AMBER Archive (2003)

Subject: AMBER: "irstrnt=1"in input file for RESP

From: Mi-Kyung Seo (mkseo98_at_hotmail.com)
Date: Mon Aug 11 2003 - 17:26:30 CDT

Hi Amber users,

I am trying to get RESP charges for carbohydrates with AMBER 7.0
I have questions about parameters for penalty function to calculate RESP.
(Amber manual p259)

In input included in the "-i" file for RESP, there is "irstrnt" (irstrnt=1 :
hyperbolic restraint to charge of zero, default) based on
J.Phys.Chem.97,10269(1993) (A well-behaved electrostatic potential based
method using charge restraints for deriving atomic charges: The RESP model).

In modified the penalty function to hyperbolic restraint form (irstrnt=1),
there are two parameters, a scale factor and "tightness" of the hyperbola
around its minimum.

A scale factor can be chaged with "qwt" in input but I can't find about any
explanation for "tightness" of the hyperbola around its minimum.

Where is the definition of "tightness" in input format?
How can I control "tightness" parameter in RESP input file? Is always it
fixed?

Thanks.
Mikyung

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