I want to retrieve the isotopic evolution from a previous deplete calculation using openmc.deplete.Results and the export_to_materials() method.
When I compare the materials from materials.xml and the one retrieved, I do not get the exact same quantities, and I notice a difference in the density unit. In the materials.xml file, the unit is "g/cm3", whereas in the retrieved material I get [sum].
This is due to normalization, where openmc will recalculate the density based on atomic percentages instead of what you had set, as with depletion this can change significantly in certain situations. If you want to double check try dividing the atomic percentages from the new material by the old and you’ll see the same factor or normalization across the nuclides.