AMBER: antechamber and multiplicity

From: Cenk Andac <>
Date: Mon, 14 Mar 2005 11:57:27 -0800 (PST)

Dear amber community

I have been trying to compute Mulliken charges at AM1
Hamiltonian level with bond charge corrections for an
aminoacid-CU+2 derivative. The net charge of the
molecule is +1. I executed antechamber as follows

antechamber -i aaCU2.pdb -fi pdb -o aaCU2.mol2 -fo
aaCU2.mol2 -at gaff -c bcc -nc 1 -m 3 -j 5

I think I may have problem with the multiplicity value
because I keep getting an error message regarding the
total number of electrons.

When I set the charge of the molecule to 0 and set m
to be 1, then divcon is OK with charge computations.

As stated in AMBER8 manual, multiplicity is (2S+1).

Electronic configuration for CU+2 is

So, there is one unpaired electron in 3d shell.

Does this mean that S=1?

What (additional/optimal) parameters should I use in
the antechamber line above to make my molecule gain +1



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Received on Mon Mar 14 2005 - 20:53:00 PST
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