AMBER Archive (2004)

Subject: AMBER: About the Amber constraint constant

From: Yuhui Cheng (
Date: Sun Aug 15 2004 - 03:12:50 CDT

     When Sander set the harmonic constraint using NMR metnod, Dr. Alan Grossfield mentioned in his WHAM program that the constraint energy should be "E=k*(x-x0)^2" instead of "E=(1/2)*k*(x-x0)^2". I checked the fortran source code "_disnrg.f" in the $AMBERHOME/src/sander/ and found that the comments line use the formula "E=(1/2)*k*(x-x0)^2" but the program line neglected the "1/2". Is my understanding correct?

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