The HarmonicBond interaction implements a simple harmonic bond potential with a nonzero rest length. The potential energy $V(r)$ for two covalently bonded particles separated by a distance $r$ is given by

$V(r) = \frac{\kappa}{2} ( r - l )^{2}$

Different values are defined for the parameters $\epsilon$ and $l$ for each bond type.

Values of the parameters $\kappa$ , $l$ are denoted in the parameter file and source code by array-valued variables named "kappa", and "length", respectively. The parameter file format is:

kappa Array<float>

length Array<float>

Both arrays are entered in column form, with one entry per line, with the first entry after the label. The parameter block a system with two bond types (nBondType=2) might thus look like this:

kappa     100.0
          150.0
sigma     1.00
          0.90