How to setting tilt component in colvars module

From: 서용일 (
Date: Mon Sep 23 2013 - 01:21:35 CDT

Dear NAMD users

I want to get the tilted angle of protein.
So, I using tilt component in colvars module.
My colvars configuration file is below:

colvar {
    name Rotation_protein

    width 1

    lowerboundary -1
    upperboundary 1

    tilt {
        atoms {
            psfSegID 8RA
            atomNameResidueRange CA 1-8
        refPositionsFile ../colvars_orient/pdb file
        refPositionsCol B

harmonic {
    colvars Rotation_ring
    forceConstant 1000.0
    centers 1.0
    targetcenters 0.0
    targetnumsteps 500000
    targetnumstages 90

I have some question.

1. I know the value of lowerboundary, upperboundary, centers and
targetcenters are cosine(theta).
    but what is value of the width??
    I guess the value of width: the angle of degree? or radian? or other
    well, I put the degree, In my colvars configuration file.

2. The harmonic oscillator is k(x - x_0).
    But, I don't know x. x is theta? or cosine(theta)?

Thanks for reading.

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