Angular Restraints

In DL_POLY_2 angle restraints, in which the angle subtended by a triplet of atoms, is maintained around some preset value $\theta_0$ is handled as a special case of angle potentials. As a consequence angle restraints may be applied only between atoms in the same molecule. Unlike with application of the ``pure'' angle potentials, the electrostatic and van der Waals interactions between the pair of atoms are still evaluated when distance restraints are applied. All the potential forms of the previous section are avaliable as angular restraints, although they have different key words:

1. Harmonic: (-hrm)
2. Quartic: (-qur)
3. Truncated harmonic: (-thm)
4. Screened harmonic: (-shm)
5. Screened Vessal[24]: (-bv1)
6. Truncated Vessal[25]: (-bv2)
7. Harmonic cosine: (-hcs)
8. Cosine : (-cos)

In DL_POLY_2 angular restraints are handled by the routine ANGFRC.