def sigma_Flynn(Vc):
    """Calculates Lennard-Jones molecular diameter.
    Uses critical volume. CSP method by [1]_ as reported in [2]_.

    .. math::
        \\sigma = 0.561(V_c^{1/3})^{5/4}

    Parameters
    ----------
    Vc : float
        Critical volume of fluid [m^3/mol]

    Returns
    -------
    sigma : float
        Lennard-Jones molecular diameter, [Angstrom]

    Notes
    -----
    Vc is originally in units of mL/mol.

    Examples
    --------
    >>> sigma_Flynn(0.000268)
    5.2506948422196285

    References
    ----------
    .. [1] Flynn, L.W., M.S. thesis, Northwestern Univ., Evanston, Ill. (1960).
    .. [2] Stiel, L. I., and George Thodos. "Lennard-Jones Force Constants
       Predicted from Critical Properties." Journal of Chemical & Engineering
       Data 7, no. 2 (April 1, 1962): 234-36. doi:10.1021/je60013a023
    """
    Vc = Vc * 1000000.0
    sigma = 0.561 * (Vc ** (1 / 3.0)) ** 1.2
    return sigma
