Subject: Fw:(by [email-masked])=?gb2312?B?SG93IHRoZSBwYXJ0aWFsIGNoYXJnZXMgYmUgY29tcHV0ZWQgaW4gQ1ZGRiBmb3JjZSBmaWVs

From: "������" <[email-masked]>
Date: Thu, 21 Mar 2002 11:08:43 +0800 (CST)

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Dear all the CCLers:
    I am a user of InsightII of Accelrys(former MSI). When I perform comutations,such as molecular minization or dynamics,I often use CVFF force field. I always use FF (Force Field). This command is activated on the left side by clicking on the FF button. Then select Forcefield/Potentials and make sure that all of the settings as follows.
            Potential Action [Fix]

            Partial Charge Action [Fix]

            Formal Charge Action [Fix or Accept] 

    My question is how the partial charges of my molecules are computed? In my opinion,the partial charges are part of the CVFF force field. When CVFF is used, the partial charges are automatically loaded from the system file. This is quite different from MM2 (Tripos) method which often calculate partial charge through Gasteiger-Huckel method for small molecules.Is this so? I have referred several papers, but find no how the charges are computed.

    I am eager to get any helpful suggestions.

    Thank you in advance!

Song Yunlong
[email-masked]

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From: Oliver Hucke <[email-masked]>
Date: Sun, 24 Mar 2002 19:35:37 +0100

Dear Song Yunlong,

I have used InsightII in conjunction with the charmm forcefield and
Delphi to perform electrostatics calculations.
In this case the partial charges are obtained from the topology file of
the forcefield. It should be the same with cvff? In the directory

[Insight instalation path]/I2000/irix6m4/biosym_lib/ 

I can find a file cvff.rlb which seems to contain the atomic partial
charges...

Best,

Oliver

-- 
____________________________________________________________________________

Oliver Hucke
Inst. fuer Physikalische Chemie II
Universitaet Freiburg
Albertstr. 23a
D-79104 Freiburg

Tel. :  +49-761-203-5130 (/-6179)
Fax. :  +49-761-203-6189
email:  [email-masked]
____________________________________________________________________________