rock_deriv

rock_deriv(coords, i, j, k, /, order=1, method='expansion', angle_ordering='ijk', 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

  d e r i v a t i v e s

o f

t h e

a n g l e

w i t h

r e s p e c t

t o

a t o m s

i ,

j ,

a n d

k