Energy expansion in the extended geminal model Original Research Article

The FCI correlation energy is decomposed into a sum of single electron pair, double pair, triple pair and higher-order contributions. It is shown how this decomposition can be used to perform more accurate and efficient ab initio calculations. The model is accurate enough to compute the weak three-body interaction in rare gases. Test calculations are presented for the non-additivity in the (H2)3 trimer, the Ne atom and the Ne2 interatomic potential.