Hi, I am not used to Q-Chem and RI-MP2 methods. But I have found several techniques to improve convergence on this page: https://manual.q-chem.com/5.3/sect_convergence.html

In general, it is useful to look at the last energy values of the SCF procedure. If the energy oscillates, maybe some damping is enough to favour the convergence. If the energy always decreases and does not oscillate (a pare from rare cases), maybe you should increase the maximum number of steps.

I found some details on how to deal with damping on Q-Chem here: https://manual.q-chem.com/5.3/sect_damp.html

I hope this may help

Best regards

This is my rem section

$rem

ECP=def2-ECP

jobtype=opt

geom_opt_max_cycles=600

BASIS=def2-tzvpd

AUX_BASIS=rimp2-def2-tzvpd

GUI = 2

METHOD = rimp2

MAX_SCF_CYCLES =1200

$end