def METHOD_NAME():
    # Instantiate the energy group data and file object
    groups = openmc.mgxs.EnergyGroups(group_edges=[0.0, 0.625, 20.0e6])
    mg_cross_sections_file = openmc.MGXSLibrary(groups, 6)
    # Make the base, isotropic data
    nu = np.array([2.50, 2.50])
    fiss = np.array([0.002817, 0.097])
    capture = np.array([0.008708, 0.02518])
    absorption = capture + fiss
    scatter = np.array(
        [[[0.31980, 0.06694], [0.004555, -0.0003972]],
         [[0.00000, 0.00000], [0.424100, 0.05439000]]])
    total = np.array([0.33588, 0.54628])
    chi = np.array([1., 0.])
    decay_rate = np.array([0.013336, 0.032739, 0.12078, 0.30278, 0.84949,
                           2.853])
    delayed_yield = np.array([0.00055487, 0.00286407, 0.00273429, 0.0061305,
                              0.00251342, 0.00105286])
    inv_vel = 1.0 / np.array([1.4e9, 4.4e5])
    mat_1 = openmc.XSdata('mat_1', groups, num_delayed_groups=6)
    mat_1.order = 1
    mat_1.set_fission(fiss)
    mat_1.set_kappa_fission(fiss * 200e6)
    mat_1.set_nu_fission(nu * fiss)
    mat_1.set_beta(delayed_yield / 2.5)
    mat_1.set_decay_rate(decay_rate)
    mat_1.set_absorption(absorption)
    mat_1.set_scatter_matrix(scatter)
    mat_1.set_total(total)
    mat_1.set_chi(chi)
    mat_1.set_inverse_velocity(inv_vel)
    mg_cross_sections_file.add_xsdata(mat_1)
    # Write the file
    mg_cross_sections_file.export_to_hdf5('2g.h5')