def coordination_number(rij, cij, r_cut, cutoff_func):
    """Pairwise contribution to many-body descriptor based on number of
        atoms in the environment

    Args:
        rij (float): distance between atoms i and j
        cij (float): Component of versor of rij along given direction
        r_cut (float): cutoff hyperparameter
        cutoff_func (callable): cutoff function
    Return:
        float: the value of the pairwise many-body contribution
        float: the value of the derivative of the pairwise many-body
        contribution w.r.t. the central atom displacement
    """

    fij, fdij = cutoff_func(r_cut, rij, cij)

    return fij, fdij