It looks like your issue with Si2 is the same as here. The CC equations aren’t converging…
@hokru, did you look into the convergence failures after your last post on that topic?
I don’t know what the problem with Be2 is, but I suspect that’s a Psi4 bug where we are somewhere assuming that every irrep has amplitudes. I’ll do some preliminary investigating later today and get an issue filed if it indeed seems to be a Psi bug.