[gmx-developers] adding angle dependent non-bonded interactions?

[Julius Su]

Hello,

Is it possible/easy to add an angle dependent non-bonded interaction to
GROMACS of the form --

  E = (1 + (cos theta)^2) exp(-a r)

where theta is the angle between two vectors:
  (1) radial vector.
  (2) normal vector defined by atom and 2 bonded neighbors.

This would be used to implement a proton dynamics force field.  I
already have the formulas for analytical gradients with respect to all
atoms involved.

Thanks,

Julius