Hi guys, I am trying to calculate the macroscopic cross section (scattering and absorption) for high energy neutrons between 1 MeV and 10^7 MeV in Silicon. I am using the macroscopic cross section to determine the mean free path. To calculate the macroscopic cross section, i need to know the microscopic cross section for the given material, as a function of neutron energy, as given in the following link: http://www.tpub.com/content/doe/h1019v1/css/h1019v1_113.htm" Is there an analytical expression to generate this curve for a given material, or can i get this curve from some type of database online? I need the curve for both scattering and absorption. Thanks, any help is appreciated, Pete.