While performing some verification tests comparing various homogenised cross sections evaluated with OpenMC and another code, I observed approximatively equal result for all isotopes except for Am242.
As for OpenMC I used the “ENDF/B-VIII.0” library available in your the OpenMC website, section LANL-Based Data Libraries. As for the other code I used “Lib80x” ACE library.
I’m aware that in ACE files distributed by LANL, Am242m1 has ZAID 95242, while Am242 has ZAID 95642, which is quite counterintuitive.
I’ve reason to believe that in the .h5 libraries distributed with OpenMC the isotopes Am242m1 and Am242 are inversed.