Two link atoms in QCHEM/CHARMM QM/MM

Dear All,

I am trying to do QM/MM calculation of protein using QCHEM/CHARMM however, I am facing a problem with link atoms. When I add one link atoms using the command addlink atoms it works fine however, when I try to add second link atom it gives error like no QM parameters found. Could you please share your experience about two link atoms?

NB: I add parameters and topology files for both the link atoms.

Hello suranjan,

Can you post the snippet of the output? I suspect that the linked MM atoms not being carbon cause the error. You may have to increase/decrease the QM region so the linked MM atoms are always carbon.