Truncated CI Question

Hi guys,

Firstly, wonderful job on PSI4 - I’ve started digging into it recently and it’s a great learning resource.

I was wondering, in the context of CIS, CISD, CISDT… etc, is it possible (with some development) to specify exactly which determinants should be included in the MC wavefunction? I.e not to consider all possible n-tuply excited determinants, but a subset defined by their occupations.

I’ve been looking into DETCI for exactly this, however, the alpha/beta string method doesn’t look particularly amenable to modification…

Is there anyone that could give me some tips as to how this might be achievable?