ENERGY EXPANSION IN THE EXTENDED GEMINAL MODEL

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 comp ute the weak three-body interaction in rare gases. Test calculations a re presented for the non-additivity in the (H-2)(3) trimer, the Ne ato m and the Ne-2 interatomic potential.