multi-reference CI approaches with cfour

Hello everyone,

I want to do multi-reference CC calculation with cfour to get the energy of excited states. The system I'm interested in is LiFH, which is open-shell. I can't find such example on the cfour manual, can it be done with cfour?

Unfortunately you cannot define the active space in the cfour input file, so you should also write a separate input file for mrcc. In the cfour input (ZMAT) you need:
CC_PROG=MRCC
INPUT_MRCC=OFF
In the mrcc input (MINP) you need:
iface=cfour
and you should set the multiplicity (keyword mult), the memory (mem), and define the active space using the nacto/nactv or the active keywords, see the mrcc manual for details.