rock_deriv

rock_deriv(coords, i, j, k, /, order=1, method='expansion', angle_ordering='ijk', cache=None, reproject=True, zero_thresh=None, fixed_atoms=None, expanded_vectors=None): 

Gives the derivative of the rocking motion (symmetric bend basically)

• coords: np.ndarray

• i: int | Iterable[int]

  index of the central atom

• j: int | Iterable[int]

  index of one of the outside atoms

• k: int | Iterable[int]

  index of the other outside atom

• :returns: np.ndarray

  derivatives of the angle with respect to atoms i, j, and k