CR differential number density spectra dn/dp for the ¹²C (top) and ¹¹B (bottom) isotopes in model A1 (left) and model C1 (right), after 500 Myr evolution, taken at five different altitude points in the box (with x = y = 0). The red dashed lines represent the initial slope a of the primary injection spectrum. For each spectrum, a fit slope estimation is given, with a_L being the slope at nonrelativistic energy and a_R being the slope at relativistic energy. The slopes differ in those energy ranges because of the different energy-dependent spallation, Coulomb energy loss, and diffusion processes.