A priori identification of configurational deadwood

A method is given for the a priori assessment of those terms in a configuration interaction expansion that can be deleted if a given error in the energy is tolerated. The truncations are performed independently for the quadruple, quintuple and sextuple excitations on the basis of information derived from the double and triple excitations. The effectiveness of the method is illustrated by application to SDTQ56-CI wavefunctions of the molecules HNO, N2 and NCCN.