I cannot guarantee that the fchk file produced by Q-Chem is always compatible with Multiwfn, since I am not a Q-Chem user.

You can provide me (via E-mail or netdisk) your .fchk files, as well as corresponding input file of Q-Chem, so that I can check the reason of crash.

I'm trying to load .fchk files to do QTAIM calculations on some Ln complexes. The La, Ce, and Lu files open fine. Once I try to go to Pr, Eu, Gd, etc. then multiwfn crashes for some reason. The window flashes by too fast to actually see what the error is. I am running multiwfn 3.8 and the fchk files are generated in Qchem. All of the metal atoms have the Stuttgart small core ecp. All of the fchk files have been produced the same way.