AMBER Archive (2002)

Subject: about dummy parameter of multiplicity

From: sxzheng (sxzheng_at_mail.shcnc.ac.cn)
Date: Thu Oct 10 2002 - 02:55:15 CDT

Dear all,

I have a organic molecule to be perturbed.
I have completed the process:saveamberparm. When I use "saveamberparmpert",there is many proper torsion parameters missed.I feel something confused as followed:

***Proper torsion parameers missing ***
atom names:C12-C11-C10-C13
atom types: c3-c3-c3-c2 =pert=> c3-c3-c3-c3
Please add a dummy parameter of multiplicity 1
for the no-pert types to your parameter set.
-e.g. c3-c3-c3-c2 1 0.0 0. 1.

At the same time ,it also advises to add a dummy parameter of multiplicity 2 as:
atom names:C12-C11-C10-C13
atom types: c3-c3-c3-c2 =pert=> c3-c3-c3-c3
Please add a dummy parameter of multiplicity 2
for the no-pert types to your parameter set.
-e.g. c3-c3-c3-c2 1 0.0 0. 2.

While I think the PN parameter of torsion x -c3-c3-x should be 3.
So why it advise 1 and 2 for PN that is conflictory and why it is not 3.
further,why it's dummy parameter and what's the effection of the system.

Thank you very much
sxzheng