²³⁸U neutron scattering cross sections calculated with the Free Gas and Crystal Lattice Models as shortly described in Sections 2.1 and 2.2. The top plot (a) compared the two models up to 100 eV, in which the dot blue line defines the thermal cutoff energy of 4 eV. The bottom plots (b), (c) and (d) highlight the results for the first three s-wave resonances of ²³⁸U obtained with the Free Gas and Crystal Lattice Models. The CLM calculation was performed by introducing in Equation (15) the phonon density of states shown in Figure 2.