[molpro-user] relaxed Pople cluster corrections

[harding]

If one does a multi-reference, ci calculation using a full valence 
active space (5 orbitals, 5 electrons) on the quartet sigma minus state 
of CH one finds that the relaxed-reference, Pople, cluster correction is 
exactly zero (the fixed-reference, Pople, correction is non-zero and 
both the fixed and relaxed, Davidson corrections are non-zero). The same 
is true for the triplet P state of carbon atom. This is not true for any 
of the doublet states of CH.

Can anyone explain to me why this is?

   Larry Harding