Force constant for Umbrella Sampling

From: Buddhadev Maiti (
Date: Mon Feb 14 2011 - 19:19:02 CST

Dear NAMD Users,
I am performing Umbrella sampling using NAMD-2.7 version. Basically I would like to know whether in this calculations, as far as the force constant is concerned, the selected part of the different atoms can be regarded as a single effective "atom" or the force constant refers to individual atoms inside each selected region. Also, I would like to know what is the appropriate value of the force constant. Also please suggest me if any problem in file, it will be great help for me.
Have a nice day,

Colvarstrajfrequency 1000
Colvarsrestartfrequency 1000
colvar {
name GRrmsd
width 0.1
lowerboundary 19.955
upperboundary 21.955
lowerwallconstant 100.0
upperwallconstant 100.0
rmsd {
atoms {
atomsFile 1.pdb
atomsCol O
atomsColValue 1.0
refPositionsFile ep.pdb
refPositionsCol O
refPositionsColValue 1.0
harmonic {
colvars GRrmsd
centers 20.955
forceConstant 10.0

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