PC GAMESS/Firefly-related discussion club

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Alex Granovsky
gran@classic.chem.msu.su

normally, if the ground state is ionic and is well described by HF or DFT,
you do not need to do anything special, as SCF will converge to corresponding ionic solution without any problems.

In more difficult cases, you may need to use better initial guess orbitals
(e.g., combined orbitals of monomers, or for positively charged system),
possibly changing filling order of guess using norder/iorder instructions,
and sometimes to restrict orbital interchanges using RSTRCT keyword of $SCF group.

In the most difficult situations, you may need to go beyond SCF to describe ionic states.

However, as this is QC, there is no way to forcibly assign a charge to the part of the molecule...

Regards,
Alex Granovsky

On Fri Mar 20 '09 10:42am, Mahesh Bhatt wrote
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>Dear Sir,
>We can make pdb file of netral atom or molecule ( CuPc or C60). In that we can load another neutral atom or molecule over previously loaded one. My question is now: Can we deposit an anion (CuPc+) over a cation (C60-)in pcgamess? I can not understand this in the way that cation or anion can only be made when we give some negative or positive charge to neutral atom or molecule and do calculation; then pdb file becomes output file.
>I request you to let me know the way of depositing an anion over a cation in pcgamess before doing calculation.
>Sincerely
>Mahesh Bhatt
>University of Tsukuba
>Japan