AMBER Archive (2008)

Subject: AMBER: improper dihedral in ff03 united atom forcefield

From: اطو©و© (sansanqin00_at_mails.tsinghua.edu.cn)
Date: Tue Jul 22 2008 - 20:49:28 CDT

Dear amber-users:

      I have a question about the improper dihedral in ff03 united atom forcefield. As we know, in order to prevent inversion of the stereochemistry of sp3 carbons, the united atom CH groups - sp3 carbons with one implicit hydrogen should be designed with improper dihedral parameters. However in frcmod.ff03ua, I can't see any improper dihedral parameters dealing with CH group. If I want to simulate some alkanes with branch, can I use the 03 united atoms? If so, how does it deal with improper dihedrals?

     This confuses me a lot, will somebody give me some explanation? Thanks very much in advance.

Shanshan Qin

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