# Partial charges on the atom

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 Btam125 Member Profile Send PM
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 7:37:09 AM PDT - Mon, Apr 27th 2015 Hi all, Is it possible to have a partial charge when doing a QM energy calculation in nwchem? or is that even possible in Quantum physic calculation? Thank you!

 Sean bureaucrat Profile Send PM
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 11:48:19 AM PDT - Mon, Apr 27th 2015 Within the geometry block, you can specify an arbitrary nuclear charge for each atom. The charge directive is then used to set the number of electrons in the system with the constraint that the number of electrons must be an integer. So it is possible for the total charge of the systems to be non-integer, but the number of electrons must always be an integer. For example: geometry ```H 0.0 0.0 -0.5 charge 1.25 H 0.0 0.0 0.5 charge 1.25 ``` end charge 0.5 would simulate H2 with 2 electrons and a total charge of 0.5 Best, Sean

 Btam125 Member Profile Send PM
 Clicked A Few Times Threads 9 Posts 26
 2:50:16 AM PDT - Fri, May 1st 2015 Thank you, however I have an error after submitting this input file: start MgMOF-74 title "MgMOF-74" memory 5000 mb geometry C 8.59886355 17.68912997 15.23024421 O 7.79422064 18.43388815 14.85345853 O 9.40505759 16.94410501 15.60704709 Mg 7.88418289 20.67609980 14.51097681 charge 13.5 end basis ``` C library 6-31+G* O library 6-31+G* Mg library 6-31+G* ``` end charge 1.5 scf uhf singlet end It gives me this error: ``` Superposition of Atomic Density Guess ------------------------------------- ``` The number of electrons -1 in the ECP does not accord with a known set of completely filled shells !!! ```------------------------------------------------------------------------ unrecognised pseudopotential 911 ------------------------------------------------------------------------ There is an error in the input file ------------------------------------------------------------------------ For more information see the NWChem manual at http://www.nwchem-sw.org/index.php/NWChem_Documentation ``` ```For further details see manual section: Can you help me with that because I do not know what is wrong. Thank you! ```

 Sean bureaucrat Profile Send PM
 Forum Regular Threads 1 Posts 187
 2:10:33 PM PDT - Fri, May 1st 2015 The error is being caused by the assigned nuclear charge not playing nice with the set up for the atomic scf guess. The easiest fix is to switch your initial guess to hcore, i.e. scf uhf singlet vectors input hcore end This should eliminate the error and my test calculation ran successfully. Best, Sean

 Btam125 Member Profile Send PM
 Clicked A Few Times Threads 9 Posts 26
 2:47:49 AM PDT - Tue, May 12th 2015 Thanks it is working now!

 Btam125 Member Profile Send PM
 Clicked A Few Times Threads 9 Posts 26
 2:48:03 AM PDT - Tue, May 12th 2015 Thanks it is working now!

 Btam125 Member Profile Send PM
 Clicked A Few Times Threads 9 Posts 26
 2:48:05 AM PDT - Tue, May 12th 2015 Thanks it is working now!

 Btam125 Member Profile Send PM
 Clicked A Few Times Threads 9 Posts 26
 2:48:07 AM PDT - Tue, May 12th 2015 Thanks it is working now!

 Btam125 Member Profile Send PM
 Clicked A Few Times Threads 9 Posts 26
 8:39:33 AM PDT - Mon, May 18th 2015 Hi sorry to bother again. Can you tell me if it is possible to have 33 electrons, 34 proton but + 1.5 charge in total? If it is possible, how can I do it? Thank you.

 Sean bureaucrat Profile Send PM
 Forum Regular Threads 1 Posts 187
 9:52:18 AM PDT - Mon, May 18th 2015 If you would like a system with 33 electrons and a total nuclear charge of +34 while having a total charge of +1.5, you would have to add an external point charge (see http://www.nwchem-sw.org/index.php/Release65:Bq) For example: geometry C 8.59886355 17.68912997 15.23024421 O 7.79422064 18.43388815 14.85345853 O 9.40505759 16.94410501 15.60704709 Mg 7.88418289 20.67609980 14.51097681 end basis print C library 6-31+G* O library 6-31+G* Mg library 6-31+G* end charge 1.0 bq ```0.0000 0.0000 0.0000 0.5 ``` end scf uhf doublet vectors input hcore end task scf The charge directive only considers the nuclear charge, hence the charge of +1 in order to get 33 electrons and then the Bq charge of +0.5 so that the total charge of the system should be +1.5.

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