JH> One more question: please does anybody have an experience which of the  
JH> available charges is best to use for calculation of Coulombic forces  
JH> between atoms?
JH> 
JH> Thank a lot for any advice.
JH> Jiri Houska
JH> Dpartment of Engineering Physics
JH> Ecole Polytechnique de Montreal
JH> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.