This really depends on what you are trying to do. Basically, you would follow the very same procedure as has been originally used for the force field you plan to combine your new charges with. As far as I am aware of AMBER force fields have traditionally only used HF/6-31G* for charge derivation. The IOPs 6/41 and 6/42 determine the number of layers and the density of points to compute the potential at. The tighter you define the grid the less dependent you will be on translational and rotational variation of your input structure. But at this point you may just want to look into R.E.D. and associated papers to understand what motivates this and more elaborate protocols.
________________________________________
From: Robin Jain [robinjain.chem.gmail.com]
Sent: 18 July 2015 08:16
To: amber
Subject: [AMBER] help in resp charge
Dear all,
For resp charge fitting, i have some confusion
1. Should i use this
#HF/6-31G* SCF=tight TEST Pop=MK iop(6/33=2) iop(6/42=6) opt
Or
#opt b3lyp/6-311+g(d,p) geom=connectivity iop(6/33=2, 6/42=10, 6/41=10)
pop=mk scf=tight test
Which one is better and correct and what is your opinion and suggestion in
this regard.
--
Robin Jain
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Received on Sat Jul 18 2015 - 01:30:03 PDT
