def raman_intensity(R):
    """
    Scattering intensity

    Args:
        R (3x3 numpy array): Susceptibility tensor

    Returns:
        float: scattering intensity according to Eq 7, Phys Rev B 73, 104304 2006
    """
    return (
        4 * (R[0, 0] ** 2 + R[1, 1] ** 2 + R[2, 2] ** 2)
        + 7 * (R[0, 1] ** 2 + R[0, 2] ** 2 + R[1, 2] ** 2)
        + R[0, 0] * R[1, 1]
        + R[0, 0] * R[2, 2]
        + R[1, 1] * R[2, 2]
    )