Does ROTATE use a force field to optimize the geometries?

ROTATE does not use a classical force field algorithm for optimization, but applies a symbolic (or empirical) energy function. This symbolic energy function is derived from the torsion angle library (TAL) that contains the
distribution of torsion angles of over 1,000 four-atomic torsion angle patterns.
The distributions are stored in histogram (from 0 to 360 degree). The frequencies of the individual torsion angle values are used to derive a symbolic energy value for each torsion angle value for a specific torsion angle pattern and a gradient optimizer identifies the minimas.